Soil and Water Assessment Tool (SWAT) Helps Develop Better Understanding of Irrigated Agricultural Watersheds Globally

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newly-published review supported by the South Central CASC explores how researchers use the Soil and Water Assessment Tool (SWAT) to understand changes in water availability and quality in a changing climate. 

A wide, shallow stream flows through a rocky canyon covered in dry grass and green shrubs.

Water resources in arid regions, like this stream in the Pajarita Wilderness in the Coronado National Forest in Arizona, are under increasing stress due to climate change and agricultural use.

(Credit: Alan Cressler, USGS) 

(Public domain.)

Freshwater is a critical resource for different ecosystems and communities; changes in water availability such as droughts or floods can alter the fortunes of entire regions. Much of the world’s freshwater is used to irrigate crops, particularly in naturally dry ecosystems like arid and semi-arid regions. As climate change creates hotter and dryer conditions and population expansions increase local water demand, many regions face unprecedented uncertainty about their water supply.  

Scientists and resource managers have developed a number of tools to understand current and future water use patterns. One such model is the Soil and Water Assessment Tool (SWAT), which simulates hydrological processes under different water use, land use, and climate change scenarios. A recently published study funded by the South Central CASC reviewed how the SWAT tool has been used to assess agricultural water use in arid/semi-arid watersheds. 

The authors found that the tool has been used globally to develop better understandings of the challenges communities face in developing sustainable agricultural water use systems in arid/semi-arid ecosystems. Most studies used SWAT to understand changes in water availability, with comparatively fewer studies using the tool’s full capacity to predict future water quality. They recommend that researchers use real-life irrigation data to parameterize the model and incorporate metrics of water quality to improve the accuracy and real-world relevance of SWAT results. The authors hope that these recommendations improve the utility of SWAT assessments of dry ecosystems in the future. 

This project was funded by the South Central CASC project “Understanding New Paradigms for ‘Environmental Flows’ and Water Allocation in the Middle Rio Grande River Basin in a Changing Climate.” 

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