Application of hydrological model SWAT in hydrographic units in Nicaragua: Simulation of surface runoff

Abstract

Water resources are the most sensitive to the effects of Climate Change, so the assessment of their resulting state is essential for the well-being of the Nicaraguan population. In order to generate quantitative information on the dynamics of surface runoff to guide the prioritization of comprehensive management in watersheds with water deficit, the surface runoff of hydrographic units in Nicaragua was estimated with the SWAT hydrological model. The analysis was carried out considering three combinations of climatic scenarios and land uses: first, with the climate of the period 1988-2017 with land use of 2015; the second, the pessimistic climate scenario (RCP 8.5) for the period 2040-2069 with land use from 2015; and the last one, the pessimistic climate scenario (RCP 8.5) for the period 2040-2069 with a proposal to replace agricultural areas on slopes greater than 15 % by agroforestry and silvopastoral systems. In total, 66 hydrographic units were simulated, of which 29 presented a deficient hydrological response. In the 1988-2017 period, surface runoff varied from 65.5 to 497.9 mm and from 70.76 to 689.76 mm in the 2040-2069 period. With the land use proposal, runoff is expected to range from 36.57 to 683.9 mm, reflecting an average decrease of 70.27 mm. Based on these variations, it was concluded that the highest priority units to be managed are those located in Madriz, Nueva Segovia, Estelí and Matagalpa, located within the dry corridor.