Phosphorus effluence in artificial water reservoirs of Kalmykiya from cattle breeding companies

Artificial water reservoirs in Kalmykiya, which has limited water resources, were developed for a potable water supply for the local population, cattle breeding, and irrigation. Currently, they are strongly contaminated by biogenic substances. Calculations are provided in this study that confirm the hypothesis that cattle breeding (watering points of cattle and run-off from cattle breeding areas) developed in the water catchment area suppl 1–2 tons or from 20 to 700 g of phosphorus per 1 m² of water surface per year in the absence of other contaminants; this is the main reason that phosphorus content in all water reservoirs exceeds the maximum allowable concentration established for fishery water reservoirs (MAC_f) by tens of thousands of times. The highest proportion (80%) of the overall volume of incoming phosphorus originates from the bovine cattle. Phosphorus loads exceed the allowed and critical values for functioning of the water ecosystem by from 1 to 3 orders of magnitude, forming conditions for eutrophication and rendering water of these reservoirs unsuitable for potable water supply, including for cattle watering points.