Fisheries and Stream Habitat
The City of Aspen is committed to environmental stewardship and is working to ensure the CCEC will preserve healthy fisheries and stream habitat. The City has volunteered to operate the CCEC under a "slow start" program, basing future production levels on the stream health indicators within its inter-agency monitoring program.
The City of Aspen and the Colorado Division of Wildlife have entered into a Memorandum of Understanding establishing a comprehensive stream monitoring and adaptive management regime ensuring the sustained health of Castle and Maroon Creeks’ stream habitats.
Review environmental studies on the Studies and Reports page.
Non-Consumptive Use
The use of water for the CCEC is "non-consumptive." All water diverted for the production of electricity will be returned to Castle Creek approximately 2.4 miles from the points of diversion. In addition, this non-consumptive use preserves the City's senior water right.
Reduced Diversions for Municipal Water
Since 1993, the City of Aspen Water Department has reduced municipal water diversion rates from Castle and Maroon Creeks by over 45% (or 4.65 cfs) despite the fact that connections have increased by 70% during that time period. This was achieved through proactive conservation measures including, but not limited to, leak detection and repair, pump and systems upgrades, and demand reduction initiatives.
Minimum Streamflow
The Colorado Water Conservation Board (CWCB) has instream flow water rights on Castle Creek and Maroon Creek. Although Aspen's water rights are senior to these instream flow rights, Aspen is committed to protecting stream habitat and has agreed to operate its hydroelectric water rights to make sure the instream flows are met in both creeks downstream of the City's municipal intakes. The City's consulting biologist has recommended an increase in the Castle Creek instream flow from 12 cubic feet per second (cfs) to 13.3 cfs. The City has agreed, in connection with its hydroelectric operations, to bypass 13.3 cfs at its Castle Creek municipal intake, and 14 cfs at its Maroon Creek municipal intake.
The hydrograph above depicts the CCEC running at full production. In June/July, 16 cubic feet per second (cfs) diverted equates to 4%-7% of the available water in Castle Creek because streamflow is at its peak. Conversely, in November, when streamflow is at its lowest, 15.3 cfs (planned Castle Creek hydroelectric diversion at full production) represents 39% of the available water in Castle Creek. The remaining 61% is more than the recommended instream flow of 13.3 cfs.
The same goes for Maroon Creek: at low flows in November, 12.3 cfs diverted for hydroelectric production would be 28.9% of the average streamflow. In June, when the stream is generally at its highest flow, a diversion of 23.4 cfs only accounts for 5.8% of the average flow of the stream.
All the water that is diverted from both streams is returned to Castle Creek just below the hydropower plant.