Capillary rise simulation using UPFLOW model in sugarcane Agro-industries of Khuzestan.

The upward movement of water through capillary rise from the shallow water-table (1–1.5 m) to the root zone (0.4–0.6 m) is an important incoming flux in the soil system. UPFLOW is a specialized model for determining capillary rise, which is a simple model with a small amount of input data. This research was conducted to assess the efficiency of the UPFLOW model in the simulation of capillary rise in shallow water-table conditions, based on the observed capillary rise using a lysimeter in the agro-industry of Amirkabir, Khuzestan. The input data of the model include: crop(root-water uptake rate at different sections of root zone, crop cover type, crop coefficient), soil(number of soil layers and their thickness, mean soil-water content of the profile, anaerobiosis point of the soil, saturated hydraulic conductivity of the soil profile), weather(maximum and minimum temperature, solar radiation, wind speed, and relative humidity, ET0) and water-table(depth to water-table from the soil surface, salt content of the groundwater) were measured. Then, the capillary rise was calculated for each month during the stages of sugarcane growth. The performance of this model was evaluated by the statistical indices including determination coefficient (R2), mean absolute error (MAE), root mean square error (RMSE), relative error (RE), and model efficiency (EF). The results of the field measurement showed that the highest amount of capillary rise (1.6 mm) was observed in July, with the maximum evapotranspiration (400 mm) and the maximum growth of sugarcane. The lowest value (0 mm) also was observed in the months when sugarcane growth stopped, i.e., November, December, January, and February. The results of this research have shown that the UPFLOW model in the studied area has not shown suitable efficiency (based on statistical indicators) in the simulation of the upward flow in specific conditions of water-table, crop, soil, climate, and management measures (R2:0.23, MAE:8.71, RMSE:9.10, RE:180.50, EF: -136.40). Therefore, this model, in shallow water-table conditions, to accurately estimate capillary rise, requires comprehensive evaluations of various effective factors and, if possible, to modify and adjust this model in this area.