Hydrological simulation of the Laja River basin with the WEAP model

Abstract

The Laja River basin is located between parallels 21° 32' 58", 20° 16'14" N, and meridians - 100° 6' 28'' - 101° 30'44" W. In 2014, the basin was classified with a high degree of pressure on the water resource (Conagua, 2014). It also ranked second as an administrative hydrological region with the highest population density, and it presents strong problems with supply and demand. All the previous reasons motivated this work. The objective was to calibrate, validate and estimate runoff surface, considering the effects of changes in precipitation, Therefore, hydrological modeling was performed in WEAP (Water Evaluation and Planning) using the soil moisture method. The information used was on soil use and physical characteristics; crop coefficients; average monthly data on precipitation; average temperatures; relative humidity; and wind speed. The calibration and validation processes were carried out at four points in the basin, for five years on a monthly period. The hydrometric stations were Puente Dolores, Begoña II, Tres Guerras and Pericos. For each station, the coefficient of determination (r²) and Nash-Sutcliffe efficiency index (NSE) were estimated. The values obtained in the calibration phase were an r² of 0.8 to 0.82 and NSE from 0.55 to 0.77. In the validation phase, the values for r² range from 0.65 to 0.86 and NSE from 0.57 to 0.75. Climate information was generated with WGEN for 10 years, to generate runoff scenarios, with the RCP8.5 projections, for the period 2012-2022. In conclusion, WEAP is a software capable of correctly simulating, with the soil moisture method, the response of the Laja River basin. WEAP correctly simulated flows measured in the gauging station with an average absolute error of less than 10 %.