Abstract: The Yinnan Irrigation District is located in the upper reaches of the Yellow River in China. Due to historical reasons, the district diverts a large amount of irrigation water from the Yellow River and consequently discharges a relatively large amount of drainage water to the downstream river. In order to mitigate the negative impact of the current water management practice on water quality of the Yellow River, a comprehensive analysis was conducted on the drainage system of the irrigation district. The calculation results showed that, for the paddy fields, the annual drainage through field ditch was as high as 56 cm, accounting for 58% of total subsurface drainage; for the dryland crop fields, the annual drainage through field ditch was only 1.0 cm, accounting for 4% of the total subsurface drainage. Therefore, it is feasible to implement controlled drainage practice in the rice growing areas in order to reduce drainage discharge and save irrigation water.