Issuu

The

IGS Geode ACTIVITIES OF THE IOWA GEOLOGICAL SURVEY, 2024–25

The IGS Across Iowa

The IGS Geode

Contents

From the State Geologist

Activities of the Iowa Geological Survey, 2024–25 O N THE COV ER: The IGS in the field – please see the articles featured herein for further information about the various projects the Survey has been involved in over the past year. (top-left photo) IGS geophysicist Jason Vogelgesang collecting data for an electromagnetic (EM) terrain conductivity survey along a levee in downtown Des Moines, Iowa. This work is part of a five-year directive to survey all of Iowa’s levees in partnership with the Office of Levee Safety (Iowa Department of Homeland Security and Emergency Management [HSEMD]).

From the State Geologist

State Parks Around the Iowa Great Lakes

New Insights into the Geology, Hydrology, and Nutrient Cycling of the Iowa Great Lakes

Evaluating the Effectiveness of Stacked Practices: Utilizing Modified Blind Inlets at Terrace Sites for N and P Load Reductions

Effectiveness of a Roadside Two-Stage Ditch for Nutrient Reduction in an Agricultural Watershed

Updates to the IGS Sediment Laboratory

Assessing Long-Term Sustainability of Farm Ponds in Southern Iowa

Tracking the Impact of Prairie Installation on Water Quality

Iowa River Alluvial Aquifer Mapping and Groundwater Budget

Recap: Year Two of the Levee Surveying Program

Leveraging Legacy Downhole Geophysical Data for Geologic Hydrogen Research in Iowa

Drilling Deep into Iowa’s Geologic Past: The USGS STATEMAP Program Provides the IGS with New Opportunities to Study the Subsurface

IGS State Legislative Activities

Publications

Presentations

Projects

IGS Financials

(top-right photo) IGS geologists Ryan Clark and Jack Malone collecting a bedrock core as a part of a multiyear mapping effort in Dubuque County that is being funded by the USGS STATEMAP Program. (bottom photo) State Geologist Keith Schilling and IGS soil scientist Matthew Streeter join collaborators from Iowa State University to sample wells at a grass waterway monitoring site near Reinbeck, Iowa. Monitoring is being conducted as part of a new IGS project funded by the Iowa Nutrient Research Center (INRC).

THE I GS M I S S I O N : To collect, reposit, and interpret geologic and hydrogeologic data; to conduct foundational research; and to provide Iowans with the knowledge needed to effectively manage our natural resources for long-term sustainability and economic development. THE I GS V I S I O N : To be a nationally recognized leader in geologic and hydrogeologic sciences, building upon our rich scientific heritage and serving Iowans through research, education, and outreach. E D ITOR S : Alyssa M. Bancroft and Rosemary Tiwari D E SI G N : Benson & Hepker Design

C ONTACT U S : Iowa Geological Survey The University of Iowa 300 Trowbridge Hall Iowa City, Iowa 52242 Office: 319-335-1575 Email: iihr-iowa-geological-survey@uiowa.edu Web: iowageologicalsurvey.uiowa.edu www.facebook.com/IowaGeologicalSurvey twitter.com/IowaGeoSurvey

2 | The IGS Geode

BACK COVER

Ten Years with the University of Iowa

Anniversaries are a wonderful thing. They come around on a yearly basis and force you to look back from where you’ve come and help point where you want to go in the future. For marriages, anniversaries are indeed very special, and they are often celebrated with much greater attention with each passing decade. At the Iowa Geological Survey, in December 2024, we celebrated the 10year anniversary (marriage, of sorts) with IIHR—Hydroscience and Engineering (IIHR, within the College of Engineering) at the University of Iowa. If you’re new to the IGS and our history, a brief recap is in order. The Survey has existed in some form since it was established in 1892 as a separate agency of state government. So, one anniversary we could celebrate in 2025 might be our 133rd birthday since the founding! For the next 94 years the IGS operated as an independent agency of the state, then in 1986 jurisdiction of the IGS moved to the Iowa Department of Natural Resources (IDNR). In 2014, 10-years ago, IGS moved its jurisdictional home to IIHR and the University of Iowa, and this anniversary was certainly a reason to take pause and celebrate (note that the back cover of The Geode showcases some photos from the event). The move from IDNR to IIHR was quite a change and there were some initial growing pains. Under the leadership of IIHR Director, Larry Weber, the IGS reformulated under a new boss and a revitalized mission. We celebrated this past December to highlight the amazing progress and success of the IGS over the last 10-years. Here is a look at a few of the numbers: • Despite flat funding support from the Iowa Legislature, the IGS increased its

annual base budget by over $1,000,000. This was done by acquiring contract funding from a wide variety of outside entities, including federal government agencies, state organizations, municipal utilities, and others • The IGS doubled in staff. • IGS geologists produced 76 bedrock and surficial maps. • IGS hydrogeologists produced 11 water resources investigation reports. • IGS staff were lead author or co-author on 142 peer-reviewed publications – an output that would be the envy of many academic departments at top-tier research universities. Of course, no one at the IGS wants to rest on this success. As I noted above, a second reason to celebrate an anniversary is to take stock of current conditions and look forward to things to come. This issue of The IGS Geode provides a great snapshot of what the Survey is currently working on and serves as a partial roadmap for the future. Last year, it was with great appreciation that I reported we had received new funding from the Iowa Legislature to map and assess the condition of Iowa’s aquifers. With these initial one-time funds, we selected the Iowa River alluvial aquifer system from Marshalltown to Iowa City as our first focus area and we’re pleased to share the results of this work in The Geode. Led by Greg Brennan and Phil Kerr, we evaluated over 5,000 well logs, conducted geophysical surveys, installed wells, and mapped this alluvial corridor to produce a groundwater budget. Going forward, after the spring 2025 legislative session, the IGS received a new recurring appropriation of $200,000 to continue these groundwater mapping and assessment efforts. Our near-term plan now includes conducting alluvial aquifer assessments across western Iowa, including the Ocheyedon, West Nishnabotna, and Boyer rivers. This year’s issue of The Geode highlights other work completed during the past year as well. Thomas Doyle and Phil Kerr report on a multi-year water and nutrient diagnostic study of the Iowa Great Lakes in Dickinson County. Among the many insights gleaned from this work, have you ever wondered why West Lake Okoboji is the deepest lake in Iowa? Read and find out! The IGS continues to be

T H E IG S TEA M , S U M M ER 2 0 2 5 : (front, left-to-right) Stephanie Tassier-Surine, Valerie DiazGibertini, Joe Honings, Elliot Anderson, Jason Vogelgesang, Rosemary Tiwari, Jack Malone, Rachel Walenceus, and Ryan Clark; (back, left-to-right) Tom Stoeffler, Alyssa Bancroft, Greg Brennan, Calvin Wolter, Keith Schilling, Matthew Streeter, Phil Kerr, and Larry Weber (Director of IIHR—Hydroscience and Engineering). Rick Langel and Thomas Doyle were not present for this photograph.

heavily involved with nutrient reduction efforts in Iowa. With funding from the Iowa Nutrient Research Center (INRC), Iowa Department of Transportation (IDOT), and Iowa Department of Homeland Security and Emergency Management (HSEMD), IGS staff continue to develop, monitor, and quantify watershed processes, conservation practices, and levee effectiveness. Herein we report on blind inlets, farm ponds, long-term watershed monitoring, twostage roadside ditches, and provide an update on the levee surveying program by IGS scientists Matthew Streeter, Elliot Anderson, Joe Honings, and Jason Vogelgesang, respectively. Geologic characterization and mapping remain foundational for the IGS, and we’ve been able to greatly expand our ability to obtain deeper geological cores for analysis with funding support of the U.S. Geological Survey. Two of these new cores are discussed herein, including a rotosonic core of Quaternary deposits led by Stephanie Tassier-Surine and Phil Kerr and a new bedrock core described by Ryan Clark, Jack Malone, and Alyssa Bancroft. Continuing to enhance and develop our

geologic databases, invest in new field data collection, and expand laboratory capacities will be critical for current and future IGS staff, and we also highlight new capacities at the IGS in this issue. As you can probably tell from my remarks in this message and the articles included in this year’s issue of The Geode, the future remains very bright for the IGS. We are blessed with an extremely talented and productive staff that is supported by IIHR, the College of Engineering, and the University of Iowa. With ongoing funding from the legislature and continued success in obtaining outside contracts, we will continue to work to serve the interests of all Iowans by gaining new understanding needed to effectively manage our natural resources for generations to come. With that in mind, I’m confident there will be even more to celebrate when the 20-year anniversary comes along in 2034!

KEITH E. SCHILLING, PhD

State Geologist and Director

Activities of the Iowa Geological Survey, 2024–25 | 3

State Parks Around the Iowa Great Lakes K E IT H SCH ILLIN G A N D TH O M A S D OYLE

FIGURE 1. The locations of the four state parks around the Iowa Great Lakes region in Dickinson County.

4 | The IGS Geode

THE IOWA GREAT LAKES (IGL) region in Dickinson County is home to four state parks that capture the natural beauty and cultural significance of the area (Figure 1). It consists of a connected group of several natural lakes including Iowa’s largest natural lake by surface area, Big Spirit Lake, as well as the deepest and largest by volume, West Okoboji Lake. Each year over 1,000,000 visitors are drawn to the area due to the abundance of outdoor recreational opportunities including boating, fishing, hunting, hiking, and biking, among others. The state parks in this area play an important role in providing access to the lakes and highlighting the unique and important history of the region. No account of the IGL can begin without starting at their formation. The IGL are located along the western edge of the Des Moines Lobe (DML) ice sheet, the southernmost extension of the Laurentide Ice Sheet that surged into Iowa approximately 15,000 years ago. The initial advance of the DML ice stagnated across the landscape but was followed by several readvances over the next 3,000 years. As a result, the landscape in the Iowa Great Lakes region is dominated by knob and kettle terrain associated with other features that formed in direct contact with slowly disintegrating ice. The terrain, dotted by numerous pothole wetlands, marshes and sloughs, extensive sand and gravel deposits, and large natural lakes, provides the backdrop upon which four of Iowa’s more unique state parks, MiniWakan, Elinor Bedell, Pikes Point, and Gull Point, are located. Established in 1936, Mini-Wakan State Park sits on the north shore of Big Spirit Lake. This locality was an important site for the inhabitants of Iowa for millennia.

An archeological investigation at MiniWakan State Park in 2017 uncovered several Native American artifacts including pottery fragments that are over 1,000 years old. Elinor Bedell State Park lies on the east side of East Okoboji Lake and is one of Iowa’s newest state parks, established in 1998. The land for this park was donated by Elinor and Berkley Bedell. Berkley represented northwest Iowa in the U.S. Congress for over a decade. Pikes Point and Gull Point State Parks overlook the northeast and southwest sides of West Okoboji Lake, Iowa’s deepest natural lake by more than 100 feet. Both parks were established in the 1930s and have nearly 100-year-old shelters built by the Civilian Conservation Corps that are listed on the National Register of Historic Places. Lakeside Laboratory, an Iowa Board of Regents institution, is also located along the shore of West Okoboji Lake just northwest of Gull Point State Park. Views from any of these state parks certainly attest to the beauty of the Iowa Great Lakes region and beckon folks to visit (see photographs). As you consider driving or biking from one park to the next, check out the views of the lakes and countryside and imagine how the glacial and post-glacial history shaped the landscape. Further, think about how the area has been used throughout history — from Native American settlement to the present premier tourist destination of the state.

P H OTO GR APH 1 . Overlook of West Okoboji Lake at Gull Point State Park.

P H OTO G R A P H 3 . An area where archeological investigations were previously conducted at Mini-Wakan State Park.

P H OTO G R A P H 2 . Path leading to the beach at Pikes Point State Park.

Activities of the Iowa Geological Survey, 2024–25 | 5

New Insights into the Geology, Hydrology, and Nutrient Cycling of the Iowa Great Lakes T H O M A S D OYLE A N D PH IL K E R R

THE IOWA GREAT LAKES (IGL) region, located in northwest Iowa (Dickinson County), contain both the largest and deepest lakes in the state, Big Spirit and West Okoboji, respectively. The region and its lakes, formed by the last ice advance into the state, attract over half a million tourists a year. The landscape around the IGL was entirely formed from glacial materials deposited by multiple continental-scale glaciations over the last 2.58 million years. The most recent advance of the Des Moines Lobe, around 15,000 years ago, stopped just south of West Okoboji Lake and was responsible for carving out the region’s celebrated waterbodies (Figure 1). Despite their size, and similar to other waterbodies in the Midwest, the Iowa Great Lakes struggle with nutrient-related impairments like high turbidity and algae blooms.

The IGS recently completed a multi-year study to better understand the hydrology and nutrient cycling within the IGL region. Data were collected from 40 groundwater wells and 20 surface water sites from 2021– 2024, making this study one of the most comprehensive efforts in the region to date. To provide context for these groundwater data, a detailed mapping exercise of the glacial landscape and landforms was also conducted. From this framework, several new insights into the region’s groundwater system were made. One finding of this study resulted in an updated interpretation of the formation of West Okoboji Lake. This lake, over 130 feet deep in parts, is four times deeper than other lakes in the area. The singularness of this deep lake is likely due to a specific interaction between the advancing ice sheet and the old landscape. One telling detail is that there is no terminal moraine

around Milford, south of West Okoboji Lake. Drilling logs from the area north of the lake indicate that there is a substantial package of buried sand and gravel which corresponds with the lake’s bottom elevation and width. Geologists at the IGS have interpreted this linear buried aquifer to be a former river valley that was filled with coarse-grained materials from meltwater of the advancing ice. As the glacier reached its terminal position meltwater from the base of the glacier formed a subglacial lake pressurized by the overlying ice, while meltwater from the top of the glacier drained into a proglacial lake (Glacial Lake Spencer; Figures 2A, 2B). The interaction of buoyant ice with the water of Glacial Lake Spencer eventually resulted in the catastrophic release of meltwater and sediment from the subglacial lake (Figures 2B, 2C). While exiting from the base of the ice sheet,

MN IA

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Big Spirit Lake

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FIGURE 1. Topography and moraines of the Iowa Great Lakes region.

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oboji Lake

Milford Moraiin ne

Ok West

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terminal moraine

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East Okoboji Lake

Milford

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6 | The IGS Geode

520

Kilometers

the pressurized water cut down into the buried aquifer forming West Okoboji Lake (Figures 2C, 2D). This event also eroded a section of the Milford Moraine, leaving the conspicuously flat topography around the city of Milford. Further investigations into deep groundwater interactions with West Okoboji Lake are necessary but based on these findings there appears to be an important connection between the regional buried sand and gravel aquifer and the state’s deepest lake. The movement of shallow groundwater in the region was shown to be highly dependent on the local topography rather than regional flow. In other words, the shape of the water table is largely a reflection the land surface (Figure 3). This relationship causes shallow groundwater to drain into the numerous pothole wetlands, which are characteristic features of the recently glaciated landscape. These wetlands effectively act as groundwater sinks, as water leaves the local hydrologic system via evapotranspiration. As a result, up to 30% of shallow groundwater recharge in the IGL watershed may never reach the lakes. This study also provided a better understanding of nutrient-related impairments in the IGL region. Ground and surface water nutrient concentrations were higher in row crop dominated watersheds than in watersheds where a majority of the land was developed or had perennial vegetation cover. The various wetland complexes and shallow lakes in

the region are very effective at buffering the IGL from elevated nutrient inputs. At the monitoring site downstream of West Hottes Lake (a small lake draining into Big Spirit Lake) for example, the average nitrate and orthophosphorus (OP) concentrations leaving the site were 0.05 and 0.02 mg/L, respectively. In comparison, a watershed with similar land use but without water interception by wetlands or small lakes had average concentrations of 7.7 mg/L nitrate and 0.10 mg/L OP. A broader conclusion from this work is that the water budget of the lakes is heavily dependent on annual weather trends. From 2021–2023 surface water runoff was a very small proportion of the lakes’ inputs and outputs; however, in 2024 above-average rainfall caused surface water to make up over 70% of the volumetric fluxes into and out of the lakes. On a similar note, nutrient loading was higher in 2024 than in the previous three years combined. The work done for this study improved our understanding of the hydrology and nutrient cycling of the IGL region that we hope will be useful for informing management decisions in the future. There are several avenues for research that still need to be pursued: developing a detailed hydrologic/water quality model for the lakes, investigating the impact of tile drainage on nutrient cycling, and exploring the connection between buried aquifers and West Okoboji Lake.

For a more detailed report about this work, please visit the IGS publications website: https://igs.iihr.uiowa.edu/igs/publications/search Doyle, T.B., K.E. Schilling, P.J. Kerr, and M.T. Streeter, 2025. “Iowa Great Lakes Hydrology and Diagnostic Study,” Iowa Geological Survey, Technical Information Series (TIS) 60, 83 p.

glacial till

wetland

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subglacial lake Dows Fm.

B - Advance and Formation of Breach

ice decouples from frozen base

C - Catastrophic Release fully drained moulin

catastrophically drained subglacial lake tunnel valley

D - Modern Bathymetry

lack of moraine outwash West Okoboji Lake

FI G U R E 2 . Proposed formation of West Okoboji Lake (for further detail, please refer to the discussion within the article).

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local flow

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ai n

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seepage through till

Glacial Lake Spencer

Paleo-Iowa River outwash

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water filled crevaces

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A - Okoboji Sublobe Nears Terminus

fine-textured Wisconsin till

regional flow

FI GU R E 3 . Conceptual model of groundwater flow in the Iowa Great Lakes region. Generalized groundwater flow paths are shown by the arrows in Panel 1. The white circles along the crosssection line in Panel 1 represent the wells that are depicted in the cross-section in Panel 2.

Activities of the Iowa Geological Survey, 2024–25 | 7

Evaluating the Effectiveness of Stacked Practices: Utilizing Modified Blind Inlets at Terrace Sites for N and P Load Reductions M A T T H E W S T R E E TE R A N D E LLIOT A N D E R SO N

BLIND INLET TILE INTAKES are a highly efficient method for reducing sediment export from drainage tiles in the Midwest. Traditional blind inlets work by replacing the more common standing surface inlet, which is usually located behind a terrace or water and sediment control basin (WASCOB), with a drainage field comprised of a large pit that is backfilled with gravel. Following a rainfall event, surface water enters the drainage field, where soil sediments are filtered out before flowing into a perforated drainage tile. Blind inlets have been shown to reduce sediment and phosphorus (P) losses by 80 to 98%, but these gravel filter blind inlets are not effective for trapping dissolved nutrients like nitrate. Stacked conservation practices are often necessary to provide adequate reduction benefits for both dissolved and particulate nutrients. While stacked conservation often takes the form of multiple distinct practices, the IGS has been investigating stacking nutrient reduction benefits within the same basic system. In a pilot project, we explored the effects of incorporating a woodchip bioreactor—a practice effective at removing nitrate—into a traditional infield blind inlet. Significant reductions in nitrogen (N) and P concentrations were observed in this modified blind inlet during both small and large rain events,

FIGURE 1. Modified blind inlet equipped with a suite of sensors to estimate nutrient export and drainage rates.

8 | The IGS Geode

and we documented a 43% reduction in average nitrate concentrations (Wilson et al., 2024). Following the success of this pilot project, the IGS constructed two new modified blind inlets near the towns of Walcott and Keota and outfitted them with a suite of monitoring equipment needed to explore nitrate conveyance following a variety of rainfall events (Figure 1). These new practices contained real-time flow and nitrate sensors, rain gages, and automated water samplers that collected pre- and post-treatment samples over the duration of several rainfall events. Using the flow and nitrate sensors, we calculated

the nitrate loads exported downstream at both modified blind inlets. Monitoring took place over a two-anda-half-year window, and a wide range of nitrate levels (from 0 to 40 mg/L) were observed at both sites (Figure 2). For each rainfall event, we were able to examine the subsequent flow rates and changes in nitrate concentration using our monitoring setup. Figure 3 illustrates the dynamic nature of flow and nitrate following 1.2 inches of precipitation across 5 hours at the Walcott site. Over 20 distinct wet weather events occurred at this location, and we estimated a total flow of approximately 150,000 gallons draining

This work has been published in the peer-reviewed scientific journal, Water: Wilson, C.G., M.T. Streeter, W.E. Ettema, B.K. Abban, A. Gonzalez, K.E. Schilling, and A.N. Papanicolaou, 2024. “Assessing the effectiveness of alternative tile intakes on agricultural hillslopes,” Water, 16(2):309.

through the practice. This site’s average nitrate concentration was 15.9 mg/L, and the total nitrate exported downstream was 15.6 lbs. Measurements at the Keota site were complicated by the presence of downstream water occasionally backflowing into the blind inlet, but we were able to estimate that at least 50,000 gallons drained through the practice over the course of 25 rainfall events. This site had an average nitrate concentration of 7.6 mg/L, and at least 2.5 lbs of nitrate drained downstream. We also calculated the theoretical time needed by these inlets to drain various storm events. These theoretical flow rates, along with the flows measured by our monitoring, suggest that modified blind inlets drain water at rates comparable to typical standing tile inlets. This is vital information, as it shows that converting traditional tile intakes into modified blind inlets will not result in excess surface water ponding. Our next step with this project will involve quantifying the impact of the practices on several water quality parameters, including N and P, by analyzing the water flowing into and out of the practice during rainfall events. We also plan to expand the implementation of this practice by working with the National Resources Conservation Service (NRCS) to incorporate modified blind inlets into their suite of conservation practice standards. The initial results of our work have been promising, and we hope that modified blind inlets can become a widely used tool that helps drain farmlands while simultaneously improving water quality.

FIGURE 2. Daily nitrate concentrations at the two new modified blind inlet sites.

FIGURE 3. Example of live nitrate and flow measurements collected during a rain event at the Walcott site in May of 2023.

Activities of the Iowa Geological Survey, 2024–25 | 9

Effectiveness of a Roadside Two-Stage Ditch for Nutrient Reduction in an Agricultural Watershed J O E H O NIN G S A N D K E ITH S CH ILLIN G

FIGURE 1. Location (yellow box) of the two-stage ditch pilot study along U.S. Highway 30 in Benton County. The catchment area (orange polygon) is approximately 194-hectares (0.75 mi2) that drains to Prairie Creek just to the west and south of the study area. This project was completed in coordination with the Iowa Department of Transportation (IDOT). FIGURE 2. The two-stage ditch construction design conceived by the Iowa Department of Transportation (IDOT). FIGURE 3. Histogram of the data collected for the roadside two-stage ditch pilot study. The y-axis is the number of days (frequency) where both upstream and downstream measurements were able to be collected, whereas the x-axis is showing the upstream turbidity (In[Up Turb]) minus the downstream turbidity (In[Down Turb]). There is a clear increase in the reduction of turbidity between water years 2021 (blue; pre-installation) and 2024 (tan; post-installation).

F I GUR E 2 .

10 | The IGS Geode

NONPOINT SOURCES OF AQUEOUS

nutrients, like nitrate-nitrogen (NO3-N) and phosphorus (P), exported from agricultural areas contribute to degradation of streams, rivers, and lakes at local and regional scales. Midwestern states have adopted a variety of different strategies to reduce nutrient export. However, the most desired practices are those that enhance nutrient processing while minimizing loss of crop production. In some agricultural areas, conventional trapezoidal drainage ditches have been modified to include floodplain benches constructed alongside the main stream channel — termed two-stage ditches. During storm events, the benches become inundated, allowing flood flows to spread out and slow down. Shear stresses of high flows are reduced and the increased residence time of water in this modified ditch facilitates sediment and P deposition while enhancing water infiltration and subsequent vegetation assimilation of nutrients and denitrification. While the two-stage ditch has been traditionally deployed as an edge-of-field practice, the IGS, in collaboration with the Iowa Department of Transportation (IDOT), took an innovative approach and investigated the effectiveness of this strategy in a conventional roadside ditch. The area for this pilot study was located along the north side of U.S. Highway 30 in Benton County, east of Prairie Creek, in a ditch receiving runoff from

an approximately 194-hectare watershed (Figure 1). The 450-meter-long ditch was designed so that the inset bench would be inundated during an annually occurring rainfall runoff event (Figure 2). Turbidity monitored before and after construction showed the effectiveness of the ditch in reducing sediment export (Figure 3). Vegetation surveys completed by the University of Northern Iowa Tallgrass Prairie Center also revealed a marked improvement in vegetation composition and an increase in plant diversity following the modified ditch construction and reseeding. Upstreamdownstream grab sampling for dissolved ions, including NO3-N, orthophosphate, chloride, and sulfate, during four storm events did not show statistical differences. Converting a roadside ditch to a twostage design was a novel application of a conservation practice that has been traditionally applied only to agricultural drainage ditches in the Midwestern United States. Using the design criteria established for this pilot project, we identified that there could be as many as 185 potential locations along state highways and an additional 129 sites along county roads in Iowa where roadside ditches could be converted to a twostage design. Demonstrating the benefits of the two-stage ditch design in a unique roadside setting expands potential deployment opportunities to other locations around the state and region.

F IGURE 3.

Updates to the IGS Sediment Laboratory VA LE RI E DI A Z - G IB E RTIN I A N D M A T TH E W S TR E E TE R

THE IGS SEDIMENT LABORATORY critically serves the IGS by providing Quaternary materials and water quality analyses. Since its establishment in 2014, the lab has undergone almost continuous expansion with the addition of new equipment increasing our capacity to perform a broad spectrum of analyses. In the spring of 2025, the lab relocated and is now housed in the Physiology Research Laboratory (PRL) on the University of Iowa Oakdale Campus in Coralville. This new lab space offers more than double the square footage of the previous lab, which has immediately opened doors for more ambitious experiments and projects. While many lab services are conducted in the lab at PRL, like geomorphic soil descriptions (Photograph 1) and nitrate loss experiments (Photograph 2), much of our work is conducted in the field. For example, in 2025, we set up a “mobile lab” and have begun conducting bromide tracer studies at conservation practice field sites (Photograph 3). We also have been assisting the University of Iowa’s athletics department in assessing sediment and water quality in a pond at a local golf course (Photograph 4). The lab performs several thousand analyses each year including multiple forms of soil particle size analysis, sand fractionation, soil elemental analyses including total carbon and total nitrogen, soil organic matter as well as bulk density and saturated hydraulic conductivity. The lab also analyzes a suite of water quality analytes via ion chromatography, which has been fundamental for several projects that aim to better understand nutrient processing in the state. Finally, the lab maintains a large inventory of field monitoring equipment including well transducers for monitoring groundwater levels, multiparameter water meters, and other water quality sensors. The lab is open daily, is managed by Matthew Streeter, and staffed by Valerie Diaz-Gibertini and Marty St. Clair.

P H OTO GR APH S 1 , 2 , 3 , AN D 4 . Examples of data collection and lab experimentation undertaken by the IGS Sediment Laboratory (for further detail, please refer to the article).

PHOTOGRAPH 1.

PHOTOGRAPH 3.

PHOTO GR AP H 2 .

PHOTOGRAPH 4.

Activities of the Iowa Geological Survey, 2024–25 | 11

Assessing Long-Term Sustainability of Farm Ponds in Southern Iowa M A T TH E W S TR E E TE R

SMALL PONDS AND LAKES dominate the distribution of global water bodies and have many ecological benefits. Across Iowa and the Midwest, ponds have been constructed to aid the reduction of sediment export from watersheds and for flood control purposes. These ponds are often given an expected lifespan when designed and constructed based on expected sedimentation rates, but studies that compare actual rates of sedimentation to expected rates have not been completed. Further, the potential nutrient holding capacity of these ponds has not been assessed. The IGS has a very successful record of completing research projects that assess the environmental benefits and feasibility of agricultural conservation practices across the state. Many of these projects have been funded and supported by the Iowa Nutrient Research Center (INRC) at Iowa State University. Recently, IGS staff completed an INRC-supported study uniquely focused on farm ponds in the Soap Creek watershed in southern Iowa. This research will be published in full in an upcoming edition of the Journal of Soil and Water Conservation. In this study, the IGS used a GISbased LiDAR difference tool to estimate net sediment erosion from contributing watersheds of three Natural Resources Conservation Service (NRCS)-designed ponds (Figure 1) in the Soap Creek watershed, completed sediment surveys and estimated sediment storage for each pond, and quantified rates of sedimentation for each pond. We found that gully erosion was the primary contributor of pond sediment regardless of other catchment characteristics. We quantified storage of phosphorus (P), carbon (C), and nitrogen (N) in pond sediments (Photograph 1) and found that the ponds were storing significant

12 | The IGS Geode

quantities of exchangeable and total P. Concentrations of C and N were relatively low. On average, the ponds were infilling at rates 25% faster than design estimates. Therefore, ponds projected to have a 50year lifespan will likely cease to provide flood control or sediment capture 10 years earlier than expected, decreasing the actual usable lifespan to 40 years. Since the primary purpose of pond construction

by the NRCS is flood control, management requirements should be considered that prevent diminishment of that pond benefit. Stabilizing existing and potential gully locations using modern conservation practices like terrace construction prior to pond installation should be considered. In doing so, gully contributions could be reduced, and pond lifespans could increase significantly.

FIG U RE 1.

FI GU R E 1 . An example of NRCS “as-built” farm pond design specifications used by the IGS to determine original pond sediment and nutrient holding capacities. P H OTO GR APH 1 . Valerie Diaz-Gibertini sampling the headwaters of a farm pond.

PHOTOGRAPH 1.

Tracking the Impact of Prairie Installation on Water Quality E LLIOT A N D E R SO N

THE LANDSCAPE OF MODERN IOWA looks very different from its native condition. Tallgrass prairies and oak savannas that were once common have now largely been replaced by row crops, pastureland, and urban developments. However, there is one place in Iowa where prairie is still widespread. The Neal Smith National Wildlife Refuge (NSNWR) is located in Jasper County—about a 20-minute drive southeast of Des Moines. This refuge was founded in the early 1990s with the goal of restoring Iowa’s native ecosystems within its borders. Between 1995 and 2010, most of the land within this 6,000-acre property was converted from conventional cropland to prairie. Prairies now comprise over 80% of the NSNWR, making it one of the few locations in the Midwest with a mostly native landscape. This unique, large-scale transition from cropland to prairie has presented a valuable opportunity to study the longterm impacts of land use change on

water quality. The NSNWR lies entirely within the Walnut Creek watershed. This perennial creek begins upstream of the NSNWR and then flows through the heart of the refuge before discharging into the Des Moines River. The IGS monitored conditions as part of a 10year paired watershed study from 1995 to 2005, and since this time the IGS has collaborated with the Agricultural Research Service (ARS) to monitor streamflow and water quality at two sites along Walnut Creek: one located just upstream of the NSNWR and another directly downstream. This setup has enabled us to examine the impact that the restoration of the NSNWR has had on water quality by comparing the amounts of waterborne pollutants entering the refuge to those leaving it. This past year marked the 30th anniversary of monitoring in Walnut Creek, allowing us to comprehensively study its impact on nitrate and sediment (two pollutants that have long degraded

Iowa’s surface water) over the past three decades. In this study, we estimated yearly nitrate and sediment loads at both the upstream and downstream monitoring sites. We then calculated the percentage of these loads coming from the lower portion of the Walnut Creek watershed, where the NSNWR is located. For both pollutants, the percentage of the load originating from the lower portion of the watershed declined over the 30 years (Figure 1), indicating that the widespread installation of prairie has markedly improved Walnut Creek’s water quality. However, we also noted that these percentages can vary considerably from year to year, suggesting that water quality improvements following land use change often take multiple decades to become detectable at statistically significant levels. This new analysis adds to the large body of work that the IGS has conducted at Walnut Creek, and the NSNWR remains an important location for education, recreation, and scientific research. FI GU R E 1 . Annual percentage of nitrate (left) and sediment (right) loads originating from the lower portion of the Walnut Creek basin. The prairie landscape of the Neal Smith National Wildlife Refuge (NSNWR) is shown in the background.

Activities of the Iowa Geological Survey, 2024–25 | 13

FIGURE 1. The map at the top of the page depicts the elevation of the land surface and the data collected in the modern Iowa River Valley. The map at the bottom of the page portrays a recreation of the bedrock surface and interpretations of the former configurations of the Iowa River based on buried bedrock channels. Older river courses are represented by darker blue and grade to light blue for more recent configurations, while the modern channel is the lightest blue. Both maps (top and bottom) have the same elevation scale; on the top map the dashed white line shows the boundary of the bedrock surface map (bottom) and the A-A’ cross-section line, west of Belle Plaine, is shown in Figure 2.

L AND SURFACE

Legend

Be m is

oin es

Marshalltown

Lob

250

ine ora M

cross-section

geophysics point

elevation (ft)

1250

20 km

Iowa River Alluvial Aquifer Mapping and Groundwater Budget G RE G B RE N N A N A N D PH IL K E RR

WITH INCREASING INDUSTRIAL and irrigation use and emerging water quantity demands for new users such as data centers, it is imperative that we better understand the quantity and sustainability of groundwater resources available to the state. To aid in this effort, the IGS was awarded an appropriation

BEDROCK SURFACE

from the Iowa Legislature in fiscal year 2025 for a groundwater planning and resource assessment project. While there are many aquifers to choose from across the state, we selected the alluvial aquifer system of the Iowa River Valley (Figure 1, top) from Marshalltown (Marshall County) to Iowa City (Johnson County) for our

initial evaluation. This aquifer was chosen because the IGS had completed water supply projects in Marshalltown, Belle Plaine, and Iowa City and the one-time funding could be best utilized by hitting the ground running and connecting the dots between these three localities along the river. The goal of this effort was to

Relative Age of Buried River Valleys modern Iowa River recent old

A Tama

Marshalltown

14 | The IGS Geode

Belle Plaine A’

Marengo

r ve

i aR

lt C

ree k

Iow

Belle Plaine A’

Cedar Rive

Tama

Iowa City

Marengo

assess the aquifer’s potential to support existing and future water supply needs for cities, rural water systems, irrigation, industry, and private wells.

GEOLOGIC HISTORY

Within this 110 square mile project area of the Iowa River Valley, a stratigraphic evaluation of the data from more than 5,000 previously drilled water wells (available in the IGS GeoSam database) was conducted. This effort was further complemented by targeted field studies using geophysical methods, unconsolidated drill core collection, and monitoring well installation. These data were integrated to better understand the glacial and post-glacial history of the valley and map the distribution of the Quaternary

and alluvial aquifer sediments. In the end, this seemingly simple valley of the Iowa River was revealed to be exceedingly complex with a highly variable subsurface marked at depth by deeply incised bedrock channels (Figure 1, bottom). Valleys that were cut hundreds of feet into bedrock, including the Belle Plaine channel (Figure 2), are not reflected in the topography of the modern landscape. These buried valleys are filled with coarse-grained packages of sand and gravel separated by clay-rich glacial till sediments. During the Pleistocene (2.6 million years ago) continental glaciers repeatedly advanced and retreated across the Midwest from Canada, with some lobes terminating as far south as central Missouri. With each new glacial advance, the pre-existing drainage network

was disrupted and these bodies of ice both eroded and buried portions of the former landscape. As a glacier entered a watershed, the valleys were inundated with meltwater laden with coarse-grained sediment (outwash), which was deposited in bedrock channels. The modern Iowa River Valley between Marshalltown and Iowa City overlies this sequence of outwash and till deposited by successive glacial advances and meltwater outwash deposits (Figure 2). The uppermost sediment in the modern floodplain consists of silty to sandy alluvium deposited over the last 13,000 years by the meandering Iowa River.

Iowa River Alluvial Aquifer Mapping continues on page 16.

A’

900

Iowa City

feet above sea level

850 800

w66244

loess

Salt Creek

eolian sand

Holocene alluvium

colluvium

Iowa River IGS well

750

w27294 outwash

700 650

till buried outwash

600 550 500

shale 20x vertical exaggeration

FIGURE 2. Cross-section from A-A’ (depicted on the top and bottom maps of Figure 1), just west of the city of Belle Plaine (Benton County) illustrating the generalized geology of the Iowa River Valley.

Activities of the Iowa Geological Survey, 2024–25 | 15

Iowa River Alluvial Aquifer Mapping continues from page 15.

It was the geologic mapping of this river valley system that provided the framework necessary for developing a conceptual model of this alluvial aquifer system. Furthermore, it is notable that the deeper bedrock channels along this segment of the river valley likely contain unmapped buried outwash deposits that may also be viable aquifers.

GROUNDWATER BUDGET

A water budget can be created for an aquifer if inputs and outputs can be quantified. The difference between inputs and outputs is reflected in changes in groundwater storage within the aquifer. Groundwater inputs (Figure 3, Panel 1) include infiltration of precipitation, river-to-groundwater seepage, pumping induced recharge, groundwater seepage from the river valley walls, and subsurface flow losses from tributary valleys. Output components (Figure 3, Panel 2) include groundwater-to-river seepage (baseflow), groundwater pumping, and groundwater seepage to deeper aquifers. Based on the geologic mapping and characterization of the aquifer (or “container”), we estimated that there are approximately 188 billion gallons of water stored in the Iowa River alluvial

F I GUR E 3 , PA N EL 1 .

aquifer between Marshalltown and Iowa City. Inputs and outputs to the aquifer system were determined to be relatively minor when compared to the amount of groundwater available (Figure 3). With current withdrawal estimated to be 1.1 billion gallons per year, there would appear to be abundant water in the system to support future development. However, the volume of water stored in the aquifer is not the same as the availability of groundwater for pumping. For unconfined aquifers, like the Iowa River alluvial aquifer, the saturated thickness and available water level drawdown are typically the most important constraints on pumping. Drawdown in a well can be limited by the depth of the pump, or by drawdown interference if there are multiple wells nearby. For alluvial aquifers, the dominant recharge (input) is the infiltration of precipitation. During severe drought conditions, precipitation recharge can be reduced by 25% or more, resulting in a drastic reduction in recharge to the aquifer. For example, during the drought year of 2012 annual precipitation was reduced from about 36 inches to 22 inches along the Iowa River corridor. This resulted in an approximate 80% reduction of annual recharge to this alluvial aquifer. During this drought the volume of water stored in the aquifer was reduced from about 188 to 153 billion gallons. While this volume remained sufficient to meet demands, the effect of the drought on

F IGURE 3, PANEL 2.

FIGURE 3. Pie charts showing the main water balance components for the Iowa River alluvial aquifer. The inputs (recharge to aquifer; Panel 1) and outputs (discharge from aquifer; Panel 2) are dominated by precipitation and baseflow, respectively. PWS = public water supply.

16 | The IGS Geode

water table levels and the availability of drawdown was drastic. The water level in the aquifer declined by 5 to 10 feet, thereby reducing the saturated thickness and available drawdown to water users. The reduction in water level caused emergency conditions for irrigation and drinking water supply wells, where pump settings and/or wells had to be deepened, and water use restrictions had to be implemented. Overall, our results from this assessment of the Iowa River alluvial aquifer have demonstrated that while accurately accounting for groundwater storage within the aquifer is important, assessing the various inputs and outputs of the water budget are critical for long-term management of this essential resource. Should a large water user such as an ethanol plant or data center wish to locate in the valley, the foundation is now in place to evaluate the sustainability of the aquifer against new withdrawal permits. Following this one-time appropriation, a recurring source of funding was authorized by the Iowa Legislature for groundwater resource mapping. Efforts are currently underway at the IGS to conduct similar alluvial aquifer assessments in the Ocheyedan, Boyer, and West Nishnabotna river valleys of western Iowa in the coming years. Stay tuned for updates on the results from these projects in future editions of The Geode!

Recap: Year Two of the Levee Surveying Program JA SO N VO G E LG E SA N G

IOWA HAS NEARLY 900 MILES of levees protecting its towns, agricultural land, and critical infrastructure. Assessing the stability of these levees is a vital component of ensuring that these structures are resilient in anticipation of future flood events. Last autumn marked the second field season of a five-year campaign to assess the stability of Iowa’s levee system. This collaborative effort with the Office of Levee Safety, within the Iowa Department of Homeland Security and Emergency Management (HSEMD), uses field-based geophysics to survey and determine the condition of each levee in the state, helping focus remediation efforts and direct new funding to those systems in need of repair. The IGS collects data from an electromagnetic (EM) terrain conductivity meter run along the top and toe slope of each levee. If there are any ‘anomalous’ areas within the interpreted EM data, then an electrical resistivity (ER) tomography survey is conducted to provide further detail (Figure 1). Based on information listed in the National Levee Database, a publicly accessible online database managed by the U.S. Army Corps of Engineers (USACE), approximately 200 miles of levees were surveyed by the IGS in Year Two of this project. A total of 38 levee segments representing 18 systems were assessed, and these were split between geographic areas of Iowa in both urban and rural settings (Photographs 1 and 2). To-date, a combined total of approximately 300 miles of levees (a total of 63 levee segments representing 29 systems) have been surveyed. Our attention is now focused on Year Three, during which approximately 200 more miles of Iowa’s levees will be imaged using these geophysical methods.

FIGURE 1. A generalized cross-section of a levee showing potential locations for geophysical data collection to assess the structural integrity of the system. EM = electromagnetic terrain conductivity imaging along the top and toe slope of the levee; ER = electrical resistivity tomography conducted if areas of an imaged levee system are flagged as ‘anomalous’ after interpreting the EM data.

P H OTO G R A P H 1. The electromagnetic (EM) terrain conductivity equipment is mounted to a utility-terrain vehicle to collect these geophysical data. Collection of EM data along the top a levee in Sioux City, Iowa.

P H OTO GR APH 2 . The electromagnetic (EM) terrain conductivity equipment mounted to a utilityterrain vehicle and parked along the top of a levee near Council Bluffs, Iowa.

N ATION A L LE VE E DATA BA S E : HT TPS : // LE VE E S .S E C.US ACE. ARMY. MIL/

Activities of the Iowa Geological Survey, 2024–25 | 17

Leveraging Legacy Downhole Geophysical Data for Geologic Hydrogen Research in Iowa JO E H O N IN G S

FIGURE 1. Map of Iowa depicting the subsurface igneous rocks, which are a potential source of geologic hydrogen, specifically the Thor Volcanics (light green) of the Midcontinent Rift System (MRS) and the Northeast Iowa Intrusive Complex (NEIIC; dark green). The black dots are petrophysical logs from the MRS that are being digitized as part of an IGS USGS NGGDPP project. The IGS has also begun to digitize legacy 2D seismic lines (orange lines) collected by Amoco in the 1980s for oil and gas exploration along the MRS. The light purple box denotes the Vincent Structure, an abandoned natural gas storage field near the city of Vincent in Webster County.

18 | The IGS Geode

THE U.S. GEOLOGICAL SURVEY (USGS) recently released a prospectivity map of geologic hydrogen accumulations (known as ‘white’ or ‘gold’ hydrogen). One of these regions is the Midcontinent Rift System (MRS), which consists of large volumes of mafic igneous rocks and has become a destination for geologic hydrogen exploration in recent years (as Ryan Clark reported in last year’s edition of The Geode). A portion of the MRS trends northeast-southwest in the subsurface of Iowa (Figure 1), presenting enormous potential for Iowa to become a clean energy hub. Legacy geophysical data from past oil and gas exploration and natural gas storage field delineation,

which are all reposited at the IGS, could serve as the springboard for this new frontier. Drilling, logging, and storing samples from exploration wells is expensive, so when deep boreholes are drilled by those in the energy industry, a variety of geophysical tools are lowered down the hole to measure the various properties of the rock. These petrophysical logs ultimately allow geologists to interpret the types and thicknesses of the rocks in the succession, as well as the physical properties of those rocks (such as porosity, permeability, and the type[s] of fluid[s] in the pore space). As part of the USGS National Geological

FIG U RE 2.

FIGURE 2. A portion of a legacy gamma ray log (see black dots on Figure 1) digitally traced within a reference grid using Neuralog software. Once digitized these data can be imported and visualized in other geologic software programs, such as PetrelTM, for geologic hydrogen research (see Figure 3). FIGURE 3. Petrophysical logs from three wells (Hofmann #1, #2, and #3, left-to-right [west-to-east], respectively) in the Vincent Structure. These logs were digitized using Neuralog software and then imported and displayed in PetrelTM subsurface software donated by SLB. Abbreviations: SSTVD = Subsea True Vertical Depth; brown hues = gamma ray logs (GR); blue hues = neutron logs (NEUT); green hues = sonic logs (DT); purple hues = lateral resistivity logs (LAT); and light blue hues = single-point resistivity logs (SPR).

and Geophysical Data Preservation Program (NGGDPP), the IGS was able to purchase and use Neuralog software to digitize its legacy petrophysical logs (Figure 2), allowing these data to be imported, visualized, and analyzed in other geologic software platforms. This work is a collaborative effort with the University of Iowa School of Earth, Environment, and Sustainability (SEES) faculty and a few of its undergraduate students that have been hired as interns to assist with this initiative. Current research efforts are focused on logs from characterization wells drilled into the Vincent Structure, an abandoned natural gas storage field near the city of

Vincent in Webster County (light purple box in Figure 1). In 1969, the USGS sampled four Vincent wells, two of which yielded measurements of 34% and as high as 96% molality hydrogen gas — and this merits further investigation. As a result, IGS geologists and interns are actively working to digitize the legacy geophysical logs from the area. These data are then imported into PetrelTM subsurface software that has been kindly donated by SLB, a global technology company (Figure 3). The goal is to integrate all available information into a model to better understand the regional geology and delineate the geologic hydrogen potential in central Iowa. Stay tuned for updates in future editions of The Geode!

F I GUR E 3 . Activities of the Iowa Geological Survey, 2024–25 | 19

Drilling Deep into Iowa’s Geologic Past: The USGS STATEMAP Program Provides the IGS with New Opportunities to Study the Subsurface ST E P H A N I E TA SSI E R- SU RI NE , PH IL K E RR , RYA N CL A RK , A N D JA CK M A LO N E

FOR MORE THAN 30 YEARS the IGS has been actively involved in the United States Geological Survey (USGS) STATEMAP Program. This yearly competitive grant opportunity, with a 50:50 funding match between state and federal dollars, has allowed the IGS to pursue various mapping initiatives across Iowa. With increased USGS funding available in recent years (Award Numbers G23AC00407 and G24AC00332), as well as cost share from the University of Iowa School of Earth, Environment, and Sustainability, the IGS has been able to leverage additional funding to drill deep cores to support multi-year bedrock and surficial mapping projects in both Dubuque and Muscatine counties. These new cores add much needed detail to the geologic framework for mapping projects that the IGS would not have been able to acquire otherwise. In addition to rock core, the IGS Rock Library on the University of Iowa Oakdale Research Campus also houses drill chip samples from over 40,000 boreholes across Iowa, most from water wells. This collection holds chips from more than 1,000 wells in Dubuque County and almost 350 wells in Muscatine County. Despite this seeming abundance, wells are not evenly distributed, and map areas often have data gaps greater than one square mile in size. Additionally, chip samples have several limitations as they are usually collected at five-foot intervals and the chips themselves are typically less than 5 mm in size, making it difficult to fully characterize rock units or sediment packages. These limitations

20 | The IGS Geode

also complicate accurate correlation of lithologic units between wells. On the other hand, cores are cylinders of sediment or rock collected continuously using specialized drilling techniques (Figure 1). Cores provide a more comprehensive picture of the subsurface materials encountered when drilling.

DUBUQUE COUNTY

As part of a multi-year effort to map the bedrock geology of Dubuque County, the IGS was able to drill a rock core (IGS31-Callahan) at a site northeast of the city of Peosta to a depth of 360 feet (see cover photo). Of particular interest is the Ordovician Maquoketa Formation, a stratigraphic unit consisting primarily of shale and dolostone that can be up to 200 feet thick. This formation extends well beyond Iowa’s borders and varies laterally in both thickness and lithology (rock type). The Maquoketa Formation also serves as a regional aquitard separating the Silurian aquifer above from the Ordovician Galena Group aquifer below. Figure 2 illustrates the various lithologies and stratigraphic units captured by this core. Additionally, the lowest member of the Maquoketa Formation, the Elgin, has been the focus of recent studies on critical minerals such as rare earth elements (REEs). The Elgin Member is a complex package of shale, dolostone, and a unique rock type called phosphorite. Recent geochemical analyses of this phosphorite showed elevated concentrations of REEs, up to ten times higher than typical

sedimentary rocks. A photo of the core showing the Elgin phosphorite in contact with the underlying dolostone of the Dubuque Formation is featured in Figure 3. For the first time in almost 20 years, IGS geologists were able to drill a rock core in the precise location for gaining the maximum amount of knowledge from the subsurface. This core will not only greatly benefit the geologic mapping of Dubuque County and further our understanding of critical minerals in Iowa but will also be available at the IGS Rock Library for future study. Drilling Deep into Iowa’s Geologic Past continues on page 22.

FI G U R E 1. Photograph of the drill bit attached to drill stem used to collect the rock core in the Peosta Quadrangle, Dubuque County (hand for scale).

feet 200

Lithology loess

Hopkinton

dolostone

Sweeney

shale

Blanding

calcareous shale

FI G U R E 2 . Lithologic profile of the IGS-31-Callahan core drilled in the Peosta Quadrangle, Dubuque County, with stratigraphic units denoted (capitalized text = group name; bold and italicized text = formation names; italicized text = member names; bold line on left side of diagram denotes the boundary between the Silurian and Ordovician systems).

Potters Mill

50 250 Dyas

SILURIAN

Tete des Morts

Mosalem

Elgin

ORDOVICIAN

Maquoketa 100 Brainard 300

GALENA Dubuque

Fort Atkinson

Wise Lake

150 350

Symbols

Body & Trace Fossils

Clermont

200

ammonoids brachiopods burrows crinoids crinoid molds lingulid brachiopods gastropods graptolites trilobite stromatoporoids

argillaceous chert hardground laminations iron nodules phosphate grains pyrite red laminations sphalerite stylolites vertical fractures vugs vugs - calcite filled

FI G U R E 3 . Photo of core box showing dark brown shale and phosphorite of the Elgin Member of the Maquoketa Formation above the gray limestone of the Dubuque Formation of the Galena Group (red arrow is marking the contact between the two formations). Horizontal power drill marks are locations on the core where powders for carbonate carbon (δ13Ccarb) isotope chemostratigraphic samples were taken. Blue tape on box dividers are locations on the core where nondestructive elemental composition data were collected using an Olympus VantaTM portable X-ray Fluorescence (pXRF) Analyzer loaned to the IGS by the University of Iowa School of Earth, Environment, and Sustainability.

Activities of the Iowa Geological Survey, 2024–25 | 21

Drilling Deep into Iowa’s Geologic Past continues from page 21.

feet 0

fine coarse

MUSCATINE COUNTY

The collection of deep, continuous sediment cores in Muscatine County is providing additional insight into the Cleona Channel, a deep bedrock valley filled with more than 300 feet of an alternating sequence of fine-grained glacial deposits and sand and gravel. A better understanding of the distribution and connectivity of these sand and gravel bodies is essential because nearly two-thirds of the wells in Muscatine County utilize these aquifers for their water supply. Standard mapping techniques provide valuable data for the uppermost sediments but cannot provide a full picture of sediments at depth, nor their threedimensional architecture. While continuous core provides insight into the deeper sediments in the Quaternary succession, recovering loose sediment (sand and gravel) with traditional mud rotary drilling is very challenging. Rotosonic drilling, which consists of highfrequency resonant energy (vibration) combined with rotation to advance the barrel, is used to drastically improve recovery for sediment cores (Figure 4). After collection, these cores are taken to the IGS Rock Library for detailed description and sampling for both lithologic and chemical analyses. Over the last two years the IGS has had the opportunity to collect four, four-inch diameter rotosonic drill cores to help evaluate the thicknesses and lateral distribution of the sand and gravel bodies in the Cleona Channel. Three were advanced to a depth of 150 feet and one reached a depth of 300 feet. These are the first rotosonic cores collected by IGS geologists and they are, by far, the deepest unconsolidated sediment cores that the Survey has been able to study. The lithology of the 58-Cone Marsh core, drilled north of the Iowa River, is depicted in Figure 5. This year the IGS will be able to continue collecting deep cores as part of its USGS STATEMAP projects and planning is underway for one bedrock core (drilled to 500 feet) in Dubuque County and two sediment cores (each drilled to 150 feet) in Muscatine County. The detailed information gained from these valuable cores will enhance mapping efforts in the eastern region of the state.

upper aquifer

confining unit 50

intermediate aquifer

confining unit 100 Lithology

FIGURE 4. The rotosonic drill rig used to collect continuous sediment core in Muscatine County. One of the drillers (middle) is holding a plastic sleeve around the drill stem to collect the sediment recovered from depth.

loess lacustrine paleosol sand gravel till

150 22 | The IGS Geode

FI GU R E 5 . Lithologic profile of the 58-Cone Marsh sediment core illustrating the sand and gravel sequences (which are aquifers) separated by finegrained lacustrine (lake) sediments and glacial materials (till), both of which are confining units for the aquifers.

IGS State Legislative Activities RYA N C L A R K A N D K E ITH S CH ILLIN G

EVERY SPRING THE IGS joins IIHR— Hydroscience and Engineering and the Iowa Flood Center at the State Capitol for its annual Legislative Breakfast to showcase specific research initiatives for Iowa Legislators (Photograph 1). This annual event gives lawmakers the opportunity to learn about the vital work being done by the IGS, and it has begun to pay off in many ways (Photograph 2). After being granted a one-time $250,000 increase to its annual appropriation in fiscal year 2025, the IGS successfully demonstrated the benefits of targeted aquifer mapping. The featured article in this year’s Geode details the efforts and outcomes of mapping the alluvial aquifer system of the Iowa River from Marshalltown to Iowa City. This year the IGS received a permanent increase of $200,000 to its state appropriation to continue this valuable work in other areas of the state. Legislators are often faced with the daunting task of comprehending complex issues, preparing arguments for debate, and making rulings in a relatively short time. It is important for them to have accurate information from trusted sources when contemplating changes to Iowa’s laws. Two examples from the recent 2025 session have demonstrated the utility of consulting with the IGS about legislation that would impact Iowa’s natural resources. In response to increasing water demands from data centers and other users, State Geologist Keith Schilling gave a presentation to the Environmental Protection Commission on the “Status of Iowa’s Aquifers”. Later in the session, bills introduced in both the House and Senate proposed changes to rules regarding exploration drilling for natural resources. IGS geologists were subsequently invited to the Capitol to meet with legislators and inform them about the status of current

drilling regulations and how the proposed bills may affect the ability of the Iowa Department of Natural Resources (Iowa DNR) and the IGS to reliably evaluate Iowa’s natural resources so they can be effectively managed for long-term sustainability and economic development.

P H OTO G R A P H 1 . (left-to-right) Representing the IGS at this year’s Legislative Breakfast in March were Jason Vogelgesang, Keith Schilling, Ryan Clark, and Valerie Diaz-Gibertini.

P H OTO GR APH 2 . (left-to-right) IGS Director and State Geologist, Keith Schilling, speaking with University of Iowa Director of State Relations, Keith Saunders, and Representative David Sieck (Iowa House District 16).

Activities of the Iowa Geological Survey, 2024–25 | 23

IGS Publications from Summer 2024 – Summer 2025 *IGS Student Intern Anderson, E.S., K.E. Schilling, C.L. Just, and B.C. Seo, 2024. “Quantifying the impact of a constructed wetland on downstream nitrate concentrations and loads in the U.S. Midwest,” Frontiers in Environmental Science, 12:1416018. Anderson, E.S. and K.E. Schilling, 2024. “Intensive short-term sampling with long-term consequences: Characterizing pollutant transport with implications for developing monitoring,” Environmental Monitoring and Assessment, 196:1130. Anderson, E.S. and K.E. Schilling, 2025. “Quantifying the impact of Iowa’s flood-mitigation reservoirs on sediment and nutrient loss,” Journal of the American Water Resources Association, 61(3):e70035. Anderson, E.S. and K.E. Schilling, 2025. “Baseflow index trends in Iowa rivers and the relation to other hydrologic metrics,” Hydrology, 12(5):116. Anderson, E.S., K.E. Schilling, and L.J. Weber, 2025. “Monitoring phosphorus during high flows: Critical for implementing surrogacy models,” Water, 17(15):2194. Bancroft, A. and P. Kerr, 2025. Bedrock Geologic Map of the Durant 7.5’ Quadrangle, Muscatine, Cedar, and Scott Counties, Iowa: Iowa Geological Survey, Open File Map OFM-251, 1:24,000 scale map sheet. Bancroft, A. and P. Kerr, 2025. Bedrock Elevation and Quaternary Thickness Map of the Durant 7.5’ Quadrangle, Muscatine, Cedar, and Scott Counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-3, 1:24,000 scale map sheet. Bancroft, A. and P. Kerr, 2025. Bedrock Geologic Map of the West Liberty 7.5’ Quadrangle, Muscatine, Cedar, and Johnson Counties, Iowa: Iowa Geological Survey, Open File Map OFM-254, 1:24,000 scale map sheet. Bancroft, A. and P. Kerr, 2025. Bedrock Elevation and Quaternary Thickness Map of the West Liberty 7.5’ Quadrangle, Muscatine, Cedar, and Johnson Counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-5, 1:24,000 scale map sheet. Bancroft, A. and P. Kerr, 2025. Bedrock Elevation and Quaternary Thickness Map of the Walcott 7.5’ Quadrangle, Muscatine and Scott Counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-7, 1:24,000 scale map sheet.

24 | The IGS Geode

Bancroft, A. and P. Kerr, 2025. Bedrock Elevation and Quaternary Thickness Map of the Cotter 7.5’ Quadrangle, Louisa and Washington Counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-9, 1:24,000 scale map sheet. Bancroft, A. and P. Kerr, 2025. Bedrock Elevation and Quaternary Thickness Map of the Columbus Junction 7.5’ Quadrangle, Louisa and Muscatine Counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-11, 1:24,000 scale map sheet. Craddock, J.P., D.H. Malone, E.P. Craddock, S.J. Baumann, J.E. Malone, and R. Porter, 2025. “Deformation of the “Anorogenic” Wolf River batholith, Wisconsin, USA: Understanding the Baraboo Orogeny hinterland,” Geosciences, 15(4), 150. Doyle, T.B., K.E. Schilling, P.J. Kerr, and M.T. Streeter, 2025. “Iowa Great Lakes Hydrology and Diagnostic Study,” Iowa Geological Survey, Technical Information Series (TIS) 60, 83 p. Feng, W., X. Wan, Y. Zhang, J. Quensen, T.A. Williams, M. Thompson, M.T. Streeter, Y. Zhang, S. Jiao, G. Wei, Y. Zhu, J. Gu, J.M. Tiedje, and X. Qian, 2025. “Diversification, niche adaptation, and evolution of a candidate phylum thriving in the deep Critical Zone,” Proceedings of the National Academy of Sciences (PNAS), 122(12):e2424463122. Gomez, A., A. Arenas, and K.E. Schilling, 2025. “Surface-subsurface modeling of water dynamics in drained and farmed wetlands in the Prairie Pothole Region,” Agricultural Water Management, 313:109477. Kerr, P., S. Tassier-Surine, and A. Bancroft, 2025. Surficial Geologic Map of the Durant 7.5’ Quadrangle, Muscatine, Cedar, and Scott Counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-2, 1:24,000 scale map sheet. Kerr, P., S. Tassier-Surine, *R. Walenceus, and A. Bancroft, 2025. Surficial Geologic Map of the Walcott 7.5’ Quadrangle, Muscatine and Scott Counties, Iowa,” Iowa Geological Survey, Open File Map OFM-25-6, 1:24,000 scale map sheet. Malone, J., R. Clark, and P. Kerr, 2025. Bedrock Geologic Map of the Peosta 7.5’ Quadrangle, Dubuque County, Iowa: Iowa Geological Survey, Open File Map OFM-25-12, 1:24,000 scale map sheet. Malone, J., R. Clark, and P. Kerr, 2025. Bedrock Elevation and Quaternary Thickness Map of the Peosta 7.5’ Quadrangle, Dubuque County, Iowa: Iowa Geological Survey, Open File Map OFM-2513, 1:24,000 scale map sheet.

Mount, J., Y. Sermet, C.S. Jones, K.E. Schilling, P.W. Gassman, L.J. Weber, W.F. Krajewski, and I. Demir, 2024. “An integrated cyberinfrastructure system for water quality resources in the Upper Mississippi River Basin,” Journal of Hydroinformatics, 26(8):1970-1988. Schilling, K.E., E.S. Anderson, J. Mount, K. Suttles, P.W. Gassman, N. Čerkasova, M.J. White, and J.G. Arnold, 2024. “Evaluation of flood metrics across the MississippiAtchafalaya River Basin and their relation to flood damages,” PLoS ONE, 19(10):e0307486. Schilling, K.E., M.T. Streeter, P. Kerr, C.F. Wolter, E.S. Anderson, A. Gomez, and A. Arenas-Amado, 2025. “Hydrogeology and groundwater flow in a hummocky prairie pothole complex, northern Iowa,” Wetlands, 45(3). Tassier-Surine, S., P. Kerr, and A. Bancroft, 2025. Surficial Geologic Map of the Cotter 7.5’ Quadrangle, Louisa and Washington counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-8, 1:24,000 scale map sheet. Tassier-Surine, S., P. Kerr, and A. Bancroft, 2025. Surficial Geologic Map of the Columbus Junction 7.5’ Quadrangle, Louisa and Muscatine Counties, Iowa: Iowa Geological Survey, Open File Map OFM-25-10, 1:24,000 scale map sheet. Theiling, C., A. Calomeni, N. Bosco, S. Dinsmore, H. Howe, T. Gosselink, K.E. Schilling, M.T. Streeter, and P. Thostenson, 2024. “Advancing Lake Red Rock Reservoir management practices to maximize ecological benefits: From planning to monitoring,” Wetland Science & Practice, 42(3):224-230. Waldeck, A.R., H.C. Olson, P.W. Crockford, A.M. Couture, B.R. Cowie, E.B. Hodgin, K.D. Bergmann, K. Dewing, S.E. Grasby, R.J. Clark, F.A. Macdonald, and D.T. Johnston, 2025. “Marine sulphate captures a Paleozoic transition to a modern terrestrial weathering environment,” Nature Communications, 16:2087. Wolter, C.F., K.E. Schilling, M.T. Streeter, and E.S. Anderson, 2025. “Using LiDAR-based DEM elevation difference calculations to estimate net streambank erosion in an Iowa River, USA,” River Research and Applications, 41(7):1418-1426. Zhou, Y., X. Liang, E. Ma, K. Chen, K.E. Schilling, T. Zheng, Y. Zheng, Y.-K. Zhang, and C. Zheng, 2024. “Spectral analysis of hydrological signals to estimate watershed properties considering impacts of unsaturated zone,” Water Resources Research, 60(11):e2023WR036680.

IGS Presentations from Summer 2024 – Summer 2025 *IGS Emeritus Geologist Anderson, E.S., “Quantifying the Impact of Iowa’s Flood Control Reservoirs on Nutrient and Sediment Loss,” Iowa Water Conference, Coralville, Iowa, September 11, 2024. Anderson, E.S., “Utilizing Iowa’s Flood Control Reservoirs to Facilitate Waterborne Nutrient Removal,” Iowa Flood Center Seminar, Iowa City, Iowa, September 18, 2024. Schilling, K.E., “Unoxidized Glacial Till Controls Aquifer Vulnerability in the U.S. Midwest,” Geological Society of America (GSA) Connects – Annual Geoscience Meeting and Expo, Anaheim, California, September 22, 2024. Langel, R.J. and K.E. Schilling, “Groundwater Level Monitoring in Iowa: Resurrected in Time to Reveal Current and Future Challenges,” Geological Society of America (GSA) Connects – Annual Geoscience Meeting and Expo, Anaheim, California, September 23, 2024. Anderson, E.S., “The Potential for Natural Infrastructure Implementation: Spatial Patterns in the Mississippi Basin,” American Water Resources Association (AWRA), Universities Council on Water Resources (UCOWR), National Institutes for Water Resources (NIWR) 60th Anniversary Joint Water Resources Conference, St. Louis, Missouri, October 1, 2024. Schilling, K.E., “Using Baseflow to Quantify Groundwater Recharge and Drought at a Regional Scale,” Association of American State Geologists (AASG), Water Forum Online, October 18, 2024.

Kerr, P.J., “Glacial Influence on Drainage Networks,” Department of Earth and Environmental Sciences Seminar, Michigan State University, East Lansing, Michigan, October 18, 2024. Schilling, K.E. and T.B. Doyle, “Iowa Geological Survey, Evaluation of Local and Regional Groundwater Flow Systems in the Recently Glaciated Landscape,” Fall 2024 Iowa Groundwater Association (IGWA) and Environmental Professionals of Iowa (EPI) Joint Conference, Johnston, Iowa, November 13, 2024. Anderson, E.S., C.F. Wolter, and J. Terry, “What is in Our Rivers? Central Iowa Source Water Research Assessment (CISWRA) a Two-Year Water Quality Improvement Project Commissioned by Polk County, Iowa,” Fall 2024 Iowa Groundwater Association (IGWA) and Environmental Professionals of Iowa (EPI) Joint Conference, Johnston, Iowa, November 13, 2024. Vogelgesang, J.A., “Hydrogeophysics at the IGS: Using Near Surface Geophysical Methods to Characterize Shallow Aquifers,” Minnesota Geological Survey Seminar, Virtual Presentation, December 5, 2024. Schilling, K.E., “Reducing Nutrient Loss from Field to Watershed Scale: Assessing Spatial and Temporal Patterns to Optimize Conservation Effectiveness,” American Geophysical Union (AGU) Annual Meeting, Washington, D.C., December 11, 2024. Kerr, P.J., “Insights into the Dynamics of the Des Moines Lobe Using Newly Mapped Subglacial Landforms,” American Geophysical Union (AGU) Annual Meeting, Washington, D.C., December 12, 2024.

Schilling, K.E., “The Iowa Geological Survey at the University of Iowa: Ten-Year Review,” University of Iowa, Iowa City, Iowa, December 18, 2024. Streeter, M.T., K.E. Schilling, J. Merryman, and C. Porter, “Unlocking the Potential of Saturated Grassed Waterways for Nutrient Reduction,” Iowa Learning Farms Virtual Field Day, January 23, 2025. Honings, J.P., “Investigation of Buried Channel Aquifer Systems in Iowa,” Iowa Water Well Association (IWWA) Annual Conference, Altoona, Iowa, January 30, 2025. Clark, R.J., “The Iowa Geological Survey: A Driver of Economic Development in Iowa,” Iowa Economic Development Authority, Innovation Council Board Meeting, Iowa City, Iowa, January 30, 2025. Schilling, K.E., “Iowa Geological Survey Legislative Update,” Iowa House of Representatives Agricultural and Natural Resources Subcommittee, Des Moines, Iowa, February 10, 2025. Honings, J.P. and T.B. Doyle, “Buried Channel Aquifer Mapping in the Lower Cedar River Basin,” Lower Cedar Watershed Management Authority Meeting, February 11, 2025. Schilling, K.E., “Status of Iowa’s Aquifers,” Legislative Briefing to Environmental Protection Committee, Des Moines, Iowa, February 12, 2025. Anderson, E.S. and K.E. Schilling, “Summary of the Iowa Geological Survey’s Research on Reservoir Sedimentology and Influence on Water Quality,” Des Moines River Collaborators Meeting, Pella, Iowa, February 20, 2025. Doyle, T.B. and P.J. Kerr, “How the Glacial History of the Iowa Great Lakes Region Impacts Groundwater Discharge into the Lakes,” Iowa Chapter of the Wildlife Society Winter Meeting, Ames, Iowa, February 26, 2025. Clark, R.J., “Critical Mineral Potential of Mine Waste in Quarries,” Iowa Limestone Producers Association (ILPA) Annual Convention, Coralville, Iowa, February 26, 2025. Kerr, P.J., “A Glacial Confluence: Illinoian Ice, Late Wisconsin Sediments, and Modern Consequences,” Geologic Mapping Forum Online, March 19, 2025.

Elliot Anderson (IGS, at the podium) was part of a distinguished panel of scientists speaking about the water quality of central Iowa. This public event was hosted by The Harkin Institute (Drake University, Des Moines, Iowa) and the other panelists (seated on the stage, left-to-right) included Larry Weber (Director of IIHR Hydroscience and Engineering), Jerald Schnoor (IIHR Hydroscience and Engineering), and Claire Hruby (Drake University).

Tassier-Surine, S.A., “Iowa’s Loess Record: Source, Deposition, and Environmental Implications,” Cedar Valley Rocks and Minerals Society – Annual Rock, Mineral, and Fossil Show, Cedar Rapids, Iowa, March 22, 2025.

Activities of the Iowa Geological Survey, 2023–24 2024–25 | 25

Selected IGS Projects from Summer 2024 – Summer 2025 Kerr, P.J., “Geologic Mapping of the Des Moines Lobe,” Cedar Valley Rocks and Minerals Society – Annual Rock, Mineral, and Fossil Show, Cedar Rapids, Iowa, March 23, 2025. Kerr, P.J., “Where was the Mississippi River during the Illinoian?,” Cedar Valley Rocks and Minerals Society – Annual Rock, Mineral, and Fossil Show, Cedar Rapids, Iowa, March 23, 2025. Schilling, K.E., “Risk-Based Aquifer Vulnerability Mapping Applied to a Mixed Agricultural-Urban County in Iowa,” Geological Society of America (GSA) Joint Northeastern and North-Central Section Meeting, Erie, Pennsylvania, March 27, 2025. Clark, R.J., “Iowa’s Hydrogen Potential,” Iowa Groundwater Association (IGWA) Spring Conference, Cedar Rapids, Iowa, April 2, 2025. Schilling, K.E., “An Enhanced Risk-Based Aquifer Vulnerability Index Applied to Black Hawk County, Iowa,” Iowa Groundwater Association (IGWA) Spring Conference, Cedar Rapids, Iowa, April 2, 2025. Vogelgesang, J.A., “Using Field-Based Geophysical Methods to Survey Levees: A Recap of Years 1 and 2 of a 5 Year Effort,” American Society of Civil Engineers, Iowa Section, Cedar Rapids, Iowa, April 8, 2025. Schilling, K.E., “Iowa Groundwater and Data Centers,” Iowa County Zoning Administrators Conference, Iowa City, Iowa, May 9, 2025. Malone, J.E., D.H. Malone, *R.R. Anderson, and R.J. Clark, “Refining the Age and Occurrence of Basement Rocks in Northwest Iowa: Implications for Precambrian Tectonics and Magmatic Evolution of the Laurentian Midcontinent,” Institute of Lake Superior Geology 71st Annual Meeting, Mountain Iron, Minnesota, May 16, 2025. Schilling, K.E., “A Watershed Emphasis on Mapping and Monitoring at the Iowa Geological Survey,” Association of American State Geologists (AASG) Annual Meeting, Baton Rouge, Louisiana, June 2, 2025. Anderson, E.S., “Quantifying Iowa’s Annual Phosphorus Budget,” Iowa Learning Farms Webinar, June 25, 2025. Kerr, P.J., “Iowa Was Entirely Glaciated,” Trees Forever Webinar, July 9, 2025. Anderson, E.S., L.J. Weber, J.L. Schnoor, and C. Hurby, “Our Water, Our Future: A Look at the Central Iowa Water Quality Report,” The Harkin Institute at Drake University, Des Moines, Iowa, August 4, 2025.

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A Vision Toward a More Resilient Iowa Great Lakes: Keith E. Schilling: Iowa Department of Natural Resources (IDNR) #DiverseCornBelt: Resilient Intensification through Diversity in Midwestern Agriculture: Keith E. Schilling: U.S. Department of Agriculture (USDA) Earth Mapping Resources Initiative (Earth MRI): Mine Waste at Browns Bottom Quarry: Ryan J. Clark: U.S. Geological Survey (USGS) Earth Mapping Resources Initiative (Earth MRI): Geochemical Reconnaissance of Pennsylvanian Black Shales of the U.S. Midcontinent: Alyssa M. Bancroft: U.S. Geological Survey (USGS) Earth Mapping Resources Initiative (Earth MRI): Geochemical Reconnaissance of Devonian Metalliferous Black Shales of the Illinois Basin: Alyssa M. Bancroft: U.S. Geological Survey (USGS) Earth Mapping Resources Initiative (Earth MRI): Geochemical Reconnaissance of the Upper Mississippi Valley Zn-Pb District: Ryan J. Clark: U.S. Geological Survey (USGS) Earth Mapping Resources Initiative (Earth MRI): Geological and Geochemical Mapping of the REE-Enriched Graf Phosphorite of the Lower Maquoketa Formation in Northeastern Iowa, USA: Ryan J. Clark: U.S. Geological Survey (USGS) Electrical Resistivity and Passive Seismic Geophysical Surveys at a Fort Dodge Landfill Site: Jason Vogelgesang: SCS Engineers Evaluating a Two-Stage Roadside Ditch Design to Improve Environmental Performance: Keith E. Schilling: Iowa Department of Transportation (IDOT) Evaluating the Effectiveness of Stacked Practices: Utilizing Modified Blind Inlets at Terrace Sites for N and P Load Reductions: Matthew T. Streeter: Iowa Nutrient Research Center (INRC) Geologic and Hydrologic Assessment of Spillville Well #2: Joseph P. Honings: Northeast Iowa Resource Conservation & Development (RC&D), Winneshiek County Soil & Water Conservation District (SWCD) Investigating Long-Term Nutrient Trends and High-Resolution Orthophosphate Dynamics in a Restored Prairie Ecosystem: Elliot S. Anderson: Iowa Nutrient Research Center (INRC)

Joint Iowa-Kansas-Missouri-Nebraska Working Group for the Unification of PreIllinoian Till Stratigraphy: Stephanie A. TassierSurine: U.S. Geological Survey (USGS) Levee Survey – Geophysical Imaging Project: Jason Vogelgesang: Iowa Department of Homeland Security and Emergency Management (HSEMD) Managing Pool Levels in Saylorville Reservoir for Nitrate Load Reductions: Keith E. Schilling: U.S. Army Corps of Engineers (USACE) National Geological and Geophysical Data Preservation Program (NGGDPP) – Data Preservation and Critical Minerals Activities in Iowa 2024-2025: Richard J. Langel: U.S. Geological Survey (USGS) National Ground-Water Monitoring Network (NGWMN) – Iowa FY2024 NGWMN Project: Richard J. Langel: U.S. Geological Survey (USGS) Nitrate Reduction via Reservoir Water Level Management in Central Iowa: Keith E. Schilling: U.S. Army Corps of Engineers (USACE) Polk County Science Advisory Committee: Elliot S. Anderson: Polk County, Iowa Quantifying Nutrient Load Reduction Practices and Export at Field and Landscape Scales: Keith E. Schilling: Iowa Nutrient Research Center (INRC) Quantifying Nutrient Load Reduction Practices at Multiple Field Sites: Keith E. Schilling: Iowa Nutrient Research Center (INRC) Soil and Plant Health Analysis: Matthew T. Streeter: Perimeter Solutions STATEMAP FY2024 – Geologic Mapping in Iowa: Stephanie A. Tassier-Surine: U.S. Geological Survey (USGS) Well Drilling at Forney Lake Wildlife Management Area (WMA): Keith E. Schilling: Iowa Department of Natural Resources (IDNR)

IGS Financials The Iowa Geological Survey (IGS) is funded by a combination of different sources. A state appropriation provided approximately 36% of our annual operating budget during the past year, and we were pleased to have this amount supplemented with a one-time increase by the Iowa Legislature to further assess the state’s groundwater. This additional funding has now become a permanent increase to the IGS’s state appropriation (FY2026) and will allow us to continue to evaluate Iowa’s groundwater resources. The IGS then leverages this base funding to obtain support for a diverse portfolio of projects from a variety of funding sources. In 2024–2025, these funding sources included local municipalities,

state agencies, the U.S. Geological Survey (USGS), the Iowa Department of Transportation (Iowa DOT), the U.S. Army Corps of Engineers (USACE), and the Iowa Nutrient Research Center (INRC), among others. The University of Iowa (UI) School of Earth, Environment, and Sustainability (SEES), formerly the Department of Earth and Environmental Sciences (EES), continues to allow the IGS to leverage a portion of its own state appropriation to secure additional funding from the USGS STATEMAP Program—the continued collaboration and support of the UI-SEES is sincerely appreciated!

16%

FY2025 $2,633,172

Additional state funding will be necessary to complete our statewide groundwater resource assessments at a faster pace. It is this funding that allows the IGS to leverage even more when applying for outside support—meaning that the state’s return on its investment in the IGS also increases, as do the benefits for Iowans. Ultimately, state funding ensures that the IGS can focus on regional statewide initiatives and provide science-based information to manage Iowa’s natural resources for long-term sustainability and economic development.

Municipal City Water Projects ($78,232) State Appropriation ($945,000 ) INRC Iowa Nutrient Research Center ($131,986 )

36%

Federal Agencies U.S. Geological Survey ($1,048,718) Other Iowa DNR, Iowa DOT, Iowa HSEMD, Non-Government Contracts ($429,236)

40%

FY2021

FY2022

FY2023

FY2024

FY2025

$1,807,632

$1,715,862

$1,983,265

$2,458,209

$2,633,172

Activities of the Iowa Geological Survey, 2023–24 2024–25 | 27

P H OTO G R A P H 1 . Keith Schilling, IGS Director and State Geologist, providing a brief history of the Iowa Geological Survey with a focus on the last decade. P H OTO G R A P H 2 . The Dean of the College of Engineering, Dr. Ann F. McKenna (left); IGS Director and State Geologist, Dr. Keith E. Schilling (middle); and the Director of IIHR—Hydroscience and Engineering, Dr. Larry J. Weber (right) all posing after presentations were completed. P H OTO G R A P H 3 . Attendees enjoying breakfast during presentations at the Iowa Memorial Union.

PHOTOGRAPH 1.

Ten Years with the University of Iowa A 10-year celebration of the Iowa Geological Survey becoming a research unit within the Iowa Institute of Hydraulic Research (IIHR—Hydroscience and Engineering, College of Engineering, College of Engineering, University of Iowa) was held December 18, 2024, at the Iowa Memorial Union. Over the past decade the IGS has doubled its staff, employed more than 60 student interns, increased its number of public databases from one to five, published 76 geologic maps, written 11 water resource investigation reports, lead or coauthored 142 peer-reviewed publications, and led countless public engagements. P HOTOGRAPH 4. (front, left-to-right) Jack Malone, Elliot Anderson, Valerie Diaz-Gibertini, Jason Vogelgesang, Stephanie Tassier-Surine, Rosemary Tiwari, Joe Honings, and Keith Schilling; (back, left-to-right) Matthew Streeter, Tom Stoeffler, Thomas Doyle, Calvin Wolter, Rick Langel, Ryan Clark, Alyssa Bancroft, and Greg Brennan. Phil Kerr was not present for this photograph.

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PHOTOGRAPH 3.

PHOTOGRAPH 4.

PHOTOGRAPH 2.