Article
Forest Cover and Locality Regulate Response of Watershed Discharge to Rainfall Variability in Caribbean Region Qiong Gao and Mei Yu * Department of Environmental Sciences, University of Puerto Rico, Rio Piedras, San Juan, PR 00925, USA * Correspondence: meiyu@ites.upr.edu
Citation: Gao, Q.; Yu, M. Forest Cover and Locality Regulate Response of Watershed Discharge to Rainfall
Abstract: Reforestation often occurs when the economy shifts from agriculture to industry and services such as tourism. However, there is a lack of coherent knowledge and investigation about the impact of reforestation in the tropics on hydrological variability as well as flood risks. It is unclear how changes in forest cover and pattern will affect flood risks and watershed response to future altered rainfall intensity. This study uses the Soil Water Assessment Tool (SWAT+) to simulate the impact of reforestation, the locality of forest, and the concentrated rainfall on the hydrology of the largest watershed in Puerto Rico. SWAT+ is a computer model simulating watershed hydrology driven by meteorological input and the characteristics of soils and land use. We hypothesized that increased forest cover, especially at low elevation range, would reduce flood risk and that reduced rain days while maintaining the mean annual rainfall invariant would increase stream discharge variability. We found that reforestation significantly reduced large discharges but increased small discharges; that forest at low elevation tended to reduce large and extreme discharges in comparison with forest at high elevation; and that more concentrated rainfall not only increased the rainfall variability but also increased the discharge variability. However, both the impact of shifting forest locality and the response of watershed to altered rainfall intensity strongly depended on geophysical factors such as ranges of elevation and slope. Moving forests to lower elevation in subbasins with steeper slopes showed a stronger reduction in extreme discharges than in subbasins with flatter slopes. On the other hand, subbasins with steeper slopes tended to response more strongly to more concentrated rainfall with greater increase in discharge variability than subbasins with flatter slopes. To cope with future increased climate variability, our results favor reforestation at lower elevation for watershed with large elevation ranges and steep slopes. Keywords: hydrological variability; Puerto Rico; land use pattern; discharges; rainfall variability
Variability in Caribbean Region. Forests 2024, 15, 154. https:// doi.org/10.3390/f15010154
1. Introduction Academic Editor: Matthew Therrell Received: 22 November 2023 Revised: 6 January 2024 Accepted: 9 January 2024 Published: 11 January 2024
Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).
Climate variability often refers to how the values of temperature or precipitation differ from the mean values [1]. Natural climate variability arises from perturbation-caused positive and negative feedbacks within the atmospheric system [2]. However, the main component of present climate variability is a result of human activities [3]. Warming increased the energy of the earth’s system, and the progressive loss of glaciers and ice caps reduced the cooling of ocean water. These external forcings caused more frequent and extreme oceanic and atmospheric events such as localized high atmospheric pressure interwoven with mega tropical cyclones. Consequently, more frequent extreme weather conditions impact coastal and terrestrial ecosystems as well as human societies [4]. Alternating drought and extreme large rainfall brought about by major storms increased hydrological variability and flood risk and reduced the availability of water for terrestrial ecosystems and human consumptions [5]. Not only does hydrological variability link to climate processes but it also heavily depends on how terrestrial ecosystems respond to the climate variability [6]. The hydrological responses of terrestrial ecosystem to rainfall events are complex. Soil and vegetation hold
Forests 2024, 15, 154. https://doi.org/10.3390/f15010154
https://www.mdpi.com/journal/forests