Water - Horsekeeping on a Small Acreage - page 441

Asaponddriesup,asshownhere,thestagnantwaterbecomesaconcentratedsource
of disease-causing organisms.
Natural water sources. Creeks, springs, and streams can provide a fresh supply of drink-
ing water, but they also may be a source of contaminants from upstream. Ponds can serve
as watering spots but may become stagnant. Because ponds don't have free-running water
refreshing them, and because birds, rodents, and other animals frequent them, ponds can
become reservoirs of disease-causing organisms such as those associated with equine pro-
tozoal myelitis (EPM) and West Nile virus.
In addition, ponds can collect agricultural runoff and have quite high nitrate levels (see
page 241 ) . Ponds with high bacteria, nitrate, and phosphorus levels often develop an over-
growth of algae. Certain algae are toxic and can cause sudden death. To prevent algae
buildup, decrease runoff contamination with diversion ditches or uphill retention ponds,
maintain a buffer zone, clean out the pond bottom periodically, and, if appropriate, consider
stocking the pond with algae-eating fish. When in doubt about the suitability of natural wa-
ters on your property, contact your county health department to have the water tested.