The high desert of Central Oregon is a special region, blessed with abundant summer sunshine and a moderate climate. The thread that binds the fabric of this region together is an anomaly: a clean, cold-water river in an otherwise arid landscape. Born from springs high in the Cascades, the Deschutes flows through Bend as a highly modified body of water: beautiful to look at, but a pale shadow of what it once was.
Any portrayal of conditions in the river should begin with an acknowledgement of the groups that have worked tirelessly to improve it. The Upper Deschutes Watershed Council and Deschutes River Conservancy have built key collaborative relationships with the irrigation districts to secure additional in-stream water rights and restore habitat where opportunities have arisen. To be sure, conditions in the river today, particularly in the middle Deschutes (below the North Unit Canal Dam) are better than they have been in some time.
Historically the Deschutes River was characterized by extremely stable flows, primarily as a result of the unique geology and hydrology of the region. Unlike many western rivers, the Deschutes was not a system prone to flooding. The entire ecological community in the reach, from aquatic insects and plants to native trout species (bull trout), was uniquely adapted to that stability and consistent water quality. Installation of dams and diversions all along the reach changed the flow regime, and thus the river ecosystem, dramatically.
Dams on the Deschutes significantly influence stream flow (which varies up to 90 percent between winter and summer months), reduce stream velocity and disrupt natural sediment movement throughout the river system. Although there is little research on the specific impact of flow variation upstream on sediment loads through Bend, it is clear that rapid and severe changes in flow accelerate natural erosion processes along the river. Land use and management upstream of Bend and within city limits are additional sources of sediment in the river. The combination of increased sediment and reduced velocity results in increasing stream temperatures and reductions in dissolved oxygen.
To comply with the Clean Water Act states are required to monitor and report water quality conditions within their boundaries. Standards for each body of water are developed based on biological requirements for key species and human health. Waters that are below standard, called impaired waters, must be accounted for on the state’s 303(d) list with specific reference to sampling location and which standards are not being met. The Bend reach of the Deschutes is currently listed as impaired for temperature, sediment and dissolved oxygen.
Sediment, temperature and dissolved oxygen all influence habitat for biological communities in streams. Temperatures in particular limit which species are present and can determine whether or not reproduction occurs for a variety of species. As indicated above, sediment and temperature are correlated, but sediment itself can lead to reduced fish spawning by covering spawning gravels and cementing them in place.
It is an oft-celebrated fact that the Deschutes played a major role in the establishment and development of Bend, primarily serving as a vehicle for transporting logs downstream to feed the once-thriving mills. To maximize log-transport efficiency the river was cleared of large woody debris and frequently dredged. These activities and modification of the river downstream at Mirror Pond have reduced overall habitat quality and quantity for native species.
No matter what the ultimate decision is for the future of Mirror Pond, all options will come with a significant price tag. Generally speaking, solutions to Mirror Pond will require some combination of federal and/or state funds, local government funds, grant funds or funds from the general public (e.g. special tax district). Acquisition of federal funds and grants will potentially delay the process and is not a guarantee, especially for any future maintenance costs. Public funds, as in the case of a special tax district, will require the community to vote with our dollars. Either way, when we dam rivers and alter natural flow regimes, at some point the bill comes due. We’ve been served.
Source: The Source Weekly ©2013