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Overland Flow from Sloping Land: Effects of Perched Water Tables and Subsurface Drains
Author(s) -
Lowery B.,
Kling G. F.,
Vomocil J. A.
Publication year - 1982
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1982.03615995004600010018x
Subject(s) - surface runoff , hydrology (agriculture) , subsurface flow , geology , water table , environmental science , soil science , groundwater , geotechnical engineering , ecology , biology
Overland flow from fall‐planted agricultural subwatersheds in the Willamette Valley was found to be associated with ephemeral perched water tables, high antecedent soil moisture levels, and seepage zones. The transient perched water tables developed because of restrictive layers commonly found near the ground surface in most soils in the area and due to storm characteristics. The water table was also closer to the ground surface in lower landscape positions, which produced higher moisture conditions and seepage zones. The average annual precipitation for this area is about 1,000 mm with approximately 90% being received during the 9‐month period from September to May. This coincides with most of the growing season for fall‐planted small grain and grass crops in the area. Rainfall, runoff events, depth to water table, piezometric head, and matric suction data were collected from two subwatersheds for 2 years. Following this, subsurface drains were installed in a 1.4‐ha subwatershed (E4) to determine the feasibility of this management practice for reducing runoff caused by saturated soil conditions. Subsurface drains eliminated seepage areas and reduced the occurrence of an ephemeral perched water table. They also eliminated base flow from the watershed hydrograph. Runoff resulting from a surfaced water table and capillary fringe at or near the ground surface was markedly decreased, although overland flow continued to occur following rare storm events with high rainfall intensity or extremely long duration.