The United States Geological Survey recently studied nitrate levels in streams around the country. The study found that nitrate – which can be dangerous in drinking water – can affect water systems for decades.
Although none of these study areas were in Idaho, Michael Lewis says the study is worth a closer look.
Lewis is the director of the USGS Idaho Water Science Center in Boise. As he explains the national study, high nitrate levels can remain in streams and groundwater for decades.
“Nitrogen loading to the land surface – which can impact groundwater quality – is significant in much of Idaho," says Lewis. "Particularly across the Snake River Plain which is agriculturally dominated.”
Lewis’ office conducted a separate study of the Snake River Plain for just this effect. Because of the concentration of dairy and crop farmers in the area, it’s no surprise nitrate levels are particularly high there. Lewis says 300,000 head of cattle were added between 1987-2007 and all that manure adds up. Plus there’s the common use of nitrogen-based fertilizer for crops.
But Lewis says one part of the Snake River Plain study that is surprising has to do with the idea of turning back the clock.
“If we were to cease nitrogen loading to the aquifer – I mean just completely cut it out to zero – the model results indicated that it would take 20-50 years to go back to a baseline, natural nitrate concentration.”
Lewis says the USGS hasn’t looked in great detail yet at other aquifer systems around Idaho. But he points to the Department of Environmental Quality. It has a list of nitrate priority areas – places nitrate contamination in drinking water is higher.
From the 2008 list, Twin Falls, Ada and Canyon County were at the top.
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