DRAINAGE DESIGN FOR WATER-QUALITY MANAGEMENT - OVERVIEW

Drainage design for water quality management in irrigated areas requir es use of hydrodynamic models that delineate flow paths of subsurface water moving to drains. Use of only traditional drainage design equati ons for protection against water logging and salinization are inadequa te for water quality management; these equations should be coupled wit h mechanistic models that account for transport and chemical changes i n the vadose and saturated zones that replace those associated with a leaching fraction, or requirement concepts. Drainage designs should no w make use of hydrodynamic and chemical models that simulate flow and transport of water and chemical constituents from infiltration to drai nage discharge. Management should be able to manipulate the models pri or to implementing steps aimed at controlling the quantity and quality of drainage discharge.