presented by: scott d. mcdermott 01/31/2012 ggs 656 hydrosphere a presentation of: sedimentation and...
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PRESENTED BY: SCOTT D. MCDERMOTT01/31/2012
GGS 656 HYDROSPHERE
A Presentation of: Sedimentation and
sustainability of western American reservoirs
Introduction
Sedimentation is a major threat to Reservoir sustainability as it reduces storage capacity.
Threats of Sedimentation: Reduces Storage Capacity. Negatively Impacts Recreation. Change in Wildlife Habitat. Blocks intake works for hydropower generation.
WATER RESOURCES RESEARCH, VOL. 46, W12535, 13 PP., 2010 doi:10.1029/2009WR008836
Objective
Verify popular writer’s concerns that the major reservoirs are at a threat of sedimentation within a few hundred years.
Authors in questions: T. Palmer (1986) L. Powell (2009) M. Reisner (1986)
(Official) Objectives
Determine how rapidly American reservoirs are filling with sediments
Determine spatial and temporal variations in loss of storage capacity
Calculate the reasonable life expectancies specifically for reservoirs in the interior west.
Test Sites
Western American Dams and Reservoirs
100th Meridian Arid Land “Cadillac Desert”
Methods – Calculate Sediments Filling
U.S. Geological Survey Reservoir Sedimentation Survey Information System (RESIS II)http://pubs.usgs.gov/ds/ds434/
Data used to access the sedimentation in individual reservoirs.
Provide general “trend”. Not great for finer assessments.
Distribution of reservoirs with Sedimentation Surveys in RESIS II
Circles represent original reservoir capacity.
Provide an insight of the capacity the dams provide in the test site.
Methods – Spatial Variation
Sediment Delivery RatioAll things equal: The larger the basin (downstream) the greater the internal storage of sediments
Annual Rate of Reservoir Storage Loss
Expected Life of a Reservoir
Methods – Temporal Variations
Higher erosion and sediment yields greater during periods between drought and copious convective rainfall.
Test case: Colorado River Basin Long record of sediment transport with sediment
yield from all major sub basins. Compilations from Sediment Discharge Database.
Result– Calculate Sediments Filling
Five of Six regions with the highest annual loss of storage capacity in the interior west.
Life Expectancy: Short
Results– Spatial Variation
Sediment Delivery Ratio Missouri River displays
a long life span scenario. (larger downstream areas
Colorado River is an exception.
Life Expectancy: Longer for downstream areas.
Results – Temporal Variations
Results – Temporal Variations (con’t)
Results – Temporal Variations (con’t)
Analysis Conclusion
The message that science should be sending to popular writers and managers is that [sedimentation]…for reservoirs in the interior western U.S. in general is the end is not near.
Conclusion (part 2)
Most large reservoirs have life expectancies of 200-1,000 years or more.
Appear to be sustainable parts of a regional water management system.
Sedimentation loss varied spatially and temporal.
Conclusion (part 3)
Without further dam and reservoir construction, however, it is also clear that managers will be faced with a gradual long-term decline in total storage capacity.
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