Development of a decision support system for irrigation management to control groundwater withdrawal

Hebei Province is an important grain production area in China. The high grain production of the main crops, winter wheat and summer maize, depends on irrigation, which primarily comes from underground water sources. However, the over-extraction of groundwater for many years has caused the groundwater level in this region to decline continuously, threatening the sustainable development of irrigation agriculture. Under the national policy of limited groundwater extraction, achieving the goal of controlling groundwater extraction, and simultaneously using available water to maintain regional food productivity, is of great importance to achieve regional food security and sustainable water usage. In this study, we proposed and tested an irrigation decision system designed to set a limit on the groundwater withdrawal amount and to optimize irrigation scheduling, with the aim of using the limited irrigation water efficiently. We proposed that the water drawn from underground was to be controlled by real-time recordings of irrigation electricity consumption, based on the electricity meter readings collected by the State Grid Hebei Electric Power Company, which has implemented a project to update the electric recording of pumping-wells in the Hebei Plain, and the electricity consumption of each pumping well to allow remote recording in real time. By converting “electricity consumption to irrigation water use”, the electricity meters was used to regulate and control groundwater withdrawal to achieve the groundwater withdrawal target. The pumping limit setup for each well was to be decided based on the available groundwater, which was adjusted annually based on the groundwater recharge amounts from rainfall, surface water, and lateral flow. Based on the available groundwater, water rights could be endowed to each piece of land, which could be regulated by converting the total electricity used in pumping water based on the conversion coefficient of “electricity consumption to irrigation water use” for each well. Under limited groundwater pumping, we established an optimized irrigation schedule using calibrated crop models based on field experiments, with the soil water low limit for guiding the irrigation schedules being set up for winter wheat and summer maize. We used the calibrated crop model, Agricultural Production Systems sIMulator (APSIM), to simulate the crop production under a total annual irrigation amount of 210 mm with irrigation application numbers of three to ten and irrigation amounts of 70 to 21 mm per irrigation, based on meteorological data from the Luancheng Station for the period 2009–2019. Based on the simulation results, we determined the irrigation scheduling and the soil water content lower limit to guide the irrigation regulation. Furthermore, we developed and tested methods to forecast soil water changes, with the aim of determining the timing and amount of irrigation required based on the soil water threshold levels simulated by the crop model. Ultimately, we suggested the integration of groundwater withdrawal control by electric meters, and the calculation of irrigation timing and quantity under the limited water supply, based on soil water forecasting, to form a precisely controlled irrigation decision support system that achieved the goal of groundwater withdrawal control and improves the water use efficiency of crops under a limited water supply. This system, which ultimately has practical benefits for irrigation management applications, provides an efficient management tool for the government to control underground water withdrawal, as well as individual farmers who have different cultivating land areas, allowing them to use their limited water resources more efficiently.