CADDIS Volume 2: Sources, Stressors & Responses
Water withdrawals & transfers
Water withdrawals and transfers associated with meeting urban water demand can have significant repercussions for stream systems. Their effects depend upon many factors, including:
Where the water comes fromWhere the water goes
- Surface water vs. groundwater
- Within catchment vs. imported from another catchment (i.e., water transfers)
- Direct intake from channel vs. from water supply reservoir
- Small vs. large streams
- Within catchment vs. exported to another catchment (i.e., water transfers)
- Small vs. large streams
Freeman & Marcinek (2006) examined how surface water withdrawals for municipal water supplies affected stream fish assemblages in the Georgia Piedmont, using a withdrawal index that represented the amount of water withdrawn on a monthly average basis, relative to the 7-day, 10-year recurrence low flow in those streams (7Q10). They found that:
- Richness of fluvial specialist fishes (e.g., many minnows and darters) decreased as the amount of water withdrawn increased (Fig 36).
- This decrease generally occurred when permitted withdrawal rates exceeded approximately 0.5-1 7Q10-equivalent of water (Fig 36).
- As water withdrawals increased, so did the probability that sites would be classified as impaired based on their Index of Biotic Integrity scores.
- The type of water intake also was important, as reservoir presence (along with withdrawal rate and drainage area) were significant predictors of fluvial specialist richness.
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A New Orleans pump station that withdraws water from the Mississippi River and transfers it to a nearby treatment facility (left), and an intake structure for a water supply plant on the Duck River, TN (right).
Courtesy of Charlie Brenner (left) and USGS (right).
Courtesy of Charlie Brenner (left) and USGS (right).
Figure 36. Richness estimates for (A) fluvial specialist and (B) habitat generalist fishes vs. water withdrawal index values [ln(permitted monthly average withdrawal/7Q10)]. Squares indicate sites where water intake was directly from channel; triangles indicate sites directly downstream from water supply reservoirs. Data were collected in 28 Georgia streams used for municipal water supplies, 2001-2003.
From Freeman MC & Marcinek PA. 2006. Fish assemblage responses to water withdrawals and water supply reservoirs in Piedmont streams. Environmental Management 38(3):435-450. Reprinted with permission from Springer.
From Freeman MC & Marcinek PA. 2006. Fish assemblage responses to water withdrawals and water supply reservoirs in Piedmont streams. Environmental Management 38(3):435-450. Reprinted with permission from Springer.