A FIELD APPROACH TO ESTIMATION OF HUMID AREA DRAINAGE COEFFICIENTS

On a 20 ha area of the College of Agricultural Sciences, Sari, Iran, s elected to represent a large area requiring drainage, an experiment wa s performed to estimate the subsurface drainage coefficient. By measur ement of water table depths, hydraulic conductivities, and impermeable layer depth, the drain discharge rates were calculated, assuming a st eady-state condition. The design drain discharge rate or drainage coef ficient was estimated to be 2.2 mm day(-1). The coefficient estimated was within the range of the local and some published values.