Sustainable Development of Groundwater Resources under the Large-Scale Conversion of Dry Land into Rice Fields

The sustainable use of groundwater resources is highly important for regional groundwater system safety and food security, especially in large-scale agricultural planting areas. In the Sanjiang Plain (SJP) in Northeast China, irrigation water consumption has increased sharply due to the large-area ''conversion of dry land (mainly maize and soybean fields) into rice fields'', threatening the regional groundwater system security. However, little is known about the impact of large-scale agricultural planting structure adjustment (i.e., changes in cropping systems) on regional groundwater sustainability. This study estimated the groundwater storage anomaly (ΔGWS) using the Gravity Recovery and Climate Experiment (GRACE) satellite data and the Global Land Data Assimilation System data. Additionally, the groundwater sustainability index (SI) of this region was evaluated based on GRACE Groundwater Drought Index (GGDI). Collectively, the influence of agricultural planting restructuring on the SJP groundwater sustainability was analyzed. The findings were: (1) The groundwater reserves in SJP and Xingkai Lake Plain decreased with maximum declines of 6.79 and 10.37 cm/year, respectively. (2) The groundwater sustainability deteriorated rapidly after 2009, from extremely high to extremely low levels. The lowest sustainability was observed in the Jiansanjiang area, which underwent the most drastic adjustment of agricultural planting structure. (3) Although precipitation increase can alleviate groundwater overexploitation, the groundwater sustainability continued to deteriorate due to the sharp increase in irrigation water consumption arising from the large-scale land conversion. Curbing the expansion of paddy rice fields or reducing their planting areas can restrain the demand for irrigation water. Moreover, proactively designing diversion projects to increase available surface water supply can also effectively achieve sustainable agricultural development in this region.