Assessing Different Wetting Front Patterns for Surface Drip Irrigation Systems in Sloping Lands

Estimation of wetting front dimensions enhances the water use efficiency and optimal use of water. Since, globally, most of the cultivated lands are not flat, full recognition of the moisture advance front is essential for proper management and operation of surface drip irrigation in these areas. In this study, two physical rectangular cubic models were constructed to measure the soil moisture advance front. The smaller model was used for experiments with lower discharge and the larger model was used for experiments with higher discharge. The experiments were carried out in four different slopes (0, 10%, 20%, and 30%), three soil types with different textures (light, medium, heavy), with three emitter discharges (2, 4 and 6 liters per hour). The results showed that the moisture distribution (for upstream and downstream of the emitter) was different in sloping lands (for different flow rates and different soil texture). Therefore, in relation to the position of the emitter and plant, drip system should be designed differently in the sloping land in comparison to flat lands. According to the nature of the sloping lands, the plant position was downwardly shifted and its exact positions are suggested for different scenarios (for different discharge rates, slopes, and soils) in this study. The results showed that the percent of downstream wetted radius in sloping lands for the three types of heavy, medium, and light textured soils were between 49.2-81.5%, 49.2-76%, and 48.3-70.7%, respectively. These values for the percent of the upstream wetted radius of the emitter ranged between 18.5-50.8%, 24-50.8%, and 29.3-49.7%, respectively. The results of this study can be used as a general guide in the design of drip irrigation systems in sloping land to determine the plant and emitter position relatively accurately.