Water Management Report for Cumberland River Basin

Wolf Creek/Lake Cumberland

Lake Cumberland is the key to coordinated water management in the Cumberland River Basin. Lake Cumberland is formed by Wolf Creek Dam at Cumberland River Mile (CRM) 460.9. It is the one of the largest reservoirs east of the Mississippi River. Normally, water stored in Lake Cumberland is gradually released during the summer and fall to provide downstream flows that support multiple uses of the Cumberland River. Since Lake Cumberland is such a significant source of water for the maintenance of the Cumberland River, human populations have adapted and adjusted to take advantage of this generally dependable source of water.

Now, major repairs are underway to stem the leakage of water through the dam's foundation which threatens the structure's overall integrity. Early in 2007 the lake was lowered to an elevation of 680 feet above mean sea level (msl), which is 43 feet below the top of the power production pool of 723. The Corps now attempts to maintain a near flat pool at the 680 elevation. With the loss of the 43 feet of storage in Lake Cumberland and the restrictions in operational flexibility imposed by the flat pool operation, water management options are severely limited. Dam repairs are expected to take several years.

At Wolf Creek Dam a work platform has been created on the embankment and repairs such as grouting are well underway.

The lowering of the pool has resulted in some impairment of the lake's recreational uses. Lake Cumberland is a popular, regional tourist destination and is heavily used by local residents. Marina operators have had to adjust to the drastically lower water levels. Some boat launching ramps are no longer usable or have restricted usage at the elevation of 680; however, approximately 13 ramps are usable at the 680 target elevation. Several water intakes will be threatened if water levels drop much below 680. At 650, about 200,000 people would be without water because intakes would be above water. With this said, some water users have opted to extend their intakes deeper into the lake to increase their reliability.

Overall, water quality conditions in the lake have not significantly deteriorated so far. In part this is due to the significant cooling that occurred back in the winter followed by a relatively dry spring. This fortunate set of circumstances allowed the retention of a large body of very cold, highly oxygenated water in the lake. The low rainfall during the spring and early summer has preserved much of the coolwater habitat in the lake and lessened the chance of a fish kill in the fall. In effect, the low rainfall allowed more of the cool, oxygenated, winter-stored water to remain in the lake, which is good news for the striped bass, walleye, and smallmouth bass fisheries. Barring unforeseen circumstances, the lake should maintain adequate water quality through the critical late summer/fall period when conditions are typically the worst despite the lake level restrictions, drought, and warm weather.

At the same time, downstream environmental considerations are significant and varied and depend largely upon having an adequate supply of cold water. Up until early June 2007 various release regimes were tried at Lake Cumberland to seek to maintain the cold tailwater fishery and meet multiple downstream river system needs that extend well beyond the immediate tailwater. Ultimately, after a period of very warm weather in late May and early June, concerns over possible degradation of the important tailwater trout fishery led to cessation of hydropower generation and the beginning of sluice-only releases. Sluicing maintains colder water by drawing from approximately 115 ft below the surface of Lake Cumberland at the elevation of 680 ft. The temperature at this depth is about 47° F. Sluicing also provides good oxygenation due to the turbulence of the release. On the down side, sluicing is a more involved process to start and stop, requiring additional labor to operate the machinery. Sluicing only offers less flexibility in flatling lake level maintenance versus using the hydropower units for releases. In addition, the sluices were also not designed to operate with the frequency with which they are being used, leading to future maintenance and reliability concerns.

Various sluice release regimes have been experimented with including one sluice four hours on and two hours off and the preferred operation of three hours on and three hours off. Based upon field water quality measurements, and a request on June 7th from KDFWR water has been released exclusively from sluice gates in the dam. The current schedule is to release water from one sluice gate for three hours and then have no water released for the next three hours and then repeat that cycle 3 additional times each day. Temperature monitoring near Winfrey's Ferry Ramp and other locations along the river has documented that the water has been somewhat cooler with this newest release pattern. However, the further downstream one travels from the dam the more the low flows allow the river temperature to be affected by the surrounding air temperature. The temperature of the river from the dam to Winfrey's Ferry remains very cold (50-62° F) and is always favorable for trout to thrive even on the warmest days. The river temperature from Winfrey's Ferry to Burkesville is warmer (60-66°F) but still in a range where trout will continue to feed and grow. So, barring any reductions in the volume or temperature of water released from the dam, trout fishing should remain excellent from the dam to Burkesville for the foreseeable future.

However, thinking that there may be a fish kill due to the warming water downstream of Burkesville, on June 16th the KDFWR instituted an emergency measure which liberalized the trout regulations on a 40 mile stretch of river from the state line to a point 100 yards upstream of the public boat ramp at Burkesville in Cumberland County. The temporary liberalization of the regulations from Burkesville to the state line has been rescinded since water conditions have improved somewhat, due to cooler weather. Therefore; the standard more restrictive regulations are again in force for the entire river.

Another benefit of sluicing was to protect municipal water intakes for Burkesville and Cumberland County, Kentucky. With the intense summertime heating, the greater distance from Wolf Creek Dam, and the limited quantity of cold water available for release, the tailwater stretch below Burkesville is simply more problematic to maintain under the current restrictions. The Corps and the KDFWR have stepped up environmental monitoring in the tailwater so that the effects of flow schedules or regimes can be monitored. Monitoring involves placement of data loggers at various points and additional data collections by monitoring crews.

The Nashville District has greatly intensified the collection of water quality data in the Wolf Creek Dam tailwater as a result of flow restrictions. Data collected is used to manipulate the river system to meet needs.

All releases from Wolf Creek Dam have been made using the project's sluices since early June. This has helped preserve the cold water fishery in the tailwater.

Immediately downstream from Wolf Creek Dam is the Wolf Creek National Fish Hatchery (WNFH) operated by the US Fish and Wildlife Service. The hatchery has a multilevel water intake on the face of the dam. With the drawdown, the operation of the intake is partially compromised, particularly during the warm months. In order to provide an alternate source of cold water, the Corps has installed pumps and piping to transfer water from the tailwater to the hatchery. This system has been installed and testing of its operation is underway. Options for providing a continuous flow to the hatchery are being examined. These options include the current pulsed sluicing and may later include a special release gate placed in one of the sluice openings to provide a continuous, though reduced flow.

Two pumps have been installed below Wolf Creek Dam to convey cold water to the Wolf Creek National Fish Hatchery.

Water will be pumped through this recently installed pipe system to help maintain the Wolf Creek National Fish Hatchery (Background).

The most recent collection of water quality data from Lake Cumberland and the tailwater by the Corps occurred on August 8th. That data indicated a seemingly adequate supply of cold water exists in the lake to meet downstream needs. This is dependent upon weather however. A very large storm system that dumps several inches of rain over the Lake Cumberland basin could cause the Corps to have to flush out much of the remaining cold water in order to get the lake levels back to the 680 guideline. A large storm could also flush large amounts of warm water into the tailwater, raising temperatures to a level that could damage the current cold water fishery. As a general guideline, moderation in precipitation at this point in the year would be best for maintenance of the current situation.

While temperature in Lake Cumberland is currently acceptable, dissolved oxygen(DO) is becoming a challenge. As the water is dumped from the dam, newly aerated and cold from the lower lake levels, it's holding good DO and temperature for 30-40 miles. By the time it's getting to Cordell Hull (CHu) it's getting too warm with falling DO which is encouraging stripers to move upstream and trout moving as far as Celina in the Obey watershed.

Conditions on Lake Cumberland, Wolf Creek Dam and its Tailwaters
Fall 2007

August 2007 was intensely hot and dry across the Cumberland Basin with 100+ degree days becoming commonplace. With the heat came continually drier conditions and management of Lake Cumberland and the tailwater area below the dam became more challenging each day. As inflows into the lake dropped, so did the pool (lake) level, reaching elevation 680.0 on August 29. In order to conserve the Lake Cumberland pool and protect water intakes in the lake and in the Cumberland River downstream from Wolf Creek Dam, a number of sluice release patterns were tried. Management into early fall required reduced flows from the dam because there was a need to conserve water in Lake Cumberland, and no guarantee of any rainfall any time soon. One measure tried with some success was coordinating with Eastern Kentucky Power to obtain generation water from Laurel River Lake. Laurel River Lake is a deep but relatively small reservoir with the only water in storage that was available to help the ever-shrinking Lake Cumberland. Fortunately by late September, the worst of the intense heat had passed and by October some small rain systems began pushing through. However because the land was so dry, it took a number of weather systems to produce noticeable runoff to help lake levels rise. The low point of the Lake Cumberland pool was reached on October 22 when it registered 678.61.

The coolwater fisheries (striped bass, walleye, and smallmouth bass) survived the critical late summer and fall period when temperature and oxygen conditions were the worst. Wintertime will bring cooler weather and more favorable conditions for these fish. As the lake cooled in the fall, the thermocline (the layer of water separating two layers of warmer and cooler water) broke down and the lake eventually experienced turnover, reoxygenating the water column. Water quality in the lake should remain good through the winter and early spring.

At the dam, sluicing which had been maintaining the cold water regime of the upper tailwater (down as far as Burkesville, Kentucky) was helped somewhat when another of the main sluices was outfitted with an orifice gate originally designed for Center Hill Dam. This device was placed on the intake to one of the six sluice conduits and now produces a continuous flow of approximately 260 cubic feet of cold water per second. The orifice gate provides a way to “stretch” the supply of cold water by allowing a continuous though smaller flows giving water managers more options. Indications are that the discharge from the orifice gate aerates to a slightly lower, but still acceptable, degree than an unrestricted sluice discharge. KDFWR has requested that the COE continue the use of the orifice sluice gate through March 31, 2008 during any daily period of no power generation. With two more orifice gates being built, Wolf Creek Dam will have two of the devices and the original will be returned to Center Hill Dam.

View of the orifice gate discharge at Wolf Creek Dam. In left foreground iis another set of sluice openings.

By the end of October, sluice releases were limited to one in each 12 hour time period, augmented by the orifice gate release. This situation continued until December when rising pool levels combined with improving water quality conditions (associated with fall mixing) in the lake allowed resumption of some hydropower generation.

Intensive monitoring of water quality conditions at Lake Cumberland and the tailwater continues. The Corps collects biweekly samples of temperature and dissolved oxygen (DO) at two locations upstream from the dam and does grab sampling in two or three locations to monitor the tailwater. The Kentucky Department of Fish and Wildlife Resources (KDFWR) worked closely with the Corps of Engineers (COE) through the summer and fall 2007 to monitor water quality conditions in the Cumberland tailwater. KDFWR personnel deployed temperature loggers at five locations in the tailwater (Winfrey’s Ferry, Big Willis, Bakerton, Cumberland Co. Water Plant, and Cloyds Landing) to record hourly water temperatures. Data from the loggers showed suitable water temperatures for trout (<68 F) existed in the upper 30-35 miles of the tailwater throughout the summer; however, lower portions of the tailwater were often too warm for trout. Fortunately, no fish kills occurred during the critical summer/fall period and water temperatures have cooled sufficiently in the fall.

Grouting and stablization work continues on the long embankment section of Wolf Creek Dam.

During the summer, adequate DO existed in the top 35 feet of the lake. By late November, as the waters mixed, adequate DO levels had only reached down 65 feet, thus limiting the ability of the Corps to generate power. The most recent data collected in mid-December indicates mixing down to 85 feet of depth. This is still well short of complete turnover but enough to permit the generation of hydropower. Turnover is also important to life in a lake as it mixes nutrients and oxygen more deeply in the lake. Monthly water quality monitoring trips are planned to keep tabs on conditions in Lake Cumberland. Over winter data collection is vital for managers to determine the “set up” conditions for the next warm season. Water conditions in the tailwater should remain favorable throughout the winter and early spring. Temperature and oxygen levels will be suitable for trout throughout the Kentucky portion of the tailwater. Also, the increased rainfall in the fall should allow adequate flows in the tailwater. Wade fishing opportunities should remain good. As usual, the big unknown is the weather.

Pictured is a "redd" or salmon nest in the Cumberland River downstream from Wolf Creek Dam. Redds were observed at numerous locations in the Wolf Creek tailwater.