Sedimentation and sustainability of western American reservoirs

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PRESENTED BY: SCOTT D. MCDERMOTT

01/31/2012

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



100
th

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 Ratio

All 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.