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In humid regions with flat topography and poor natural drainage, the installation of subsurface drains is a well-established method to lower the water table and improve the aeration in the root zone to promote better crop production. The diameters and positions of subsurface drain pipes have commonly been designed with some traditionally accepted values of maximum drainage rate (or drainage coefficient) with no observations, or calculations, of the water table levels to be expected in the field or the region. Some agronomic observations indicate that crop losses due to poor drainage are associated with the time of occurrence of high water tables and the number of days the water table remains close to the soil surface within the root zone. It seems evident that the dates and durations of high water tables should be associated with the precipitation and evapotranspiration in a region, and with parameters affecting soil drainability, such as: hydraulic conductivity and drainable porosity, and hydraulic capacity, entry resistance and depth of subsurface drain pipes. These are features which change from one climatic region to another and from one soil type to another.
a model to predict water table depths for flat lands
Broughton, R.S. and N. Foroud 1978. A MODEL TO PREDICT WATER TABLE DEPTHS FOR FLAT LANDS. Canadian Agricultural Engineering 20(2):81-86.
81 - 86