Estimation of Evaporation From Reservoirs

Engineer Research and Development Center

US Army Corpsof Engineers

Estimation of Evaporation From Reservoirs

Kevin Stamm, Kellie Bergman, Tim Temeyer

Water Management, Omaha DistrictDr. Steven F. Daly

ERDC/CRRELSecond Annual Missouri Basin River

Forecaster’s Meeting15-17 November 2010



Overview

• Results from a long term, relatively low cost study to estimate evaporation from reservoirs in the Omaha District and NWD-RCC

• Requirements: - Physically based - No new instrumentation installed in field- Remove existing evaporation pans- Work within the CWMS framework





Evaporation EstimationTwo Processes:• Bulk flux evaporation estimation • 1-D temperature heat budget to

estimate vertical temperature profile in reservoir

Using:• Met data available through Internet

from NWS or estimated• Reservoir geometry data



Bulk-Flux Algorithm

• Estimate reservoir surface roughness based on wind speed

• Assume neutral stratification in air• Estimate transfer coefficients• Calculate fluxes• Estimate air stratification







Surface Temperature is Key

Surface temperature has a strong influence on the evaporation flux because the saturation humidity immediately above the water is a strong function of the water temperature



1-D temperature heat budget to estimate surface temperature

• Heat transfer through surface with atmosphere

• Distribution of heat throughout depth of reservoir: 1-D



Flow Through times



Heat transfer through surface with atmosphere

• Sensible heat flux• Latent heat flux• Solar radiation• Long wave radiation in and out - Both solar and long wave require

information on cloud cover – NWS METAR



Distribution of heat throughout depth of reservoir: 1-D

• Solar Radiation penetration• Thermal diffusion• Mixing due to Wind• Mixing due to Potential Energy



Solar Radiation penetration

• Majority of solar radiation is absorbed at surface

• But the remaining solar energy can penetrate to depth and be absorbed below the surface

• The clearer the water the deeper the penetration

• Measured using Secchi disk



Wind and Density Mixing

• Density mixing cause denser water to mix with less dense water below. (Primarily in the fall)

• Wind mixing uses the work of the wind blowing over the surface to mix denser water from below with less dense water above (Anytime the wind blows.)

• Algorithms are available for both





Elev

(ft)

54225424542654285430543254345436

2000 2001 2002 2003 2004 2005 2006 20072000 2001 2002 2003 2004 2005 2006 2007

Flow

(cfs

)

0100200300400500600700800900

1000

CHFI-CHATFIELD DAM-SOUTH PLATTE 0168 ELEV CHFI 0168 FLOW-RES INCHFI 0168 FLOW-RES OUT

TriLakes Chatfield



2000 2001 2002 2003 2004 2005 2006 20072000 2001 2002 2003 2004 2005 2006 2007

C

-10

-5

0

5

10

15

20

25

EVAP OBS WT1 EVAP CALC WT1

TriLakes Chatfield





Elev

(ft)

1445145014551460146514701475

2000 2001 2002 2003 2004 2005 20062000 2001 2002 2003 2004 2005 2006

Flow

(cfs

)

0200400600800

100012001400

PIST-PIPESTEM DAM-PIPESTEM 0168 ELEV PIST 0168 FLOW-RES INPIST 0168 FLOW-RES OUT

Pipestem



2000 2001 2002 2003 2004 2005 2006 20071999 2000 2001 2002 2003 2004 2005 2006 2007

C

-5

0

5

10

15

20

25

30

35

EVAP OBS WT1 EVAP CALC WT1

Pipestem



2000 2001 2002 2003 2004 2005 2006 20072000 2001 2002 2003 2004 2005 2006 2007

MM

/DAY

0

5

10

15

20

25

30

EVAP CALC EVAP

Pipestem



Oahe



Oahe



Application

• Operating in Omaha District CWMS• Each reservoir is assigned a NWS

station• Decode NWS METAR messages• CWMS runs model once each day

for each reservoir• Stores evap. and water temperature

profile for next run



Project St. METAR Station

Multipurpose Pool

(ft msl)

Volume (ac-ft)

Surface Area (ac)

Avg Reservoir Depth

(ft)

Inflow (cfs)

Flow though Time (days)

wind shelter coeff

Audubon ND KBIS Bear Creek Lake CO KAPA 5558.00 1974.00 107.00 18.45 33.53 29.68 0.12

Big Bend SD KPIR 1420.00 1.621E+06 5.701E+04 28.44 18707.73 43.70 1.00 Bowman-Haley ND KBPP 2753.00 15857.00 1493.00 9.0 29.97 266.75 ? Chatfield Lake CO KAPA 5432.00 27428.00 1429.00 19.19 131.87 104.87 0.82

Cherry Creek L. CO KAPA 5550.00 12805.00 847.00 15.12 23.53 274.38 0.64 Coldbrook SD KCUT 3585.00 520.00 36.00 14.44 1.09 241.63 0.04

Cottonwood Sprs. SD KCUT 3875.00 655.00 41.00 15.98 0.06 5497.34 0.05 Fort Peck MT KGGW 2231.00 1.437E+07 2.037E+05 70.55 6917.12 1047.52 1.00

Fort Randall SD KYKN/K9V9 1351.00 3.202E+06 7.871E+04 40.68 2.025E+04 79.70 1.00 Garrison ND KBIS/KISN 1836.00 1.765E+07 3.004E+05 58.77 1.737E+04 512.30 1.00

Gavins Point SD KYKN 1207.00 3.837E+05 2.669E+04 14.38 2.214E+04 8.74 1.00 Oahe ND/SD KPIR/KMBG 1602.00 1.719E+07 2.880E+05 59.68 1.944E+04 445.74 1.00

Papio 11 NE KOMA 1121.00 3262.00 377.00 8.65 7.81 210.55 0.37 Papio 16 NE KOMA 1104.00 1285.00 125.00 10.28 1.87 346.32 0.14 Papio 18 NE KOMA 1110.00 3037.00 259.00 11.73 4.73 323.76 0.27 Papio 20 NE KOMA 1095.80 2682.00 239.00 11.22 1.78 760.62 0.25 Pipestem ND KJMS 1442.50 8944.00 840.00 10.65 69.91 64.50 0.64

Salt Creek 10 NE KLNK 1244.90 1627.00 211.00 7.71 6.85 119.75 0.23 Salt Creek 12 NE KLNK 1232.90 1912.00 217.00 8.81 2.14 450.76 0.23 Salt Creek 13 NE KLNK 1341.00 2161.00 236.00 9.16 2.36 461.92 0.25 Salt Creek 14 NE KLNK 1244.30 7813.00 739.00 10.57 4.75 830.11 0.59 Salt Creek 17 NE KLNK 1242.40 783.00 123.00 6.37 6.41 61.61 0.14 Salt Creek 18 NE KLNK 1284.00 5088.00 1847.00 2.75 12.84 199.83 0.89 Salt Creek 2 NE KLNK 1335.00 1100.00 162.00 6.79 2.32 238.96 0.18 Salt Creek 4 NE KLNK 1307.40 2531.00 309.00 8.19 5.79 220.25 0.31 Salt Creek 8 NE KLNK 1287.80 2053.00 277.00 7.41 4.56 226.93 0.29 Salt Creek 9 NE KLNK 1271.10 1451.00 195.00 7.44 3.99 183.34 0.21



Further Work

• Resolve CWMS problems• Ice cover model• Convective heat transfer (inflow

and outflow)

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Estimation of Evaporation From Reservoirs

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