GroMoPo Metadata for Minqin Basin MODFLOW model

The Minqin Basin is at the lower reach of the Shiyang River of Gansu province in northwest China. Dramatic decline in groundwater level has resulted from over-abstraction of groundwater since the late 1950s to satisfy increasing irrigation and other demands. Severe water shortage led to environmental degradation. To better understand the spatial-temporal variation of groundwater levels and to evaluate the groundwater resources in the region, a three-dimensional regional groundwater flow model was built and calibrated under transient condition. The MODFLOW program was used and the research area was discretized as a square network with cell size of 400 x 400 m. The model showed that the aquifer was under destructive stress, with a groundwater resource deficit of 260 million cubic meters per year (Mm(3)/year) on average. Since the inflow of surface water from the upstream basin has declined to about 100-150 Mm(3)/year in recent decades, the irrigation return flow had become the main recharge and accounted for 60.6% of total recharge; meanwhile, abstraction by pumping wells took 99.2% from the total groundwater discharge.

民勤盆地位于中国西北甘肃省石羊河下游。自20世纪50年代末以来，为满足日益增长的灌溉及其他用水需求，当地长期超采地下水，导致地下水位大幅下降，进而引发严重的水资源短缺与区域环境退化。为明晰该区域地下水位的时空变化特征并评估地下水资源状况，研究团队基于非稳定流条件构建了三维区域地下水流模型并完成率定。本次研究采用MODFLOW程序，将研究区划分为单元格尺寸为400×400米的正方形网格进行离散。模型结果表明，该区域含水层正承受破坏性开发压力，年均地下水资源亏缺量达2.6亿立方米（Mm³/年）。近数十年来，上游流域入境地表水径流量已降至约100~150 Mm³/年，因此灌溉回渗补给成为地下水的主要补给来源，占总补给量的60.6%；与此同时，机井抽采量占地下水总排泄量的99.2%。