Simulation of salinity distribution in the overlap zone with double-point-source drip irrigation using HYDRUS-3D.
Salinity is a serious and chronic problem for agriculture in arid and semi-arid regions. Drip irrigation is widely used in such regions because it can decrease salinity in the soil. With drip irrigation, there is a region of confluence between each pair of emitters, termed the overlap zone, in which plants are grown. Hence, knowledge of the salinity distribution in the overlap zone is important to achieve high crop yields. The salinity distribution in and around the overlap zone was investigated empirically and in simulation (using HYDRUS-3D) for double-point-source drip irrigation with different irrigation volumes (8 L, 10 L, and 12 L) and emitter spacings (30 cm and 40 cm) in a sandy soil near Korla in Xinjiang Autonomous Region. The predictions from HYDRUS were found to be very close to the observed data in terms of the coefficient of correlation ( R 2 ) and the root-mean-square error (RMSE). The R 2 varied from 0.69 to 0.92 and the RMSE from 0.003 to 0.008. Additional simulations with HYDRUS were used to evaluate the effects of various design parameters on the desalination zone. The relationship between irrigation volume and the size of the desalination zone was found to follow a power function ( R 2 = 0.951), and that between emitter discharge and the size of the desalination zone was found to follow an exponential function ( R 2 = 0.9995). A negative relationship was found between emitter spacing and the size of the desalination zone. For loam, the vertical extent of desalination was found to be about 1.3 times that of the horizontal. For loamy sand, the vertical extent of desalination far exceeded the horizontal extent, owing to its large hydraulic conductivity. We hope that these simulation results with HYDRUS-3D can provide a basis for designing suitable drip irrigation systems.