Projects by Discipline / Environmental Science

South Boulder Creek Instream Flow Enhancement Study

Hydrosphere performed a study of options available to increase winter base flows in South Boulder Creek. South Boulder Creek is the major tributary of Boulder Creek. Land use along the creek is primarily rural agriculture and dedicated open space except near its confluence with Boulder Creek, where the setting is urban. Over the last two hundred years the creek has been both physically altered and dewatered, first by irrigated agriculture and then by urbanization. The reach of interest is a cold water, pool and riffle type stream transitioning from the mountain front to the high plains.

The Boulder Flycasters' Chapter of Trout Unlimited has long worked to restore South Boulder Creek to a physical and biological environment more reflective of its natural character: one that is closer to a self-sustaining aquatic ecosystem. The limiting factor, however, has been lack of an adequate base flow, particularly in mid-winter, due to water diversions for various uses. Because the value of water in the region is so high and there are so many entities that have vested interests in the water diversions, the most practical approach to keeping more water in the stream was to facilitate cooperation among the stakeholders. This meant bringing together a variety of water users who had traditionally existed in a culture of competition for water but who also had the knowledge and creativity to help achieve the objective. It involved addressing both the technical issues and the institutional obstacles to leaving more water in the stream.

Interviews with the major water rights owners, tabulation of the water rights of record, knowledge of the actual administration of these rights and other technical information were consolidated. This enabled the development and analysis of conceptual ideas for moving water around in time and space to accomplish the objective. The ideas ranged from minimal cost items and support of current practices that keep water in the stream, to moderate cost multiple entity exchanges, transfers, changes in points of diversion and even trans-basin movements of water that involve capital costs exceeding $1M. A report was published presenting the results of this work. Another round of meetings to present the results of the study and set the stage for further implementation discussions occurred after the report was published. A symposium to bring all the parties together is scheduled for early winter 2004.