Pond Evaporation Calculation

6/21/25

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

2025

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

or Avg.

Ovid

Avg. Temp ° F

22.49

23.56

42.84

49.13

58.28

69.02

#N/A

44.22

Ref date as of 6/20/2025

Total Precip "

0.24

0.31

1.43

0.53

4.72

2.46

#N/A

9.69

Site Type: Fully irrigated

Total Alfalfa ETr "

2.21

2.97

6.29

7.27

8.11

6.41

#N/A

33.26

Total Growing Degee Days from March 1

196

241

344

349

#N/A

1130

Gross Pond Evap

Total "

1.86

2.49

5.28

6.11

6.81

5.38

#N/A

27.93

Net Pond Evap

Total "

1.69

2.28

4.28

5.74

3.51

3.66

#N/A

21.16

Crook

Avg. Temp ° F

22.07

24.33

42.84

48.39

57.82

67.69

#N/A

43.86

Ref date as of 6/20/2025

Total Precip "

0.14

0.24

0.49

0.4

2.91

2.66

#N/A

6.84

Site Type: Fully irrigated

Total Alfalfa ETr "

2.16

3.14

6.6

7.28

7.95

6.23

#N/A

33.36

Total Growing Degee Days from March 1

194

240

344

333

#N/A

1111

Gross Pond Evap

Inch

1.81

2.64

5.54

6.12

6.68

5.23

#N/A

28.02

Net Pond Evap

Inch

1.72

2.47

5.2

5.84

4.64

3.37

#N/A

23.24

Sterling

Avg. Temp ° F

21.42

25.54

43.16

48.17

58.28

67.72

#N/A

44.05

Ref date as of 6/20/2025

Total Precip "

0.36

0.31

0.33

0.89

1.04

2.89

#N/A

5.82

Site Type: Fully irrigated

Total Alfalfa ETr "

1.85

3.09

6.35

6.68

8.16

6.07

#N/A

32.2

Total Growing Degee Days from March 1

208

235

358

335

#N/A

1136

Gross Pond Evap

Inch

1.55

2.6

5.33

5.61

6.85

5.1

#N/A

27.04

Net Pond Evap

Inch

1.3

2.38

5.1

4.99

6.13

3.08

#N/A

22.98

Brush

Avg. Temp ° F

20.64

26.28

43.56

47.75

56.89

66.55

#N/A

43.61

Ref date as of 6/20/2025

Total Precip "

0.88

0.38

0.87

0.66

0.89

3.54

#N/A

7.22

Site Type: Fully irrigated

Total Alfalfa ETr "

1.51

2.74

5.97

6.47

6.83

5.32

#N/A

28.84

Total Growing Degee Days from March 1

211

250

343

333

#N/A

1137

Gross Pond Evap

Inch

1.27

2.3

5.01

5.43

5.74

4.47

#N/A

24.22

Net Pond Evap

Inch

0.65

2.04

4.41

4.97

5.11

1.99

#N/A

19.17

Fort Morgan

Avg. Temp ° F

22.75

27.63

45.08

49.54

58.99

68.84

#N/A

45.47

Ref date as of 6/20/2025

Total Precip "

0.39

0.31

1.24

0.7

1.38

3.75

#N/A

7.77

Site Type: Fully irrigated

Total Alfalfa ETr "

1.63

2.69

5.59

6.2

7.13

5.42

#N/A

28.66

Total Growing Degee Days from March 1

218

258

372

356

#N/A

1204

Gross Pond Evap

Inch

1.37

2.26

4.7

5.21

5.99

4.55

#N/A

24.08

Net Pond Evap

Inch

1.1

2.04

3.83

4.72

5.02

1.93

#N/A

18.64

Wiggins

Avg. Temp ° F

21.47

26.6

43.9

48.18

57.21

67.78

#N/A

44.19

Ref date as of 6/20/2025

Total Precip "

0.33

0.29

0.93

0.43

2.17

2.15

#N/A

6.3

Site Type: Fully irrigated

Total Alfalfa ETr "

1.78

2.99

6.29

6.8

7.42

6.13

#N/A

31.41

Total Growing Degee Days from March 1

209

247

342

335

#N/A

1133

Gross Pond Evap

Inch

1.5

2.51

5.28

5.71

6.23

5.15

#N/A

26.38

Net Pond Evap

Inch

1.26

2.31

4.63

5.41

4.71

3.64

#N/A

21.96

Fort Collins East

Avg. Temp ° F

21.94

29.23

44.8

47.65

56.86

65.54

#N/A

44.34

Ref date as of 6/20/2025

Total Precip "

0.37

0.13

0.88

0.5

2.33

0.81

#N/A

5.02

Site Type: Fully irrigated

Total Alfalfa ETr "

2.1

3.27

6.29

6.5

7.24

5.23

#N/A

30.63

Total Growing Degee Days from March 1

184

223

332

311

#N/A

1050

Gross Pond Evap

Inch

1.76

2.75

5.28

5.46

6.08

4.39

#N/A

25.72

Net Pond Evap

Inch

1.51

2.66

4.67

5.11

4.45

3.83

#N/A

22.23

Eaton

Avg. Temp ° F

22.02

27.93

44.18

47.88

56.78

65.29

#N/A

44.01

Ref date as of 6/20/2025

Total Precip "

0.34

0.22

1.08

0.35

2.87

2.19

#N/A

7.05

Site Type: Fully irrigated

Total Alfalfa ETr "

1.99

3.15

6.48

6.71

6.47

4.82

#N/A

29.62

Total Growing Degee Days from March 1

190

231

331

309

#N/A

1061

Gross Pond Evap

Inch

1.67

2.65

5.44

5.64

5.43

4.05

#N/A

24.88

Net Pond Evap

Inch

1.43

2.49

4.69

5.39

3.43

2.52

#N/A

19.95

Johnsons Corner

Avg. Temp ° F

23.42

29.52

46.14

48.65

56.65

66.31

#N/A

45.12

Ref date as of 6/20/2025

Total Precip "

0.63

0.44

1.36

0.62

2.51

1.8

#N/A

7.36

Site Type: Fully irrigated

Total Alfalfa ETr "

1.77

2.91

5.85

6.11

6.46

5.1

#N/A

28.2

Total Growing Degee Days from March 1

177

217

311

309

#N/A

1014

Gross Pond Evap

Inch

1.49

2.44

4.91

5.13

5.43

4.28

#N/A

23.68

Net Pond Evap

Inch

1.05

2.14

3.96

4.7

3.67

3.02

#N/A

18.54

Gilcrest

Avg. Temp ° F

21.11

28.43

45.65

49.34

58.06

67.74

#N/A

45.06

Ref date as of 6/20/2025

Total Precip "

0.43

0.26

1.47

0.5

3.02

2.24

#N/A

7.92

Site Type: Fully irrigated

Total Alfalfa ETr "

1.7

6.07

6.41

7.03

5.66

#N/A

29.87

Total Growing Degee Days from March 1

199

241

346

327

#N/A

1113

Gross Pond Evap

Inch

1.43

2.52

5.1

5.38

5.91

4.75

#N/A

25.09

Net Pond Evap

Inch

1.13

2.34

4.07

5.03

3.79

3.19

#N/A

19.55

Longmont South

Avg. Temp ° F

23.65

30.45

46.65

48.69

56.17

66.35

#N/A

45.33

Ref date as of 6/20/2025

Total Precip "

0.67

0.27

1.57

1.03

2.66

0.74

#N/A

6.94

Site Type: Fully irrigated

Total Alfalfa ETr "

1.82

3.01

6.33

5.76

6.09

5.17

#N/A

28.18

Total Growing Degee Days from March 1

183

214

310

298

#N/A

1005

Gross Pond Evap

Inch

1.53

2.53

5.32

4.84

5.12

4.34

#N/A

23.68

Net Pond Evap

Inch

1.06

2.34

4.22

4.12

3.25

3.82

#N/A

18.81

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

19.91

25.9

42.59

54.59

64.07

#N/A

42.18

Ref date as of 6/20/2025

Total Precip "

0.43

0.31

1.25

0.79

4.14

1.42

#N/A

8.34

Site Type: Fully irrigated

Total Alfalfa ETr "

1.29

2.21

4.63

5.08

5.74

4.39

#N/A

23.34

Total Growing Degee Days from March 1

141

187

275

291

#N/A

894

Gross Pond Evap

Inch

1.08

1.86

3.89

4.27

4.82

3.69

#N/A

19.61

Net Pond Evap

Inch

0.78

1.64

3.01

3.71

1.92

2.69

#N/A

13.75

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

24.75

31.08

47.51

50.09

58.23

68.01

#N/A

46.61

Ref date as of 6/20/2025

Total Precip "

0.39

1.49

0.65

1.9

1.82

#N/A

6.25

Site Type: Fully irrigated

Total Alfalfa ETr "

1.57

2.7

5.37

5.57

6.15

4.92

#N/A

26.28

Total Growing Degee Days from March 1

185

224

326

337

#N/A

1072

Gross Pond Evap

Inch

1.32

2.27

4.51

4.68

5.17

4.13

#N/A

22.08

Net Pond Evap

Inch

1.32

3.47

4.22

3.84

2.86

#N/A

17.71

Longmont West

Avg. Temp ° F

23.46

30.83

46.8

49.43

57.45

128.28

#N/A

56.04

Ref date as of 6/20/2025

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

1.37

2.57

5.36

5.81

5.48

32.6

#N/A

53.19

Total Growing Degee Days from March 1

185

220

314

504

#N/A

1223

Gross Pond Evap

Inch

1.15

2.16

4.5

4.88

4.6

27.38

#N/A

44.67

Net Pond Evap

Inch

1.15

2.16

4.5

4.88

4.6

27.38

#N/A

44.67

Fort Lupton

Avg. Temp ° F

23.63

29.67

47.31

50.22

58.92

69.86

#N/A

46.6

Ref date as of 6/20/2025

Total Precip "

0.62

0.32

1.83

0.82

2.5

1.79

#N/A

7.88

Site Type: Fully irrigated

Total Alfalfa ETr "

2.2

3.38

6.67

6.65

7.18

5.92

#N/A

Total Growing Degee Days from March 1

210

248

356

352

#N/A

1166

Gross Pond Evap

Inch

1.85

2.84

5.6

5.59

6.03

4.97

#N/A

26.88

Net Pond Evap

Inch

1.41

2.62

4.32

5.01

4.28

3.72

#N/A

21.36

Boulder NW

Avg. Temp ° F

25.63

31.39

46.49

48.33

56.1

66.26

#N/A

45.7

Ref date as of 6/20/2025

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

1.77

2.71

5.28

5.05

5.75

4.23

#N/A

24.79

Total Growing Degee Days from March 1

168

206

304

301

#N/A

979

Gross Pond Evap

Inch

1.49

2.28

4.44

4.24

4.83

3.55

#N/A

20.83

Net Pond Evap

Inch

1.49

2.28

4.44

4.24

4.83

3.55

#N/A

20.83

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

28.17

32.79

47.65

49.25

56.91

67.17

#N/A

46.99

Ref date as of 6/20/2025

Total Precip "

#N/A

Site Type: Fully irrigated

Total Alfalfa ETr "

2.15

3.01

5.71

5.3

6.09

4.44

#N/A

26.7

Total Growing Degee Days from March 1

151

197

290

329

#N/A

967

Gross Pond Evap

Inch

1.81

2.53

4.8

4.45

5.12

3.73

#N/A

22.44

Net Pond Evap

Inch

1.81

2.53

4.8

4.45

5.12

3.73

#N/A

22.44

Greeley04

Avg. Temp ° F

21.9

27.4

44.49

48.02

56.75

66.02

#N/A

44.1

Ref date as of 6/20/2025

Total Precip "

0.08

0.1

1.12

0.52

2.96

1.3

#N/A

6.08

Site Type: Fully irrigated

Total Alfalfa ETr "

1.73

2.75

6.01

6.6

7.64

5.51

#N/A

30.24

Total Growing Degee Days from March 1

202

233

335

318

#N/A

1088

Gross Pond Evap

Inch

1.45

2.31

5.05

5.54

6.42

4.63

#N/A

25.4

Net Pond Evap

Inch

1.4

2.24

4.26

5.18

4.35

3.72

#N/A

21.15