Application of soil-water-atmosphere-plant model to assess performance of subsurface drainage system under semi-arid monsoon climate

Abstract

The Soil-Water-Atmosphere-Plant (SWAP) model was evaluated for its capability to predict groundwater table behaviour under drained conditions for a semi-arid monsoon climate in the state of Haryana (India). SWAP simulated and observed values ranging within absolute deviation of 0.17-0.18m for groundwater table, 0.87-1.07mmday-1 for drainage discharge rate and 7.8-39.4mm for cumulative drain discharge. The calibrated and validated model was used to predict excess water stress utilizing the SEW30 index, which is the sum of daily exceedances (cm) of the groundwater table depth above the depth of 30cm below the soil surface for different spacing under varying rainfall situations. The maximum annual SEW30 of 5years having all the combinations of rainfall was 297.0cmday with drains spaced at 75m, 92.7cmday with drains spaced at 50m and 15.1cmday for drains spaced at 25m. These results reveal that there would be no aeration problem with drains spaced at 25m in all the years and in years with below normal rainfall in all of the test spacing. Long-term simulations revealed that there is no residual effect of a year's rainfall pattern on the groundwater table during the next year under drained conditions. © 2013 John Wiley & Sons, Ltd.