We believe the long-term health of the Eastern Snake Plain Aquifer (ESPA) depends on proactive, science-based and collaborative action. That’s why Idaho Ground Water Appropriators (IGWA) and its member districts are leading efforts to conserve groundwater, improve aquifer recharge and manage Idaho’s water resources more strategically.

View Our Mitigation Plans

The Eastern Snake Plain Aquifer is Idaho’s largest water source, stretching across 10,800 square miles and 16 counties. Beneath the surface, it contains an estimated 1 billion acre-feet of water, roughly equivalent to the fourth-largest Great Lake, Lake Erie. This makes it one of the most productive aquifers in the world.

This hidden resource fuels life across the state, supplying water to 1.1 million acres of farmland, dozens of cities, hundreds of businesses and nearly half a million Idahoans. It also powers the economy, supporting about one-fifth of all goods and services produced in Idaho and contributing roughly $10 billion each year.

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Using Less Water More Efficiently

IGWA members are committed to smarter irrigation practices that reduce aquifer stress while keeping Idaho farmland productive.

Key Strategies

We maximize sustainable use of Idaho’s groundwater resources and protect the rights of groundwater users by promoting smart policy, responsible stewardship, strategic water management and sound science.

Retiring marginal farmland
Switching to crops that require less water
Installing flow meters and monitoring systems to use water more carefully and efficiently

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Putting Water Back into the Aquifer

IGWA members have invested tens of millions of dollars in managed aquifer recharge—a proven strategy that replenishes the ESPA with surface water during high-flow periods. These efforts are funded primarily through assessments paid by groundwater users (mostly farmers) through their local groundwater districts. It’s a system of water users investing in long-term solutions that benefit their land, communities and the aquifer we all rely on.

Recharge techniques include:

Recharge basins: shallow areas where water seeps naturally into the aquifer
Recharge wells: engineered systems that sink water directly underground

Switching to Surface Water Where Possible

In regions where surface water is available, IGWA members have invested millions of dollars to convert farmland from groundwater irrigation to surface water irrigation. This dual-source strategy improves water flexibility and reduces aquifer withdrawals.

Improving Surface Water Delivery Systems

IGWA partners with canal companies and irrigation districts to manage surface water deliveries more strategically and efficiently, while also protecting incidental aquifer recharge. These efforts focus on modernizing infrastructure in ways that improve water delivery without undermining natural recharge benefits.

Key improvements include:

Upgrading diversion structures for better flow control
Installing telemetry to track and optimize water movement
Expanding dual-source infrastructure where farms can access both surface and groundwater
Diverting surplus surface water into managed recharge sites to increase aquifer storage
Converting farmland from groundwater to surface water irrigation

While IGWA supports lining canals in select cases to prevent unnecessary water loss, it opposes canal lining in areas where seepage plays a vital role in aquifer recharge. Seepage through irrigation canals is the No. 1 contributor to aquifer storage—and preserving that benefit is critical to sustaining the agricultural economy of Idaho.

Saving More Water for Dry Years

IGWA advocates for smarter and expanded reservoir storage to improve drought resilience and maintain water availability for both surface and groundwater users.

Efforts include:

Supporting new storage infrastructure
Utilizing surplus storage water for recharge and ground-to-surface water conversions
Collaborating with state agencies on long-term water planning

View Interactive Map View IWRB Managed Recharge Program

Source: IDWR (idwr.idaho.gov)

Source: IDWR (idwr.idaho.gov) - Map updates weekly

Boosting Snowpack from the Sky

To improve snowpack—the main source of ESPA recharge—IGWA contributes to Idaho’s scientifically supported cloud seeding program.

Used globally for over 75 years, cloud seeding is a forward-looking, environmentally safe tool to address long-term water shortages.

Here’s how it works:

Aircraft or ground-based towers release microscopic particles into storm clouds.
These particles trigger snow formation.
Meltwater from snowpack eventually recharges the aquifer.

See Most Recent Map Data

Why Mitigation Matters

Under Idaho’s water law, junior-priority users—often groundwater users —must curtail water use when senior surface water users experience shortfalls. To avoid disruptive shutoffs, IGWA develops mitigation plans that offset the impact of groundwater pumping.

These plans help:

Keep farmland in production
Protect senior surface water rights
Stabilize rural economies

Sustain long-term groundwater access
Prevent costly legal disputes
Manage the aquifer sustainably

Mitigation for the Surface Water Coalition

The Challenge

In 2005, the Surface Water Coalition (SWC), a group of senior surface water users who divert from the Snake River, filed a delivery call with the Idaho Department of Water Resources (IDWR). When dry years occur, IDWR may forecast a water supply shortage and order junior rights be curtailed.

But forecasts shift during the growing season, creating costly uncertainty for farmers:

Early curtailment (April): too risky to plant
Mid-season curtailment (July): crops wither and die

Landmark Agreements

2015 Agreement

Annual ESPA groundwater pumping reductions
Fixed delivery of storage water to the SWC
Aquifer stabilization targets

2024 Agreement

Maintains 2015 agreement for ESPA conservation and SWC storage delivery
Introduces four-year compliance periods to increase flexibility for groundwater users
Provide variable storage to SWC depending on water needs, up to 75,000 acre-feet in dry years
Defines implementation protocols for clarity
Avoids large-scale curtailment of junior groundwater rights

Past Strategies

From 2009 to 2015, IGWA mitigated its water needs by leasing water from Upper Snake River reservoirs to deliver to the SWC. But it was costly and unpredictable, with millions spent upfront, sometimes unnecessarily.

Timeline of Landmark agreements for Idaho Water

Read the 2024 Agreement

The Challenge

The Thousand Springs area, along the mid-Snake River corridor, is fed by the ESPA and supports fish hatcheries and other senior water uses. As surface water farms converted from flood to sprinkler irrigation and groundwater use expanded, spring flows declined, creating conflict. IGWA and its members have invested tens of millions of dollars to protect groundwater rights from curtailment despite aquifer drawdowns through things like piping systems, purchasing fish hatcheries, and subordination of senior surface water rights.

IGWA's Approach

Keep farmland in production
Protect senior surface water rights
Stabilize rural economies

Conserving Water.
Recharging the Aquifer.

Using Less Water More Efficiently

Key Strategies

Putting Water Back into the Aquifer

Recharge techniques include:

Switching to Surface Water Where Possible

Improving Surface Water Delivery Systems

Key improvements include:

Saving More Water for Dry Years

Efforts include:

Boosting Snowpack from the Sky

Here’s how it works:

IGWA’s mitigation work helps Idaho’s farmers avoid water curtailment, ensuring crops stay in the ground, senior water rights are honored, and groundwater pumping remains sustainable.

Why Mitigation Matters

These plans help:

The Challenge

IGWA's Approach

Learn More

Conserving Water.Recharging the Aquifer.

Using Less Water More Efficiently

Key Strategies

Putting Water Back into the Aquifer

Recharge techniques include:

Switching to Surface Water Where Possible

Improving Surface Water Delivery Systems

Key improvements include:

Saving More Water for Dry Years

Efforts include:

Boosting Snowpack from the Sky

Here’s how it works:

IGWA’s mitigation work helps Idaho’s farmers avoid water curtailment, ensuring crops stay in the ground, senior water rights are honored, and groundwater pumping remains sustainable.

Why Mitigation Matters

These plans help:

The Challenge

IGWA's Approach

Learn More

Conserving Water.
Recharging the Aquifer.