Background

The Southwest is one of the most rapidly growing areas of the United States and also one of the most arid. Conflicts over scarce water resources have a long history in the region. In order to efficiently utilize this precious resource in a sustainable manner, a complex set of physical structures—including dams, reservoirs, and interconnected groundwater pumping and delivery systems—have been built. Likewise, over the years, an increasingly complex institutional structure has emerged to mediate competition over water allocation and use.

Water Supplies Vary

Surface water accounts for more than half of Arizona's water supplies. The Central Arizona Project—a 335 mile long canal and series of pumping stations and reservoirs—delivers water from the Colorado River to parts of the state, including the large urban areas of Phoenix and Tucson. Groundwater resources in the Southwest are unevenly distributed, with some areas having large volumes of groundwater and some having very little.

Climate variability directly affects many of the region's water resources, as surface water supplies are dependent on annual rainfall amounts and minimization of evaporative loss. Groundwater supplies in many areas also depend on rainfall that infiltrates back into the ground.

Water Policy and Population Growth

In 1980, Arizona's Groundwater Management Act established "Active Management Areas" (AMA) within the state where groundwater withdrawals are closely regulated. The Arizona Department of Water Resources estimates that more than 80 percent of the state's water use occurs within the five AMAs. While much of this goes to agriculture, the demand for water in urban areas is increasing as Arizona cities grow. Projections by the Arizona Department of Economic Security indicate that both the Phoenix and Tucson metropolitan areas will grow by about 40 percent by 2025.

Climate Variability and Information Use

The urban water sector is one of the more climate-sensitive sectors in the Southwest. Water managers and other decision makers must balance the needs of exponentially expanding populations with the physical reality of limited water supplies. Weather- and climate-related events, such as unusually hot weather, prolonged drought, or flood events frequently add additional stress to urban water systems.

One way that water managers and other decision makers may prepare for and cope with such events is through expanding their use of climate information and forecasts. However, the climate research community lacks sufficient knowledge about the use of information by local water managers, exactly which types of weather and climate events managers find most difficult to contend with, and what their specific information needs are. Water managers, on the other hand, may have limited knowledge of what products are available, where to access them, and how to apply them to their decision-making processes.

Conservation in Flagstaff

Overview

This study examined the emergence of water conservation measures in Flagstaff, Arizona. During recent years, similar to many other non-metropolitan areas in the West, Flagstaff has faced on-going drought conditions, population growth, and an economy increasingly dependent on natural amenity values.

The purpose of this study was to learn how the community balances the competing demands for scarce water supplies that this situation engenders, particularly with regard to the implementation and support of conservation polices.

Research Methods

Two main research methods were used in this study. First, archival research of historic and contemporary climate, hydrology, economy, regulations, and population set the biophysical and socio-economic context of Flagstaff.

Second, a content analysis was conducted (fall of 2002–early 2003) using qualitative data from 30 interviews with area water policy makers, scientists, and community interest groups. Substantive statements about pressing water problems, their causes, favored management responses, information sources, and influences on the decision-making process were selected for analysis.The community interest groups included representatives from the following types of organizations:

• conservation/environmental
• economic development
• forestry/fuels management
• land development
• significant industrial water users
• large local employers
• significant reclaimed water users
• ranching
• tourism/recreation

Results

Interview findings indicate that three times as many study informants support conservation measures over supply augmentation policies, such as drilling new wells or tapping new water sources. Support for supply augmentation as an alternative means of coping with water scarcity is limited to a few (but quite influential) area water policy makers. The majority of informants who supported conservation measures supported some sort of water use curtailment method, such as limiting urban growth or implementing year-round landscape watering restrictions. The popularity of water conservation measures in Flagstaff can be linked to on-going drought conditions, population growth, a local political economy that is increasingly dependent on the value of healthy ecosystems to draw tourists and new residents, as well as an effective local social movement that has organized around the broader environmental movement and is questioning historical policies that deplete local water resources.

However, the study also found that so-called conservation measures promote three different ends:

1. economic growth by exploiting natural resources (i.e., resource instrumentalism);
2. economic growth based on maintaining naturally scenic areas through more measured use of water resources; and
3. tenets of the broad environmental movement (i.e., inherently valuing natural resources for non-human uses, like riparian or wildlife uses).

Although the latter two ends appear to overlap, the degree of support for conservation measures by those interested in preserving the scenery around Flagstaff will most likely depend on the extent that this industry maintains economic dominance in Flagstaff over the long term. This research highlights the necessity for community dialogue regarding the full implications and consequences of conservation measures.

Because drought conditions and population growth are forecast to continue in the future, these findings suggest that adopting and implementing a water budget and integrating long-term climate forecasts into the local decision-making framework would partially mitigate future conflicts among the water conservation faction in Flagstaff.

Sensitivity Analysis

Overview

The urban water sensitivity analysis examines the impacts of climatic variability and population growth on water supply and demand in five urban areas of Arizona, and highlights the distinct sensitivities that each of these areas is likely to experience under one-, five-, and ten-year severe drought conditions.

The purpose of the urban water sensitivity analysis (conducted in 1998–1999) was to illustrate to water managers and policy makers the importance of factoring climatic variability into assessments and projections of water supply and demand variability. Our ultimate objective is to encourage the use of climate information, including historical and paleo data as well as forecasts, in water resource planning and decision making at time scales ranging from seasonal to annual, interannual, and multidecadal.

Research Methods

In order to examine the impacts of climatic variability on a variety of water management areas, we chose five sites that vary in population size, type of water demand, and available water resources. The study sites included the Phoenix AMA, the Tucson AMA, the Santa Cruz AMA, and the Benson and Sierra Vista subwatersheds of the San Pedro River.

The first step of urban water sensitivity analysis was to calculate the impacts of the most severe one-, five-, and ten-year droughts on record if they were to recur today, and at projected 2025 population levels, in order to better understand how increasing population pressure affects the urban water sector. We combined the water supply and demand budgets provided for each region by the Arizona Department of Water Resources with historical records from the Western Regional Climate Center.

The analysis also considered the possible impacts of changes to water supply and demand: supply was altered in some scenarios by eliminating Central Arizona Project (CAP) water, which is drawn from the Colorado River and subject to basin-wide drought; and demand was decreased by eliminating agricultural water use in other scenarios.

Results

This component of the project has now been completed. Our calculations show what percentage of an area's water supply would have to be mined from groundwater reserves under the different climatic, water use, and population growth scenarios, and allowed us to evaluate the relative sustainability of water use in each situation.

For example, we found that under conditions equal to the worst one-year drought in the Phoenix AMA’s history, combined with increased water demand projected to meet the needs of the population anticipated by 2025, demand would outstrip the area's sustainable supply by 79 percent. A five-year drought could force the overdraft of 47 percent of the AMA's water supply, or 5.5 million acre-feet; and the ten-year drought scenario projected an overdraft of 9.2 million acre-feet would be necessary to meet the 39 percent of the water demand that could not be met by renewable sources.

The results of this study are included in CLIMAS Report #CL1-00: Assessing the Sensitivity of the Southwest's Urban Water Sector to Climate Variability: Case Studies in Arizona.

Urban Water Providers

Overview

This aspect of the urban water study provides insight into the ways in which climate- and weather-related factors affect urban water systems in Arizona, as well as whether and how water providers use available information in coping with weather-related situations.

In this study, the four major communities examined in the sensitivity analysis (Phoenix, Tucson, Nogales, and Sierra Vista) were revisited in 2000–2001, this time to gather water providers' perceptions of their vulnerability to climate variability and their use of climate information.

Research Methods

In order to conduct a holistic assessment of the wide range of water providers in terms of population served, size of service area, administrative structure, water resources utilized and infrastructure available, large water providers (those serving over 250 acre-feet of water per year) in four areas of southern Arizona were investigated using a mailed survey and follow-up interviews in 2000–2001. A total of 54 surveys were mailed or faxed to large water providers in the study areas, and 28 of those surveys were returned. We then conducted follow-up interviews with 22 selected water providers.

Both the survey and interview questions were intended to address the sensitivity, adaptability, and vulnerability of each water system. Questions regarding the sensitivity of a system attempted to determine the degree to which the specific system responds to weather and climate. Those eliciting information about the adaptability of a system focused on how much practices, processes, or structures of systems could be adjusted to respond to past climactic fluctuations or a changing future climate. Questions designed to determine the vulnerability of a system provided a means to assess the extent to which weather and climate may impede its capacity to carry out its function in the future.

The survey and interviews provided both quantitative and qualitative data, which are analyzed and discussed in the report. Quantitative analysis of the database generated by the survey was conducted, and major trends were expounded upon using the interview data.

Results

This component of the project has now been completed, and the results indicate a pronounced awareness of the impacts of weather events, but a much lower overall perception of the importance of longer-term climatic variability to water availability and use.

Our study revealed a range of perceived levels of vulnerability to weather-related situations. The weather-related event providers cited most often as causing the most disruption to urban water systems was lightning strikes, which debilitate electrical pumping systems. The second most commonly cited impact was short-term high temperatures that cause spikes in demand, which may be difficult for water providers to meet. Longer-term climatic fluctuations, such as droughts or longer periods of above-average precipitation and flooding, were seldom cited as having important impacts on water systems in the study areas.

The study also found that providers are less than eager to use climate forecasts and other related information due to their lack of information about the accuracy of available products and limited perceptions of the value of such information in improving water management. The report documented comments and suggestions from the water providers regarding potential improvements to forecasts in terms of relevance and clarity.

The results of this study are included in CLIMAS Report #CL1-03: Climate and Urban Water Providers in Arizona: An Analysis of Vulnerability Perceptions and Climate Information Use.

Water Law and Policy

Overview

Any assessment of climate impacts on water resources must take into account the legal and institutional structure within which decision making is framed. This project summarized significant climate implications embedded in key international, federal, state, and local laws and policies.

Research Methods

The methodology for this component of the project consisted of content analysis of a wide variety of legal sources, technical reports, policy analyses, media reports, and websites containing information about water management and climatic variability in Arizona. The analysis was completed in 2000.

Federal, state, tribal, and local water regulations were considered, as well as international agreements between the U.S. and Mexico. The major issues and implications of the findings for the state of Arizona, particularly the Tucson and Phoenix AMAs, were identified and discussed.

Results

This component of the project has been completed. We concluded that Arizona has a reasonably well-developed institutional structure for governing water management in the more stringently managed areas of the state, such as the Active Management Areas (AMAs). This structure provides a basis for balancing climatic and ecological factors with human stresses, especially rapid population growth, on the state’s environmental and natural resource base.

However, the institutional foundation of the state is based on a relatively narrow conceptualization of climate variability, and thus is a source of potentially serious constraint to effective water management in times of climatic stress. Some of the existing institutions and policies, especially those addressing water rights, water storage and recovery, interstate and intrastate water marketing, water transfer, and consumer pricing, need to be broadened in scope and authority to manage water resources effectively under conditions of severe stress.

The results of this study are included in CLIMAS Report #CL2-01: An Examination of Arizona Water Law and Policy from the Perspective of Climate Impacts.

Related Publications

Carter, R. and B. Morehouse. 2003. Climate and urban water providers in Arizona: An analysis of vulnerability perceptions and climate information. Tucson, AZ: Climate Assessment for the Southwest, The University of Arizona.

Carter, R. and B. Morehouse B. 2001. An examination of Arizona water law and policy from the perspective of climate impacts. Tucson, AZ: Climate Assessment for the Southwest, The University of Arizona.

Carter, R., P. Tschakert, and B. Morehouse. 2000. Assessing the sensitivity of the Southwest's urban water sector to climatic variability. Tucson, AZ: Climate Assessment for the Southwest, The University of Arizona.

Morehouse, B. 2002. Climate impacts on urban water resources in the Southwest: the importance of context. Journal of the American Water Resources Association, 36(2):265-277.

Morehouse, B. 2002. Integrating climate into water policy. Southwest Hydrology 1(2):16-17, 28.

Morehouse, B. 2001. Can Tucson’s water supply survive a drought on the Colorado River? WaterWords 19(1).

Morehouse, B., R. Carter, and T. Sprouse. 2000. The implications of sustained drought for transboundary water management in Nogales, Arizona and Nogales, Sonora. Natural Resources Journal 40(4): 783-817.

Morehouse, B., R. Carter, and P. Tschakert. 2002. Sensitivity of urban water resources in Phoenix, Tucson, and Sierra Vista, Arizona to severe drought. Climate Research, 21(3):283-297.

Workshop Details

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