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Evapotranspiration Data Collection Site Locations Listing and Site Models

SITE LOCATIONS AND BRIEF DESCRIPTIONS:

The number in parentheses is site/map number used in WRI-00-4217. Lat and long are latitude and longitude in degrees, minutes, and seconds. The following abbreviations are used in the comments column. SFWMD, South Florida Water Management District; ENR, test area for the Everglades Nutrient Removal Project; WCA1, Water Conservation Area 1, also known as Loxahatchee National Wildlife Refuge; WCA2, Water Conservation Area 2; WCA3, Water Conservation area 3; ENP, Everglades National Park; C111, a drainage canal.

SITE
Lat
Long
Community
Comments
Cat (1):
263910 0802432 Cattails SFWMD ENR: flow regulation
Open_enr (2):
263740 0802612 Open water SFWMD ENR: open water, flow regulation
Open_lox (3):
263120 0802011 Open water WCA1, Open water with lily pags
F4 (4):
261855 0802257 Dense sawgrass WCA2, dry part of some years
Camp23 (5):
261530 0804417 Medium sawgrass WCA3, dry part of some years
Nesrs3 (6):
254443 0803011 Medium sawgrass ENP, never dry
P33 (7):
253659 0804208 Sparse sawgrass ENP, Shark Valley, never dry
Ing (8):
252111 0803802 Sparse rushes ENP, Old Ingraham HW, dry part of year
C111 (9):
252135 0803146 Sparse sawgrass C111 area, dry part of year
L1 :
253640 0810121 Very spase rush ENP, pheriphyton heavy at times
X2 :
253240 0805753 Sparse sawgrass ENP, dry part of year
X1.5 :
253044 0805559 Thick sawgrass ENP, dry part of year

SITE MODELS:

All site models are modified Priestley-Taylor models of the following form:

Le = alpha * (delta/(delta+gamma) * A, where (equation 1)

Le is evapotranspiration expressed in latent heat (watts/meter*meter),
alpha is the Priestley_Taylor coefficient (dimenionless),
delta is the slope of the saturation vapor-pressure curve, in kilopascals per degree Kelvin,
gamma is the psychrometric constant, in kilopascals per degree Celsius, and
A is the measured available energy (sum of net solar radiation, soil heat flux, and water heat storage)

Models are developed using least-squared regression of measured Le and A data at 30-minute intervals, representing alpha as a function of water depth in feet (D) and incoming solar radiation in watts/meter*meter (Rs) as follows:

alpha = C0 + C1 * D + C2 * Rs + C3 * Rs * Rs

The regression coefficients C0, C1, C2, and C3 are given in the table below, together with the coefficient of determination (R^2), and the coefficient of variation (CV), the standard error or regression, in percent of mean Le). The coefficient C3 is in scientific notation, where "E" represents 10 raised to the power indicated by the following digits.

The site models listed here were used to calculate Et for intervals where input data did not pass all screening criteria.

Site
Period
C0
C1
C2
C3
R^2
CV
Cat
1996-97
1.060
0.0161
-0.000574
1.460E-07
0.73
52
Open_enr
1996-97
1.157
0.0150
0.000078
-1.860E-07
0.85
34
Open_lox
1996-97
1.071
0.0364
0.000341
-3.150E-07
0.95
19
F4
1996-97
1.322
0.0618
-0.001142
4.620E-07
0.90
32
F4
1998-99
1.488
0.0572
-0.001533
8.049E-07
0.87
31
Camp23
1996-97
1.182
0.1072
-0.001036
5.760E-07
0.89
27
Nesrs3
1996-97
0.959
0.1029
-0.000651
3.970E-07
0.90
31
P33
1996-97
1.125
0.0846
-0.000935
6.300E-07
0.89
23
P33
1998-00
1.249
0.0662
-0.001418
8.754E-07
0.74
38
P33
2001-03
1.200
0.0610
-0.001055
0.201E-07
0.9
27
Ing
1996-97
1.013
0.1884
-0.000574
1.730E-07
0.89
33
Ing
1998-00
1.167
0.1562
-0.000774
0.238E-07
0.94
21
Ing
2001-03
1.148
0.1369
-0.000763
0.803E-07
0.92
27
C111
1997
1.080
0.2052
-0.000697
3.110E-07
0.95
23
L1
2001-03
0.958
0.1660
-0.00005
-2.200E-08
0.93
22
X2
2001-03
1.076
0.1296
-0.000673
3.949E-07
0.87
27
X1.5
2002-03
1.286
0.0844
-0.001631
.002E-06
0.81
32

PERFORMANCE OF REGIONAL MODELS GIVEN IN WRI 00-4217:

The regional models of alpha and A described in WRI 00-4217 were developed using data for 1996-97 from 9 sites. The regional model for estimating alpha is:

alpha = C0 + C1 * D + C2 * D * D + C3 * Rs + C4 * Rs * Rs (equation 2)

where C0 = 1.1263, C1 = 0.1156, C2 = -0.0271, C3 = -0.000821, and C4 = 3.95e-7 for vegetated sites.

The regional model for estimating available energy is:

A = C0 + C1 * Rs + C2 * (709.5 * D * (Tair-T2.5) (equation 3)

where C0 = 5.171, C1 = 0.2165, and C2 = 0.0654 for vegetated sites, T2.5 is the mean air temperature for the previous 2.5 hours (Celsius) and Tair is the mean air temperature for the previous 15 minutes (Celsius).

Estimates of latent heat can be made if available energy measurements are available by using equation (2) to estimate alpha for use with equation (1). If no available energy data are available, the available energy can be estimated using equation (3). Using the estimated available energy and the estimated alpha in equation (1) provides a method of estimating latent heat from water depth, solar intensity, and air temperature data.

The models for vegetated sites were tested using the additional data for 1998 - 2003, both at sites used to develop the regional models and at other sites not used in model development. The comparison between measured and estimated et is given in the table below, where Et is the measured Et sum (inches), Rm1 is the estimated Et sum obtained from measured A and alpha estimated from equation (2), Rm2 is the estimated Et sum from alpha estimated from equation (2) and A estimated from equation (3), dif1 is the difference between measured Et and Rm1, dif2 is the difference between measured Et and Rm2, and Yrpct is the fraction (in percent) of the year with data. All Et sums are normalized to a full year of data. Thus for some years (for example 1999 at F4) Et data and data necessary for estimating Et were only measured for about 8 months (63.3 percent of the year), and the averages of the measured Et values were used to estimate the totals for the year.

Site
Year
Et
Rm1
Rm2
dif 1
dif 2
Yrpct
F4
1996
47.2
45.6
46.5
1.6
0.7
98.3
1997
45.3
43.1
44.6
2.2
0.7
99.9
1998
53.6
47.2
51.2
6.4
2.4
90.1
1999
48.8
43.8
46.7
5.0
2.1
63.3
Nesrs3
1996
48.2
46.9
47.9
1.3
0.3
99.7
1997
46.2
47.2
45.9
-1.0
0.3
100.0
1998
45.2
51.4
54.4
-6.2
-9.2
65.3
P33
1996
52.4
50.0
48.1
2.4
4.3
100.0
1997
50.1
48.2
47.1
1.9
3.0
99.6
1998
50.6
49.8
52.8
0.8
-2.1
99.8
1999
48.3
47.9
51.1
0.4
-2.8
98.8
2000
48.7
48.9
50.4
-0.2
-1.7
91.7
2001
41.2
40.4
44.4
0.8
-3.2
99.1
2002
43.5
45.0
46.8
-1.5
-3.4
96.7
2003
49.2
50.0
48.8
-0.7
0.5
82.9
Ing
1996
43.3
41.0
39.2
2.3
4.1
99.6
1997
43.5
40.3
40.2
3.2
3.3
97.4
1998
47.5
42.0
42.7
5.5
4.8
100.0
1999
44.3
38.8
40.7
5.5
3.6
93.3
2000
45.2
41.6
42.1
3.6
3.1
91.4
2001
40.2
35.4
38.1
4.8
2.1
99.9
2002
43.3
38.3
41.3
5.0
2.0
96.9
2003
43.6
42.4
43.3
1.2
0.2
74.8
C111
1997
43.3
42.3
40.5
1.0
2.8
95.3
1998
42.9
42.4
45.4
0.5
-2.5
95.4
L1
2001
48.4
44.4
43.1
4.0
5.3
96.9
2002
51.5
45.6
45.4
5.8
6.0
99.3
2003
57.7
49.1
48.3
8.5
9.3
83.3
X2
2001
49.2
45.3
43.9
3.9
5.3
100.0
2002
50.5
47.4
45.5
3.1
5.0
100.0
2003
56.8
51.5
48.9
5.3
7.9
83.3
X1.5
2002
47.5
47.8
45.1
-0.3
2.4
69.5
2003
49.3
50.7
47.1
-1.3
2.3
74.8
Max
 
57.7
51.5
54.4
8.5
9.3
 
Min
 
40.2
35.4
38.1
-6.2
-9.2
 
Mean
 
47.5
45.2
45.7
2.3
1.8
 

ERRATA

The following errors are noted for printed copies of WRI 00-4217:

Page 18, Table 5: The coefficient C2 for Site 1 should be -0.000574.

Page 23, Equation 14: The equation should be: W = 709.5 S (T2.5 - Tair). This formulation is consistent with the formulation of the energy budget given on page 8, equation 1, in which an increase in water temperature during a computation interval represents an increase in the water-heat storage term (W), resulting in a lower amount of available energy than if water temperature remained constant.

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Last updated: 15 January, 2013 @ 12:42 PM(TJE)