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.