Aquifers & Irrigation

Approximately 3.4 million acres of Idaho farmland are irrigated with water that a growing urban population  competes to use instead.

Irrigation is crucial to food production in Idaho. But cities and towns, like all human settlements, are also absolutely dependent upon adequate supplies of clean freshwater.  In Idaho, as in most places, these vital sources are both “surface” water (lakes, rivers, streams) and “groundwater” (aquifers). 

An aquifer is an underground “reservoir” of water contained in one or more layers or strata of permeable rock or unconsolidated materials. Groundwater from aquifers can then be pumped from water wells and distributed for use on farms, in factories, and across municipalities, whether to cook food, take a bath, or irrigate exterior landscaping. (Read the full section on aquifers here.)

Three of Idaho’s aquifers are classified by the Environmental Protection Agency (EPA) as “sole source aquifers”. That means they are the only or principal source of drinking water for the hundreds of thousands of residents in those regions. 

  • The Eastern Snake River Plain Aquifer
  • The Spokane Valley-Rathdrum Prairie Aquifer
  • The Lewiston Basin Aquifer
Kootenai County alone has more than doubled in population size since 1990.  This growth and development is replacing agricultural water use with domestic and municipal water use. 
88% of the county’s population depends on water from the SVRP Aquifer. 
The SVRP Aquifer is now used mostly for municipal purposes, not agriculture.

Just as human demands on the SVRP Aquifer are increasing, a changing climate is also putting pressure on the aquifer by creating earlier springs and drier summers. Higher temperatures for longer periods lead to more evaporation; increased evaporation results in more intensive storms and faster melt of the snowpack; this in turn means less water infiltrating into soil and the aquifer; finally, less soil moisture leads to an increase in summer water use, as well as more drought and wildland fires.

Projected future population growth in the SVRP Aquifer counties will increase the number of water consumers. At what point the increasing population will begin to overdraft and draw down the aquifer is uncertain. At the same time, what is certain is that increasing land development, impervious surfaces (pavement and roofs), and human and industrial activities will expose this unconfined aquifer to an increasing amount and variety of pollutants. (Read Here.)

In sum, while the SVRP Aquifer is still healthy today in spite of the population growth and development that have occurred over the past century and more, as the 21st century proceeds, increasing human numbers and a changing climate are likely to place it under greater and greater stress.  A century from now, or perhaps much sooner, whether or not it can continue to meet human and ecological needs for clean water in the region is an open question.    
The threat to Idaho’s aquifers is indicative of a nationwide problem. The New York Times crisscrossed the United States for half a year, examining data from more than 84,000 groundwater monitoring wells, and consulting with more than 100 experts on the nation’s groundwater resources and their management and depletion. 

The authors of the study concluded in 2023: 

  • “A wealth of underground water helped create America, its vast cities and bountiful farmland.  Now, Americans are squandering that inheritance.”

  • “America’s life-giving [groundwater] resource is being exhausted in much of the country, and in many cases it won’t come back. Huge industrial farms and sprawling cities are draining aquifers that could take centuries or millenniums to replenish themselves if they recover at all.”

  • Water levels at nearly half of the 84,544 groundwater monitoring wells included in the nationwide database have declined “significantly” over the last 40 years, due to pumping rates exceeding replenishment rates.

  • In the past decade, four out of every 10 wells reached all-time lows, and 2022 was the worst of all. As one groundwater expert, Warigia Bowman at the University of Tulsa, told The Times, “From an objective standpoint, this is a crisis.  There will be parts of the U.S. that run out of drinking water.”

For now, when Idaho citizens are confronted with a choice of diverting water from the state’s agriculture to provide water for drinking or any other urban use, they side with agriculture, according to polling done for this study.

In Idaho, approximately 3.3 million acres of farmland are irrigated, and irrigation is crucial to food production in the state. Cities and towns compete for scarce water with agriculture. Should water used to irrigate farmland be diverted to support additional human population growth in Idaho?

73% 14% 12% 73% 14% 12% water should not be diverted from agriculture to support more residents not sure water should be diverted from agriculture to support more residents

Three of Idaho's aquifers are classified as sole source aquifers. These aquifers are the only or principal source of drinking water for residents in those regions. How important is it to protect Idaho’s sole-source aquifers from over-pumping and depletion?

79% 16% 2% 2% 1% very important somewhatimportant not sure not veryimportant not at allimportant