Computing And Study On Irrigation Requirement In Field Of Bojili Irrigation District

The Yellow River Basin (YRB) is one of the serious water scarce regions in China. Water savings for irrigation becomes a more important task of water management at both irrigation district and basin levels. This paper takes the Bojili Irrigation District (BID) as an example to study crop water requirements and irrigation scheduling for improvement of water management at both levels.There are four main parts in the paper. The first part is about the computing of crop water requirements (or crop evapotranspiration) and net irrigation requirements (NIR) of ten crops in Bojili irrigated district. Then the traditional irrigation schedules of winter wheat and summer maize, which are the main crops in Bojili, were evaluated with simulating model ISAREG. Third, the field application efficiency in the experimental areas was evaluated from three methods. In the fourth part, the field irrigated water requirement were gotten based on the recommended irrigation schedules and irrigated areas often crops.In this paper, the reference evapotranspition ET0 in three counties in BID was computed by Penman-Monteith method and the crop coefficients, Kc of ten crops by KCISA model and the crop water requirements, ETc, were computed simply by Kc×ET0. Meanwhile, four representative years by frequency analysis are gotten according to net irrigation requirements and planted areas of different crops in Bojili irrigation district.Comparing observed and simulated soil water contents using the data from two irrigation experimental fields validated the ISAREG model. Then the irrigation schedules of winter wheat in 1998-2000,which are the experimental years, were evaluated by the simulating results with ISAREG. It shows that the traditional irrigation schedule should be modified.To evaluate exist field irrigation performance, irrigation tests were performed and simulation model, SRFR, was used. Evaluated results of irrigation efficiency are 0.68 and 0.52 in Huimin and Wudi respectively. So the potential water-savings is very large, especially in Wudi County.The irrigation scheduling optimization is based on the simulation with ISAREG model. According to the optimal irrigation scheduling, the irrigation demand hydrographic in four representative years of Huimin and Wudi are computed. Comparing with the average amount of water diverted from the Yellow River, it shows that the distributed water for Huimin is abundant, but that for Wudi is short. The countermeasures that deal with the water shortage should be sought.