Evaluation of intensive irrigation on hydrological responses in a Peruvian arid plateau

Abstract:

The Majes district is one of the main areas for agricultural production in southern Peru, and has been intensively irrigated over the last four decades. Low seasonal precipitation and increasing water demands for agriculture, industry, and human consumption have made water supply projections a concern. The objective of this study is to evaluate the impacts of intensive irrigation on hydrological responses in the Majes region (i.e. runoff, infiltration, evapotranspiration, groundwater recharge, and return flow to the Siguas river), using the watershed-scale model Soil and Water Assessment Tool (SWAT). Each cultivated field was considered to be a hydrological response unit (HRU), so that management practices could be applied according to actual scenarios. The HRU designation within SWAT was modified to include different operation schedules such as crop rotation, irrigation, harvest, and tillage. Eleven years (2009-2020) of streamflow data were used to calibrate and validate the model to further investigate the utility of alternate agricultural-water use best management practices (BMPs). Specific alternative management schemes included (1) reduced irrigation volumes; (2) reduced fertilizer loading; (3) conservation tillage and no tillage operations; and (4) combinations of the previous three. Results of this study provided a guideline for stakeholders and decision makers to inform future sustainable water resources management within the region.