Serving as the headwaters for major river systems, mountains are an integral component of the upstream-downstream paradigm of watersheds. Over the past 30 years, the arid coast of Peru has emerged as an agro-industrial hub fed by abundant mountain-derived water resources.
The Río Santa watershed, which originates with the Cordillera Blanca, exemplifies the importance of mountain water resources to coastal landscapes and aquifers. In 2022, Peru exported 23 billion USD of agricultural products. In the southern coast of La Libertad, the number one agro-exporting region of the country, the canal system CHAVIMOCHIC draws water from the Río Santa for irrigation, industry, and domestic uses. Similarly, the canal system CHINECAS transports Río Santa water southward. These activities require massive amounts of water for growing water-intensive crops in desert valleys, including blueberries, sugarcane, and rice.
We construct a water budget of the Río Santa Watershed, incorporating the coastal canal system and agricultural activities. We consider the watershed to extend beyond its geographic boundaries, encompassing coastal regions that receive water from the Río Santa, transported hundreds of kilometers via canals. We create a hydrological and hydrogeological dataset of the region through archival government reports, fieldwork, and modeling. We estimate the contribution of mountain water to coastal irrigation regimes and aquifer recharge, called mountain transfer recharge. In addition to offering a comprehensive description of the current state of this extended hydrological system, our findings allow us to assess the vulnerability of the region’s hydroscape to future change, across the mountain to coast continuum. The research highlights the importance of mountain regions for coastal water resources and food production.