Evaluation of the most proper management scale on water use efficiency and water productivity: A case study of the Heihe River Basin, China

Abstract

Increasing agricultural water use efficiency (WUE) and water productivity (WP) is imperative to alleviate water scarcity and achieve sustainable agriculture in inland river basins. The confusion on the use of the two indicators at demarcated scales in this issue has been addressed. Analysis of the literature, however, lacks evaluation of the most proper management scale. The Heihe River Basin (HRB) in China was selected as the study area and WUE and WP were calculated spatially at the field crop, irrigation district, and county scales using the remote sensing-based evapotranspiration (ET), grid rainfall, land use, and statistical data. In addition, the most proper management scale was firstly evaluated by comparing WUE and WP based on statistical properties and spatial distributions. The results show that higher WUE and WP were observed at the field crop scale. The differences between WUE and WP are significant at field crop scale but the gap narrows with increasing spatial scale. Spatial analysis reveals that WP was higher in the plain oasis area and lower in the mountainous and desert oasis area. Among three scales, the WUE and WP are relatively lower and the variances of them are relatively larger at the irrigation district scale. WUE ranges from 0.1 to 0.85 (mean 0.34) and WP varies from 0.08 kg/m3 to 0.8 kg/m3 (mean 0.48 kg/m3) across irrigation districts in the whole basin. The large differences indicate the presence of a tremendous management gap among irrigation districts. We thus declare that mesoscale views are more suitable and irrigation district scale is the most proper management scale for resolving water resource utilization problems in arid river basins. Further, agricultural water management at the irrigation district scale should target at improving irrigation technology and adjusting crop structure.