Pond Evaporation Calculation

4/19/26

Weather Station Data provided by Northern Colorado Water Conservancy District

See Weather Station Location Map at:

http://www.northernwater.org/WaterConservation/WeatherandETData.aspx

Notes:

Current month reflects values through "Reference Date".

Pond Evap. calculated per recent Division 1 Water Court decree language:

Lower South Platte Home Page

Gross Pond = .84(Alfalfa ETr)

Pond Evaporation Reports Main Menu

Net Pond = .84(Alfalfa ETr) - .7(Total Precip)

Alfalfa reference ETr computed by Standard ASCE equation from daily weather data.

Winter pond evap. is a reference for unfrozen ponds.

For Growing Degree Days:

Tmax = 86° F, Tmin = 50° F and Tbase = 50° F

Totals

Weather Station

2026

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

or Avg.

Ovid

Avg. Temp ° F

29.62

39.26

48.5

49.99

#N/A

41.84

Ref date as of 4/18/2026

Total Precip "

0.08

0.04

0.21

0.23

#N/A

0.56

Site Type: Fully irrigated

Total Alfalfa ETr "

3.76

5.14

4.34

#N/A

21.24

Total Growing Degee Days from March 1

289

150

#N/A

439

Gross Pond Evap

Total "

3.16

4.32

6.72

3.65

#N/A

17.85

Net Pond Evap

Total "

3.1

4.29

6.57

3.48

#N/A

17.44

Crook

Avg. Temp ° F

29.45

39.1

48.58

50.34

#N/A

41.87

Ref date as of 4/18/2026

Total Precip "

0.05

0.07

0.3

0.33

#N/A

0.75

Site Type: Fully irrigated

Total Alfalfa ETr "

3.89

5.39

8.12

4.7

#N/A

22.1

Total Growing Degee Days from March 1

295

154

#N/A

449

Gross Pond Evap

Inch

3.27

4.53

6.82

3.95

#N/A

18.57

Net Pond Evap

Inch

3.23

4.48

6.61

3.72

#N/A

18.04

Sterling

Avg. Temp ° F

29.15

38.83

48.75

49.83

#N/A

41.64

Ref date as of 4/18/2026

Total Precip "

0.04

0.12

0.46

0.34

#N/A

0.96

Site Type: Fully irrigated

Total Alfalfa ETr "

3.44

4.86

7.67

4.42

#N/A

20.39

Total Growing Degee Days from March 1

297

156

#N/A

453

Gross Pond Evap

Inch

2.89

4.08

6.44

3.71

#N/A

17.12

Net Pond Evap

Inch

2.86

6.12

3.47

#N/A

16.45

Brush

Avg. Temp ° F

28.91

38.31

48.55

48.96

#N/A

41.18

Ref date as of 4/18/2026

Total Precip "

0.29

0.24

0.81

0.14

#N/A

1.48

Site Type: Fully irrigated

Total Alfalfa ETr "

3.38

4.79

7.13

4.18

#N/A

19.48

Total Growing Degee Days from March 1

297

159

#N/A

456

Gross Pond Evap

Inch

2.84

4.02

5.99

3.51

#N/A

16.36

Net Pond Evap

Inch

2.64

3.86

5.42

3.41

#N/A

15.33

Fort Morgan

Avg. Temp ° F

29.9

39.5

49.46

50.05

#N/A

42.23

Ref date as of 4/18/2026

Total Precip "

0.09

0.16

0.83

0.22

#N/A

1.3

Site Type: Fully irrigated

Total Alfalfa ETr "

3.14

4.18

6.43

3.76

#N/A

17.51

Total Growing Degee Days from March 1

293

157

#N/A

450

Gross Pond Evap

Inch

2.64

3.51

5.4

3.16

#N/A

14.71

Net Pond Evap

Inch

2.57

3.4

4.82

#N/A

13.79

Wiggins

Avg. Temp ° F

38.62

49.33

49.52

#N/A

41.62

Ref date as of 4/18/2026

Total Precip "

0.05

0.13

0.76

0.31

#N/A

1.25

Site Type: Fully irrigated

Total Alfalfa ETr "

3.44

4.71

7.23

4.38

#N/A

19.76

Total Growing Degee Days from March 1

294

159

#N/A

453

Gross Pond Evap

Inch

2.89

3.96

6.07

3.68

#N/A

16.6

Net Pond Evap

Inch

2.85

3.87

5.54

3.46

#N/A

15.72

Fort Collins East

Avg. Temp ° F

31.71

39.74

51.07

50.46

#N/A

43.25

Ref date as of 4/18/2026

Total Precip "

0.32

0.17

0.03

#N/A

0.52

Site Type: Fully irrigated

Total Alfalfa ETr "

3.52

4.6

7.51

4.45

#N/A

20.08

Total Growing Degee Days from March 1

290

153

#N/A

443

Gross Pond Evap

Inch

2.96

3.86

6.31

3.74

#N/A

16.87

Net Pond Evap

Inch

2.73

3.86

6.19

3.72

#N/A

16.5

Eaton

Avg. Temp ° F

30.46

38.92

49.86

49.3

#N/A

42.14

Ref date as of 4/18/2026

Total Precip "

0.26

0.05

0.59

0.08

#N/A

0.98

Site Type: Fully irrigated

Total Alfalfa ETr "

3.6

4.69

7.38

4.39

#N/A

20.06

Total Growing Degee Days from March 1

285

143

#N/A

428

Gross Pond Evap

Inch

3.02

3.94

6.2

3.69

#N/A

16.85

Net Pond Evap

Inch

2.84

3.9

5.79

3.63

#N/A

16.16

Johnsons Corner

Avg. Temp ° F

33.15

43.11

52.56

50.77

#N/A

44.9

Ref date as of 4/18/2026

Total Precip "

0.32

0.62

0.11

#N/A

1.05

Site Type: Fully irrigated

Total Alfalfa ETr "

2.89

4.31

6.4

3.87

#N/A

17.47

Total Growing Degee Days from March 1

286

143

#N/A

429

Gross Pond Evap

Inch

2.43

3.62

5.38

3.25

#N/A

14.68

Net Pond Evap

Inch

2.2

3.62

4.94

3.17

#N/A

13.93

Gilcrest

Avg. Temp ° F

30.45

39.87

50.75

50.84

#N/A

42.98

Ref date as of 4/18/2026

Total Precip "

0.17

0.05

0.45

0.08

#N/A

0.75

Site Type: Fully irrigated

Total Alfalfa ETr "

2.99

4.19

6.81

4.17

#N/A

18.16

Total Growing Degee Days from March 1

298

152

#N/A

450

Gross Pond Evap

Inch

2.51

3.52

5.72

3.5

#N/A

15.25

Net Pond Evap

Inch

2.39

3.48

5.41

3.45

#N/A

14.73

Longmont South

Avg. Temp ° F

33.89

43.43

53.14

50.97

#N/A

45.36

Ref date as of 4/18/2026

Total Precip "

0.32

0.1

0.43

0.26

#N/A

1.11

Site Type: Fully irrigated

Total Alfalfa ETr "

2.93

4.6

6.98

3.68

#N/A

18.19

Total Growing Degee Days from March 1

298

138

#N/A

436

Gross Pond Evap

Inch

2.46

3.86

5.86

3.09

#N/A

15.27

Net Pond Evap

Inch

2.24

3.79

5.56

2.91

#N/A

14.5

Fort Collins NW

Avg. Temp ° F

#N/A

Ref date as of 5/2/2010

Total Precip "

#N/A

Site Type: Turf

Total Alfalfa ETr "

#N/A

Total Growing Degee Days from March 1

#N/A

Gross Pond Evap

Inch

#N/A

Net Pond Evap

Inch

#N/A

Fort Collins Central

Avg. Temp ° F

#N/A

Ref date as of 122823/0/2023

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

#N/A

Total Growing Degee Days from March 1

#N/A

Gross Pond Evap

Inch

#N/A

Net Pond Evap

Inch

#N/A

Windsor

Avg. Temp ° F

#N/A

Ref date as of 5/2/2010

Total Precip "

#N/A

Site Type: Turf

Total Alfalfa ETr "

#N/A

Total Growing Degee Days from March 1

#N/A

Gross Pond Evap

Inch

#N/A

Net Pond Evap

Inch

#N/A

Greeley West

Avg. Temp ° F

31.44

40.6

51.26

50.82

#N/A

43.53

Ref date as of 4/18/2026

Total Precip "

0.49

0.39

0.69

0.22

#N/A

1.79

Site Type: Fully irrigated

Total Alfalfa ETr "

2.28

3.12

5.27

3.35

#N/A

14.02

Total Growing Degee Days from March 1

280

141

#N/A

421

Gross Pond Evap

Inch

1.92

2.62

4.43

2.81

#N/A

11.78

Net Pond Evap

Inch

1.57

2.35

3.94

2.66

#N/A

10.52

Loveland

Avg. Temp ° F

#N/A

Ref date as of 122823/0/2023

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

#N/A

Total Growing Degee Days from March 1

#N/A

Gross Pond Evap

Inch

#N/A

Net Pond Evap

Inch

#N/A

Berthoud

Avg. Temp ° F

33.46

43.43

53.05

51.52

#N/A

45.37

Ref date as of 4/18/2026

Total Precip "

0.15

0.38

0.1

#N/A

0.63

Site Type: Fully irrigated

Total Alfalfa ETr "

2.45

3.76

5.89

3.59

#N/A

15.69

Total Growing Degee Days from March 1

289

145

#N/A

434

Gross Pond Evap

Inch

2.06

3.16

4.95

3.02

#N/A

13.19

Net Pond Evap

Inch

1.95

3.16

4.68

2.95

#N/A

12.74

Longmont West

Avg. Temp ° F

33.22

42.79

52.85

51.6

#N/A

45.12

Ref date as of 4/18/2026

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

3.06

5.42

3.16

#N/A

13.64

Total Growing Degee Days from March 1

296

136

#N/A

432

Gross Pond Evap

Inch

1.68

2.57

4.55

2.65

#N/A

11.45

Net Pond Evap

Inch

1.68

2.57

4.55

2.65

#N/A

11.45

Fort Lupton

Avg. Temp ° F

33.8

42.94

52.4

50.81

#N/A

44.99

Ref date as of 4/18/2026

Total Precip "

1.88

1.62

1.31

0.63

#N/A

5.44

Site Type: Fully irrigated

Total Alfalfa ETr "

3.41

4.5

6.94

3.95

#N/A

18.8

Total Growing Degee Days from March 1

291

140

#N/A

431

Gross Pond Evap

Inch

2.86

3.78

5.83

3.32

#N/A

15.79

Net Pond Evap

Inch

1.55

2.65

4.91

2.88

#N/A

11.99

Boulder NW

Avg. Temp ° F

35.67

43.23

52.58

49.71

#N/A

45.3

Ref date as of 4/18/2026

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

3.18

3.73

5.99

3.25

#N/A

16.15

Total Growing Degee Days from March 1

278

127

#N/A

405

Gross Pond Evap

Inch

2.67

3.13

5.03

2.73

#N/A

13.56

Net Pond Evap

Inch

2.67

3.13

5.03

2.73

#N/A

13.56

Boulder East

Avg. Temp ° F

#N/A

Ref date as of 5/2/2010

Total Precip "

#N/A

Site Type: Turf

Total Alfalfa ETr "

#N/A

Total Growing Degee Days from March 1

#N/A

Gross Pond Evap

Inch

#N/A

Net Pond Evap

Inch

#N/A

Boulder Flatiron

Avg. Temp ° F

#N/A

Ref date as of 5/2/2010

Total Precip "

#N/A

Site Type: Turf

Total Alfalfa ETr "

#N/A

Total Growing Degee Days from March 1

#N/A

Gross Pond Evap

Inch

#N/A

Net Pond Evap

Inch

#N/A

Boulder SW

Avg. Temp ° F

38.83

46.57

55.06

51.82

#N/A

48.07

Ref date as of 4/18/2026

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

4.08

4.56

7.06

3.68

#N/A

19.38

Total Growing Degee Days from March 1

309

125

#N/A

434

Gross Pond Evap

Inch

3.43

3.83

5.93

3.09

#N/A

16.28

Net Pond Evap

Inch

3.43

3.83

5.93

3.09

#N/A

16.28

Greeley04

Avg. Temp ° F

30.07

39.13

50.14

#N/A

42.37

Ref date as of 4/18/2026

Total Precip "

0.18

0.23

#N/A

0.41

Site Type: Fully irrigated

Total Alfalfa ETr "

3.01

4.04

6.81

4.22

#N/A

18.08

Total Growing Degee Days from March 1

289

148

#N/A

437

Gross Pond Evap

Inch

2.53

3.39

5.72

3.54

#N/A

15.18

Net Pond Evap

Inch

2.4

3.39

5.56

3.54

#N/A

14.89