BOISE — The Idaho Conservation League announces the release of its new and updated report on groundwater in the Magic Valley, which details a trend of worsening water quality as a result of contaminants, primarily nitrogen and phosphorus.

The Eastern Snake Plain Aquifer (ESPA) holds as much water as Lake Erie and supplies drinking water to over 300,000 Idahoans, but it’s increasingly impacted by contamination that is directly attributable to human activities across the Snake River Plain. For instance, the estimated 425,000 dairy cows in the Magic Valley create as much manure as a city of 12 million people – if that city had no wastewater treatment plants. The nitrogen and phosphorus from fertilizer, animal waste, and other sources far exceed what typical crops can uptake, with the remainder susceptible to leaching into the groundwater. 

“Idahoans deserve to know what’s in their drinking water and if they’re at risk from contamination,” said Josh Johnson, ICL’s Central Idaho conservation associate. “The problem of worsening water quality in the ESPA affects everyone who relies on groundwater in the Magic Valley. A combination of best management practices industry-wide, including cover crops, residue management, and no-till planting, as well as stricter regulation of fertilizer and manure application by state agencies is needed to help solve this problem.” 

He added, “We all share a responsibility to address the issue whether it’s a dairy operation with 10,000 cows or individual homeowners who fertilize their front yards.” 

ICL’s key findings since the last groundwater report in 2019:

  • For the third straight year, elevated total phosphorus concentrations were measured at a number of springs fed by the ESPA, continuing a troubling trend of worsening water quality identified in the 2019 report
  • County-level analysis of groundwater data for the Magic Valley indicates that the highest and most harmful nitrate concentrations are typically found in Twin Falls, Cassia, and Minidoka counties. 
  • There is growing epidemiological evidence that long-term ingestion of nitrate in drinking water increases the risk for a myriad of adverse health effects, particularly colorectal cancer. This increased risk is tied to nitrate levels below regulatory limits, indicating that the current drinking water standard may not adequately protect the public from nitrate-related health conditions. 


ICL was founded to be a strong voice for clean water. Several years ago, High Country News referred to the Snake River as “Idaho’s sewer system”. As it flows west, the river picks up so much pollution that, by the time it reaches Idaho’s western border, it is so contaminated that the State of Idaho warns people not to let their pets swim in it. ICL’s long-term goal is to make the Snake River across southern Idaho safe, fishable and swimmable again.