Drinking water for horses should be clean, palatable, and free of chemical or microbial contaminants. Scheme water supplied for human consumption normally meets these criteria, but problems may arise with water from dams, bores, rivers, ponds, and storage tanks. Contamination of water troughs etc. by feed, manure and urine is common whilst groundwater supplies may contain chemicals such as Nitrates, Nitrites, Sulphates, or heavy metals. Seepage from nearby septic tanks can contaminate groundwater with coliform bacteria and toxic blue green algae occasionally contaminate pond and stream water. Growth of bacteria is favoured by warm temperatures and light stimulates algal growth if unchecked. Water quality is dynamic and constantly changing under the influence of rainfall, run off, growth of microorganisms and access by livestock etc. Intake by horses can be reduced by e.g., fecal contamination and low temperature. A measure of quality is the Total Dissolved Solids TDS and a reading of TDS in the range 0-4000 is regarded as suitable for livestock whereas a TDS higher than 6000 may affect health and normal productivity though these guidelines were not developed specifically for horses.
Information on specific contaminants and standards can be sourced from ANZECC (2000) Water Quality Guidelines. Where there is uncertainty over water quality, testing by an accredited laboratory should be undertaken. It is essential to seek prior advice from the lab with regard to sampling technique and suitable containers for water sample storage and transport.