Quantification of Environmental Flow Requirements to Support Ecosystem Services of Oasis Areas: A Case Study in Tarim Basin, Northwest China

Abstract

Recently, a wide range of quantitative research on the identification of environmental flow requirements (EFRs) has been conducted. However, little focus is given to EFRs to maintain multiple ecosystem services in oasis areas. The present study quantifies the EFRs in oasis areas of Tarim Basin, Xinjiang, Northwest China on the basis of three ecosystem services: (1) maintenance of riverine ecosystem health, (2) assurance of the stability of oasis–desert ecotone and riparian (Tugai) forests, and (3) restoration of oasis–desert ecotone groundwater. The identified consumptive and non-consumptive water requirements are used to quantify and determine the EFRs in Qira oasis by employing the summation and compatibility rules (maximum principle). Results indicate that the annual maximum, medium, and minimum EFRs are 0.752 × 108, 0.619 × 108, and 0.516 × 108 m3, respectively, which account for 58.75%, 48.36%, and 40.29% of the natural river runoff. The months between April and October are identified as the most important periods to maintain the EFRs. Moreover, the water requirement for groundwater restoration of the oasis–desert ecotone accounts for a large proportion, representing 48.27%, 42.32%, and 37.03% of the total EFRs at maximum, medium, and minimum levels, respectively. Therefore, to allocate the integrated EFRs, focus should be placed on the water demand of the desert vegetation’s groundwater restoration, which is crucial for maintaining desert vegetation to prevent sandstorms and soil erosion. This work provides a reference to quantify the EFRs of oasis areas in arid regions.