Impacts of irrigation development on water quality in the San Salvador watershed (Part 1)

Abstract

The development of irrigation involves a change in land use and management and has implications for water quality and quantity. It is critical to design conservation practices and best management practices consistent with sustainable agricultural intensification. The objective of this work was to understand and characterize key processes affecting hydrology, nutrient export and transport, and quantify impacts in the San Salvador watershed. For such purpose, the Soil & Water Assessment Tool (SWAT) was implemented, calibrated for water quantity, and water quality was adjusted using soft calibration techniques. The model reproduces water quantity and nutrient balance, and aids in characterizing the nutrient delivery and transport in the watershed. The magnitude of runoff affects the balance of nutrients. In high flows, diffuse sources are more prevalent, while in low flows, point sources and direct livestock manure to the river are more significant. The main outcomes of this work contribute to the design of strategies to achieve sustainable agricultural intensification. It also describes a new modeling tool freely available that could be used in further studies.