Influence of the integrity of the riparian zone on the Capão Comprido Stream Water Basin (DF) by simulating different spatial discretizations with the SWAT+ model

Abstract

Riparian zones are areas bordering waterbodies that provide various environmental services. However, the inappropriate use of these spaces, with conversion for urban expansion and agricultural frontiers, has compromised their ecological integrity. The objective of this work was to verify a new perspective for analyzing the influence of the integrity of the riparian zone in river basins based on different possibilities of spatial discretization and landscape representation, of the terrestrial phase of the water balance, from the perspectives of the landscape units available in the Soil and Water Assessment Tool (SWAT+) model. The Capão Comprido Stream basin in the Federal District (DF) was defined as a case study. There were difficulties in calibrating and verifying the model using SWAT Toolbox software, with Nash-Sutcliffe Efficiency (NSE) and logarithm (log)NSE values below 0.5; percent bias (PBIAS) above ±15, and coefficient of determination (R2) below 0.6. These results, although better than those of the initial simulation, are still unsatisfactory acording to the metrics and values adopted as reference. Despite that, based on the determination of landscape units available in SWAT+, hydrological modeling of river basins has the potential to improve the representation of river basins by differentiating the characteristics of the higher parts of the relief (uplands) from the lower riparian zone (floodplains). Riparian zones proved to be relevant for the conservation of water resources. The simulations confirmed that the increase in these areas contributed to the reduction in surface runoff and sediment load in the river basin. However, it contributed to an increase in lateral flow, percolation, return flow, and deep aquifer recharge.