Evapotranspiration and Precipitation Data for Calculating Irrigation Water Requirements in Utah Shital Poudyal and Anju Chaudhary
Introduction
Reference evapotranspiration (ETo) and precipitation data are essential for developing water budgets and calculating irrigation water requirements. However, it is crucial that the data used for such purposes are recent and easily accessible to stakeholders. In this fact sheet, we calculated average reference evapotranspiration and precipitation data for multiple locations in Utah, USA. To accomplish this, we collected the data from the Utah Climate Center and compiled it to show an average of 20 years of data by month in an easily digestible format. We compiled data for 69 locations in Utah, making it easy to find one close to your site. However, it is important to note that the data might not be accurate in every location, as some locations may have distinct microclimate. Nevertheless, stakeholders can use this data to develop a water budget and calculate irrigation water requirements for their area.
Evaporation and Transpiration
Evapotranspiration or actual evapotranspiration (ETa) is made up of two words: evaporation and transpiration. The amount of water lost through soil surface and water bodies is referred to as evaporation, whereas transpiration is the loss of water via plants' leaves, stems, and other surfaces. Several factors can influence evapotranspiration rates, including solar radiation, temperature, humidity, wind, soil moisture, topography, atmospheric pressure, and surface coverings, such as plant type, plant density, and mulch layer. While ETa is the amount of water that is actually lost for soil and plant surfaces, reference evapotranspiration (ETo) is a standardized method of estimating the potential water loss from a well-watered, uniform cool-season grass or reference crop under specific meteorological conditions. The cool-season grass or reference crop has a uniform height and is assumed to always have sufficient water supply. ETo is a theoretical reference value that represents the maximum evapotranspiration that can occur under those idealized conditions. Therefore, ETo is often used as a standard, baseline, or reference for estimating crop water needs and scheduling irrigation. There are several methods that can be used to calculate ETo values; however, the Penman-Monteith method is most widely used. It is important to have accurate and reliable meteorological data, as generating precise ETo values depend on quality meteorological data used in the calculations.
Evapotranspiration Data in Utah
Utah is a climatically diverse state with varying geographical conditions, such as topography, altitude, and vegetation. As ETo is a function of various climatic and geographical conditions, ETo varies in different parts of the state. To understand this, let us consider the interaction between two factors: latitude (proximity to equator) and evapotranspiration. St.