Simulation of Soil Salinity using DRAINMOD-S Model under Subsurface Drainage System in Arid and Semi-arid Regions of Punjab, India

Abstract

Water management simulation model DRAINMOD-S was calibrated (1995-96) and validated (1997) using 3-year experimental field data (1995-1997) from the installed subsurface drainage system at 1.8 m drain depth with 40, 60, and 80 m drain spacing at Golewala watershed, Faridkot, Punjab, India. Sensitivity analysis of the model parameters revealed that lateral saturated hydraulic conductivity, drain depth, and drain spacing are the most effective parameters in changing the model output. The root means square error, efficiency, and coefficient of determination between observed and simulated soil salinity ranged from 0.01to 0.06 dS.m-1, 0.647 to 0.834 dS.m-1, and 0.957 to 0.999 dS.m-1 for three drain spacings (40, 60, and 80 m), respectively, during calibration and validation period. The calibrated and validated model was used to predict the soil salinity (EC) for five consecutive years (1998-2003). The average soil salinity of root zone (300-600 mm), (600-900 mm), and (900-1200 mm) decreased from January 1998 to December 2003. The predicted values of soil salinity were found to decrease from 2.23, 2.34, and 1.92 dS.m-1 to 1.68 dS.m-1, 1.70, and 1.42 dS.m-1 for 40 m drain spacing at root zone depth of 300-600 mm, 600-900 mm, and 900-1200 mm, respectively. Similarly, the salinity values for the same period and root zone depth were found to decrease from 2.20, 2.31, and 1.90 dS.m-1 to 1.75,1.78, and 1.74 dS.m-1 for 60 m drain spacing; and 2.21, 2.31, and 1.93 dS.m-1 to 1.80,1.82, and 1.48 dS.m-1 for 80 m drain spacing, respectively, at the end of five years. DRAINMOD-S model was reliably applicable for predicting soil salinity under sub-surface drainage system in arid and semi-arid region of Punjab, India