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In an intensive water study done at four forest streams in the Stanislaus National Forest, water quality samples collected last summer by CSERC staff and tested by an independent laboratory showed high levels of contamination once livestock were present alongside the streams. The detailed CSERC water study report has now been released for scientific review and public consideration.
Background
For the past 15 years, CSERC staff has carefully monitored livestock impacts to meadows and riparian areas within the Stanislaus National Forest. Under the leadership of the Center's biologists, CSERC staff has measured grass heights of key species at agency-specified locations before cows begin grazing in forest meadows. Then the staff measures those same areas again near the end of the grazing season to compare measurements. Using the Forest Service's own protocols, CSERC has found that most years there are many areas where livestock grazing violates the agency's clearly spelled out standards and guidelines. Utilization of meadow grasses by livestock is either beyond the limits or stubble height standards are not met. Put simply, that means the meadows are overgrazed. |
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The result for the ecosystem is that there is often little habitat value left for wildlife. Streambanks are frequently denuded or trampled. Sediment erodes into streams.
But despite the obvious resource impacts at heavily grazed meadows and stream areas, the question of water quality impacts was far less certain. Even where cows trampled a streambank or significantly over-grazed the grass in a meadow, there was no proof that water quality was actually being affected. |
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Research Approach
To try to find science-based answers, CSERC planned a study project last summer that was consistent with State Water Board protocols and depended upon independent laboratory testing of water samples. Lindsey (CSERC biologist) started the effort by spending weeks developing a carefully developed Quality Assurance Project Plan that would spell out exactly how the water study would be done. Then she and CSERC’s director John began visiting four meadows where monitoring from previous years showed that cows grazed fairly early in the summer season.
The Center took multiple water quality samples in the weeks before cows arrived at the four meadows. Once cows were present in the general area, CSERC continued to take water samples. Following the established protocol, all of the samples were carefully collected, kept out of sunlight on ice in a cooler, and turned over to the independent laboratory in less than six hours. |
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Results
The results were startling. Prior to the time that cows arrived at meadows alongside the forest streams, the water quality was generally good. State water quality standards for recreational contact objectives were met. But soon after cows arrived, the level of bacterial contamination in the water significantly increased. Testing of samples showed that the water was contaminated by excessive levels of total coliform, fecal coliform, and E. coli. The fecal coliform contamination was proven to be at levels that exceeded Basin Plan levels for recreational contact, let alone for drinking.
To read more about CSERC's water study, click here....
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