Mismatch between crop water requirements and irrigation in Heihe River Basin, Northwestern China

Heihe Inland River Basin is the second largest in China. Water use for agriculture in the middle section of the basin accounts for over 90% of total usage; this leads to lake shrinkage, river blanking, and desertification of the downstream basin. Crop water requirements within the Ganzhou district of the Heihe River Basin in Northwestern China were modeled using a parameter calibration of the CROPWAT model, based on household survey data on crop coefficients and water usage, taking into account effective precipitation. The results show that modeled evapotranspiration for seed maize was consistent with evapotranspiration determined from observed data based on eddy covariance, as adjusted R2 values approached 0.73 (P < 0.001). Vast differences were observed between actual irrigation and water requirements across the study area. Excessive water was used for irrigation, particularly in the case of maize, where mismatches in dates were widespread between actual irrigation and water requirements. Thus, to save water and increase yield, a set schedule for irrigation was recommended.