Gross Reservoir
Gross Reservoir, located in Boulder County, Colorado, is owned and operated by Denver Water. Completed in 1954, the reservoir has a surface area of 440 acres, and the spillway sits at 7,225 feet elevation.[1]
| Gross Reservoir | |
|---|---|
 The reservoir in 2014. | |
  Gross Reservoir  Gross Reservoir | |
| Location | Boulder County, Colorado |
| Coordinates | 39°56′31″N 105°22′22″W |
| Type | reservoir |
| Etymology | Named for Denver Water former Chief Engineer Dwight D. Gross.[1] |
| Primary outflows | South Boulder Creek |
| Basin countries | United States |
| Managing agency | Denver Water |
| Water volume | 41,811 acre⋅ft (51,573,000 m3) |
| Surface elevation | 2,222 m (7,290 ft)[2] |
The reservoir receives water from the western side of the Continental Divide through the Moffat Tunnel. South Boulder Creek flows out of the 340 foot-high dam.
Recreation
The reservoir provides opportunities for fishing (including ice fishing), hiking, canoeing, kayaking, and some camping. No water-contact sports such as swimming or wading are allowed. Only non-motorized boats are permitted — the type that can be attached to the top of a car.[1]
Expansion project
The proposed expansion of Gross Reservoir would allow Denver Water to store 77,000 additional acre feet of water, drawn mostly from the Fraser and Williams Fork Rivers.[3] Construction on the project, expected to be complete around 2025, will raise the level of the dam by 131 feet (40 meters), resulting in an additional 77,000 acre-feet (95,000,000 cubic meters) of water storage capacity in the reservoir and making it the tallest dam in Colorado.[4]
Denver Water applied to the U.S. Army Corps of Engineers for a permit under section 404 of the Clean Water Act, required to construct the expansion, and that permit was granted in 2017.[5] In response, several environmental groups sued USACE on grounds that the agency's deliberations about granting the permit violated the Clean Water Act, Endangered Species Act, and National Environmental Policy Act.[6] In July 2020 the Federal Energy Regulatory Commission granted a required modification to the Federal Power Act license granted to Colorado Water for Gross Dam before it was built.[7]
A contract for design services was awarded to Stantec, an engineering consulting firm, in 2017.
Boulder County announced in spring 2019 that it would require Denver Water to obtain a land use permit under Colorado law before commencing the expansion project.[8] Denver Water submitted its application for that permit in September 2020.[9]
Preparation work for the expansion is well underway. Overall the expansion is planned to raise the height of the dam by 131 feet which will triple the volume of the reservoir. The project is scheduled to be completed in 2025. This will make the reservoir's dam the largest dam in the state of Colorado.[10]
Climate
According to the Köppen Climate Classification system, Gross Reservoir has an oceanic climate, abbreviated "Cfb" on climate maps. The hottest temperature recorded at Gross Reservoir was 94 °F (34.4 °C) on July 9, 2003, June 23, 2012, June 26, 2012, and June 22, 2016, while the coldest temperature recorded was −24 °F (−31.1 °C) on February 2, 2011.[11]
| Climate data for Gross Reservoir, Colorado, 1991–2020 normals, extremes 1978–present | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 67 (19) |
64 (18) |
72 (22) |
78 (26) |
89 (32) |
94 (34) |
94 (34) |
92 (33) |
91 (33) |
81 (27) |
70 (21) |
64 (18) |
94 (34) |
| Mean maximum °F (°C) | 57.7 (14.3) |
58.1 (14.5) |
66.3 (19.1) |
72.3 (22.4) |
78.7 (25.9) |
88.0 (31.1) |
89.8 (32.1) |
87.7 (30.9) |
84.7 (29.3) |
75.5 (24.2) |
66.5 (19.2) |
58.1 (14.5) |
91.0 (32.8) |
| Average high °F (°C) | 39.3 (4.1) |
39.7 (4.3) |
47.2 (8.4) |
52.2 (11.2) |
60.8 (16.0) |
72.6 (22.6) |
79.3 (26.3) |
77.1 (25.1) |
69.7 (20.9) |
56.8 (13.8) |
47.0 (8.3) |
39.5 (4.2) |
56.8 (13.8) |
| Daily mean °F (°C) | 28.1 (−2.2) |
28.2 (−2.1) |
34.7 (1.5) |
39.7 (4.3) |
48.1 (8.9) |
58.1 (14.5) |
64.5 (18.1) |
62.3 (16.8) |
55.2 (12.9) |
44.1 (6.7) |
35.3 (1.8) |
28.5 (−1.9) |
43.9 (6.6) |
| Average low °F (°C) | 16.9 (−8.4) |
16.7 (−8.5) |
22.1 (−5.5) |
27.1 (−2.7) |
35.4 (1.9) |
43.6 (6.4) |
49.6 (9.8) |
47.6 (8.7) |
40.6 (4.8) |
31.3 (−0.4) |
23.5 (−4.7) |
17.5 (−8.1) |
31.0 (−0.6) |
| Mean minimum °F (°C) | −4.5 (−20.3) |
−6.1 (−21.2) |
5.4 (−14.8) |
13.7 (−10.2) |
23.3 (−4.8) |
35.7 (2.1) |
43.9 (6.6) |
40.0 (4.4) |
30.6 (−0.8) |
15.5 (−9.2) |
4.9 (−15.1) |
−5.2 (−20.7) |
−11.8 (−24.3) |
| Record low °F (°C) | −13 (−25) |
−24 (−31) |
−14 (−26) |
0 (−18) |
11 (−12) |
28 (−2) |
35 (2) |
27 (−3) |
16 (−9) |
−1 (−18) |
−14 (−26) |
−19 (−28) |
−24 (−31) |
| Average precipitation inches (mm) | 0.71 (18) |
0.90 (23) |
1.94 (49) |
2.73 (69) |
2.89 (73) |
1.87 (47) |
2.04 (52) |
2.12 (54) |
1.99 (51) |
1.35 (34) |
0.96 (24) |
0.78 (20) |
20.28 (514) |
| Average snowfall inches (cm) | 9.4 (24) |
14.0 (36) |
21.0 (53) |
19.8 (50) |
3.9 (9.9) |
0.1 (0.25) |
0.0 (0.0) |
0.0 (0.0) |
0.9 (2.3) |
6.9 (18) |
12.0 (30) |
11.1 (28) |
99.1 (251.45) |
| Average extreme snow depth inches (cm) | 7.7 (20) |
8.2 (21) |
11.3 (29) |
10.4 (26) |
3.4 (8.6) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.9 (2.3) |
5.1 (13) |
7.3 (19) |
7.9 (20) |
18.4 (47) |
| Average precipitation days (≥ 0.01 in) | 4.7 | 5.6 | 6.3 | 8.4 | 10.5 | 8.1 | 10.2 | 10.9 | 7.3 | 6.0 | 4.9 | 4.9 | 87.8 |
| Average snowy days (≥ 0.1 in) | 4.0 | 4.7 | 4.8 | 4.6 | 1.3 | 0.0 | 0.0 | 0.0 | 0.4 | 1.9 | 3.8 | 4.0 | 29.5 |
| Source 1: NOAA[12] | |||||||||||||
| Source 2: National Weather Service[11] | |||||||||||||
References
- Denver Water. Gross Reservoir. Viewed 2014-09-22.
- "Gross Reservoir". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. Retrieved 2014-09-23.
- Gardner-Smith, Brent (20 April 2016). "Denver Water official says more West Slope water projects 'not on our radar'". Aspen Journalism. Retrieved 25 November 2020.
{{cite news}}: CS1 maint: url-status (link) - Brennan, Charlie (2 January 2018). "Denver firm awarded $13M design contract for expansion of Boulder County's Gross Reservoir". Boulder Daily Camera. Boulder, CO. Retrieved 25 November 2020.
{{cite news}}: CS1 maint: url-status (link) - Ingram, Elizabeth (12 July 2017). "Denver Water approved to expand reservoir behind Gross Dam". Hydro Review. Retrieved 25 November 2020.
{{cite news}}: CS1 maint: url-status (link) - Brennan, Charlie (19 December 2018). "Environmental groups sue to block expansion of Boulder County's Gross Reservoir". Boulder Daily Camera. Retrieved 25 November 2020.
{{cite news}}: CS1 maint: url-status (link) - Jones, Corey H. (17 July 2020). "Boulder County's Gross Reservoir Can Proceed With Expansion Following Lawsuit". CPR News. Retrieved 25 November 2020.
{{cite news}}: CS1 maint: url-status (link) - Lacey, Hank (24 November 2020). "Gross Reservoir Expansion Proposal Presents Water Demand, Environmental Concerns". Law Week Colorado. Retrieved 25 November 2020.
{{cite news}}: CS1 maint: url-status (link) - Swearingen, Deborah (5 October 2020). "County's review of proposed Gross Reservoir expansion underway". Boulder Daily Camera. Retrieved 25 November 2020.
{{cite news}}: CS1 maint: url-status (link) - https://yourhub.denverpost.com/blog/2022/05/construction-kicks-off-at-gross-reservoir/290911/.
{{cite news}}: Missing or empty|title=(help) - "NOAA Online Weather Data – NWS Boulder/Denver". National Weather Service. Retrieved February 7, 2023.
- "U.S. Climate Normals Quick Access – Station: Gross RSVR, CO". National Oceanic and Atmospheric Administration. Retrieved February 7, 2023.