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.