Muddy Lake Cures
Muddy Water in Ponds and Lakes
Causes, Prevention, and Remedies
All ponds and small lakes can become muddy on occasion due to inclement
weather. In most cases, these muddy conditions are short-lived and will
clear in several days if no further rainfall occurs. Occasionally, a
pond will become muddy (or turbid) and will fail to clear. These
situations may necessitate measures to eliminate the turbidity and
prevent future occurrence. Muddy water, as described in this fact sheet,
is caused by soil particles (typically clay) and is usually a chocolate
brown color. Water that is green in color is caused by an algae bloom as
a result of excessive nutrients.
Impact of Muddy Water
Many ponds and lakes in Texas are built to provide recreational
activities and aesthetic benefits. Chronically muddy water makes a pond
or lake very unattractive and most swimmers will avoid swimming in such
water. Fishing is impacted because a chronically muddy lake reduces the
amount of sunlight penetrating into the water which in turn reduces the
amount of aquatic food produced by the pond's food chain. This
ultimately reduces the amount of fish biomass (pounds of fish) that can
be supported. Additionally, desirable fish species such as bluegills and
largemouth bass are sight feeders. High turbidity levels negatively
impact the ability of these species to feed and maintain themselves in a
Causes of Muddy Water
The two primary biological causes of muddy water are fish and waterfowl
(ducks and geese). Large populations of common carp, goldfish, and
bullheads can cause muddy water due to their spawning and feeding
activities in shallow water. The constant splashing and rooting around
in shallow water not only causes re-suspension of bottom soils, but is
detrimental to shallow water vegetation that helps protect shorelines
from wind-induced wave action. Large numbers of domesticated ducks and
geese cause similar problems. Additionally, waterfowl often eat bank
vegetation which can increase erosion.
Activities in the watershed are a leading cause of muddy ponds. Lakes
that receive runoff water from nearby soils that are frequently
disturbed with agricultural equipment are prone to be muddy. This is
particularly true if farming is done right up to the pond bank. Another
agricultural activity that causes muddy ponds is allowing livestock
access to the pond. The frequent trips to drink cause considerable
disturbance in shallow water. Construction within the pond's watershed
can also result in considerable input of suspended clay into a pond. A
watershed that is too small for the size of pond it flows into can cause
muddy water due to wave action along exposed mud shoreline as water
levels drop during periods of low rainfall.
Prevention is the key to eliminating
the need for costly remedial action to clear a pond or lake
* Do not stock and prevent the introduction of carp, goldfish, and
bullheads into the lake. A major source of these nuisance fish species
is the bait bucket. It is not unusual to see carp and bullhead
fingerlings in buckets of minnows. If the bait bucket is dumped into the
pond, a muddy water problem may develop. Many pond owners prohibit
fishing with minnows or any bait fish.
* Maintain dense populations of largemouth bass. This predator species
can control nuisance fish species in ponds.
* Try to keep domestic geese and ducks away from the pond. One pair per
surface acre is tolerable, but anything more could lead to a problem.
* In planning a lake, make sure to match watershed size correctly to
lake size. A good rule of thumb is about 10-15 acres of watershed for
each surface acre of lake. Except in case of drought, this should keep
the lake "bank full" and minimize turbidity from wave action.
* Try to maintain vegetative cover throughout the watershed. If the
watershed is largely agricultural, muddy water can be prevented by
maintaining most of the watershed in hay crops rather than field crops.
* If hay crops are not an option or the pond owner does not control all
the entire watershed, maintain a wide buffer strip of vegetation around
the pond. Typically, buffer strips of 100-150 feet are suggested.
* Establish and encourage moderate vegetative growth around the pond
edge. Shorelines that have areas of rushes, sedges, and cattails are
better protected from wave action and therefore less likely to add clay
particles to the pond.
* It is important to fence livestock away from the pond to prevent
erosion of the pond bank and disturbance of shallow water soils.
* If construction must occur in the watershed, timely completion and
immediate reseeding of the affected areas can prevent a long-term muddy
If nuisance fish species are already present and causing muddy water,
they need to be removed. Either drain the pond and remove them or treat
the pond with a fish toxicant to eliminate the fish community. Restock
with desirable species. If nuisance species are present but water
clarity is acceptable, be sure to maintain a dense population of
largemouth bass to ensure future control of the nuisance fish species.
This can be accomplished by limiting harvest of the bass.
Keeping Canada geese away from ponds is becoming increasingly important
as their population increases. If geese have caused a muddy water
problem, harassment tactics are an option used by many. They range from
air cannons to scare the birds away to dogs (border collies are often
used) that continually harass the birds until they leave. There are also
products on the market that make the vegetation and lawns around the
pond unpalatable to geese. If they do not like the taste, they will
eventually leave to find food elsewhere. Remember, the willful
out-of-season shooting or poisoning of waterfowl is a federal offense!
Some watershed activities disturb clay materials that can result in
muddy water problems that are extremely difficult to correct. A prime
example of this is construction activity in the watershed. Colloidal
clay particles are very small and can take a very long time to sink to
the bottom. If you take a jar of water from your pond and after several
days it is still very cloudy in appearance, you likely have a problem
with clay particles. Several techniques exist that allow the pond owner
to greatly reduce the levels of suspended clay particles. All of these
techniques involve the "binding" of clay particles into larger particles
which sink to the bottom much faster.
A time-honored method of removing suspended clay particles is the
application of dry hay. Dry hay should not be confused with straw. The
hay should be loosely distributed throughout the shallow areas of the
pond. Recommended application rates are about 500-550 pounds per
acre-foot of water. Quite often a muddy pond will not need the
full application to clear the water. You may wish to consider adding
about 50% of the required amount, waiting 10-14 days, and then assessing
whether additional hay is needed. A good rule of thumb is that if water
transparency reaches 18-24 inches deep, enough hay has been added. There
is one important reason to use as little hay as necessary. The addition
of large amounts of organic material, such as hay, can lead to oxygen
depletion as the material decomposes. This is especially true in July
and August. If hay application must occur in summer, supplemental
aeration may be needed to prevent a fish kill.
Agricultural gypsum is another material for removing suspended clay and
does not cause the concern of a fish kill associated with adding hay.
Gypsum is also chemically neutral and therefore does not cause possible
pH problems associated with alum, another commonly used material.
Typical application rates are from 1,000-1,500 pounds per surface acre
of water, depending on the severity of the clay suspension. Again, it is
wise to add the gypsum at a conservative rate of 250-500 pounds per
surface acre of water, wait several days, and determine if additional
gypsum is needed. This prevents excessive application and therefore
helps keep costs down. Dissolve the gypsum in clean water and spray over
the surface on a calm day. Late evening is often an ideal time to make
the application as most nights are wind-free. Water movement from the
wind prevents the suspended clay from quickly settling out, reducing the
effectiveness of gypsum.
Alum (aluminum sulfate)
Alum is the most effective material for clearing clay turbidity from a
pond, often within a few hours. Application rates are typically 100-450
pounds per surface acre. As before, add 1/3-1/2 of the required amount,
wait a day, and then determine if additional alum is required to
increase transparency to about 18 inches. Application procedures are
identical to those described for gypsum.
For alum, there is a very good reason to use the minimum amount
necessary. After application, there is a chemical reaction that impacts
the pH (acidity) of the water. The reaction produces small amounts of
sulfuric acid which can decrease pH significantly in some waters to
levels harmful to aquatic life.
Therefore, alkalinity and pH should be tested prior to application.
Alkalinity should exceed 100 mg/l and pH should be greater than 7.0. If
not, hydrated lime needs to be added simultaneously to buffer the
effects of the acid produced by the alum addition. Application rate for
lime is 50 pounds per acre-foot. It is wise to re-check alkalinity and
pH repeatedly as more alum and lime is added. In situations where 400
pounds of alum may be needed, pH may begin to drop quickly even in
waters where pH was initially deemed to be adequate for lesser
additions. Hydrated lime also removes suspended clay, although not as
effectively as alum.
Limestone (calcium carbonate)
Agricultural limestone is a material commonly used to removed suspended
clay from the water. Application rates of 500-1,000 pounds per surface
acre are typically used. Limestone can be added in the same manner
described for gypsum.
If the pond is used for home or livestock drinking water, the use of
minerals (alum, gypsum, limestone) is not recommended. The purity of the
mineral substances is unknown, and its application to the pond could
result in the inadvertent addition of undesirable substances.
Preventative measures, such as proper pond construction and maintaining
well-vegetated watersheds, typically will keep a lake from becoming
muddy. Prevention is far less expensive to accomplish than correcting an
existing problem or clearing a pond with a variety of mineral
substances. However, lakes in Texas are occasionally muddy and excessive
rainfall is often the general culprit. On rare occasions, a pond will
become muddy and not clear up. The first activity for the pond owner is
to investigate if a correctable event or condition has occurred. The
owner should first examine watershed use, pond shorelines, and the
presence or absence of undesirable fish and animal species and assess
whether they may have contributed to the muddy water problem. If so,
correct if possible and monitor improvements in water clarity. If no
improvement is noted, the owner may wish to apply hay or a crushed or
powdered mineral to remove the suspended turbidity from the water. It is
always wise to start with partial applications to prevent over
application and unnecessary expense.
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