Engineering of Controlled-Drainage Systemsby James L. Fouss, USDA, Baton Rouge, United States,
James S. Rogers, USDA, Baton Rouge, United States,
Cade E. Carter, USDA, Baton Rouge, United States,
Abstract: Soil-water management by water table control (via a dual purpose subdrainage-subirrigation system) is becoming popular in humid regions of the U.S. and Canada. Controlled-drainage is an important operational mode of this total water management system. Proper and timely control of subsurface drainage effluent can: (1) reduce duration of excess soil-water conditions in the root-zone caused by rainfall, (2) prevent overdrainage of the soil profile for more efficient use of naturally occurring rainfall, and (3) reduce the need for pumping subirrigation water. In geographic areas where a water source for subirrigation is not readily available, and for specific soils, properly designed and managed controlled-drainage systems can optimize crop production potential by efficient utilization of available rainfall. Controlled-drainage also has the potential to reduce the accumulative losses of plant nutrients carried in drainage effluent, and reduce the potential for ochre formation in the drainlines since they are submerged much of the time. Controlled-drainage is recommended for use in many humid regions rather than conventional subsurface drainage with free gravity flow or continuously pumped outlets. This paper presents an engineering design procedure for controlled-drainage systems which is based upon running selected computer models to simulate the performance of various system designs to aid in the selection of the best design (e.g., drain depth and spacing) and the best operational mode (optimum timing for control of outlet water level). The design procedure also presents a means to evaluate the advantages of and/or need for automated operation of the controlled-drainage mode. Examples of simulation results are presented.
Subject Headings: Systems engineering | Soil water | Computer models | Rain water | Subsurface drainage | Irrigation | Humidity | North America | Canada
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