Assessing the feasibility of sprinkler irrigation schemes at the regional scale using a distributed agro-hydrological model

Abstract

Quantitatively assessing the feasibility of sprinkler irrigation at the regional level from the perspectives of water, food and economy could provide the basis for decision-making on how to implement sprinkler irrigation according to local conditions to alleviate the severe contradiction between groundwater shortages and food production. In this study, the distributed agro-hydrological model, after establishment, calibration and validation, was applied to the eastern central part of the North China Plain (NCP), where deep groundwater has been seriously overexploited. The model was used to simulate 11 sprinkler irrigation scenarios for winter wheat for 20 rotation years and to analyze the effects on crop yield, water productivity (WP), soil water balance and farmers’ net income. Then, the irrigation method and the corresponding irrigation scheme were selected from the sprinkler and surface irrigation scenarios to maximize the yield or WP of winter wheat or farmers’ net income under three irrigation quotas, three precipitation levels and 17 soil texture profiles. Next, the sprinkler irrigation scheme was optimized for each precipitation level to achieve the highest WP under the constraint of a specific threshold of irrigation quota reduction compared with the current irrigation schedule, and the effects on water saving and reducing deep groundwater exploitation were evaluated. The main results were as follows. (1) On average, the reduction in the irrigation quota within the set range decreased the winter wheat yield and WP under the 11 scenarios; with respect to the specific irrigation quota, the average differences in the yield and WP of winter wheat between sprinkler and surface irrigation did not exceed 300 kg hm−2 and 0.10 kg m−3, respectively. The application of sprinkler irrigation to winter wheat led to the stability or increase in yield and WP of the following summer maize, and the spatial–temporal differences in the yields and WPs of the two crops decreased under sprinkler irrigation compared with surface irrigation. (2) Less transpiration and soil water consumption and greater evaporation were estimated for the winter wheat season under sprinkler irrigation than under surface irrigation. The income increase under sprinkler irrigation was less than the cost increase, leading to a negative change in farmers’ net income. (3) To maximize the yield, WP or farmers’ net income, surface irrigation is recommended for winter wheat in most of the study area, while sprinkler irrigation is recommended in the area with sandy soils in each layer or sandy soils in the 0–70 cm layer and loamy soils in the >70 cm layer. (4) The fixed sprinkler irrigation scenarios dominated the optimized irrigation schemes, and when the specific threshold was 60%, compared with the current irrigation schedule, the optimized sprinkler irrigation schemes achieved 123% of the target value of reducing deep groundwater exploitation (i.e., 6.05 × 108 m3) in the normal season, with a yield reduction of 74.3%.