Impacts of the Flood Impoundments on Water Balances of Downstream Riparian Corridors

Abstract

Over 10,450 flood control damns have been built in 47 states. Many are nearing their design life of 50 years and have significant rehabilitation needs, the cost of which approaches over $540 million. While assessment of the engineering safety is a major consideration, little is known about the effects of these structures on downstream riparian corridors. Detailed monitoring of local water budgets conducted downstream of one structure has verified links between the flow regime of the damn and the riparian vegetation. Stream flow, soil water and transpiration rates were measured in a downstream riparian communityfor a one-year period. This monitoring showed that riparian vegetation is linked directly to both the stream and the groundwater system. The riparian zone is enhanced be low flow release from the upstream structure in which plants utilize available stream water via a groundwater pathway. This positive feedback system has direct benefits for the downstream ecosystem through increased and constant water availability.