Optimization of the border size on the irrigation district scale - Example of the Hetao irrigation district

To improve the performance of border irrigation, this study analyzed the spatial variability characteristics of the soil particle content and bulk density, based on soil physical parameters measured at 86 sampling points in the Hetao irrigation district (HID). The soil hydraulic parameters were determined using the RETC, and HYDRUS-1D was then adopted to estimate infiltration parameters of the Kostiakov equation at different locations. The optimal layout patterns of border size were proposed under the consideration of various combinations of different typical soil textures and field slopes by WinSRFR. The results indicated that the spatial distributions of clay and silt particle contents were generally high in the middle and low at both sides of the HID, while the sand was the opposite. The results proved that the soil physical parameters are only to be measured at depths of 0?20 and 20?40 cm to meet the needs of infiltration parameter estimation which can significantly reduce the workload of soil sample collection. Moreover, two types of optimal border layouts of different combinations of the soil textures (silt loam and silt clay loam) and field slopes (no more than 1%o, 1?3%o, and 3?5%o) were proposed, which can guarantee the application efficiency and distribution uniformity no less than 85%, and be the guidance for practical field irrigation in the HID.