Drain Depth and Subirrigation in Layered Soils

by Yau K. Tang, Research Assoc.; Dept. of Biological and Agricultural Engrg., North Carolina State Univ., Raleigh, N.C.,
R. Wayne Skaggs, Prof.; Dept. of Biological and Agricultural Engrg., North Carolina State Univ., Raleigh, N.C.,


Serial Information: Journal of the Irrigation and Drainage Division, 1980, Vol. 106, Issue 2, Pg. 113-122


Document Type: Journal Paper

Abstract: The Richards equation for two-dimensional saturated—unsaturated water movement was solved for subirrigation from buried drains in layered soils. Numerical solutions were obtained for soils that have subsurface layers with high hydraulic conductivities. Results showed that increasing the drain depth so that it approaches or penetrates a high conductivity bottom layer will reduce head loss due to convergence near the drain. Deeper drains significantly increased subirrigation rates for deep soils and narrow drain spacings but had a smaller effect for shallow profiles and wide spacings. The response to deeper drains also increased with hydraulic conductivity and thickness of the bottom layer. The results showed that the drain should be placed at the interface of the high conductivity layer when possible. Further increases in the depth of the drain did not result in significant increases in subirrigation rate or water table rise.

Subject Headings: Drainage | Irrigation | Layered soils | Saturated soils | Hydraulic conductivity | Spacing | Water management | Soil water

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