Effects of Water-Saving Irrigation on Hydrological Cycle in an Irrigation District of Northern China

Abstract

In an arid and semi-arid irrigation district, water-saving practices are essential for the sustainable use of water resources. The Soil and Water Assessment Tool (SWAT) was used to simulate hydrological processes under three water-saving scenarios for the Jinghui Canal irrigation district (JCID) in Northwest China. Due to the lack of available hydrometric stations in the study area, the model was calibrated by Moderate Resolution Imaging Spectroradiometer Global Evaporation (MOD16) from 2001 to 2010 on monthly scale. The simulation results showed that using MOD16 to calibrate the SWAT model was an alternative approach when hydro-meteorological data were lacking. It also revealed that the annual average surface runoff (SURQ) decreased by 4.13%, 8.37% and 12.08% and the percolation (PERC) increased by 3.67%, 7.59% and 11.19%, with the improvement of the water-saving degree (the effective utilization coefficient of irrigation water (EUCIW) increased by 0.1, 0.2 and 0.3). Compared with the above two components, the change in actual evapotranspiration (ET) was not obvious. From the perspective of the spatial scale, the changes in every component in the east regions were generally greater than those in the west regions. On a monthly scale, the change in every component was mainly during these two periods. The analysis results of water balance in the study area showed that the proportion of SURQ in water balance decreased (from 14.02% to 12.33%), while that of PERC increased (from 10.99% to 12.22%) after the application of the water-saving irrigation. The decrease in the variation in soil water content indicates that the improvement of the water-saving degree plays a positive role in maintaining the sustainable development of water resources in irrigated areas. This study demonstrates the potential to use remotely sensed evapotranspiration data for hydrological model calibration and validation in a sparsely gauged region with reasonable accuracy. The results of this study also provide a reference for the effect of water-saving irrigation in the irrigated area.