BOZEMAN — Montana’s lakes and streams have a number of issues with the quality of water, a state report says.
In the 2014 edition of its Water Quality Integrated Report, the Montana Department of Environmental Quality describes the impairments of streams, lakes and groundwater and the safety of drinking water over the past two years. The biennial report on water conditions is required by the U.S. Clean Water Act.
Samples from more than 22,000 miles of streams and 518,000 acres of lakes show that more than 70 percent of Montana’s rivers, streams and lakes are not supporting aquatic life, due to too much sediment, chemical pollution or bank and vegetation degradation, which contributes to increased water temperatures.
Water in the majority of lakes and reservoirs is also not suitable for drinking but can support recreational use.
The Bozeman Daily Chronicle reports that the state has assessed almost 1,050 of the almost 1,100 stream sections and 72 lakes or reservoirs.
Of those, the report says about 460 are considered polluted or impaired and in need of an improvement plan, compared to 565 two years ago.
All of those have quality issues related to excess sediment or silt, the No. 1 reason for impairment.
Other common pollutants include phosphorus, nitrogen, lead, copper and arsenic.
The report identifies grazing on riverbanks or shorelines as the No. 1 confirmed cause of poorer water quality, affecting 136 bodies of water. Irrigated crop production comes next, affecting 52 water bodies.
The report said that causes could be confirmed for only 21 percent of streams or lakes.
The state uses the data for a number of programs, including the development of plans to improve stream water quality. The data will also serve as a baseline as oil and gas exploration moves into the state.
The report also details drinking water violations but said most of the violations were the result of an incomplete understanding of reporting requirements or were technical violations that didn’t have public health risks.
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