2010-11-22_REVISION - M2009023 (7)

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authorized activities in the San Juan River basin dated June 13, 1994 (ES/GJ-6-CO-94-F-027). Therefore, water depletions associated with coalbed methane development on State, Tribal, local or private lands are no longer considered as a cumulative effect. When the Corps initiated consultation on the proposed Long Hollow Reservoir on July 16, 2004, the average water depletion associated with the proposed project was stated to be 1,470 acre-feet. In a letter dated May 5, 2005, the Corps informed the Service that the average annual depletion is now 1,535 acre-feet. This change is based on updated hydrology data used to make the , hydrology model run more precise. BIOLOGICAL OPINION DESCRIPTION OF THE PROPOSED ACTION The La Plata Water Conservancy District (LPWCD) is proposing to construct a new reservoir by building a dam on Long Hollow Creek, a tributary to the La Plata River in La Plata County, Colorado. Funding will be provided by the State of Colorado. The proposed reservoir site is located several hundred feet below the confluence of Long Hollow and Government Draw, south of Red Mesa in sections 29, 32, and 33, T. 33 N., R. 13 W. The dam would be located approximately 0.5 mile upstream of the confluence of Long Hollow and the La Plata River,, approximately 4 miles upstream of the Colorado-New Mexico state line. The proposed facility will capture flows from 43 square miles of Long Hollow Creek and Government Draw watersheds. The intent is to capture perennial flows from groundwater irrigation return flows and precipitation on Red Mesa. The proposed reservoir would have a maximum pool of 5,432 acre-feet and inundate 160 acres. The reservoir would inundate 1.5 miles of Long Hollow Creek and 1.2 miles of Government Draw. The reservoir pool will fluctuate dramatically from year to year and season to season. It is only expected to reach full capacity 50 percent of the time. Most years, the reservoir will be drained entirely between April and July. Some years there will be carry-over storage of 500 to 2,500 acre-feet. The purpose of the proposed Long Hollow Reservoir is to help Colorado satisfy its water supply obligation to New Mexico as required in the 1922 La Plata River Compact. The compact requires Colorado to deliver to New Mexico one-half of the flow measured at the Hesperus gauge, not to exceed 100 cubic feet per second (cfs), between February 16`h and November 30ei. A water storage facility near the state line would facilitate the Colorado State Engineer in administering the La Plata River Compact. The new reservoir would cause an average annual water depletion of 1,535 acre-feet to the San Juan River. This includes a range of depletions from 100 acre-feet/year to 3,600 acre-feet/year. These depletions are caused by evaporative losses from the surface of the reservoir and additional depletions due to the irrigation of land within the La Plata River basin. The LPWCD will own and operate the reservoir. Typically, the reservoir will store water during the non- compact period (December 1 g` - February 15th) and other periods when water rights for the reservoir are in priority. 3