Land use and its effect on runoff modeled with SWAT

Abstract

The importance of simulation models for the monitoring of natural resources is increasing. The objective of this study was to apply the SWAT model (Soil Water Assessment Tool) to evaluate the impact of land use change on runoff and sediments in the Chapingo River basin from 1999 to 2015. Two land use maps were generated through the photointerpretation of Landsat and RapidEye images with resolutions of 15 and 5 m, respectively and field trips for verification. In the absence of reliable and recent runoff data, the monthly records for the periods 1964-1970 and 1971-1975 were used for the calibration and validation of the model. In this process the Nash-Sutcliffe coefficients were 0.58 and 0.52, respectively. The land use of the basin in the study period changed: agriculture (-6.9 %); urban area (+ 2.89 %); mining area (+5.04 %), and pasture (+7.75 %). The application of SWAT calibrated and validated only for runoff for the period 1999-2015 did not detect changes in runoff (p = 0.2351) and sediments (p = 0.4430) depending on the change in land use determined. The correlation between runoff and annual sediments simulated with SWAT was significant (p = 0.0116) with a low R² (0.36), attributable to the lack of sediment field data to calibrate and validate the SWAT, in addition to the presence of soil and water conservation practices in the basin studied.