Predictive Model of Surface Runoff as a Monitoring Strategy for Water Harvesting Structures: El Varillal Micro-watershed, San Lucas, Madriz, Nicaragua

Abstract

The Nicaraguan dry corridor is highly vulnerable to climate change. Madriz, a department in the Central-Northern region of Nicaragua and part of this corridor, faces significant challenges due to climate variability. Given the erratic behavior of the climate, it is essential to monitor surface runoff and understand its behavior under different climate scenarios to evaluate the potential of water harvesting structures. The objective of this study is to compare surface runoff under three climate scenarios to identify the impact of climate change on these structures. This study was conducted in the El Varillal micro-watershed, in San Lucas, Madriz, Nicaragua using the Soil and Water Assessment Tool (SWAT), which models hydrological behavior by considering soil characteristics, land use, and climate. A historical climate record from 2000 to 2021 was used, along with Representative Concentration Pathways (RCP) 2.6 and 8.5 for the 2040 to 2069 period, as the climate scenarios to compare. The variable studied was surface runoff, estimated from the hydrological response units of the micro-watershed. The micro-watershed has clay soils and agricultural and livestock uses on steep slopes, giving it high potential for water harvesting. However, the effectiveness of the structures depends on proper maintenance and management of the catchment area to prevent erosion and ensure water infiltration. Under future climate scenarios, it is expected that with the Representative Path of Concentration 2.6 scenario, runoff will increase by 101.56%, and with the Representative Path of Concentration 8.5 scenario, by 109.48%, compared to historical data. This suggests that, during rainfall events, the integrity of water harvesting structures could be compromised if conservation strategies and coverage management are not implemented.