evaporation in lake travis
DESCRIPTION
Evaporation in Lake Travis. Wil Sarchet Surface Water Hydrology. | Introduction |. Lake Travis. Northwest of Austin Formed in 1942 with the construction of the Mansfield Dam Average water volume of 1.13 million acre-feet Depths up to 190 feet deep A water source for Austin. - PowerPoint PPT PresentationTRANSCRIPT
Evaporation in Lake TravisEvaporation in Lake Travis
Wil SarchetSurface Water Hydrology
|Introduction| Northwest of Austin Formed in 1942 with the construction of the Mansfield Dam Average water volume of 1.13 million acre-feet Depths up to 190 feet deep A water source for Austin
Lake Travis
|Objectives| Examine the relationships between evaporation and precipitation, temperature, radiation, and time in Lake Travis Evaluate the accuracy of the available data sources for evaporation in Lake Travis
|Data Collection|
NCDC Temperature
Austin-Mueller Airport
TSRDB Solar Radiation
University of Texas Campus
US Army Corps of Engineers Lake Evaporation
Lake Lavon, Collin County, Texas
|Data Collection|TWDB
TWDB Evaporation/Precipitation
One degree quadrangles (111.3 km quadrangles)
Monthly Gross Lake Evaporation Rates Computed by a GIS based program ThEvap Based off of TWDB and National Weather Service collection sites Pan coefficients reflect both spatial and seasonal variation
|Data Collection|NARR
North American Regional Reanalysis Result of the National Centers for Environmental Prediction (NCEP) Eta Model 32 km scale Improved by the Regional Data Assimilation Systems (RDAS) Surface Evaporation & Potential Evaporation Data
Potential Evaporation Potential water vapor capacity of the air Amount of evaporation that would occur if a sufficient water source was available
1999-2004 Lake Travis Surface Evaporation
0
1
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7
8
9
January-99 January-00 January-01 January-02 January-03 January-04
Date
Ev
ap
ora
tio
n (
in.)
1954-2004 Lake Travis Surface Evaporation
0
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18
January-54 January-64 January-74 January-84 January-94 January-04
Date
Eva
po
rati
on
(in
.)|Results|
5 year and Long Term
y = -0.0000x + 5.0411
TWDB
|Results|Diurnal Variation
February 1, 2000
0
0.5
1
1.5
2
2.5
3
0 4 8 12 16 20 24
Tim e
Mo
nth
ly E
vap
ora
tio
n (
in.)
Evaporation Potential Evaporation
August 1, 2000
0
5
10
15
20
25
0 4 8 12 16 20 24
Tim e
Mo
nth
ly E
vap
ora
tio
n (
in.)
Evaporation Potential Evaporation
WinterPotential evaporation is an average of 2.9 times greater than evaporation with a max of 3.9 times greater
SummerPotential evaporation is an average of 3.5 times greater than evaporation with a max of 5.5 times greater
ComparisonThe maximum value of potential evaporation is 7.4 times greater in summer than in winter
The maximum value of evaporation is 3.3 times greater in summer than in winter
NARR
|Results|Temperature and Radiation
1999-2004 Lake Travis Average Temperature and Evaporation
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30
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50
60
70
80
90
100
January-99 January-00 January-01 January-02 January-03 January-04
Date
Tem
per
atu
re (
oF
)
0
1
2
3
4
5
6
7
8
9
Eva
po
rati
on
(in
.)
Temperature Evaporation
TWDB/NCDC/TSRDB
1999-2004 Lake Travis Average Radiation and Evaporation
0
50
100
150
200
250
300
350
January-99 January-00 January-01 January-02 January-03 January-04
Date
Rad
iati
on
(W
/m2)
0
1
2
3
4
5
6
7
8
9
Eva
po
rati
on
(in
.)
Radiation Evaporation
Energy Balance Method Er = 0.0353Rn
|Results|Precipitation
1999-2004 Lake Travis Surface Evaporation and Precipitation
0
1
2
3
4
5
6
7
8
9
January-99 January-00 January-01 January-02 January-03 January-04
Date
Ev
ap
ora
tio
n (
in.)
0
2
4
6
8
10
12
Pre
cip
itat
ion
(in
.)
TWDB
|Results|Lake Travis Evaporation Comparison
Comparison of Evaporation Data
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14
16
Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04
Date
Eva
po
rati
on
(in
.)
TWDB NARR NARR Potential TSRDB Predicted
“Evaporation estimates are notoriously uncertain”(Ruiz-Barradas and Nigam 2005)
|Results|Lake Lavon Evaporation Comparison
Army Corps/NARR PotentialAvg. = 0.885St. Dev. = 0.127
Army Corps/TWDBAvg. = 1.148St. Dev. = 0.222
NARR Potential Adjustedp value = 0.172
Comparison of Evaporation Data for Lake Lavon
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2
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10
12
14
16
Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00
Month
Ev
ap
ora
tio
n (
in.)
TWDB NARR NARR Potential Arm y Corps
Comparison of Evaporation Data for Lake Lavon
0
2
4
6
8
10
12
14
16
Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00
Month
Ev
ap
ora
tio
n (
in.)
TWDB NARR NARR Potential Arm y Corps NARR Potential Adjus ted
|Results|Lake Travis Evaporation
Comparison
Comparison of Evaporation Data
0
2
4
6
8
10
12
14
16
Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04
Date
Eva
po
rati
on
(in
.)
TWDB NARR NARR Potential TSRDB Predicted NARR Potential Predicted
Comparison of Evaporation Data
0
2
4
6
8
10
12
14
16
Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00
Date
Eva
po
rati
on
(in
.)
TWDB NARR NARR Potential TSRDB Predicted NARR Potential Predicted
|Conclusions| Significant seasonal and diurnal variation in Lake Travis evaporation data
Data supports the use of the Energy Balance Method as a valid way to predict evaporation
There is an inconsistency amongst data sources for Lake Travis evaporation
|Questions|