Hydrological responses on sodic soil against linearly increasing rainfall pattern

The study of hydrological responses such as surface runoff, velocity and depth variations against a rainfall pattern over a given soil type under controlled laboratory conditions can provide important data base for soil and water conservation. A rainfall pattern of linearly increasing intensity from 0 to 45 mm/hr was created for runoff and soil erosion study of sodic soil under controlled field laboratory condition. Runoff was measured for 94 min at a regular interval of 4 minutes. For 67.34 liter (100%) of rainfall amount occurred, 62.75 liter (92.48%) was collected as runoff and 5.06 liter (7.52%) as infiltration and deep percolation losses. The Gaussian Model explains the runoff hydrograph in the best way with correlation coefficient, R=0.96 and standard error, S=211.55 with a peak runoff rate of 2.71 liter/min (1.0265 mm/min) after 66 minutes of rainfall initiation. The measured runoff volume was 62.28 liter while the modeled runoff volume by the best fitting Gaussian Model was 63.58 liter showing a great match between observed and modeled runoff values. The Sinusoidal Fit Model explained explains the runoff velocity in a best way with R=0.978 and S=5.675 having a peak velocity of 68.4 cm/min after 66 minutes of rainfall initiation. A 4^th Degree Polynomial Model explained the variation of sediment load in the best way with R=0.929 and S=0.521. The sediment load in surface runoff was measured as 200.94 g (761.14 kg/ha) and modeled by Vapor Pressure was 200.435 g (759.22 kg/ha).