The Devils Lake Water Improvement District is soliciting comments on the lake level. In 1996 DLWID applied for a recreational water use permit to store an additional 2 feet of water (1360 acre feet). In order to maintain the additional lake level, a small dam was built on the concrete foundation that was part of the fish control structure originally required as part for the Grass Carp introductions . The dam was built with the anticipation of providing deeper water along the shorelines of Devils Lake in the summer months.
Operationally the dam is put in generally between April 15 - Oct 15. Winter storms can cause damage to the structure, so all of the metal and wooden structural components are removed during the rainy season. In March of 2006, the District repaired the aging dam. The dam basically augments the summer low level to within 6" of what the state recognizes as the mean high lake level or 10.4' above sea level.
Benefits of the Dam: The intention of the dam is for increased recreational use of Devils Lake. Higher water in the summer does provide for additional draft for watercraft. Access to the water is generally thought to be increased thus by the fact that the lake does not draw down as it would naturally in the drier season. Many property owners around the lake thus receive a social benefit to the operation of the dam.
Impacts of the Dam to Fish and Wildlife: Native Coho salmon migrate upstream during the winter when the dam is not in place, so there are no impacts to upstream migration of adult fish. The dam does meet the minimum requirements for fish passage (as seen in the picture above), however there maybe some impacts to the outward migration of young smolts in the spring. Smolts rely on the physical signal of down stream flow to trigger their migration out to sea. With the dam in place and water backing up, much of that signal is lost. The District does though pulse the flow by removing a set of boards at night during much of the month of May. This increased velocity is hoped to mitigate the potential impacts to the threatened and native Coho salmon. Other anadromous species (migratory animals with life cycles in the rivers and the ocean) may be impacted by the dam as well. These include Sea Run Cutthroat Trout and Pacific Lamprey which are less understood.
The dam is known to be an obstacle to young, flightless birds and mammals. Young birds have been often seen struggling to find passage around the dam back towards the lake. This opens the young birds up to increased predation.
Impacts to Water Quality: When the dam blocks up water, it also blocks up debris. This debris can be made up of innocuous logs and sticks, but also can consist of other organic matter such as bird feces or cyanobacteria which have an impact on water quality. Feathers from birds seen behind the dam often correlates with high
E. coli readings. When cyanobacteria are backed up behind the dam, toxins are documented as well. This is caused by the reduction in flow that would otherwise move these materials out to sea or allow for greater biodegradability.
Impacts to Wetlands: The artificial control of the lake level such as with reservoirs does impact wetlands. Wetland species are accustomed to periodic flooding events, and are maladapted to year-round inundation. Year-round saturation leaves the wetland species weakened and less able to increase root mass and form above ground shoots, leaves and stems in what would normally be the drier months of summer. The wetland plants thus are replaced with aquatic plants which have less root mass generally and thus are less capable of holding soils and sediments. Aquatic plants in Devils Lake are vulnerable to Grass Carp which then reduces the vegetated mass on the nearshore. Loss of wetlands has a negative effect on water quality.
