|Nebraska Department of Environmental Quality|
Lake Ogallala Project Ready to Move Ahead
The on-again, off-again Lake Ogallala project is finally “on”, with physical re-engineering of the lake scheduled to begin in earnest in the fall of 2009.
Small project activities may take place earlier in the year, but large-scale dredging will wait until water levels in the lake can be dropped and access is accomplished.
The project is a joint venture involving the Central Nebraska Public Power and Irrigation District (CNPPID), the Nebraska Public Power District (NPPD), the Nebraska Game and Parks Commission (NGPC) and the Nebraska Department of Environmental Quality (NDEQ).
The project was subject to review and approval by the U.S. Army Corps of Engineers and this process resulted in a substantial delay. Final approval from the Corps was received on February 20, 2009, clearing the way for work to begin.
Now that the green light has been given, the task of re-shaping a portion of the Lake Ogallala basin can start. At stake is the health and viability of one of the state’s premier cold-water fisheries.
Lake Ogallala is located immediately downstream from Lake McConaughy on the North Platte River in Keith County. It was formed in the late 1930’s when the dredging of materials for the construction of Kingsley Dam resulted in a large borrow pit. Water supplied to Lake Ogallala is primarily from deep-water releases from Lake McConaughy.
The cold temperatures of the water in these releases have been shown to be ideal for survival and growth of salmonid fishes. Lake Ogalalla has been known as one of the state’s most popular put-and-take trout fisheries, according to the Nebraska Game and Parks Commission.
Both the water quantity and quality of Lake Ogallala are dependent upon the conditions of Lake McConaughy. During the mid- and late 1970’s, escalating fossil fuel prices led to state and federal policies that encouraged the use of renewable resources, such as hydropower, to supply the state’s electricity needs. In response to these policies, Central began construction of the
Kingsley hydroelectric plant in 1981. Commercial operation began in 1984.
Prior to the installation and operation of the hydroelectric unit, water delivered to Lake Ogallala was sufficiently oxygenated to maintain aquatic life. However, once hydroelectric operations commenced, lake oxygen levels were measured to be near lethal levels for trout and other aquatic life in some areas of the lake, due to the change in the means of delivering water from one lake to the other.
During years of high water, the temperature of Lake McConaughy water released to Lake Ogallala is sufficient to support the cold-water fishery. However, reservoirs like Lake McConaughy trap sediment and other pollutants from the flowing waters in the upstream watershed. During years when water is plentiful, Lake McConaughy is subject to thermal stratification. This stratification (layering) of Lake McConaughy results in releases with depleted oxygen levels and oxygen-demanding pollutants, and oxygen demand exceeds oxygen production.
During low-water years, temperatures can be elevated, which can be a concern to the coldwater fishery. In an evaluation conducted from 1991-1994, the NGPC reported the trout fishery to be declining, with the average fish size dropping from 11.4 inches and 0.7 pounds to 10.3 inches and 0.44 pounds. The deterioration was attributed to a combination of issues; water quality, loss of food sources, disappearance of plant life, and high levels of non-game fish such as carp, alewife and white suckers.
Following a fishery renovation in 1997, Lake Ogallala began to experience periodic observations of dead and stressed trout in the late summer of both 1999 and 2000, with the problem extending into the Sutherland Supply Canal. At this time the NDEQ assessed Lake Ogallala to be impaired, and included the water body on the 2002 clean Water Act Section 303(d) List. Once included on that list, it is required that steps be taken to identify pollutants and plans for their reduction.
Based on the unique features of Lake Ogallala, several agencies expressed an interest in developing a multi-faceted management plan that takes into account and balances all uses.
From this collaboration comes the corrective action plan now being pursued. Lake Ogallala is “L” shaped, with the two arms showing considerable differences. The North-South basin is parallel to Kingsley Dam and resembles a typical reservoir. That is, this arm is deeper, has steep gradient banks and no visible current. The Keystone Basin runs perpendicular to Kingsley Dam and at times reflects a river more than a reservoir, with a uniform depth, narrow channel, visible velocity and shorter detention times.
Water released from Kingsley Dam currently flows through the south side of the basin, where the channel is deeper. Consequently, the shallower north side receives little water flow and tends to become stagnant. This contributes to low oxygenation levels and higher temperatures, and makes it an unfit habitat for the fish population.
The renovation now underway will create a 50-foot-wide channel through the north basin, running 7,000 feet from west to east. This channel will be dredged to a depth of eight feet, providing both the depth and the circulation that the Keystone Basin needs to re-establish its value as a fishery.
The partners have received more than $700,000 in grant funding for the project, made up of a $465,480 grant from the Environmental Protection Agency (EPA) and $310,000 from the Nebraska Environmental Trust Fund. That funding was contingent upon approval from the Corps of Engineers, and now that approval has been granted, renovation work can begin as soon as weather permits.
Nebraska Department of Environmental Quality
1200 "N" Street, Suite 400
P.O. Box 98922
Lincoln, Nebraska 68509