Reservoir Problems |
Rehabilitation Technigues |Lake Problems |
Rehabilitation Techniques |
River & Stream Problems |
Contingencies Plans |
Reservoir Rehabilitation Techniques
1. Reservoir drawdown: Exposing sediment and letting it air dry allows earth moving equipment
to remove sediment from the basin.
3. Fish removal: The decision to remove an existing fish community
with rotenone, a fish toxicant, is made only when few sport fish are
present and their salvage is not cost effective. The cost of renovation is much lower when the
water volume is reduced through reservoir drawdown. When refilled, the reservoir will be
stocked with desirable sport fish.
4. Excavation: When the reservoir basin dries, sediment is removed with earth moving
equipment in a fashion that will create ledges, trenches and drop-offs. Irregularities in a
reservoir's basin attract and concentrate fish. Deep reservoirs also are less subject to fish kills
than shallow ones.
5. Island Construction: Sediment spoil can be used to rebuild shorelines and create
islands. Shoreline erosion caused by wave action gradually enlarges reservoirs. However, the
extra water created is shallow, it absorbs the power of crashing waves and supports few fish. By
removing silt from areas close to shore and depositing it at the existing bank, deep, fish
supporting water can be created within casting distance of the bank. Sediment spoil excavated
from the basin also can be relocated in the basin as islands. Creating islands has the same effect
as creating more shoreline; they increase the amount of water producing desirable shoreline
species, such as large mouth bass, bluegill and black crappie. Islands must be stabilized with
rock riprap to prevent erosion.
6. Sediment and nutrient control dikes: Installed at the upper reaches of
reservoirs to form marshes, dikes trap sediment and agricultural runoff as
water enters the lake. Trapping sediment above the reservoir where it can
be removed periodically keeps the water in the reservoir clearer than if
sediment is allowed to accumulate in the basin or remain suspended. The
importance of clear water cannot be overstated.
Anglers catch more fish from clear water, and more sport fish can be supported by a reservoir
with clear water. Clear water produces more zooplankton than muddy water, and those
microscopic animals are the food on which small fish live. Regardless of size and bag limits, a
bass will never reach five pounds if zooplankton is not available when the fish is no more than an
Water clarity also affects the amount of vegetation a reservoir will support. Sunlight does not
penetrate murky water, so rooted aquatic plants, the key to good habitat, cannot grow. Aquatic
plants provide refuge for young game fish and bait fish, feeding areas for predators and shade
from summer sun, but aquatic vegetation has an even greater value. The leaves and stems provide
surfaces on which crustaceans, aquatic insects and other food organisms attach and grow, and the
plants' process of photosynthesis replenishes the water's vital oxygen supply. Sediment/nutrient
dikes also benefit terrestrial wildlife, including furbearers and waterfowl, by creating wetlands
above and below the structures.
7. Offshore breakwaters: Built near erosion-prone shorelines in
water four or five feet deep, these structures create quiet water near shore.
Structures must be connected to the shore at intervals to exclude boats,
and culverts must be included to allow fish passage. These structures are
a better alternative for stabilizing eroding shorelines than simply dumping
rock riprap. Aquatic vegetation should grow between the structures and
the shore, allowing both shore-bound anglers and boat anglers access to productive fishing water.
Jetties also can serve as spawning habitat for walleyes.
8. Jetties: At the mouths of large coves, rock breakwater piers can be built from opposing
shorelines, extending toward one another so that the opening between them is just wide enough
to allow boat passage. These structures reduce wave action and shoreline erosion in the cove and
provide anglers access to deep water. They, too, can enhance spawning habitat for walleyes.
9. Increased water storage: Summer drawdowns in irrigation reservoirs flush fish and reduce
the space and habitat available for fish. Stable water levels would increase the number of small
fish that survive beyond their first year of life, increasing the number of catchable-size fish for