Presenter
Dr. Pei Li, Chang'an University
Co-author(s)
Prof. Li Ren, China Agricultural University
Sub-theme
1. Water-Human-Economy(Agriculture, Industry, City...)-Ecology Nexus under a Changing Environment
Topic
1-4. Water security challenges in key regions
Body
Quantitatively assessing the tradeoff between groundwater exploitation and grain production at the regional scale from the multiple perspectives could provide a basis for decision-making on how to alleviate the severe contradiction between water shortages and food security according to local conditions. In this study, the distributed agro-hydrological model was established, calibrated and validated using multiple data in the eastern central part of the North China Plain, where deep groundwater has been seriously overexploited for irrigation. The model was used to quantify different irrigation strategies (e.g., limited irrigation, saline water irrigation and sprinkler irrigation) to reduce deep groundwater exploitation. The 27 irrigation scenarios under the three irrigation strategies with limited water supply were simulated for 20 rotation years, and the impacts on crop yield, water productivity (WP), soil water balance were analyzed. Further, the irrigation scheme under different strategies was optimized under the specific constraint and the effect on reducing deep groundwater exploitation was evaluated. The main results were as follows. 1) Under limited irrigation strategy, the irrigation scheme was optimized to minimize evapotranspiration under the constraint of yield reduction. With an increase in yield reduction from 4% to 61%, the reduction in the amount of deep groundwater exploitation under the optimized irrigation scheme increased from approximately 0.140 billion cubic meter to 0.715 billion cubic meter compared with the current irrigation schedule. 2) Under saline water irrigation strategy, the appropriate irrigation scheme was optimized under the two constraints of acceptable crop yield reduction and soil salt accumulation. Considering that the average salt content of the 2-m soil profile was less than 3 g/kg, when the average crop yield reduction was no more than 500 kg per hectare, 1000 kg per hectare, 1500 kg per hectare and 2000 kg per hectare, the maximum irrigation water salinity was predominantly 3 g/L, 4 g/L, 6 g/L and 6 g/L, respectively, in the study area. The average amount of saline water needed for irrigation was approximately 2.278 billion cubic meter, which was 0.191 billion cubic meter more than the exploitable amount of saline groundwater. 3) Under sprinkler irrigation strategy, the irrigation scheme was optimized to maximize WP under the constraint of irrigation quota reduction. The optimized irrigation scheme reduced deep groundwater exploitation by 81%, 123% and 124% of the target value (i.e., 0.60 billion cubic meter) in the wet, normal and dry seasons, with yield reductions of approximately 55.8%, 74.3% and 79.7%, respectively.