The future of Boise, Idaho is in question, as the level of the aquifer is dropping.

Background

Boise, located in a wide desert valley in Southwest Idaho, developed along the Boise River. This region of southwest Idaho was settled in large part due to the construction of dams and reservoirs allowing farmers and ranchers to have a reliable source of water in this arid territory. Without a vital amount of rainfall, the presence of both abundant surface water, the Boise River, and groundwater, the Snake River Plain Aquifer, has allowed for the economic growth and prosperity in Boise, and the Treasure Valley. As water demands continue rise due to a growing population base, increased use in agriculture and industry, environmental habitat requirements and atmospheric shifts from climate change, decreasing levels of groundwater will no longer be available to meet the needs of the area.

In Boise, drinking water is predominantly sourced from the ground. Treated wastewater is returned to local surface water. Agricultural irrigation, a significant water user, is drawn from surface water. Infiltration from agriculture is the primary source of groundwater recharge. While this has been an abundant and diverse water portfolio, the levels of groundwater are dropping, exacerbating challenges to the preservation this resource.

Issues

Many would observe that Boise does not appear to have any lack of supply of water as it has both plentiful surface and groundwater, however, state led water management poses challenges to Boise’s future. These threats include Western water rights laws, a ’water is plentiful’ mindset, inefficient agricultural irrigation, lack of demand management, unmetered landscape irrigation, population growth and climate change.

Western United States water Rights Law for surface water is based on The Prior Appropriation Doctrine and states that ‘first in time, first in right’ indicating that “the first user had the right to continue using the water to the exclusion of the rights of those who came later.”^[1] This rights system based on priority has led senior rights holders to use as much of their share as they are able, even if is not needed, as the rights holder may lose their share if it is not fully utilized. While this is only applicable to surface water, it has led to two important challenges to Boise water management. These rights do not acknowledge the physical linkage between surface water and groundwater, and while surface water has been historically bound to this law, groundwater has not been regulated. This allowed extensive groundwater pumping, as the aquifer does not adhere to proprietary boundaries underground. Additionally, conflict arises between water rights holders as to an appropriate amount of water the water rights holders should receive in instances when there is not a full allotment.

Similarly, this water rights law encouraged those irrigating either agriculturally or for domestic landscape purposes, to utilize all of their water, even when crop or landscape could survive on less.

This perpetuates a pervasive local mindset that water is plentiful and will exist well into the future. Seasonally, residents of Boise enjoy large green lawns, and with less than 12 inches of precipitation annually, rely heavily on irrigation to propagate these yards. Depending on the age and location of a Boise residence, the source of landscape irrigation may either be Boise drinking water, drawn from groundwater, or Boise River surface water from the neighborhood irrigation canal district. Despite residing in a desert climate, lawns are ubiquitous and kept green.

Another challenge to preserving the aquifer is inefficient irrigation practices. The methods of irrigation by Boise area farmers include flood irrigation, pressurized sprinkler irrigation, and pressurized drip irrigation methods. “Pressurized irrigation requires about ½ the water of flood irrigation but has higher infrastructure costs.”^[2] This increased infrastructural cost is a disincentive for area farmers to reduce water use. According to 2015 data by the USGS, nearly 32% of irrigation water in Idaho uses groundwater.^[3]

The City of Boise has also not implemented demand management tools to reduce water withdrawals. Residents rely on groundwater for domestic use and surface water for agricultural irrigation. Even with a tiered pricing structure for residential drinking water, prices remain low, offering little incentive to conserve.

In the last decade, irrigation canal water has been utilized for landscape irrigation in  twelve irrigation districts in the city. While better than using drinking water to irrigate lawns, the fee for this surface water is a low annual flat rate dependent on lot size not volume. This unmetered landscape irrigation is a further disincentive for residents to conserve water. While this shift from potable to non-potable water for domestic landscaping draws from surface water in the Boise River, overdrawing of surface water will ultimately put more pressure on groundwater withdrawals as these systems are connected.

Population growth will also impact water resources in the area. As groundwater reliance for domestic drinking water persists, current well monitoring data indicates dropping levels of the local aquifer. The Boise metropolitan statistical area (MSA)  had a 2020 population of 756,061^[4], with projected growth by 2031 to be over 16%^[5], the largest projected growth of all of Idaho’s six state sub-regions. Boise is the 15th fastest growing city in the US.^[6]

Climate Change will also challenge Boise’s water resources, as it will likely lead to lower levels of precipitation in the mountains, resulting in less surface water and placing more reliance on groundwater. This, coupled with higher rates of evaporation from reservoirs and canals in the Treasure Valley as temperatures increase overall will again reduce surface water levels, redoubling stress on the aquifer.

Consequences

While none of these challenges create an immediate water crisis in the Treasure Valley, they will cause future harm. Potential impacts include reduced availability of drinking water with increased costs, deeper wells being dug while bearing that increased expense, higher input costs for farming and ranching resulting in less competitively-priced commodities and less revenues for this economic driver of state (agriculture had cash receipts of $8.1 Billion in 2020^[7]) environmental degradation, loss of recreational opportunities and the costs associated with less water-based tourism (fishing and boating), eventual reduction in energy production with associated increase in costs if reliance for domestic water is shifted to surface water.

Current Strategy: Managed Supply

The Idaho Water Resource Board (IWRB) recognized that water is fundamental to the well-being of the state and all who reside there. They developed a state water plan, first adopted in 1976, while the fifth revision was accepted in 2012. Additionally, a Sustainability Section was added to the State Water Plan in 2016 which expresses, “the lives and livelihoods of Idahoans depend on a reliable supply of water. Stewardship of Idaho’s water resources begins with the realization that the water resources of the state are not inexhaustible. Therefore, it is necessary to manage and administer Idaho’s water resources and protect Idaho’s water quality.” ^[8]

While the objectives of the implementation strategies include identifying “areas where present water supplies are either inadequate for present uses or not sustainable, and develop management plans to address supply”^[9], the caveat of “while respecting private property rights” is not only affixed to this measure, but also the first implementation strategy and milestone listed. This value of prioritizing private property land and water rights has led the IWRB to resolving declining aquifer levels in the Eastern Snake River Plain Aquifer with a managed supply solution by implementing a managed aquifer recharge program. This was seen in the 2009 passage of the Eastern Snake Plain Aquifer (ESPA) Comprehensive Aquifer Management Plan by the Idaho State Legislature which outlined utilizing the existing canal system in the off-season and then managing surface water flows to mitigate aquifer depletion. The plan “establishes a long-term goal of 600 kaf [thousand-acre feet] average annual change to the aquifer water budget with implementation occurring over a 20-year period.”^[10] This long-term goal of 600 kaf will cost more than $600 million and is solely recharging this area of Southeast Idaho. A feasibility study of aquifer recharge was conducted in the Treasure Valley and completed in February 2020. While this research deemed the Boise area to be viable for managed aquifer recharge, it would need further infrastructure than was the case of the ESPA project, and so costs would likely be higher.

While increasing aquifer supply is one solution, decreasing the demands on the aquifer are another, and one that should be more closely examined and mandated state-wide for the longevity of the state.

Proposed Solution: Statewide Groundwater Management Planning

While Boise and the Treasure Valley need to consider comprehensive methods to reduce water demand and diversify their water portfolio, a comprehensive groundwater management plan and process must be put in place before demand reduction can be used effectively. Without any regulation or plan for groundwater, there is little incentive for residents to reduce their water use. As hydrologic systems do not adhere to municipal boundaries, protecting and conserving the region’s aquifers is a state level issue. Therefore, aquifer depletion can be most effectively and equitably addressed by amending the Idaho Groundwater Management Act (IGMA) of 1992 to increase regulatory and enforcement power and set state-wide reduction mandates.

Amending the 1992 IGMA to require groundwater basin management plans across the state, with respective basin-side management agencies to draft, implement and monitor will help the state meet its new goals for overall groundwater use reduction.

Groundwater Regulation Precedents

Precedents from the CA Sustainable Groundwater Management Act of 2014 and the AZ Groundwater Management Act of 1980 should be reviewed and adopted as appropriate for Idaho. The California Act empowers local agencies, landowners, and stakeholders to collaboratively manage groundwater resources and promotes buy-in and coalition building. The Arizona Act mandates groundwater conservation measures including conservation plans, metering, reporting and overall withdrawal limits, as well as a tiered groundwater pricing structure. Especially important in the Idaho paradigm is that the collective approach also reduces an escalation of conflict between water users.

Groundwater Basin Plans + Management Agencies

This amendment would require each groundwater basin in the state to create a Groundwater Sustainability Management Plan (GSMP). Each plan must include: a basin hydrology survey, sustainable management goals, measurable objectives, monitoring networks, and management actions.

In addition, each basin must create a Groundwater Sustainability Agency (GSAs), which will be overseen statewide by the Idaho Water Resource Board. The state has already determined high priority areas through establishing Critical Groundwater Areas (CGWAs), areas already in a critical state of depletion, and Designated Groundwater Management Areas (GWMAs), areas approaching critical status. These GSMP’s would build upon this existing framework to expand to all groundwater basins of the state.

Further classifying all basins with low, medium, or high risk will ascertain timelines, demand reductions and funding allocations for reaching goals. High risk basins shall have a shorter timeline, greater required demand reduction, but access to more support. The Groundwater Sustainability Agencies will have a staggered implementation timeline, 3-5 years dependent on how they fall on the high to low spectrum. All goals for reduction should be met by 2043 (20 years from passing of bill amendment). The IWRB will set state standards on groundwater pricing, metering and overall withdrawal limits.

The IWRB will support the GSA’s, including technical assistance and funding support in the development and implementation of the management plans. Funding opportunities to support plan creation would prioritize high risk basins and assist in seeking additional funding streams from other Federal and State sources including but not limited to: USDA, EPA, NFWF, State Revolving Fund, and other grants. The IWRB would also need to oversee regional coordination of basin plan creation, implementation, and continued monitoring.

Boise River Basin Groundwater Management Plan

Basin-wide planning across the state requires bringing all stakeholders to the table. In the case of the Treasure Valley, this is an effective mechanism to bring municipal and agricultural water users together to plan for managing a joint resource heavily relied upon. Boise River Basin stakeholders include cities (Boise, Eagle, Meridian, Garden City, Kuna and Star), counties (Boise, Elmore, Ada, Canyon, Gem, and Payette), water agencies, tribal groups, environmental organizations, agricultural organizations and community groups like the local Groundwater Guardians chapter.

These entities could work together to address groundwater depletion with demand management strategies appropriate to the Treasure Valley. Replicating successful water conservation programs from Las Vegas and California might be mirrored in the Treasure Valley to include: increasing residential block pricing structure, mandating the metering of landscape irrigation water, mandating new construction low-flow appliances (toilets/shower heads/washing machines/dishwashers/sprinklers), issuing rebates for the replacement of existing toilets/shower heads/sprinklers with low-flow models, proposing xeriscaping rebates, providing greywater landscape irrigation subsidies for homes watering with drinking water, mandating covered irrigation canals, subsidizing and providing Smart Wash Car Wash Coupons, Smart Irrigation Control Rebates, and Smart Leak Detector Rebates, and creating a Water Use Estimator on the Boise City Website.

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^[1] The National Agricultural Law Center, https://nationalaglawcenter.org/overview/water-law/. Retrieved 04/21/2023.

^[2] Treasure Valley Water Atlas, How Do We Use Water? https://boisestate.maps.arcgis.com/apps/Cascade/index.html?appid=9b02498d21454cd7982f4f53ead5b82f. Retrieved 04/21/2023.

^[3] USGS, Idaho Water Use, 2015.  https://pubs.usgs.gov/fs/2018/3036/fs20183036.pdf, Retrieved 04/21/2023.

^[4] St. Louis Federal Reserve Bank. https://fred.stlouisfed.org/series/BOIPOP Retrieved 04/21/2023.

^[5] Idaho Department of Labor. https://idahoatwork.com/2022/05/03/idaho-population-projected-to-top-2-million-by-2031/ Retrieved 04/21/2023.

^[6] World Population Review. https://worldpopulationreview.com/us-cities/boise-id-population Retrieved 04/21/2023.

^[7] Idaho State Department of Agriculture, https://agri.idaho.gov/main/idaho-agriculture-facts-and-statistics/ Retrieved 04/21/2023.

^[8] Idaho Water Resource Board, Final Sustainability Section, 2016. https://idwr.idaho.gov/wp-content/uploads/sites/2/iwrb/2016/20161102-SWP-adopted-Sustainability-Section.pdf. Retrieved 04/22/2023.

^[9] Idaho Water Resource Board, Final Sustainability Section, 2016. https://idwr.idaho.gov/wp-content/uploads/sites/2/iwrb/2016/20161102-SWP-adopted-Sustainability-Section.pdf. Retrieved 04/22/2023.

^[10] Idaho Water Resources Board, Eastern Snake Plain Aquifer (ESPA) Comprehensive Aquifer Management Plan. January 2009. https://idwr.idaho.gov/wp-content/uploads/sites/2/iwrb/2008/20080129-ESPA-CAMP.pdf. Retrieved 04/26/2023.

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Sources:

1. Johnson, M. P., et al. “Groundwater Recharge to Address Integrated Water Management in California.” California Water, vol. 5, no. 1, 2022, pp. 1-22. doi:10.1525/cawater.2022.1223981.
2. Idaho News. “Idaho Water Resource Board Approves Funding for Multiple Water Projects.” CBS2 News, 26 Apr. 2022, https://idahonews.com/news/local/idaho-water-resource-board-approves-funding-for-multiple-water-projects.
3. Young, Mike. “Eastern Snake River Plain Aquifer.” Idaho State University, 2023, https://digitalatlas.cose.isu.edu/hydr/snakervr/esrpa.htm.
4. Boise Watershed. https://www.boisewatershed.org/.
5. Idaho Department of Water Resources. “Eastern Snake Plain Aquifer Recharge Project – Process.” https://idwr.idaho.gov/iwrb/water-planning/camps/espa/process/.
6. Las Vegas Valley Water District. “Water Conservation Measures.” https://www.lvvwd.com/conservation/measures/index.html.
7. Idaho Department of Water Resources. “Designated Ground Water Management Areas.” https://idwr.idaho.gov/water-rights/groundwater-management-areas/designated/.
8. California Department of Water Resources. “Basin Prioritization.” https://water.ca.gov/Programs/Groundwater-Management/Basin-Prioritization.
9. Southern Nevada Water Authority. “Water Smart Landscapes Program.” https://www.snwa.com/rebates/wsl/index.html#process.
10. Idaho Department of Water Resources. “ESPA Comprehensive Aquifer Management Plan (CAMP) Steering Committee Meeting Notes.” 29 Jan. 2008, https://idwr.idaho.gov/wp-content/uploads/sites/2/iwrb/2008/20080129-ESPA-CAMP.pdf.
11. Las Vegas Valley Water District. “Water Conservation Measures.” https://www.lvvwd.com/conservation/measures/index.html.
12. Esri. “Boise City, Idaho.” Story Maps, 2023, https://storymaps.arcgis.com/stories/ff075c25b77e4b1d95ce86a82bf0fe96.
13. USDA Farm Service Agency. “Conservation Reserve Enhancement Program: Idaho Eastern Snake Plain Aquifer.”  Feb. 2017, https://www.fsa.usda.gov/Assets/USDA-FSA-Public/usdafiles/FactSheets/2017/crep_idaho_eastern_snake_plain_aquifer_feb2017.pdf
14. Las Vegas Valley Water District. “Water Conservation Measures.” https://www.lvvwd.com/conservation/measures/index.html.
15. California Department of Water Resources. “Basin Prioritization.” https://water.ca.gov/Programs/Groundwater-Management/Basin-Prioritization.
16. Las Vegas Valley Water District. “Water Conservation Measures.” https://www.lvvwd.com/conservation/measures/index.html.
17. Idaho Department of Water Resources. “Designated Ground Water Management Areas.” https://idwr.idaho.gov/water-rights/groundwater-management-areas/designated/.
18. Idaho Soil and Water Conservation Commission. “Conservation Loans.” https://swc.idaho.gov/home-2/what-we-do/conservation-programs-2/conservation-loans-2/.