Modeling groundwater recharge from the lined farm canal under shallow water table condition

Field study was conducted to quantify the groundwater recharge dynamics. Experiment was conducted on a 7-year-old cement lined rectangular watercourse (width 2W = 0.6 m; constant water head ho = 0.37 m; design discharge = 0.023 m³ h⁻¹) situated at an outlet number - RD5500 L of farm canal and 25-year-old brick lined trapezoidal farm minor (surface width 2W =4.95 m; side slope = 1:1; constant water head ho = 0.79 m; design discharge = 0.840 m³ s⁻¹)passing through soil research farm Chaudhary Charan Singh, Haryana Agricultural University, Hisar. The initial water table was at 2.54 m depths from soil surface. The height of the bottom of the watercourse (H_o) from the water table was 2.43 m. A finite element flow model, HYDRUS 2D was used to simulate the drawup in observation well pressure heads during recharge from lined watercourses and farm canal under shallow water table condition (2.54 m). The physical flowregion involved a soil profile 200 m wide and 25 m deep with a canal placed at the top of soilprofile. Constant pressure head of 0.37 m and 0.79 m was given on the bottom of the canal for calibration and validation experiments. Saturated hydraulic conductivity was estimated through inverse modeling technique using the experimental pressure heads h time pairs during recharge from the lined watercourses and farm canal. Low root mean square error RMSE (0.1–0.35) and high modeling efficiency ME (97.9–99.8%) for pressure head during recharge from the lined watercourses calibrated the model successfully. High mean modeling efficiency (99.0 - 99.9%) and low root mean square error RMSE (0.05–0.36) of predicted and experimental pressurehead value validate the HYDRUS 2D model for groundwater recharge from the lined farmcanal. The model was used to project the increase in radial influencing zone with increasein hydraulic conductivity and anisotropy of the surface soil layer. Critical water logging zone increased with increasing hydraulic conductivity and anisotropy of the surface soil layer. The study suggests that HYDRUS 2D may be adopted for simulations in ground water recharge studies.