lower santa cruz river basin study - sawua basin study.pdf · the santa cruz river is a tributary...

Lower Santa Cruz River Basin Study SAWUA Proposal Page 1

Lower Santa Cruz River Basin Study Proposal Submitted by the Southern Arizona Water Users Association

Bureau of Reclamation 2015 Basin Study April 30, 2015

Introduction The Southern Arizona Water Users Association (SAWUA) proposes to partner with the Bureau of Reclamation to conduct the Lower Santa Cruz River Basin Study under the Bureau’s FY2015 Basin Study Program. SAWUA is a non-profit organization of municipal water and wastewater providers and agricultural water users located in Southern Arizona working cooperatively to preserve and enhance Southern Arizona’s water resources. SAWUA’s member agencies include Avra Valley Water Co-op, BKW Farms, Community Water Company of Green Valley, Farmers Investment Co., Flowing Wells Irrigation District, Green Valley Water Improvement District, Kai Farms, the Town of Marana Municipal Water System, Metropolitan Domestic Water Improvement District, Oro Valley Water Utility, Pima County Regional Wastewater Reclamation Department, Red Rock Utilities, Sahuarita Water Company, the Town of Sahuarita Water Reclamation Facility and the Tucson Water Department. SAWUA member agencies have water management authority to provide municipal water and wastewater service to over 900,000 residents in the Santa Cruz River Basin. Collectively, SAWUA delivers almost 200,000 acre-feet per year of potable water and treats over 64,000 acre-feet of wastewater annually. SCR Basin Study Area The proposed Lower Santa Cruz River Basin (SCR Basin) Study will encompass the Tucson Active Management Area (TAMA) in Arizona which generally coincides with the lower Santa Cruz River Basin between the Pima County/Santa Cruz County boundary south of the Tucson metropolitan area and Pima County/Pinal County boundary to the north. The Santa Cruz River is a tributary to the Colorado River, a major river system within the Bureau of Reclamation’s service area. The SCR Basin is 3,869 square miles. Its prominent physical features are the Santa Cruz River, flowing south to north, and several surrounding mountain ranges. The Pantano Wash, Rillito Creek and Sabino Creek in the eastern central portion of the SCR Basin are tributary to the Santa Cruz River, while the Altar and Brawley Washes in the western portion of the SCR Basin flow south to the Santa Cruz River. The northern boundary of the SCR Basin is formed by the Picacho Mountains and Black Mountain in the Tortilla Mountains; on the eastern boundary are the Santa Catalina and Rincon Mountains; on the southern boundary are the Santa Rita and the Sierrita Mountains and the western boundary is formed by the Baboquivari, Roskgruge, Waterman and Silverbell Mountains. The elevation of the lowest point of the SCR Basin is 1,770 feet above mean sea level (amsl) at the northern edge and the highest elevation is 9,453 feet amsl in the Santa Rita Mountains. Land ownership by area consists of 37.8 percent State Trust Land, 31.2 percent private ownership, 25.8 percent Federal ownership (Forest Service, Bureau of Land Management, Wildlife Refuge, National Parks and Military), 4.4 percent Native American Lands and 0.8 percent other jurisdictional ownership.


Based on the 2010 US Census, the SCR Basin has a population of 980,263. The jurisdiction with the largest population, City of Tucson, operates a municipal water system. Other jurisdictions with municipal water systems include the Town of Marana and the Town of Oro Valley. Additional water providers and private well owners also provide municipal water service. Pima County, the Town of Marana and the Town of Sahuarita operate municipal wastewater utility systems.

Table 1 – SCR Basin Population

The SCR Basin watershed is comprised of two parallel sub-basins; the Upper Santa Cruz Valley sub-basin on the east and the Avra Valley sub-basin on the west. Both sub-basins flow from south to north. Figure 1 depicts the SCR Basin Study boundaries.

Figure 1 – Lower Santa Cruz River Basin Study Area

Jurisdiction Population City of Tucson 510,116

Town of Oro Valley 41,011

Town of Marana 34,961

Town of Sahuarita 25,259

City of South Tucson 5,652

Unincorporated Pima County 263,264

Total 980,263


Study Abstract Key areas in the lower Santa Cruz River (SCR) Basin are experiencing groundwater declines due to lack of access to renewable supplies and combined with drought conditions. Subsidence and loss of riparian habitat have already occurred. Degradation of groundwater quality, increased pumping costs, the need to deepen wells and shortages of supplies to municipal and agricultural users may be exacerbated without more timely intervention. For over sixty years the lower SCR Basin, including the Tucson, Arizona metropolitan area, relied on groundwater to meet water supply needs with pumping greatly exceeding replenishment. In 1993, water from the Bureau of Reclamation’s Central Arizona Project (CAP), a 336-mile long system of aqueducts, tunnels, pumping plants and pipelines, began delivery of Colorado River water to the Basin. Since then, SCR Basin water users have directly used or recharged their CAP and recycled water supplies; portions of recharged CAP and recycled water are recovered on an annual basis. Consequently, groundwater levels have rebounded in many areas. Still, there are significant spatial imbalances between supply and demand within the Basin. Reasons include a lack of transmission infrastructure, insufficient recharge and recovery capacity, a lack of recharge and recovery facilities in up gradient parts of the basin, and the cost of constructing new facilities. The lower SCR Basin faces several challenges. Population growth and new industrial development are projected to increase water demand, and may generate political and legal conflicts. The CAP has junior priority rights on the Colorado River; thus, CAP subcontractors will bear the brunt of imminent shortages. Agricultural users will be the first affected under the CAP’s priority system, but if the shortages are severe enough, reductions to municipal users will take place. In addition, Southern Arizona, which naturally experiences episodic droughts, has been in an extended drought for the last fifteen years. Water providers without physical access to renewable supplies are already experiencing falling groundwater levels. Climate change poses additional threats to the Basin, such as increased water demand, increased temperatures, and possible decreases in precipitation—which would exacerbate the impacts of future droughts. The proposed study will evaluate the current and future water supply and demand imbalances in the SCR Basin, taking climate change impacts into consideration; analyze how existing infrastructure will perform in response to changing water realities; develop adaptation and mitigation strategies, and analyze each strategy for its effectiveness in addressing these imbalances. Throughout the process, we will engage regional stakeholders, including those representing municipal, agricultural, environmental, industrial and tribal water providers and users. We will garner and incorporate their input at key intervals in the process. Our overarching goal is to identify where physical water resources are needed in order to mitigate climate change impacts and improve water reliability for municipal, agricultural and environmental sectors in the SCR Basin. The study will identify institutional, legal and regulatory constraints affecting each strategy and develop next steps toward implementation. Study Proposal The SCR Basin Study will address six key elements: 1. Extent and Consequences of Existing and Anticipated Imbalances in Water Supply and Demand

Magnitude and frequency. The Lower Santa Cruz River Basin is critical to the viability of the nearly one million residents living in Southern Arizona. For over sixty years water demand has exceeded replenishment in the aquifer beneath the SCR Basin. In 1980 Arizona recognized the need to manage


its finite groundwater resources and identified five areas with heavy reliance on mined groundwater designating them as Active Management Areas. The goal in TAMA is to achieve and maintain safe yield by 2025 and to prevent the local groundwater aquifer from experiencing long-term declines. Safe yield is achieved when no more groundwater is being withdrawn than is being annually replaced. A water supply and demand assessment prepared by ADWR projected total water demand could be 525,807 acre-feet in 20251. To meet this demand, water supplies would have to be supplemented with 259,254 acre-feet of groundwater, resulting in an increase in groundwater overdraft. Southern Arizona has been in extended drought for the last 15 years. The SCR Basin is in the arid Southwest, receiving an average of 11.6 inches of precipitation annually. Therefore drought conditions impact an area already sensitive to low precipitation. The National Weather Service cites four historic periods of extended drought2. The 1810’s experienced six years of drought, followed by seven years in the 1860’s, eight years in the 1930’s and five years in the 1950’s. The most recent drought, now in its fifteenth year, was declared in 1999 and shows no signs of abating. Climate change is expected to increase temperatures, further reducing local water availability and possibly increasing municipal and agricultural water demand. The detrimental impacts of persistent drought, such as reduced stream flow, declining groundwater levels and stressed vegetation in local riparian areas are being observed in the Lower Santa Cruz River Basin. Continued drought conditions and climate change impacts will result in loss of valuable riparian areas locally. Water providers that have no access to renewable supplies or lack of water infrastructure may experience declining groundwater levels or water service interruptions as drought conditions persist. Residents in rural areas that rely on private groundwater wells may experience water shortages resulting from ongoing drought conditions. Global climate models indicate that with continued high rates of heat-trapping greenhouse gas emissions, annual average temperatures will increase 4-5:Centigrade across the Southwest, including the Lower Santa Cruz River Basin by the 2071-2100 time period3. While there is some uncertainty about projected precipitation, increased temperatures are expected to result in drier conditions and less groundwater recharge to the regional aquifer; in fact, recent studies show a statistically significant trend toward decreases in the observed soil moisture in the region.4

Known and anticipated demands. The SCR Basin relies on water from the Colorado River delivered through the Central Arizona Project (CAP) to meet water supply and demand for municipal, industrial and agricultural sectors. Municipal and industrial sectors used 169,369 acre-feet of CAP water in 2014, while the agricultural sector took delivery of 2,635 acre-feet of CAP water. Federal delivery of CAP water to Indian tribes was 30,173 acre-feet and the Arizona Water Banking Authority

1 Tucson Active Management Area Water Demand and Supply Assessment: 1985-2025, Arizona Department of

Water Resources, January 2012. 2 Hazardous Weather Climatology for Arizona, NOAA Technical Memorandum NWS WR-282, C. Shoemaker and J

Davis, National Weather Service, Tucson, Arizona, February, 2008. 3 Garfin, G. G. F., H. Blanco, A. Comrie, P. Gonzalez, T. Piechota, R. Smyth, and R. Waskom. 2014. Chapter 20:

Southwest. Pages 462-486 in T. C. R. J.M. Melillo, and G.W. Yohe, editor. Climate Change Impacts in the United States: The Third National Climate Assessment. U.S. Global Change Research Program, Washington, DC. 4 Seager, R. and M. Hoerling. 2014. Atmosphere and Ocean Origins of North American Droughts. Journal of Climate

27:4581-4606.


took 29,759 acre-feet for long-term underground storage. In 2012 the Bureau of Reclamation published a study, Colorado River Basin Water Supply and Demand Study, which projects future imbalances between supply and demand on the Colorado River. Reclamation’s study determined demand on the Colorado River is beginning to outpace supply. Because Arizona has junior priority rights on the Colorado River and Reclamation’s study indicates shortages are likely, Arizona is expected to bear the brunt of these shortages. Initially, shortages on the Colorado River will first impact agriculture, but continued shortages could result in reductions to municipal and Indian water supplies. Since there are few perennial streams in the SCR Basin, renewable water resources are extremely important to the long-term viability of these streams. Ongoing drought in the Southwest, changes to snowpack, timing of snowpack melting, decreased runoff and declining water levels in Lake Mead could reduce water supplies to the SCR Basin in the future.

The SCR Basin area is within the Southwest’ Sun Corridor. According to the Pima Association of Governments, the study area population is expected to reach 1.45 million by 2041. Pima County’s draft Comprehensive Plan, Pima Prospers, recognizes that efficient use of existing and planned infrastructure is important to support the current and future populations and that proposed new development may impact overall water supply. The City of Tucson’s General Plan, Plan Tucson, also recognizes the importance of water resources for a healthy environment and economy for Tucson current population and projected growth. A water supply and demand assessment conducted by ADWR in 2010 described water supply and demand characteristics for 1985 through 2006 as well as projections to 2025 for the SCR Basin. The assessment included municipal, industrial, agricultural and Indian water demand and evaluated scenarios to address groundwater overdraft. A subsequent ADWR effort in 2013, Regional Groundwater Flow Model of the Tucson Active Management Area, Model Update and Calibration, projected water level changes in the SCR Basin through 2025. The model identifies areas where groundwater levels are expected to recover, stabilize, or decline. Adaptive strategies need to be developed in areas where groundwater is expected to decline. The City of Tucson recently completed its Recycled Water Master Plan for the planned use of the City’s recycled water. This effort complements their 2012 Water Plan Update that provides for long term water reliability for the Tucson Water service area through 2050. Metropolitan Domestic Water Improvement District completed its 50-year Long Range Water Resources Plan in 2015. Other regional water providers are collaborating on groundwater replenishment programs, including underground storage and recovery of Central Arizona Project (CAP) water and reclaimed water. A SAWUA-sponsored study completed in 2015, Municipal Water Demand Trends Project, evaluated anticipated trends in water use in the SCR Basin. Nature of imbalances. Climate change can be expected to impact water supply availability of CAP water to Arizona and the SCR Basin. Decreased Colorado River Basin snowpack and stream flow may result in curtailments of water deliveries to some users. The probability of a Tier One shortage declaration on the Colorado River is estimated to be 20 percent in 2016 and over 50 percent in 2017. This shortage will impact deliveries to agriculture in the SCR Basin. Additional future shortages could ultimately impact municipal and Indian water deliveries. Climate change and persistent drought conditions may also impact local water supplies. Natural recharge and mountain front recharge may be reduced from increased evaporation resulting from projected increasing temperatures and decreased precipitation from ongoing drought and future droughts generated by


variations in ocean-atmosphere interactions. Curtailments in CAP water delivery will result in increased groundwater use for municipal, industrial and agricultural sectors resulting in local groundwater declines. The projected increased temperatures and CAP water reductions will result in increased water demand for agriculture. There is uncertainty about municipal water demand impacts due to climate change and water conservation. Spatial geographic imbalances in water supply and demand within the SCR Basin need to be better understood.

Severity of potential consequences for not addressing imbalances and impacts. The consequences for failing to address projected imbalances in water supply and demand will impact municipal, industrial and agricultural sectors as well as the environment. Curtailments of CAP water to agriculture will result in increased groundwater pumping and declining groundwater levels. Subsidence has been strongly linked to increased groundwater pumping.5 Increased temperatures from climate change will result in higher agricultural water demand and groundwater pumping rates, and greater energy usage. While municipal water conservation programs have been effective, Southern Arizona has been in extended drought for the last 15 years. Water providers that have no access to renewable supplies or lack water infrastructure may experience declining groundwater levels or water service interruptions as drought conditions persist and climate change occurs.. Uncertainty about water availability and water scarcity will have adverse economic impacts to the tourism, agricultural and business sectors in the SCR Basin. Different sectors have varying ability to adapt to the impacts of water supply and demand imbalances. The large municipal water utilities have been banking renewable supplies water for years to mitigate drought and shortage. Other utilities that rely on groundwater may experience service interruptions due to declining groundwater levels and lack the infrastructure to access renewable water resources. Rural residential areas that rely on private groundwater wells for water supply may experience water shortages due to decreased mountain front recharge resulting from changes in precipitation. These residents are particularly vulnerable to the impacts of drought, climate change, and increased groundwater pumping. These vulnerable populations should be identified and mitigation strategies identified.

The risks from climate change impacts to water providers could be numerous. Water providers relying on groundwater could see higher power use and increased operational costs. Higher intensity storms could cause widespread flooding and damage CAP delivery infrastructure and water utilities’ transmission infrastructure. Shortages of CAP water delivery will also diminish the availability of CAP water available for long term storage, also known as water banking. Shortages of CAP water are expected to result in higher rates resulting in financial impacts to the municipal, industrial and agricultural sectors that take delivery of CAP water. At this time it is unknown how higher temperatures will affect residential water demand. Wildfires have been observed to increase sediment in local streams and could impact natural infiltration rates as well as in channel reclaimed water recharge projects. Large water utilities are required by ADWR to have drought response plans in place. When a Colorado River shortage declaration is declared by the Bureau of Reclamation, some water providers

5 Anderson, M. T. and L. H. Woolsey. 2005. Water availability for the western United States--Key scientific

challenges. U.S.G.S. Circular, 1261. Washington DC, USGS, 94 pp.


that rely on CAP water will implement drought restrictions, while other water providers that rely on groundwater will not. In order to be effective, coordination of drought response actions is necessary. CAP water is now the primary water supply for the major water providers in the SCR Basin. Stored or banked water will augment water supplies should CAP water delivery to municipal water provider be necessary. However, under chronic, long-term shortages, once banked water reserves are depleted, water resource managers will return to unsustainable groundwater pumping to meet water demand. Drought impacts to the environment are already being observed. Stream length in Cienega Creek, one of the few perennial streams in the SCR Basin, has declined each year since the current drought began. Stream flow is vital to the riparian habitat along these stream reaches. Agua Caliente springs flow has declined and is attributed to both drought conditions and increased regional groundwater pumping. The springs are currently being supplemented with groundwater which is not considered a sustainable mitigation strategy. Adaptation and mitigation strategies could provide protection for some of these vulnerable areas. Many riparian areas in the SCR Basin are hydrologically connected to groundwater sources. These will be adversely impacted by declining groundwater levels. Drier conditions from climate change could result in a higher possibility for wildfires as well as increased flooding because of reduced plant cover. Climate change and drought are expected to impact wildlife habitat and migration. Climate change will have numerous impacts to agriculture in the SCR Basin. Warmer winter temperatures are resulting in lower yields for crops such as wheat, as the plants mature earlier. At the most restrictive Tier Three Colorado River shortage level, agricultural pool water deliveries to farms will be curtailed resulting in either fallowing or use of groundwater for irrigation. If Colorado River curtailments affect municipal and industrial users, water deliveries to groundwater savings facilities will be curtailed as well. The cost of agricultural pool water will also increase under CAP water curtailments and adversely impact agriculture financially. Extreme flood events could also damage agricultural water delivery infrastructure.

2. Extent to which Proposal Describes and Provide Support for SAWUA’s Ability to Address Basin Study Elements with the Timeframe Required Projections of water supply and demand. Abundant data on existing and projected water supply and demand are available from ADWR’s Tucson Active Management Area Water Use and Demand Assessment. Projections are made through the year 2025. However, water supply and demand projections for the proposed basin planning horizon of 2060 will be needed. Projections will include a near-term, mid-term and long-term (2060) horizon. Water supply and demand projections developed by ADWR were updated in a subsequent report: Tucson Active Management Area Groundwater Flow Model. This model uses MODFLOW-NWT. Numerous climate change models are available for the Southwest. SAWUA partners at the University of Arizona will provide input on appropriate climate models that integrate climate change to the water supply and demand model, with input from Reclamation. SAWUA’s partners at ADWR will work with SAWUA to integrate climate change and water demand into the water supply and demand model.

Analysis of How Existing Water and Power Infrastructure and Operations will Perform in the Face of Changing Water Realities. Regional water planning for the SCR Basin is based on regionally accepted


water supply and demand projections and water delivery infrastructure has been developed consistent with these projections. Imbalances between water supply and demand and its impact to water infrastructure will need to be analyzed to take into consideration future curtailments in Colorado River water deliveries, reductions in water supply availability and changes to water demand. Although the SCR Basin has no hydroelectric power production facilities within its boundaries, water and power are interrelated. Colorado River water delivered through the Central Arizona Project is pumped 336 linear miles at an elevation increase of 2,400 feet to its terminus in Tucson, Arizona. Power to deliver Colorado River water to Central Arizona is generated at the Navajo Power Generation Station. This generating station provides more than 90% of the power to deliver CAP Water. Environmental regulations could increase the power costs to deliver CAP water resulting in financial impacts to CAP water users. Reductions in CAP water deliveries may require recovery of CAP water stored in underground aquifers. Power costs may be incurred to recovery this stored water. Imbalances between water supply and demand may require return to groundwater pumping for agriculture and municipal sectors. Power costs for water and wastewater utilities are also one of the largest budget expenses. Water use is also imbedded in power production. The SCR Basin is served by two electrical utilities; Tucson Electric Power and Trico Electric Cooperative. Much of the electricity produced for use in the SCR Basin is generated at coal-fired power plants located in Northeastern Arizona.6 Coal fired power plants use an average of 510 gallons per MW-hour.7 Projected temperature increases from climate change are expected to increase power consumption throughout all sectors, which will result in increased water consumption for power generation. Development of Appropriate Adaptation and Mitigation Strategies to Meet Future Water Demands. The proposed study will develop strategies to address water supply and demand imbalances. The Arizona Water Banking Authority, Central Arizona Water Conservation District and local water providers are storing CAP water and/or effluent in underground storage facilities throughout the SCR Basin area. Analysis of where this stored water will be needed within the basin for future demand and evaluation of the infrastructure needed to delivery it is one of the mitigation strategies that will be evaluated. The impacts of climate change on natural recharge and its impact to stream flows and groundwater levels could also influence mitigation strategies such as groundwater pumping and its impacts to rural well owners and groundwater dependent ecosystems. The Arizona Water Banking Authority has prepared a recovery plan for 600,000 acre-feet of CAP water stored in the SCR Basin Study. There are an additional 800,000 acre-feet of CAP and effluent stored underground within the basin by various entities. The timing, location and access to recover this water to meet future water demand, particularly if persistent drought and long term CAP shortages become a reality, will be key mitigation strategies in the SCR Basin’s viability. Areas in the SCR Basin that have no access to infrastructure for renewable water supply will be especially vulnerable. EPA’s climate change risk assessment tool could be used for a pilot evaluation on one of

6 Ties That Bind: Plans for New Energy Infrastructure in Pima County, Arizona, Fonseca, pg 4, J, and Connolly, N.,

Pima County Office of Sustainability and Conservation, January 2012. 7 The Water Costs of Electricity in Arizona, Pasqualetti, M. and Kelley, S, ASU School of Geographical Sciences,

December 22, 2008.


the smaller water providers. Colorado River Shortage adaptation and mitigation plans should also be reviewed, as the SCR basin receives CAP water and some sectors will be impacted by shortages.

Trade-off Analysis of the Strategies Identified and Findings. It is recommended that a scenario planning approach, coupled with modeling, be used to develop strategies for addressing water supply and demand imbalances. Tucson Water and the Bureau of Reclamation’s Colorado River Basin Study both used scenario planning and quantitative analyses and/or modeling. This study proposes to use scenario planning to evaluate water supply and demand imbalances and their impacts.

3. Need for Federal Involvement Reclamation Technical Abilities. Reclamation’s technical expertise is needed because of the nature and complexity of the issues in the SCR Basin. Reclamation’s West-Wide Climate Risk Assessment will be used to assess climate change impacts on water supply and demand and will be integrated with the groundwater predictive model for this study. Additionally, Reclamation’s experience in previous basin studies can provide guidance in the development of adaptation and mitigation strategies and analysis of these strategies. Reclamation’s involvement in implementation of Indian water rights settlements will enhance the planning process for water infrastructure and operations that benefits stakeholders in the SCR Basin, Arizona and the U.S. Multijurisdictional Issues and Issues of National Significance. Reclamation’s role in managing the Lower Colorado River and water resource projects and programs in the Southwest makes it a key partner for this study. Reclamation’s responsibility in declaring shortage on the Lower Colorado River is of regional and national significance. Because Arizona has junior priority rights on the Colorado River, Arizona is expected to bear the brunt of any shortage declared by Reclamation. Although initial shortages on the Colorado River will impact water deliveries to agriculture in the SCR Basin, all CAP customers will be impacted financially. Continued shortages could result in curtailments to municipal and Indian water supplies.

Reclamation Activity in the SCR Basin. Reclamation has a strong presence in the SCR Basin. The SCR Basin is within the Santa Cruz River, a tributary to the Colorado River, one of the major river systems within the Reclamation’s service area. Colorado River water is delivered through the Central Arizona Project, a water delivery system that provides renewable water to many municipal and agricultural sectors in the SCR Basin. Reclamation provides Colorado River water to meet Indian water rights settlement obligations in the SCR Basin. This study could complement Reclamation’s efforts to support implementation of the Southern Arizona Water Rights Settlement Act and the Arizona Water Settlements Act with the San Xavier and Schuk Toak Districts of the Tohono O’odham Nation through cooperative planning for local renewable water resources and infrastructure.

Reclamation Projects Affected by the SCR Basin. CAP, authorized by Congress in 1968, delivers Colorado Water to the SCR Basin. The Tucson Aqueduct, completed in 1993 under Reclamation’s oversight, is the last segment of a 336-mile water delivery system that delivers over 180,000 acre-feet of Colorado River water to the SCR Basin. The Central Arizona Project delivers Colorado River water to seven municipal water utilities, three Indian entities and two agricultural farms. Colorado


River water shortages will impact each of these sectors significantly. SCR Basin study partners and other entities recharging CAP water in underground storage facilities will also be impacted. Reclamation is collaborating with a local water provider on a groundwater savings project that will deliver treated wastewater to agricultural lands to accrue long term storage credits. The project participants include Metropolitan Domestic Water Improvement District, Cortaro-Marana Irrigation District, Pima County and Reclamation. Metro Water effluent and effluent allocated under the Southern Arizona Water Rights Settlement Act will be delivered to Cortaro-Marana from the County wastewater reclamation facility

4. Availability and quality of existing data and models applicable to the proposed study

List of Data and Models to be Included. The number and quality of existing data and models on water supply and demand for the municipal water sector in the SCR Basin is robust. ADWR prepares management plans every ten years. As part of the next upcoming plan, ADWR prepared a water supply and demand assessment in 2012. The assessment also included a regional groundwater flow model for the SCR Basin Study Area. The groundwater model predicts areas of decreasing groundwater levels and areas where groundwater is expected to rise. The model code simulates groundwater flow in the SCR Basin area using MODFLOW-NWT, developed by the U.S. Geological Survey. A residential water demand study8 completed in 2015 evaluates trends in municipal water demand. Results of this study will provide input on anticipated municipal changes to water demand. A number of climate change model projections exist, at varying spatial and temporal scales, to provide estimated changes to temperature and precipitation. The Bureau of Reclamation’s West-Wide Climate Risk Assessment, and updates to these projections9 will be employed to assess projected impacts to stream flows, water supplies and demands, and other relevant factors. This assessment will form the foundation for detailed analysis and development of adaptation options for the SCR Basin area. The study will collaborate with the University of Arizona to identify additional appropriate climate and paleoclimate data and climate model projection data10 11, using publicly-available resources, in order to consider additional uncertainties, including those embodied in multiple projections of summer precipitation12. Data or models to be developed. The water supply and demand projections for water planning are made through 2025. However, projections for a longer period, at least through 2060 or beyond should be considered or developed. Water supply and demand projections for the SCR Basin study area will need to be modified to take climate change into consideration.

8 Final Technical Memorandum, Pima County Residential Water Demand Study, G Woodard, Montgomery &

Associates, March 2015. 9 http://gdo-dcp.ucllnl.org/downscaled_cmip_projections/dcpInterface.html

10 Meko, D., C. A. Woodhouse, C. A. Baisan, T. Knight, J. J. Lukas, M. K. Hughes, and M. W. Salzer. 2007. Medieval

drought in the Upper Colorado River Basin. Geophysical Research Letters 34. 11

Griffin, D., C. A. Woodhouse, D. M. Meko, D. W. Stahle, H. L. Faulstich, C. Carrillo, R. Touchan, C. L. Castro, and S. W. Leavitt. 2013. North American monsoon precipitation reconstructed from tree-ring latewood. Geophysical Research Letters 40:954-958. 12

Castro, C.L., H-I. Chang, F. Dominguez, C. Carrillo, J. Kyung-Schemm, H. H-M. Juang, 2012. Can a regional climate model improve warm season forecasts in North America? J. Climate, 25, 8212-8237.


An analysis of climate change projections and determination of the appropriate set of climate change projections for the SCR basin study area needs to be determined to recalibrate projected water supply and demand deficiencies. Impacts to mountain front recharge from increased temperature and changes to precipitation will impact water supply and especially impact rural residents who rely on private groundwater wells for their water supply. The climate change impacts13 need to be translated to groundwater flow models to determine the availability of water supply and impacts to groundwater levels. The impacts of anticipated CAP shortages to water supply sectors need to be better understood. If CAP shortages result in increased groundwater pumping, the magnitude and impacts need to be better identified and understood. Expertise in model operations will be needed to run additional scenarios incorporating climate change data and projected changes to water supply and demand. Available data and models to be used in this study are listed in Table 2 below:

Data or Model Description Source

Regional Groundwater Flow Model for the Tucson Active, Arizona. Model Update and Calibration, Modeling Report No. 24. April 2013

Upgrades previous numerical groundwater flow model and provides a more current tool to assist in management of Tucson Active Management Area water resources

ADWR

Draft Fourth Management Plan for Tucson Active Management Area 2010-2020 (anticipated)

Water management programs for the Tucson Active Management Area over the next ten years. Projections about future conditions, assessment of progress toward achieving safe yield goal for groundwater and recommendations regarding future water management strategies

ADWR

Tucson Active Management Area Water Demand and Supply Assessment: 1985-2025

Historical water demand and supply characteristics for 1985 through 2006 and projections to 2025. Evaluates possible scenarios for future groundwater overdraft using low, medium and high reasonable water demand

ADWR

Arizona’s Next Century: A Strategic Vision for Water Supply Sustainability, January 2014

Assesses current and projected water demands and supplies and provides potential strategies to help Arizona meet its future water supply and demand needs over the next 100 years

ADWR

Colorado River Basin Supply and Demand Study, U.S Bureau of Reclamation, November 2013

Defines future imbalances in water supply and demand through 2060 for the seven Colorado River Basin States. Develops and analyses options and strategies to resolve imbalances

Reclamation

A Forecast Model of Single Family Residential Water Demand for Pima County, November 2014

Forecasts significant changes in single family residential demand using a dynamic simulation model

Montgomery & Associates

Recycled Water Master Plan, Tucson Water, December 2013

Provides integrated recycled water program that maximizes the benefits of the City of Tucson’s recycled water resource and provides framework for activities to ensure implementation of recycled water projects and programs

City of Tucson

13

Ajami, H., T. Meixner, F. Dominguez, J. Hogan, and T. Maddock. 2012. Seasonalizing Mountain System Recharge in Semi-Arid Basins-Climate Change Impacts. Groundwater 50:585-597.



2012 Update: Water Plan 2000 - 2050

Scenario planning based long-term water resource plan for the Tucson Water Service Area.

Tucson Water

2013 Effluent Generation and Utilization Report

Quantity of effluent produced at Pima County regional wastewater reclamation facilities and utilization of effluent in the SCR Basin Study Area

Pima County

Metropolitan Domestic Water Improvement District Long Range Water Resources Plan, Feb 2015

Strategy for managing water resources for the next 50 years. Water demand and supply scenarios through 2065

Metropolitan Domestic Water Improvement District

Recovery of Water Stored by the Arizona Water Banking Authority, April 2014

Provides strategy for recovering water stored underground by the Arizona Water Banking Authority using the Colorado River Simulation System model and a custom recovery model that calculates the probability of specific recovery volumes occurring through time based on a range of supply and demand conditions. A joint plan by Arizona Water Banking Authority, Arizona Department of Water Resources, Central Arizona Water Conservation District

CAWCD

Draft 2015 Central Arizona Groundwater Replenishment District Plan of Operation, December 2014

Provides an estimate of projected groundwater replenishment obligations for 100 years, a description of the water resources that the Groundwater Replenishment District plans to use to meet obligations and description of infrastructure and projects to be used for replenishment

CAWCD

Additional Water Demand Data

Water Providers Assured Water Supply Submittals Annual Groundwater Withdrawal Reports-last 5 years Water Service Area Maps Subsidence Maps

ADWR

Additional Water Supply Data

Underground Storage Facility Permits in the study area Groundwater Savings Facility Permits in the study area Water Storage Permits in the study area

ADWR

Additional Water Supply Data

CAP Water Deliveries to SCR Basin Study Area-last 5 years CAP Entitlements in the SCR Basin Study Area Projected CAP Shortages to SCR Basin Study Area

CAWCD

Remediated Water Use

Data associated with groundwater pump and treat systems removing contaminants from the aquifer. This volume of water pumped each year will be constant or increased through the study period. It will not be associated with pumping to meet water demands, except where occurring currently

ADWR

Water Accounting Areas

WAAs refine the study area into regions that are experiencing different aquifer responses to groundwater use. Scenarios will be evaluated to seek potential solutions and their impact on individual WAAs that are experiencing continued aquifer level declines

Safe Yield Task Force

West-Wide Climate Risk Assessments: Bias-Corrected and Spatially Downscaled Surface Water Projections, March 2011 and updates

Analysis of changes in hydroclimate variables and documentation for new hydrologic projections datasets. Will be used to assess changes in natural mountain front recharge potential

Reclamation



Assessment of Climate Change in the Southwest U.S.

Evaluates and synthesizes information from a wide range of sources and assesses climate change effects on sectors including water. Various climate change models will be reviewed to determine the optimum model to be used to assess water supply and demand in the SCR Basin area

Climas/UA

Table 2 – Data and Models Proposed Data and Model Coordination. Existing data, studies and modeling tools will be used for the Basin Study striving for a full integration of information and predictive models. A large part of the efforts will focus on the ADWR TAMA groundwater flow model which will provide the means to evaluate different water management strategies and infrastructure projects on each of the Water Accounting Areas where the regional aquifer is experiencing continued water level declines. Various module input files of the TAMA model will be manipulated based on recent water demand trends, new recent infrastructure projects affecting groundwater pumping and climate change modeling affecting stream flows and evapotranspiration, as well as, mountain front recharge. Utilizing scenario planning will provide a family of future scenarios that may address aquifer management in different water accounting areas. The TAMA model will be used to run different strategies necessary to evaluate the potential successes and feasibility of each scenario.

5. Level of Support for the Basin Study The local cost share study partner for the SCR Basin Study is the

Southern Arizona Water Users Association (SAWUA). SAWUA members represent diverse regional interests including municipal water providers, wastewater providers and agricultural interests. SAWUA members have water delivery authority to over 80 percent the study area population. Water providers in the SCR Basin Study area have a total entitlement of 196,798 acre-feet of Colorado River water and took delivery of 86 percent of their entitlement in 2014. The SAWUA members will be directly impacted by water supply and demand imbalances resulting from climate change. SAWUA members will be providing water supply and demand data, infrastructure data and long term planning information for the study. SAWUA’s in-kind contribution is $245,000 and additional partners will contribute $148,000 to the study. SAWUA support includes:

Tucson Water $75,000 Pima County $45,000 Metro Water $40,000 Oro Valley $10,000 Remaining SAWUA agencies $75,000

ADWR prepares water management plans for the basin area to address groundwater overdraft. ADWR has a regulatory authority in implementation of Arizona’s Groundwater Management Act and provides regulatory permitting of underground water storage facilities and groundwater pumping. ADWR represents the State of Arizona in policy negotiations of Colorado River operations and administration of Colorado River entitlements. ADWR will provide access to the Regional Groundwater Flow Model and will provide staff to coordinate the model with water supply and demand projections. ADWR estimated in-kind contribution is $5,000 and can also provide $50,000 cash from the Water Management Assistance Program. This program, funded from revenue from the groundwater withdrawal fees can be used for water conservation, augmentation, monitoring and studies. ADWR total cost share is $55,000.


Pima Association of Governments (PAG) is the study area’s regional metropolitan planning organization for transportation planning, environmental planning and technical services. It is the Designated Planning Agency (DPA) under Section 208 of the Clean Water Act, which addresses wastewater and non-point source pollution in stormwater. Both reclaimed water and stormwater have growing potential for utilization as a water resource in the Basin Study area. PAG’s governing body, Regional Council, consists of eight elected officials from each of the local and tribal governments, plus a representative of the Arizona State Transportation Board. In its regional planning role, PAG can provide an integrated approach to watershed planning and management, involving multiple stakeholders that cross jurisdiction and disciplines. For example, PAG’s expertise in shallow groundwater investigations and habitat issues along edges of the basin will be an asset to the Management Committee for the study. PAG will lead the stakeholder engagement process by convening outreach meetings and communications support. PAG expertise will be used to inform and engage decision makers through its Watershed Subcommittee, Environmental Planning Advisory Committee, Management Committee and Regional Council. PAG will provide its technical expertise by providing input to the study and document review. PAG’s estimated in-kind contribution to the SCR Basin Study is $73,000.

The Central Arizona Water Conservation District (CAWCD) operates and manages the Central Arizona Project which is designed to bring about 1.5 million acre-feet of Colorado River Water to central Arizona through a 336-mile system of aqueducts, tunnels, pumping stations and pipelines. CAWCD delivers over 230,000 acre-feet of Colorado River water to municipal, industrial, agricultural and Indian customers in the SCR Basin area. CAWCD is evaluating how near-term shortages on the Colorado River will impact CAP water delivery to central Arizona’s farmers and is working closely with stakeholders in the SCR Basin area to identify and address the impacts of future potential Colorado River shortages. CAWCD is also working collaboratively with Arizona and other Colorado River users to address the effects the Colorado River Basin drought conditions and impending potential Colorado River shortages. CAWCD can provide historic CAP water delivery data and water supply projections under various shortage scenarios. CAWCD also collaborates with local water providers to store CAP in underground storage basins. CAWCD recently completed a plan of operation for the Central Arizona Groundwater Replenishment District (GRD). The plan included water demand projections for water providers in its service area which includes the SCR Basin Study area. The plan also evaluates water supply utilization to assess the replenishment obligations for GRD member lands and member service areas. CAWCD’s study contribution is $15,000 of in-kind. The University of Arizona, located within the SCR Basin Area, has extensive expertise in water issues and climate change. The Climate Assessment for the Southwest (CLIMAS) housed at the University’s Institute of the Environment, conducts research on the nature, causes and consequences of climate change and variability in the Southwest. CLIMAS and colleagues from the University’s Hydrology and Water Resources, and Atmospheric Sciences Departments, will partner with Reclamation to identify appropriate climate projections that will be coordinated with ADWR Regional Groundwater Flow Model and water supply and demand projections. The Center for Climate Adaptation and Science and Solutions (CCASS), also housed at the Institute of the Environment, brings together the University’s expertise in climate impacts and vulnerability assessment at regional, national and international scales. The Water Resources Research Center, housed at the University’s College of Agriculture and Life Sciences, promotes understanding of critical state and regional water management and policy issues through research, community outreach and engagement and public education. The University’s in-kind contribution will be $5,000.


Many stakeholders in the SCR Basin area have a significant interest in the impacts of climate change on water supply and demand and are prepared to assist in this study. Letters of support from the stakeholders are included in Appendix A. There is no known opposition to the proposed study.

Stakeholder Engagement. Throughout the Lower SCR Basin Study, stakeholders will be informed and their input will be garnered and considered at key intervals as the project progresses. PAG will be the lead agency for stakeholder involvement and public communications. However, SAWUA members will be invited to participate in all events and will have input on all materials distributed. Stakeholder Information Meetings. Annual public meetings will be held to inform and garner input about the project. These three meetings will be held in a publicly accessible location and will be noticed through press releases, social media, printed media and flier distribution. Particular efforts will be made to invite key stakeholders including municipalities and tribal governments, water providers and private well owners, agricultural and industrial users, and environmental stakeholders. Regional Standing Committee Meetings. Pima Association of Governments will engage technical experts, professionals and interest groups through its Environmental Planning Advisory Committee (EPAC) and its Watershed Planning Subcommittee. EPAC is a 35-member standing committee with the following representation:

Member governments (City of Tucson, Pima County, Towns of Marana, Oro Valley and Sahuarita, City of South Tucson, Tohono O’odham Nation, Pascua Yaqui Tribe)

Citizen representatives from each of the above listed member jurisdiction area

Interest groups (public interest, professional technical, environment, natural resources conservation, energy industry, mining industry, construction industry, local business, education/research, transportation)

Ex Officio: State and federal entities (Arizona Department of Water Resources, Arizona Department of Environmental Quality, Arizona State Land Department, Davis Monthan Air Force Base, U.S. Environmental Protection Agency).

In addition, all meetings are public and widely distributed through a large mailing list. PAG plans to have presentations on the Lower SCR Basin Study at a minimum of four EPAC meetings and two Watershed Planning Subcommittee meetings during the course of the project. If needed, EPAC can also be utilized to receive direct feedback on project elements because it is a voting body with standing representation. Regional Managers and Decision Makers. This basin study will develop adaptation and mitigation strategies to address water supply and demand imbalances in the face of climate change. In order to move into future implementation and collaboration, it is essential that management and political decision makers be well informed and have opportunity to provide input during the evaluation. PAG will ensure that jurisdictional managers are informed about the Lower SCR Basin Study to through its top policy advisory committee, the PAG Management Committee. Members of this committee include the Pima County Administrator, the city managers from the cities of Tucson and South Tucson, the town managers from the towns of Marana, Oro Valley, and Sahuarita, a Tribal


Council member from the Pascua Yaqui Tribe and the Roads Division Manager from the Tohono O’odham Nation. During the study process, key elected officials will be kept abreast of project progress and results through information provided to the PAG governing board and the PAG Regional Council. The Regional Council includes a Pima County Supervisor, mayors from the City of Tucson, the City of South Tucson, the Town of Marana, the Town of Oro Valley and the Town of Sahuarita, the Vice Chairwoman from the Pascua Yaqui Tribe, the Chairman of the Tohono O’odham Nation and a member of the Arizona State Transportation Board.

6. Extent to which proposed study will employ integrated watershed planning and management

approach As the local study partner, SAWUA provides an ideal framework for regional water resource planning and management as it has a strong history in regional collaboration on water issues in the SCR Basin. Until 1993, the region relied solely on groundwater for its water supply. Regional collaboration to utilize renewable water resources has resulted in localized recovery of groundwater levels in some areas. There is great interest in addressing localized areas experiencing groundwater declines through implementation of adaptation and management strategies including water resource management, conservation, reuse, replenishment and recovery infrastructure. Because of the arid nature of the Sonoran Desert, the interconnectedness and need for balance of water resources for municipal, industrial, agriculture and environment is valued. The SCR Basin has extremely limited surface water supplies. The rare perennial creeks primarily provide water for environmental and eco-recreational benefit, ranching and one golf course. Many basin-edge streams feed water into shallow groundwater areas that support critical riparian habitat. Stormwater flows also provide much needed environmental water for the region and it is increasingly being incorporated into urban and suburban areas through green infrastructure and rainwater harvesting projects. By following Low Impact Development principles, the region realizes further benefits as it uses stormwater for landscaping instead of irrigating with potable or reclaimed water supplies. These coordinated management approaches can be incorporated into scenario planning because there is growing policy support for this type of water management in the region.

Study Cost Estimate. The proposed Basin Study is estimated to cost $785,500 with fifty percent contributed by the study partners and the remainder by Reclamation. A summary of the study costs by task is shown in Table 3.

Tasks and Description Non-Federal $ Share

Federal $ Share

Total Cost

1. Plan of Study and MOA 20,000 10,000 30,000

2. Conduct Scenario Planning 40,000 20,000 60,000

3. Develop Groundwater Model Inputs 45,000 45,000 90,000

4. Implement Groundwater Model 4,000 50,000 54,000

5. Conduct Infrastructure Analysis 26,000 10,000 36,000

6. Identify Adaptation & Mitigation Strategies 66,000 75,000 141,000

7. Analyze Alternatives & Trade Offs 40,000 20,000 60,000

8. Prepare Basin Plan 60,000 10,000 70,000

9. Conduct Technical Sufficiency Review 0 20,000 20,000


Tasks and Description Non-Federal $ Share

Federal $ Share

Total Cost

10. Communication & Outreach Plan 53,000 15,000 68,000

11. Prepare Final Report 39,000 50,000 89,000

12. Administer Study 0 56,250 56,250

13. Non-Federal Contracting 0 11,250 11,250

Total Costs $393,000 $392,500 $785,500

Table 3 – Study Costs Responsibility Assignment SAWUA is the lead partner for this study and has support and participation of several partners. In addition to the water and wastewater providers and agricultural interests represented by SAWUA, the study will include participation from the Pima Association of Governments (PAG), the Arizona Department of Water Resources (ADWR), Central Arizona Water Conservation District (CAWCD) and the University of Arizona (UA). A study management committee will oversee coordination, stakeholder outreach and overall management of the study. It will include representatives from water providers, agriculture, ADWR, PAG, CAWCD and UA. A technical committee will provide input on data collection, scenario planning, groundwater modeling and infrastructure and alternative analysis. It will include water and wastewater providers, agricultural interests, ADWR, CAWCD and the UA. The proposed study partners have access to and have developed robust data on water supply and demand in the study area. Groundwater models developed in coordination with ADWR will be updated under this study. A summary of the partners’ primary responsibility is provided in Table 4 below.

Task Description Study Partners Reclamation

1 Plan of Study and MOA X

2 Conduct Scenario Planning X

3 Develop Groundwater Model Inputs X X

4 Implement Groundwater Model X

5 Conduct Infrastructure Analysis X

6 Identify Adaptation & Mitigation Strategies X

7 Analyze Alternatives & Trade Offs X

8 Prepare Basin Plan X

9 Conduct Technical Sufficiency Review X

10 Communication & Outreach Plan X

11 Prepare Final Report X

12 Administer Study X

13 Non-Federal Contracting X

Table 4 – Primary Responsibility Assignment Study Milestone Schedule SAWUA anticipates completing the proposed Basin Study within 33 months after initiation. A schedule of milestone tasks is included in Table 5 below.


Milestone Year One Year Two Year Three Qt1 Qt2 Qt3 Qt4 Qt1 Qt2 Qt3 Qt4 Qt1 Qt2 Qt3

1. Plan of Study and MOA 2. Conduct Scenario Planning 3. Develop Groundwater

Model Inputs

4. Implement Groundwater Model

5. Conduct Infrastructure Analysis

6. Identify Adaptation & Mitigation Strategies

7. Analyze Alternatives & Trade Offs

8. Prepare Basin Plan 9. Conduct Technical

Sufficiency Review

10. Communication & Outreach Plan

11. Prepare Final Report 12. Administer Study 13. Non-Federal Contracting

Table 5 – Study Milestone Schedule

Cost-Share Partners and Study Contacts Cost share partner and contacts for this study are indicated below.

Local Share Partner Federal Partner Warren Tenney, President Southern Arizona Water Users Association Metropolitan Domestic Water Improvement District 6265 N La Cañada Tucson, Arizona 85704 [email protected]

Mary J. Reece, P.E. Manager, Program Development Division Phoenix Area Office U.S. Bureau of Reclamation 6150 West Thunderbird Road Glendale Arizona 85306-4001 [email protected]

Kathleen M. Chavez, P.E. Southern Arizona Water Users Association Regional Wastewater Reclamation Department Pima County 201 N Stone Avenue – 8th Floor Tucson, Arizona 85701 [email protected]

Eve Halper Natural Resources Specialist U.S. Bureau of Reclamation Tucson Field Office 300 W. Congress St., FB-37 Tucson, AZ 85701 [email protected]

mailto:[email protected]





Lower Santa Cruz River Basin Study

Appendix A

Letters of Support

PO BOX 638 • MARANA AZ 85653-0638 • 520-682-2516 • FAX 520-682-2517 • BKWFarms.com

Bureau of Reclamation Attn: Ms. Amanda Erath Mail Code: 84-52000 P.O. Box 25007 Denver, CO 80225 RE: Lower Santa Cruz River Basin Study Proposal Application Dear Ms. Erath, BKW Farms is pleased to support for the above-reference proposal application submitted by the Southern Arizona Water Users Association (SAWUA) to the U.S. Bureau of Reclamation’s Basin Study Program. BKW Farms is a member of SAWUA and uses CAP water on its agricultural lands. Persistent drought conditions locally and in the Southwest are expected to have significant impact on agricultural water supply and demand. We support SAWUA’s efforts to seek a partnership with the Bureau of Reclamation to analyze the potential impacts of climate change on the availability of water resources in the Lower Santa Cruz River Basin. The proposed study will be beneficial in planning for long-term water supplies to BKW Farms and to the entire Tucson Active Management Area. Please feel free to contact me if you have any questions or require additional information. Sincerely, Brian Wong S/S

lower santa cruz river basin study - sawua basin study.pdf · the santa cruz river is a tributary...

Documents