At one level, sustainability, when referring to water resources, means we are not consuming more water than can be renewed. Sustainability implies a balance between supply and demand. For example, groundwater is not an unlimited resource. If we use groundwater supplies at a greater rate than the aquifer is recharged, we are violating the principles of sustainability. Groundwater use at that level is not sustainable. This definition generally corresponds to the definition of safe yield, which is the management goal of the Tucson Active Management Area (TAMA).

Sustainability also has a broader definition, one that takes into account social, economic and environmental values. In this context, a sustained water supply involves more than matching water demand with supply. Sustainability also means that our water resources are managed in a way to preserve the environment, to maintain the economy, and to ensure that all water users share equitably in reaching and maintaining a balance between water supply and demand.

Both definitions, but especially the latter, involve a shift in mind set. What is involved is less emphasis on developing new water supplies, which has been the traditional approach, with more attention devoted to learning to use water in a way that allows current and future users to live in balance with nature and one another.

One final point: The geographical area covered by the report needs defining. Tucson as the “study area” of this report covers more territory than what is bounded by city limits. This presents some difficulties. Defining a “study area” is complex and often contextual. The most common term used in this report is the “Tucson area.” This term is meant to encompass the most heavily populated portions of eastern Pima County, from Avra Valley on the west, to the Rincons to the east, and from Green Valley on the south, to Pinal County on the north. These boundaries are approximate and are intended to roughly delineate an area in which there are extensive political and hydrologic connections.

The maps in this document show most of the Tucson area, with the exception of Green Valley. (See Figure 4.) The choice of map extent represents a compromise between showing sufficient detail in the most heavily populated areas and showing the larger geographic extent. The map boundaries are not intended to be absolute.

In many instances this report refers to more specific boundaries, usually in the context of the source of available data. For instance, many of the data in this report come from the Arizona Department of Water Resources’ Tucson Active Management Area. TAMA is based, in part, on groundwater basin boundaries.

An effort has been made to be both precise and consistent in the use of terms and geographic extent. The reader should be aware, however, that there is some inherent “fuzziness” in these definitions, due to overlapping political and hydrologic boundaries.

Each of the following chapters begins with a brief summary of its content. Background information then is provided on topics crucial to understanding Tucson’s water dilemma. The final chapter offers readers an opportunity to make their own choices from a range of options, based on the information in the previous chapters.

If this report can be said to have a single, underlying message, it is that there is no one simple, inexpensive solution to our water problems. Each proposed solution has both positive and negative impacts.

Figure 4 Study area.

All of us — Tucson Water customers, private utility customers, farmers, miners, industrial water users and those with their own wells — have straws in the same glass. What we do affects everyone else. The challenge for the community is to pick an effective and desirable solution at a price it is willing to pay.

This report was funded entirely by the University of Arizona and was produced by the UA Water Resources Research Center as a service to the community. Its intent is to provide useful, accurate information for Tucson citizens to use in making water decisions. The authors believe both scientific information and community values have important roles to play in deciding water issues. With this in mind, the authors have collected information from a wide variety of sources including federal, state and local agencies’ reports, university research, information from private water utilities and studies by nonprofit groups. Although staff members of local agencies were consulted at various times during the preparation the report, the Water Resources Research Center researchers defined the issues and summarized the information with the assistance of other university experts.