The Eastern Snake Plain Aquifer: Water Management Conflicts and Strategies

Water is at once our most precious and most mismanaged resource. Improving efficiency in how we consume our water is thus a hallmark of any effective management strategy. In the process of conducting our research along the Snake Plain, however, we found that even efficient practices are subject to conflict, controversy, and their fair share of management issues. The depletion of the Eastern Snake Plain Aquifer (ESPA) in southern Idaho presents just such a conundrum.

Sophomore College in Idaho



People, Land, and Water in the Heart of the West


The Eastern Snake Plain Aquifer: Water Management Conflicts and Strategies
Jordan Bryan, Katie Kramon, Megan, Lu and Michael Peñuelas

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The Eastern Snake Plain Aquifer

Overview of the Eastern Snake Plain Aquifer (ESPA)

Water is at once our most precious and most mismanaged resource.  Improving efficiency in how we consume our water is thus a hallmark of any effective management strategy.  In the process of conducting our research along the Snake Plain, however, we found that even efficient practices are subject to conflict, controversy, and their fair share of management issues.  The depletion of the Eastern Snake Plain Aquifer (ESPA) in southern Idaho presents just such a conundrum.  Paradoxically, the strategies in efficient allocation of water resources that have caused the depletion of groundwater reserves in this giant aquifer may in fact be crucial to replenishing those reserves.  Though it may seem bizarre, the sheer incongruity of the ESPA predicament illustrates the interconnected nature of the Snake Plain water resources.

With this connection in mind, we began our examination of the ESPA and the management strategies designed to protect it against depletion.  The ESPA is not just a vast underground well waiting to be tapped; it is a dynamic resource that also contributes its flows to the lower Snake River above the surface.  As water levels in the aquifer continue to dwindle, the rate of discharge into the Thousand Springs area decreases, and the farms, hatcheries, hydropower plants, and recreationists that rely on the water in the lower Snake River begin to see their livelihoods threatened.  The issues at stake run deeper than pure conservation of nature in its original form, and as we learned, the augmented flows that downstream water users had enjoyed for the latter half of the 20th century were not naturally occurring.

Beginning with the passage of the Carey Land Act in 1896, the Snake Plain region underwent a dramatic transformation during the beginning of the 20th century from an arid, un-irrigated landscape to a seemingly endless array of croplands.  Massive amounts of water were diverted from the branches of the Upper Snake River into canals that guided the water either directly onto the fields or through small furrows that ran through the crops.  These irrigation techniques, known as flood or furrow irrigation respectively, allowed for a great deal of water to seep into the upper layers of the soils, down into the porous volcanic rocks, and into the Eastern Snake Plain Aquifer.  From 1900 to about 1956, farmers downstream of Thousand Springs enjoyed augmented flows and their water rights were secure.  With the advent of pivot irrigation in the 1950s through 1970s, however, efficiency improved dramatically, and farmers were able to produce greater yields of crops using the same amount of water.  As efficiency increased, return flows to the aquifer decreased and downstream rights holders began to see their water rights curtailed during dry years.

The situation today is an evolving conflict, pitting groundwater pumpers with junior water rights against senior surface rights holders on the lower Snake.  Frustrations are mounting in the agricultural community, and the level of litigation has reached a breaking point.  Our investigations into this issue led us to the Comprehensive Aquifer Management Plan (CAMP) proposed by the Idaho Water Resources Board (IDWR) to deal with the depletion of the ESPA.  CAMP tackles the aquifer depletion on two fronts, focusing half of its efforts on recharging the aquifer through groundwater wells and the other half on practices in efficiency and conservation of the groundwater itself.  Ultimately, our conclusion is that CAMP provides a flawed, yet practicable solution to the problem of the ESPA.  Though its effects remain to be seen, the salient point is that the IDWR put forth a plan a conjunctive management framework for dealing with the aquifer, meaning it approached the problem by treating groundwater and surface water as a single, connected resource.  By realizing this vitally important reality and implementing it in active policies, CAMP is, at the very least, a step in the right direction. 

Annotated Presentation Slides

The Eastern Snake Plain Aquifer DescriptionTo gain a sense of the scope of the problem, we begin by introducing the aquifer itself. The Eastern Snake Plain Aquifer (ESPA) is essentially a large groundwater storage basin stretching across the Snake River Plain from Fremont and Clark counties all the way to Twin Falls. The groundwater from the aquifer is expelled at the Thousand Falls region and continues down the lower Snake River. In this sense, the groundwater and surface water downstream are intimately connected.

In the 1950s, a major shift commenced from flood and furrow irrigation, causing enormous amounts of water to pour from across the surface of the cultivated fields to pressurized pivot irrigation. As a result, only the amount of water that the crops could actually use was applied. This change significantly decreased the amount of excess water that flowed underground into the aquifer. Additionally, it led to an accelerating depletion of the aquifer because the body of water that composed it is no longer received the same level of water input. Flood irrigation water can be considered to have been used twice, “recycled” in that when it was taken from surface water, poured onto the crops, and then filtered down into the aquifer it became available for use by groundwater users or users of springwater that arose from the aquifer who could use it once again to water their crops. Pivot irrigation, however, has very little of that recycling component, or recharge, and thus is used only once. A good way to think of this situation is as a flower pot with holes in the bottom, with water seeping out those holes more quickly than the supply is being replenished by a hose at the top. It is therefore imperative, for the longterm viability of the aquifer as a source of water for productive uses, that this trend change. 

Groundwater Extraction WellsIn addition to these factors, groundwater users have begun to insert themselves into this equation. Even while increased irrigation efficiency has lead to an overall significant decrease in recharge to the aquifer, the drawing out from whatever is left in the aquifer in the form of groundwater wells has increased dramatically. This has only succeeded in placing ever-increasing stress on the aquifer and its water system.


Irrigated Land on the ESPA

Agriculture in Idaho is a significant slice of the state economy. Because of the arid nature of the land, the vast majority of that agriculture is made possible by way of irrigation. About half of that irrigation is derived from groundwater infrastructure and half from surface water (40% groundwater, 40% surface water, 20% combination thereof). The image on the left shows that a very substantial portion of that irrigated acreage, 60%, lies within the area supported by the Eastern Snake Plain Aquifer (ESPA). This makes the ESPA's water system integral to the livelihoods of an enormous number of residents of the state and thus the health of the state economy as a whole. Because the surface and groundwaters in this particular geographic area are so inexorably connected as parts of the same system, this means that managing both in order to support that irrigated agriculture into the future becomes a matter of dealing with both, not one individually.


Upstream irrigationThis diagram is designed to illustrate the mechanisms by which the water system of the ESPA functions with human influence. On the left side of the diagram is water input to agricultural systems (denoted by the corn) by the farmers themselves. This water is applied to the crops through various methods of irrigation but it is derived from either surface or groundwater infrastructure, removed physically from those systems, and applied to the crops. The growing crops consume some of that water and through evapotranspiration allow some of that water to escape the system. This combination is called “consumptive use.” What is not directly consumed flows in the form of residual flow or “recharge” back through the soils of the fields, through the volcanic (basalt) upper levels of the aquifer, and into its main body. This water will then make its way through the aquifer and emerge at the surface at various points in the form of springs. The most prolific of these is called Thousand Springs, where considerable quantities flow out of the aquifer and into the Lower Snake River.

The way humans obtain the water they use for their irrigation also has significant effects on the aquifer's system. Historically, the early settlers and farmers in the region were considered the "senior" water right holders and had the first claims on the surface water flowing into creeks and rivers. More recently, however, groundwater users (generally “junior” water right holders) are preempting their use by drilling straight into the aquifer from above and drawing their water from the aquifer's main body instead. Even if the left-hand side of the diagram (recharge) were to remain exactly the same, the right-hand side would decrease as a function of the removal of water from the system by groundwater users. Thus, the senior water rights holders would be getting their supplies curtailed, which is a significant detriment to their livelihoods.

Unfortunately, that is only one element of the equation.

Upstream irrigationThe second element is recharge. As mentioned in the previous slide, the aquifer discharges water from various springs, with Thousand Springs being the most significant in terms of flow volume. This makes Thousand Springs a good metric for the current storage levels of the aquifer overall. This graph shows very significant changes in the discharge levels of the aquifer over the period from 1902 to 2007. These changes are almost exclusively attributable to human intervention because before humans began irrigation agriculture at any impactful levels, the discharge level was effectively static. In the early 1900s, humans began to actively irrigate using flood and furrow methods, which involved applying directly to the fields vast quantities of water and was ultimately far more water than the plants could consume. This extra water percolated back down through the layers of porous rock and into the aquifer, “super-charging” it. More efficient irrigation techniques, namely the invention and proliferation of pressurized pivot irrigation, were invented in the middle of the 20th century and a veritable revolution in irrigation ensued. Farmers switched over quickly because with the same amount of water they could grow higher crop yields. The levels of consumptive use by the plants therefore rose significantly with far less recharge. Combined with the groundwater users and increased number of claimants to the surface water, the overall water use increases. When these two factors are coupled with a precipitous decline in discharge, there is no evidence that water usage will slow or cease in the future.

Upstream irrigationTo make this a bit more tangible, we liken the situation to a bank account. The initial deposit could be similar to the natural level of the aquifer's storage. Beginning in the early 1900s, there was an annual deposit of water in the form of recharge from agricultural irrigation. When groundwater wells began to appear in the system, there was additional annual withdrawal. Yet the deposits continued to outweigh the withdrawals, and the aquifer's levels continued to rise. This ceased once those deposits began to shrink as consumptive use rose due to the rising efficiency of irrigation techniques. At this point, the withdrawals outpaced the deposits, leading to a decline in the storage of the aquifer and a serious deterioration in the aquifer's long-term viability as a source of irrigation. 

 Now imagine that the slice of the pie that consists of recharge from irrigation is now shrinking. Meanwhile the other slices remain the same. Thus the area of the entire pie chart is shrinking rapidly as well because nothing is making up for that dearth of irrigation-powered recharge and thus those annual deposits are following the same trend and diminishing.


Upstream irrigationRecently, this issue has reached significant public attention. Consequently, the Idaho Department of Water Resource’s task force, the Idaho Water Resource Board, has attempted to formulate and implement a plan to address this host of issues. They proposed a plan in 2006 that was adopted by the state legislature in 2009. This plan is called the ESPA Comprehensive Aquifer Management Plan, or CAMP.


Irrigated Land on the ESPAThe ongoing Comprehensive Aquifer Management Plan, or CAMP, is an effort to bring groundwater levels in the aquifer high enough to keep pace with the demand for water and the decreasing amount of recharge. Phase I of the plan is expected to take 10 years and cost $70 million to $100 million, with the total project projected to cost $600 million. Phase I has a goal of a water budget change of 200-300 kaf/year and the complete plan has a goal of 600 kaf/year. Phase I is structured around these four categories of management: artificial recharge, demand reduction, groundwater to surface conversion, and precipitation enhancement. The bulk of groundwater budget change (85% or so), though, will come from the Artificial Recharge and Demand Reduction elements of this plan, which is why they will be the primary focus of the following slides.


Irrigated Land on the ESPAThe hydrologic process of water back into the aquifer, which is referred to as recharge, has a number of distinct significant elements. These include natural recharge (in which precipitation infiltrates into ground water aquifers), incidental aquifer recharge (defined as the unintentional placement of water into an aquifer resulting from normal water deliveries for irrigation or other uses (i.e. canal losses), and artificial or managed recharge (the artificial placement of water from a different source into a ground water aquifer). As stated on a previous slide, the fractions associated with the irrigation slice of this pie, however, have been changing the most in recent years, with particularly drastic consequences.


Irrigated Land on the ESPAManaged (artificial) aquifer recharge involves direct injection of surface water into a groundwater reservoir by way of human-created infrastructure in the form of injection pipes inserted into that reservoir. Applications of managed recharge include replenishment of depleted aquifers, water supply mitigation, and lower cost storage of large volumes that may otherwise flow out of the system. In 2007, the Idaho Department of Water Resources began experimenting with aquifer recharge and diverted 29,500 acre feet of surface water for aquifer recharge. This is only .01 percent of the capacity of the aquifer, which made sense as an experimental measure but would need to be very significantly increased to make any equally significant difference. Between 2007 and 2011, almost 80 percent of the 168,000 acre-feet of water designated for recharge made it back to the aquifer, said Mike McVay, hydrologist with IDWR. Last fall, the IDWR approved $132,700 to fund 44,245 acre-feet of recharge.


Upstream irrigationThere are, however, identified possible shortcomings of artificial aquifer recharge. Aquifer recharge may produce water table increases in some areas, but it is possible that it will not be able to create a uniform increase in the aquifer. Additionally, without flood irrigation we simply cannot keep the aquifer at the supercharged levels that were seen in the 1950s. Some have suggested going back to flood irrigation. Some scientists have observed that some of the recharge north of American Falls rises to the surface again in the form of springs before it reaches the main body of the aquifer as it moves southwards, which has implications for long-term storage. For most farmers, unfortunately, it is not economically feasible to recharge without the help of the government.

"In order to build up the aquifer’s water supply, state officials should prioritize funding projects in southern areas of the aquifer," said Mathew Weavers, senior water resource engineer for the Idaho Department of Water Resources (Times-News, July 21, 2012). “I recommend only recharging areas in the lower valley,” and “it’ll have the largest long-term benefits to the overall aquifer,” he told members of the Idaho Water Resource Board during a Friday meeting in Burley. According to Weavers, water used for recharge above American Falls tends to drain into the Snake River before it can reach the aquifer. Over time, water does not expand to other areas of the aquifer. Instead, it simply reaches the river faster, essentially going to waste. But even with a commitment to improving the aquifer’s water supply, the board remained hesitant to agree with Weaver’s recommendations. “I’m reluctant to exclude anyone right now,” Board member Jeff Raybould of St. Anthony commented. In the northern half, close to 40 percent of 220,000 acre-feet of water returned to the ESPA. An acre-foot is enough water to cover one acre, one foot deep. Based on the current IDWR water budget model, the northern valley’s recharge return rate will drop to less than 30 percent by 2017 if the same amount of water is released back into the aquifer over the next five years.



Upstream irrigationThe second main component of CAMP is contained under the heading “Demand Reduction,” and it is comprised of various measures designed to boost efficiency and conservation of groundwater. The first goal of the Demand Reduction program is to implement a project in the Aberdeen-American Falls and Bingham Groundwater Districts aiming at a reduction of groundwater usage by encouraging pumpers to change their cropping patterns, substituting high-intake crops like hay and alfalfa for lower intensity crops like barley and other grains. The gains seen from this pilot project will be supplemented by the construction of check structures and automated gates in specific reservoir sites to save surface water that can later be used for conversion into groundwater. CAMP’s other demand reduction goals will be met through programs that provide financial incentive to farmers to forego the use of part or all of their water rights. Simple buy-outs or buy-downs of these rights by the Idaho Department of Water Resources (IDWR) are coupled with Conservation Reserve Enhancement Programs (CREP) to try to minimize the rate of aquifer depletion in the ESPA. The CREP agreements themselves are a 14- or 15-year easement on the owner’s land, which provides financial incentives and rental payments in exchange for removing cropland and marginal pastureland from production, allowing the native grasses and vegetation that aid in soil retention to return to the land.

Irrigated Land on the ESPA

However, Demand Reduction projects have their own shortcomings, the most obvious of which is the sheer cost of implementing the CAMP initiatives. Phase I of CAMP alone is projected to cost $100 million, with the total project coming in at an estimated cost of $600 million. As of yet, the Idaho Department of Water Resources still has 40% of the funds for this project unsecured. Cost, however, is not the only obstacle. CREP agreements and crop exchange programs are voluntary measures, so participation is far from guaranteed, and efforts to increase involvement are often met with resistance and reluctance. Water-saving measures that involve crop exchange also run the risk of being marginalized by increased crop yields. Farmers who switch their crops are able to exercise their full water rights, and thus can use the same amount of water to grow more crops if they so choose.

Upstream irrigation

If the objectives of the CAMP plan are not met, the results are potentially disastrous for the agricultural community along the aquifer as well as the economy of the state of Idaho. Conflicts between groundwater and surface water users will escalate as uncertainties over water levels continue to increase. Based on submissions gathered by the IDWR at a public meeting that convened to discuss the CAMP framework, farmers are already frustrated with the uncertainty over water, and many growers have been forced to switch to crops with less economic potential because of unforeseen curtailment of their water rights. The amount of litigation that has erupted out of the water disputes has reached a level of such confusion that one farmer present at the meeting asked, “how many people in this room are suing themselves?” Amidst all the commotion and infighting, the reality remains that livelihoods are at stake in the battle to save the ESPA.


Upstream irrigation

In essence, when the people we met along our trip told us that the aquifer is about the size of Lake Erie, what they were really saying was that the problem is about the size of Lake Erie. The case of ESPA depletion is an especially interesting one because it is a case where efficient water use actually has lead to water shortages, at least for many right holders downstream of Thousand Springs. This sort of statement may seem paradoxical or inconsistent, but it is truly illustrative of just how connected the groundwater resources of the Snake Plain are to those on the surface. In this respect, CAMP, while limited, at least provides a conjunctive management approach to solving the problem of aquifer depletion. If nothing else, it represents a step in the right direction by crafting policy around the very salient reality that surface water and groundwater are really a single, united resource.


Works Consulted

ESPA CAMP Adopted as Part of Comprehensive State Water Plan, ID-HR 264, Legislature of the State of Idaho, (2009).

Diane Tate and Jonathan Bartsch, CDR Associates.  Eastern Snake Plain Aquifer (ESPA) Comprehensive Aquifer             Management Plan (CAMP) Framework Development Process: Summary of Public Comments Received.  Twin Falls, ID: October 18th, 2006.

Idaho Groundwater Appropriators Inc.  “IGWA Responds to Curtailment Order.”  Boise, ID: March 8, 2009. 

Idaho Dept. of Water Resources.  Letters Addressed to the Idaho Water Resource Board: Final Comments.  ID Water Resources Board: January 5th 2009.

Idaho Water Resource Board.  Eastern Snake Plain Aquifer (ESPA): Comprehensive Aquifer Management Plan.  ID Water Resources Board: January 29th,  2009.

Kimberlee Kruesi.  “Where Best to Recharge the Aquifer?”  Times-News: July 21st, 2012., (9/12/2012).

Lynn Tominaga and Chris James.  “Point/Counterpoint: What is Best Approach to Aquifer Management in the Valley?”  Times-News: July 22nd, 2012., (9/13/2012).



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