دانلود 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 0.17–0.18 m for groundwater table, 0.87–1.07 mmday¹ for drainage discharge rate and 7.8–39.4 mm 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 30 cm below the soil surface for different spacing under varying rainfall situations. The maximum annual SEW30 of 5 years having all the combinations of rainfall was 297.0 cm day with drains spaced at 75 m, 92.7 cm day with drains spaced at 50 m and 15.1cm day for drains spaced at 25 m. These results reveal that there would be no aeration problem with drains spaced at 25 m 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.