WaterSurface Evaporation in Reservoir

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Water-Surface Evaporationin Reservoir

• Vitoon Thititanapak
• December 1999

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Acknowledge
Dr. David G. Tarboton
Mark Winkelaar
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Objective

• To study the effect of evaporation in reservoir.
• To apply GIS technique in the analysis of the
  water-surface evaporation.

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Conceptual Map

• Theory Study
• The role of evaporation in reservoir (
  water-surface evaporation)
• The method for measuring the evaporation

• Data collection
• DEM from USGS
• RF1 from EPA
• Dam site from GIS DATA DEPOT and EPA
• Pan evaporation data from
• NOAA Technical Report NWS 33

• TOOL
• Arc View 3.0
• SINMAP
• TARDEM

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Theory study
62 of precipitation fall on the land - 97
is evapotranspiration - 3 is
open-water evaporation
Estimating Free-Water Evaporation -
Water-Balance Approach - Mass-Transfer
Approach - Energy-Balance Approach - Penman
or Combination Approach - Pan-Evaporation
Approach ( Class-A pan)
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Data collection
- DEM grid file from USGS http//edcwww.cr.usgs
.gov/doc/edchome/ndcdb/ndcdb.html
- rf1 shape file and Dam site shape file from
EPA http//www.epa.gov/OST/BASIN/
- Dam location USGS digital raster graphics
http//www.gisdatadepot.com/
- Pan evaporation data from NOAA technical
report NWS 33
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Step 1 Study area
The Albers Equal-Area projection
Middle Bear Basin
Cutler Dam
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Step 2 Add DEM grid files
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Step 3Locating Dam as outlet grid
Newton Dam
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Step 4Find water-surface area
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Step 5Calculate water-surface evaporation
Evaporation Number of cell count x cell size
x pan coefficient x Class-A pan evaporation
data
from National Oceanic and Atmospheric
Administration Technical report, Office of
Hydrology National Weather Service, June 1982
Map 4 Map of coefficients to convert Class A
pan evaporation to free water surface evaporation
for May - October
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Result
Evaporation in Cutler Dam, Utah U.S.A.
At elevation 1344.00 m
Number of cell count 13910, Cell size 30
x 30 m.
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Conclusion
We can apply GIS technique to find water-surface
area in reservoir at the design water level.
This technique is limited on GIS data (DEM
elevation grid data) to find water-surface area.
This method can apply to find the reservoir area
in the dam construction project planning.
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THE END
THANK YOU