ARS | Publication request: Climate variations, soil conservation and reservoir sedimentation

Submitted to: Federal Interagency Hydrologic Modeling Conference
Publication Type: Proceedings
Publication Acceptance Date: May 15, 2010
Publication Date: June 27, 2010
Citation: Garbrecht, J.D. 2010. Climate variations, soil conservation and reservoir sedimentation. Federal Interagency Hydrologic Modeling Conference, June 27- July 1, 2010, Las Vegas, NV. 2010 CD-ROM.

Interpretive Summary: Reservoir sedimentation is defined as the deposition and gradual accumulation of sediments supplied by upstream reservoir inflows. When reservoir sedimentation reaches and exceeds the storage capacity allocated for sediment retention, then any new sediment deposition begins to encroach upon reservoir storage capacities provided for other purposes. The rate of reservoir sedimentation and time of encroachment on other allocated storage capacities can be delayed by controlling upstream soil erosion and sediment delivery to the reservoir. The integrated effects of upstream soil conservation and a wetter climate on reservoir sedimentation were investigated for the Fort Cobb Reservoir watershed in west-central Oklahoma. It was found that the wetter climate since the mid-1980s led to an increase in soil erosion and downstream sediment yield that offset the reduction in sediment yield achieved by extensive soil conservation practices. Additional conservation efforts that reduce sediment yield by another 30%, as well as a drier climate, would be needed to slow the reservoir sedimentation rate enough to where allocated sediment storage capacity is not filled prematurely. It was further concluded that since the effects of conservation practices and impacts of a wetter or drier climate were of similar in magnitude, both climate variations and conservation practices should be taken into consideration when projecting the potential impacts of conservation programs on downstream reservoir sedimentation.

Technical Abstract: The integrated effects of soil conservation and a wetter climate on reservoir sedimentation were investigated for the Fort Cobb Reservoir watershed in west-central Oklahoma. A 12% wetter climate since the mid-1980s led to an increase in soil erosion and downstream sediment yield that offset the reduction in sediment yield achieved by extensive soil conservation practices. Additional conservation efforts that reduce sediment yield by another 30%, as well as a drier climate, would be needed to slow the reservoir sedimentation rate enough to where the storage capacity allocated for sediment retention is not filled prematurely. Findings indicated that conservation benefits and impacts of climate variations had similar magnitude and offset one another. Both should be taken into consideration when projecting the potential impacts of conservation programs on downstream reservoir sedimentation.