An Adapted SWAT Plant Growth Module for Tropical Vegetation with Bimodal Seasonality: A Watershed Study in the Tropical Andes
Abstract
Vegetation dynamics are key to understanding and simulating water balance in hydrological models. The Soil and Water Assessment Tool (SWAT) model represents these dynamics through a plant growth module that was originally developed based on temperate regions. Alemayehu et al. (2017) developed SWAT-T, a SWAT variant that is better suited for representing plant growth in the tropics, specifically the Leaf Area Index (LAI). Nevertheless, SWAT-T fails in simulating the bimodal seasonality that is typical of many tropical watersheds. In this study, we (1) adapted the SWAT-T to capture the bimodal seasonality of vegetation thereby producing SWAT-Tb; and (2) evaluated SWAT-Tb's ability to simulate LAI dynamics for 6 land cover types in a tropical mountain watershed in northern South America (Colombia). We compared the performance of SWAT (i.e. default version), SWAT-T, and SWAT-Tb to reproduce LAI dynamics using observations from the MCD15A2H-MODIS product for 2003-2016. Calibrated SWAT-T reproduces observed LAI better than SWAT (bias is reduced), yet both versions have a poor performance in reproducing bimodal seasonality (correlation is low). Calibrated SWAT-Tb outperforms both SWAT and SWAT-T in reproducing the observed bimodality of LAI for all of the studied land cover types. Our results illustrate the potential of SWAT-Tb to simulate bimodal LAI seasonality in the tropics, which is important for simulating streamflow, especially when studying the potential response of watersheds to vegetation change. Furthermore, our results suggest that the reported ability of SWAT to simulate streamflow in tropical watersheds may be misleading if the role of vegetation is misrepresented. This highlights the importance of getting the right answers for the right reasons when using hydrological models to inform decision-making, especially in the face of current environmental change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH004.0024S
- Keywords:
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- 1847 Modeling;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY;
- 1879 Watershed;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY