EFFECT OF GROUND WATERTABLE ONIRRIGATION SCHEDULING MODEL

Abstract

An irrigation scheduling model was developed based on daily soil water balance which takes into account the effect of water table on irrigation water requirement for wheat crop at Mosul area for eleven years. Capillary rise of water table was estimated with Darcy's equation .Crop evapotranspiration was estimated by pan evaporation method. The model inputs are daily climatological data for eleven years at Mosul Station, soil data (total available water, field capacity, permanent wilting point, allowable percent depletion, saturated hydraulic conductivity),and crop data(root depth for wheat crop, crop coefficient).The model estimates daily and seasonal actual evapotranspiration, effective rainfall, irrigation requirement and upward capillary rise from water table. Using the model for wheat, the seasonal irrigation requirements were reduced by 40% for silt loam soil and 90% for loam soil ,avoiding crop water stress or excessive irrigation.