Off-Site Drainage Discharge Limitations and Drainage Management Options

Irrigation generally is defined as the application of water to soil for the purpose of supplying the moisture essential for plant growth. On the whole it has been highly successful. More than one third of the world's total harvest has been produced on irrigated land which amounts to only about 17 percent of the world's crop land. A common consequence of irrigation in semi-arid regions of the world is the potential development of soil salinity and/or water logging. Pure water is lost through evapotranspiration (ET) and the salts become concentrated in the soil solution. Irrigation water that is applied in excess of ET percolates and transports the excess salts below the root zone. Depending upon the geologic and hydrologic system water tables rise and can reach the root zone. If the water table gets too high an artificial drainage system must be installed to remove water and dissolved chemical constituents from the root zone.