Field and Modeling Evaluation of Furrow Irrigation Hydraulic Characteristics Under Varying Furrow Lengths and Land Slopes in Clay Loam Soil

Water shortage severely restricts agricultural output in arid and semi-arid regions, rendering improved irrigation management approaches necessary. This study assessed the hydraulic behavior of furrow irrigation in non-vegetated clay loam soil, investigating the effects of different land slopes (LS) 0, 0.05, and 0.15% and furrow length (FL) 50 and 75 m. In order to do this, field tests were conducted on a privately held farm in Banha, Qalyubia Governorate, Egypt, in March 2024. The experiment utilized a split-plot design with three repetitions, and laser-based land smoothing was used to establish the desired slopes accurately. Key hydraulic variables, namely advance time, recession time, infiltration rate, application efficiency (AE), deep percolation (DP), and distribution uniformity (DU), were recorded and calculated. The field data collected were used to calibrate and validate the WinSRFR model version 5.1.1, and its predictive ability was assessed using the coefficient of determination, root mean square error, Nash–Sutcliffe efficiency, and percent bias. The results showed that shorter FL 50 m paired with steeper gradients (0.15%) achieved better hydraulic outcomes than longer ones (75 m) with gentler slopes. Statistical analysis demonstrated that furrow length exerted a highly significant influence on all hydraulic parameters ( p < 0.001). Ground slope also demonstrated a statistically meaningful influence ( p < 0.05 to p < 0.01) for selected performance indicators, and the combination of LS and FL was also significant ( p < 0.05). The most effective configuration, a 50 m FL paired with a 0.15% LS, yielded the highest DU (90%) and AE (87%) and the smallest DP (6%). The WinSRFR model showed outstanding accuracy in estimating advance times (R 2 > 0.99, RMSE < 0.55 min) and infiltration depths (R 2 > 0.98, RMSE < 1.3 mm), and reasonable performance for recession times (R 2 > 0.87, RMSE < 5.4 min). Consequently, the validated model can be confidently used to design and manage furrow irrigation in clay loam soils. These findings are anticipated to promote sustainable water consumption in farming and provide valuable input for water management policy-making.