Scientist presents major groundwater quality analysis for south central Idaho

By Rachel Cohen; Boise State Public Radio News

A water quality sampling line is fed down a groundwater well in southern Idaho. Idaho Water Science Center USGS

Water in south central Idaho has had nutrient issues for a long time. That’s according to Kenneth Skinner, a groundwater hydrologist at the U.S. Geological Survey.

But Skinner said, while several state and federal agencies have collected data in the Magic Valley area since the 1990s, there hasn’t been a recent analysis of regional groundwater contamination trends.

That’s what he set out to complete by analyzing samples of a particularly widespread pollutant, nitrogen, from over 500 groundwater wells. Some common sources of nitrogen are fertilizer and manure.

His findings, shared at the Idaho Water Quality Workshop on Wednesday, show nitrate levels in the Magic Valley were increasing from 2000 to 2009, but have not been moving in any statistically significant direction in the years since. Skinner said that’s a good sign.

“Nitrate can be a health hazard. If nitrate concentrations get too high, it’s not safe to drink,” he said.

Still, several areas in south central Idaho are on the Department of Environmental Quality’s watch list for “nitrate priority areas.” Several rural counties north of the Snake River rely on groundwater for drinking.

Skinner’s research also revealed an important area for future study: phosphorous in groundwater. Scientists don’t often pay much attention to this pollutant underground because it binds well to the soil, which means it can be harder to detect.

But Skinner said it’s important to monitor because of how well-connected underground water sources are with surface area, especially in the Magic Valley.

“All the groundwater in this area ends up in the Snake River – it comes out in the springs, goes out to the Snake River, so if there’s phosphorous in the groundwater, it’s going to end up in the Snake River itself,” he said.

More phosphorous in the river can lead to the growth of harmful algal blooms.

Skinner said phosphate levels in groundwater were also increasing in the first decade of this century, but there hasn’t been enough data to track it more recently.

The nonprofit Idaho Conservation League released a report last year conveying phosphorous levels in springs flowing into the Snake River are increasing, and the organization said it’s a growing area of concern.

Find reporter Rachel Cohen on Twitter @racheld_cohen

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