North Platte River Basin Report

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North Platte River Basin Water Supply and Utilization Report Wyoming Area Office Report for March 2021

The Wyoming Area Office of the Bureau of Reclamation is responsible for the operation of Reclamation reservoirs in Wyoming east of the Continental Divide except for Keyhole Reservoir. Four off-stream reservoirs in Nebraska commonly referred to as the Inland Lakes also fall within the Wyoming Area. The North Platte River Basin Reservoirs have a combined storage capacity of 2,800,000 acre-feet. The major reservoirs in the Shoshone and Wind/Bighorn Basins have a combined storage capacity of 1,600,000 acre-feet.

United States of America Department of the Interior Bureau of Reclamation P.O. Box 1630 Mills, Wyoming 82644-1630 Report for March 2021 WATER SUPPLY AND UTILIZATION REPORT NORTH PLATTE RIVER BASIN WYOMING AREA OFFICE

This report concerns the operation of Reclamation facilities in the North Platte River Basin.

Reclamation defines a water year as the time period of October 1 through September 30. Water year is abbreviated in this report as W. Yr.

Other organizations furnished information for the Water Supply and Utilization Report. Their cooperation is greatly appreciated.

This report is available on the Internet and can be accessed by following these steps:

1. Log on to the Great Plains Home Page at: http://www.usbr.gov/gp 2. On left side of page Select Water Operations. 3. Under Water Operations Select Water Management Information. 4. Under Water Management Select Water Supply Report. 5. Under North Platte River Basin, select Current Month or reports from the previous 12 months.

Page 1 NORTH PLATTE RIVER BASIN INFLOW

(1000 acre-feet) March March Accumulated Inflow Inflow Historical Inflow (October - March) W. Yr. 30 Yr. % of W. Yr. W. Yr. W. Yr. W. Yr. 30 Yr. % of Reservoir 2021 Avg. 5 Avg. 2020 2019 2018 2021 Avg. 5 Avg. Seminoe 42.2 57.1 74 57.5 40.2 43.1 143.3 193.0 74 Pathfinder 1, 2 4.9 11.6 n/a 7.9 11.5 8.2 3.1 38.6 n/a Glendo 3 20.8 17.4 119 23.4 14.6 19.6 63.4 66.6 95 Guernsey 4 2.2 1.7 132 2.2 1.7 1.8 9.1 9.8 93 System Total 70.2 87.8 80 91.0 68.0 72.7 218.9 308.0 71 1 It is assumed that there is no gain between Seminoe and Kortes Dams. 2 River gain between Kortes and Pathfinder Dams. 3 River gain between Pathfinder and Glendo Dams. 4 River gain between Glendo and Guernsey Dams. 5 30 year average. (1991-2020)

NORTH PLATTE RIVER BASIN RESERVOIR INFLOW March

1000X 40 TEEF

30 -

CREA 20

Seminoe Pathfinder Glendo Guernsey RESERVOIR

Average 2021 2020 2019 2018

Page 2 NORTH PLATTE RIVER BASIN OUTFLOW

(1000 acre-feet) March March Accumulated Outflow Outflow Historical Outflow (October - March) W. Yr. 30 Yr. % of W. Yr. W. Yr. W. Yr. W. Yr. 30 Yr. % of Reservoir 2021 Avg. 2 Avg. 2020 2019 2018 2021 Avg. 2 Avg. Seminoe 33.1 59.7 55 101.1 33.0 49.7 217.1 253.1 86 Kortes 33.1 59.7 55 101.1 33.0 49.7 217.0 253.0 86 Pathfinder 27.3 53.9 51 39.5 37.0 50.1 232.9 194.7 120 Alcova 26.2 52.2 50 38.3 36.3 48.2 253.6 215.3 118 Gray Reef 26.2 52.1 50 37.8 36.2 47.8 253.0 215.2 118 Glendo 1 1.7 16.1 1 11 11.5 1.7 1.7 9.6 24.8 1 39 Guernsey 0.2 12.8 1 5.3 0.9 0.2 0.9 17.4 5

1 In 1993 an outlet was constructed at Glendo Dam which is used to provide a flow of approximately 25 cubic feet per second, 27 year average (1994-2020). 2 30 year average (1991-2020).

NORTH PLATTE RIVER BASIN RESERVOIR OUTFLOW March 120

100

80 1000 X TE X 60 EF -

CRE 40 A

0 Seminoe Kortes Pathfinder Alcova Gray Reef Glendo Guernsey

RESERVOIR Average 2021 2020 2019 2018

Page 3 NORTH PLATTE RIVER BASIN RESERVOIR STORAGE

(1000 acre-feet) Total Storage End of March Total Percent End of March Historical Storage Conservation of W. Yr. 30 Yr. % of W. Yr. W. Yr. W. Yr. Storage Capacity Reservoir 2021 Avg. 1 Avg. 2020 2019 2018 Capacity Seminoe 576.6 536.4 107 748.3 616.0 798.1 1017.3 57 Kortes 4.7 4.7 100 4.7 4.7 4.7 4.7 100 Pathfinder 627.8 596.1 105 957.8 642.7 845.3 1070.0 59 Alcova 157.7 157.6 100 158.1 157.8 157.9 184.4 86 Gray Reef 1.8 1.5 117 1.8 1.8 1.8 1.8 97 Glendo 430.8 384.6 112 402.6 381.7 357.4 492.0 88 Guernsey 21.8 19.4 112 28.2 18.0 24.8 45.6 48 Total 1821.1 1700.3 107 2301.5 1822.7 2190.0 2815.8 65 1 Average is based on the 1991-2020 period.

NORTH PLATTE RIVER BASIN RESERVOIR STORAGE End of March

1200

1000

800 1000X T 1000X 600 EEF - ECR 400 A

200

0 Seminoe Kortes Pathfinder Alcova Gray Reef Glendo Guernsey RESERVOIR

Average 2021 2020 2019 2018

Page 4 NORTH PLATTE RIVER BASIN RESERVOIR STORAGE OWNERSHIP

(1000 acre-feet)

Ownership of water End of March Total Percent End of March Historical Ownership Storage of W. Yr. 30 Yr. % of W. Yr. W. Yr. W. Yr. Capacity Ownership Cap acity 2021 Avg. 5 Avg. 2020 2019 2018 Kendrick 1060.6 840.0 126 1110.1 1004.5 1130.5 1201.7 88 North Platte 1 584.0 676.6 86 928.2 644.8 855.0 1115.6 52 Glendo 130.7 134.1 97 169.6 136.5 162.4 171.7 76 Inland Lakes 2 22.8 21.2 107 25.1 18.6 21.9 46.0 50 Cheyenne 3,7 13.0 8.3 157 11.4 9.2 9.1 15.7 83 PacifiCorp 4 2.0 1.9 104 2.0 2.0 2.0 2.0 99 WWDC 0.0 0.0 N/A 0.0 0.0 0.0 N/A N/A Other 6 8.0 18.1 44 55.1 7.2 9.1 N/A N/A

1 This includes North Platte Guernsey and North Platte Pathfinder. 2 Water stored temporarily in mainstem facilities for later transfer to the Inland Lakes. This table does not reflect water currently stored in the Inland Lakes. 3 The City of Cheyenne has a storage contract to store water in Seminoe Reservoir by exchange of Upper North Platte Basin water through a system of trans-basin diversions. 4 PacifiCorp has a storage contract to store water in Glendo Reservoir for Dave Johnston Powerplant. 5 Average is based on the 1991-2020 period. 6 Water which is captured in the re-regulation space of Glendo in addition to storage rights, operational water account, and replacement of evaporation losses is labeled as "Re-regulation of Natural Flow" per Wyoming Board of Control Order Docket Number I-2000-3-8 in water Division Number One. In accordance with 2019 Natural Flow and Ownership Procedures, the October operational account can contain up to 15,000 acre-feet. On October 31, 2020, the Operational account contained 7,809 Acre-feet, the Re-Regulation space contained 0 Acre-feet. 7 Cheyenne ownership was increased to 15,700 AF on March 13, 2009 as a result of Amendment No. 1 to Contract No. 06XX6A0062.

Ownership of Water End of March

1200

1000

800 1000 X TE X 600 EF - 400 CRE A 200

0 Kendrick North Platte Glendo Inland Lakes Cheyenne PacifiCorp WWDC Other

North Platte Project

Average 2021 2020 2019 2018

Page 5 NORTH PLATTE RIVER BASIN OWNERSHIP OF WATER End of March

1300 1200 1100 1000 900

000 800 1X T 1X 700 EEF 600 - 500 CRE

A 400 300 200 100 0 Kendrick North Platte Glendo Inland Cheyenne PacifiCorp WWDC Other Lakes

Average 2021 2020 2019 2018

INLAND LAKES RESERVOIR STORAGE

Water Year 2021 3/31/2021 ( acre-feet) Total 30 Year Percent of Total Reservoir Storage Average 5 Average Storage End of March Capacity Lake Alice 55 279 20 11,034 1 Little Lake Alice 124 69 180 1,166 2 Lake Winters Creek 758 532 142 1,746 3 Lake Minatare 20,365 25,103 81 58,795 4 1 At Elevation 4182.0 2 At Elevation 4139.0 3 At Elevation 4125.0 4 At Elevation 4125.0 5 30 year average. (1991-2020)

Page 6 NORTH PLATTE RIVER BASIN GROSS GENERATION

(Energy in giga-watt hours) March March Accumulated Gross Gen. Gross Generation Historical Generation (October - March) W. Yr. 30 Yr. % of W. Yr. W. Yr. W. Yr. W. Yr. 30 Yr. % of Powerplant 2021 Avg. 2 Avg. 2020 2019 2018 2021 Avg. 2 Avg. Seminoe 3.6 9.0 40 16.4 4.1 6.7 26.1 37.0 71 Kortes 4.8 9.1 53 17.6 5.2 7.9 32.7 40.2 81 Fremont Canyon 1 6.4 13.6 47 9.5 8.2 13.4 21.1 45.4 46 Alcova 2.6 6.0 44 4.1 3.9 5.6 27.3 23.9 114 Glendo 0.0 1.2 n/a 0.0 0.0 0.0 0.0 1.3 n/a Guernsey 0.0 0.3 n/a 0.0 0.0 0.0 0.0 0.4 n/a 1 The powerplant for Pathfinder Dam is Fremont Canyon. 2 Average is based on the 1991-2020 period. NORTH PLATTE RIVER BASIN GROSS GENERATION March

12 HW 10 G 8

0 Seminoe Kortes Fremont Canyon Alcova Glendo Guernsey

POWERPLANT

Average 2021 2020 2019 2018

Page 7 NORTH PLATTE SNOWPACK WATER CONTENT The tables shown below display the Snotel Sites used in the development of the Apirl-July snowmelt runoff forecasts

SWE in inches ¹ April 1, 2021 Comparative April 1 snow-water content snow-water content WATERSHED W. Yr. 30 Yr. % of W. Yr. W. Yr. W. Yr. 2021 3 Median ² Median 2020 2019 2018 Seminoe Reservoir 19.86 21.1 94% 23.6 28.0 21.3 Pathfinder Reservoir 12.20 14.8 82% 12.4 14.4 12.1 Glendo Reservoir 12.83 11.0 117% 13.6 14.1 7.7

Seminoe Reservoir Watershed Sweetwater River / Pathfinder Reservoir Watersh SWE in inches ¹ SWE in inches ¹ Stations Water 30 Yr. Stations Water 30 Yr. (Elevation) Content 3 Median ² (Elevation) Content 3 Median ² Arapaho Ridge (10,960) 20.40 19.8 South Pass (9,040) 12.00 14.9 Columbine (9,160) 22.10 22.8 Deer Park (9,700) 12.40 14.7 Divide Peak (8,880) 16.20 19.5 Watershed Average 12.20 14.8 Joe Wright (10,120) 19.50 20.2 Laprele Creek (8,375) 11.00 9.5 North French (10,130) 27.80 28.0 Glendo Reservoir Watershed Never Summer (10,280) 17.50 19.6 SWE in inches ¹ Old Battle (10,000) 28.10 29.6 Stations Water 30 Yr. Rawah (9,020) 11.50 10.3 (Elevation) Content 3 Median ² Sage Creek Basin (7,850) 17.30 12.7 Casper (7,900) 13.40 13.4 Sand Lake (10,050) 28.90 27.5 Laprele Creek (8,375) 11.00 9.5 South Brush (8,440) 10.00 12.2 Reno Hill (8,500) 15.00 13.2 Tower (10,500) 34.20 44.0 Windy Peak (7,900) 11.90 7.8 Webber Springs (9,250) 19.50 23.0 Watershed Average 12.83 11.0 Willow Creek Pass (9,540) 11.40 11.8 Zirkel (9,340)4 22.30 26.4 Watershed Average 19.86 21.1

¹ SWE (Snow Water Equivalent is the amount of water in the snowpack expressed in inches) ² Median for the 1981-2010 period 3 Data from NRCS Snowpack Telemetry Network (SNOTEL) Sites. 4 Zirkel is a newer gage starting WY 2003, NRCS median is 7 years of data within 1981-2010 time period.

NORTH PLATTE RIVER BASIN SNOW WATER EQUIVALENT February 1st

hes) 15

SWE (inc 5

0 Seminoe Reservoir Pathfinder Reservoir Glendo Reservoir RESERVOIR BASINS Median 2021 2020 2019 2018

Page 8 NORTH PLATTE ESTIMATED APRIL-JULY RUNOFF

(1000 acre-feet) April 1, 2021 Forecast 30 Yr. Comparative Actual Forecast of April-July Runoff April-July Expected April - July Runoff Points Reasonable Reasonable Runoff % of Avg. W. Yr. W. Yr. W. Yr. W. Yr. Expected Maximum¹ Minimum¹ Avg. ² 2020 2019 2018 2017 Seminoe Reservoir 925 625 375 716 87 632 1008 393 683 Sweetwater River Above Pathfinder 45 30 15 55 55 25 58 35 159 Reservoir Alcova to Glendo 185 135 85 146 92 134 210 71 135 ¹ The probability is estimated to be 9 chances in 10 that the actual volume will fall between the reasonable minimum and reasonable maximum. ² Average is based on the 1991-2020 period.

(1000 acre-feet) April 1, 2021 Forecast of April-July Runoff 30 Yr. Forecast April-July Points Chance of Exceeding Runoff 95% 75% 50% % of Avg 25% 5% Avg. ¹ Seminoe Reservoir 375 523 625 87 748 925 716 Sweetwater River Above Pathfinder Reservoir 15 24 30 55 36 45 55 Alcova to Glendo Gain 85 115 135 92 155 185 146 ¹ Average is based on the 1991-2020 period.

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