Rough River is a reservoir located in the western part of Kentucky. During the winter months, the water level of Rough River is lowered substantially in a process known as winter pool. This is done for several reasons.
Why is Rough River lowered for winter pool?
There are a few main reasons why Rough River goes through winter pool each year:
- To allow shoreline vegetation and trees to grow
- To reduce shoreline erosion and damage
- To allow repairs and maintenance on docks/marinas
- To control invasive aquatic plants and improve water quality
By lowering the water level in the colder months, trees and vegetation along the shoreline get a chance to grow and become established above the summer pool level. This helps stabilize the shoreline and prevents erosion.
It also means marinas, docks, and other structures along the shore can undergo maintenance, repairs, and upgrades during the off season when boat traffic is lower.
Lowering the water level reduces shoreline hiding spots for invasive aquatic plants. It allows them to completely freeze and die off over winter. This improves water quality come spring.
Shoreline Vegetation Growth
When the water level is lowered for winter pool, areas along the shoreline become exposed. This allows beneficial native trees and plants to grow along the water’s edge above the summer pool elevation.
The root systems of shoreline vegetation help hold soil in place and prevent erosion. Plants also provide habitat for wildlife. Exposing more shoreline allows a larger riparian buffer to establish itself seasonally.
Reducing Erosion
Erosion can be a major problem along lake shorelines. Wave action, boat wakes, rising and lowering water levels, and loss of vegetation all contribute to erosion issues over time.
By lowering Rough River for the winter, shoreline areas are able to harden and establish root systems above the summer pool elevation. This makes them more resistant to erosion come springtime when the water level rises again.
Less erosion means clearer water, improved lake access, protected structures/docks, and better fish habitat.
Dock and Marina Maintenance
Here are some of the maintenance activities and repairs that lowering Rough River enables:
- Dredging marina basins
- Repairing or replacing floating docks
- Reinforcing shoreline retaining walls
- Performing general cleaning and maintenance
- Upgrading electrical and plumbing systems
- Larger construction projects
By temporarily reducing boat traffic over winter, marinas and docks can fix damage from the busy summer months when most boats are in use. They also have time for any needed expansion or upgrades to their facilities.
Aquatic Plant Control
Some invasive aquatic plants can take over areas of Rough River and have negative impacts. These include:
- Restricting boat access and navigation
- Choking out native plant species
- Reducing oxygen levels in the water when decaying
- Creating thick mats that prevent fish spawning
Examples of problem plants include:
- Eurasian watermilfoil
- Hydrilla
- Water hyacinth
Lowering the lake for winter exposes the plants to colder air temperatures and allows them to completely freeze and die off. This gives native plants a chance to recover in the spring.
What is the winter pool elevation?
The winter pool target elevation for Rough River is between 510-515 feet above sea level. This is approximately 15-20 feet lower than the normal summer pool level of 535 feet.
The process of lowering the lake for winter pool usually begins sometime in October or November. The lake is held at the lower winter elevation until late March or April.
Key Elevations
- Summer pool: 535 feet
- Winter pool target: 510-515 feet
- Full lake capacity: 565 feet
How is Rough River lowered for winter pool?
The water level of Rough River is controlled by a dam and hydroelectric station at the southern end of the lake. This allows the Army Corps of Engineers to regulate the lake elevation.
To lower the lake for winter pool, water is released through the dam’s floodgates and turbines. Outflow through the dam is increased, while inflows from tributaries stay relatively stable. This gradually reduces the lake level over a period of weeks until the winter pool target is reached.
Rate of Drawdown
Rough River is lowered over an extended period of time rather than all at once. This gradual drawdown of around 1-2 feet per week helps prevent shoreline damage.
A slower, controlled decrease in water level allows exposed sediment and soils to consolidate and stabilize as the water recedes. If the lake was immediately drawn down the full 20 feet to winter pool, erosion issues would be severe.
Monitoring Water Levels
Throughout the drawdown process, engineers monitor the water elevation using gauges located around Rough River. This allows them to adjust the outflow as needed to safely reach the winter pool targets.
Daily precipitation and inflow rates have to be taken into account to balance the amount of water being released downstream.
What changes when Rough River is at winter pool?
Some of the notable changes that occur when Rough River reaches winter pool elevation include:
- Exposing additional shoreline areas
- Restricted boat access to docks/marinas
- Closure of some boat ramps and recreation areas
- Concentration of fish in the deeper sections of the lake
Exposed Shoreline
The 20 foot decrease in water level exposes a significant amount of additional shoreline compared to summer pool. Narrow fingers of water are present in coves versus the wide open water of summer.
Mudflats and rocky banks emerge around the edges and in shallower arms of the lake. Trees and vegetation along the shore grow and expand down the freshly exposed banks.
Limited Boat Access
| Structure | Status at Winter Pool |
|---|---|
| Fixed docks/marinas | Ends of docks exposed, access difficult for larger boats |
| Boat ramps | Some closed due to low water levels |
| Floating docks | Removed from water for maintenance |
The lowered water line means boaters have limited access to established marinas and docks during the winter. Many boat ramps are also taken out of service temporarily until summer pool is reached again.
Fish Habitat Changes
Since roughly 20% of the lake’s surface area goes away in winter, fish become more concentrated in the remaining sections of deeper water. This makes them easier to locate for anglers.
Drawdown conditions can trigger fish to move up into tributaries and feeder creeks for the winter. Spawning grounds are also exposed for native species like bass, bluegill, and crappie.
When is Rough River brought back up to summer pool?
Refilling Rough River back to its normal summer water elevation begins in late March to early April. The lake level is slowly raised over 4-6 weeks until reaching full capacity around 535 feet above sea level.
The process involves reducing the amount of water released through the dam. Inflows from rains and tributaries start to outpace the controlled outflow, causing the lake elevation to rise under careful monitoring.
Factors Influencing Refill Date
A number of factors can influence the exact start date and duration of the Rough River refill period, including:
- Amount of winter/spring rainfall – More rain equals faster refill
- Inflow from tributaries
- Rate of snowmelt running into the lake
- Current water elevation/winter pool levels
- Boating activity and access needs
Outflow through the dam is adjusted weekly based on monitoring data to safely meet summer pool targets by early to mid May in most years.
Conclusion
Winter pool at Rough River involves carefully lowering the lake level to allow shoreline vegetation growth, reduce erosion, control invasive aquatic plants, and enable repairs and maintenance activities. This is done by increasing outflow through the dam over an extended period in fall/early winter.
The exposed shoreline and reduced boat access over winter provides environmental and recreational benefits that promote the long-term health of Rough River. Monitoring data enables the Army Corps to safely refill the lake in time for summer boating season.