Josh Johnson, Central Idaho Conservation Associate, (208) 318-5808.
Scott Ki, Communications Associate, (208) 345-6933 x 214.


Report: Groundwater quality remains poor in southern Idaho 

BOISE – The Idaho Conservation League’s latest groundwater report details a continuing trend of poor water quality in the Magic Valley. These findings solidify the serious concerns raised by ICL’s previous groundwater reports that the drinking water source for more than 300,000 Idahoans – the Eastern Snake Plain Aquifer (ESPA) – is significantly degraded. 

The ESPA holds as much water as Lake Erie and supplies drinking water to Idahoans in southern Idaho. But this critical water supply is heavily impacted by contamination, primarily from nitrogen and phosphorus pollution generated by human activities in the Snake River Plain. For instance, the approximately 469,00 dairy cows in the Magic Valley generate as much nitrate as the waste produced by a city of 16 million people. The nitrogen and phosphorus from synthetic fertilizers, animal waste, and other sources far exceed what typical crops can uptake, with the remainder susceptible to leaching into the groundwater.

“Our study shows that groundwater quality in the Magic Valley is in a bad state and indications are that it will worsen in the future,” said Josh Johnson, ICL’s Central Idaho conservation associate. “This is a serious public health and economic problem that affects everyone who relies on groundwater in the Magic Valley. Hundreds of thousands of Idahoans rely on the aquifer for their drinking water and farmers, ranchers, and others depend on the water to grow crops and keep their operations successful.”

The report concludes that properly addressing contaminated groundwater will require a significant investment of federal funds to incentivize the adoption of better manure management and best management practices on agricultural fields. Additionally, more effective and transparent management of animal waste and fertilizers is necessary to reduce nitrogen and phosphorus pollution and improve groundwater quality. 

Since the inaugural Groundwater Report in 2019, ICL has continued to aggregate new groundwater data collected by state and federal agencies, review the latest peer-reviewed literature pertaining to agricultural pollution, and engage in discussions with local stakeholders and water quality and agricultural professionals in the region. The 2021 Groundwater Report incorporates and synthesizes the latest information available regarding groundwater quality in the Magic Valley.

ICL’s key findings since the last groundwater report in 2020:

  • For the third straight year, agencies detected elevated total phosphorus concentrations at a number of springs fed by the Eastern Snake Plain Aquifer, continuing a troubling trend of worsening water quality. 
  • County-level analysis of groundwater data for the Magic Valley reveals that the highest and most harmful nitrate concentrations are typically found in Twin Falls, Cassia, and Minidoka counties.
  • A growing body of evidence indicates that long-term ingestion of nitrate in drinking water increases the risk of a myriad of adverse health effects, particularly colorectal cancer. This increased risk is tied to nitrate levels below regulatory limits, suggesting that the current drinking water standard likely does not adequately protect the public from nitrate-related health conditions. 
  • 19% of public water systems in the Magic Valley have average nitrate concentrations >5 mg/L based on samples collected in the last five years, a concern given the potential health effects of nitrate in drinking water.


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 restore the Snake River across southern Idaho to a safe, fishable, and swimmable condition.