Suitability assessment on spatial layout of pumping wells in Hongyashan irrigation district

Abstract: The suitability assessment on spatial layout of pumping wells in irrigation district plays a vital role in optimizing the layout of pumping wells and properly exploiting groundwater in arid and semi-arid regions. In this study, suitability assessment on spatial layout of pumping wells was conducted in Hongyashan Irrigation District of Shiyang River Basin. Variables of land resources (land use), hydrogeological conditions (groundwater depth, aquifer thickness, water yield of a well, and groundwater salinity), and infrastructure construction (density of pumping wells, buffer zone between canal and water systems, and buffer zone of roads) were selected as the evaluation indices of pumping wells planning. A layer was created for each evaluation index and the layers were then overlaid by the intersect function of Arc GIS. The study area was classified into 366 evaluation units in which those indices had the same or similar values within single unit. The weights of evaluation indices and the comprehensive evaluation values of evaluation units were calculated by the Entropy method. The results showed that among all the factors considered, groundwater depth and water yield of a well were the most important two factors influencing the spatial layout of wells in Hongyashan Irrigation District as the two indices had relatively large spatial variability, while the influences of aquifer thickness, distance to canal and water systems, and closeness to roads were relatively small due to less spatial variability. According to the comprehensive evaluation value of each unit, the study area was classified into five levels of suitability for spatial layout of pumping wells: unsuitable, marginally suitable, moderately suitable, suitable and highly suitable zones. Areas with deep underground depth and small water yield of a well tended to be classified as less suitable zones, while areas with shallow underground depth and large water yield of a well tended to be classified as suitable zones. The unsuitable, marginally suitable and moderately suitable zone accounted for 19.33%, 24.33% and 46.61% of the available land resources, respectively, which combined represented more than 90% of the available land resources. By contrast, the suitable and highly suitable zones occupied much less land, only 7.33% and 2.40%, respectively. According to the research results, the pumping wells should be constructed in the areas with shallow underground depth and large water yield of a well. If the policy of abandoning pumping wells will be implemented in the future, the wells located in those areas classified in this study as less suitable zones should be closed first. The study provides some valuable references for optimizing the layout of pumping wells in the irrigation district.