Effects of Combined Main Ditch and Field Ditch Control Measures on Crop Yield and Drainage Discharge in the Northern Huaihe River Plain, Anhui Province, China

Open-ditch controlled drainage is an important water management measure used to reduce drought and waterlogging stress in many areas in the world. Such measures are essential to promote the crop yield, make full use of rainfall resources, reduce regional drainage discharge (Q) and reduce water environmental pollution. To quantify its effects, an open-ditch controlled drainage and crop yield simulation model was developed in an area located in Northern Huaihe River Plain (NHRP), Anhui Province, China. The model was calibrated and validated. The changes in crop yield and Q were simulated under different main-ditch water-depth control schemes, field ditch layout and outlet weir height control schemes from 1991 to 2021. Compared with the current situation, the change in crop yield caused by the main ditch schemes was significantly higher than that caused by the field ditch schemes. The change in Q caused by the field ditch schemes was greater than that caused by the main ditch schemes, with values of 60% and 0.02%, respectively. Combined control schemes could further increase the crop yield and reduce the Q. The results have practical application value for ensuring good crop yields and reducing farmland drainage in the NHRP and other similar regions.