Effluent-Dominated Waterways in the Southwestern United States: Advancing Water Policy through Ecological Analysis

Increasing freshwater demands coupled with concerns over water scarcity have resulted in an intense and complex conflict between the development of rivers as water and energy sources, and their conservation as biologically diverse, integrated ecosystems. Nowhere is this conflict more apparent than in Arizona, where the continued support and survival of expanding urban and rural areas depend greatly on what choices are made regarding water management, including the maintenance of agriculture and other industries, and sufficient future environmental and riparian protection. It has become increasingly evident that established water policies under the current laws and management regimes do not have the inherent adaptive capacity needed to address the challenges facing water demand in the 21 century. Yet Federal and state approaches to water legislation remain somewhat fragmented and limited institutional and policy steps have been taken to develop new tools and approaches addressing these challenges. The lack of clear, reliable data on wastewater generation has led to a serious gap in knowledge regarding water reuse and environmental needs in Arizona. Spatial and temporal analyses of wastewater treatment, effluent generation, and release revealed that that hydrogeomorphic setting significantly influences downstream riparian response. Current practice has just under 50% of effluent generated released into nearby channels or waterbodies. Additional analysis showed that approximately 70% of sampled discharge points released effluent into ephemeral or deep groundwater systems. These scientific outputs inform recommendations which include the 6 need to recognize riparian habitat as beneficial use for instream flows, develop criteria specific to effluent dominated waterways, and increased adaptive capacity within management approaches. A shift toward more integrated decision frameworks will improve sustainable outcomes for future water reuse practices throughout Arizona. INTRODUCTION Much of the western United States suffers from a scarcity in natural water supplies. Yet it is the part of the country that has experienced the greatest population growth over the past half century. In the 1990s, western states experienced 20% population growth compared to a national average of 13% (Travis, 2007). Nevada, Arizona, Colorado, Utah, and Idaho grew at 37% during that same period (Getches, 2010). Since 1980, Arizona’s population has more than doubled, increasing from approximately 2.7 million to over 6.3 million residents by 2006 (Gober and Jones, 2007). Today, Arizona remains one of the fastest growing states in the country, with population growth primarily concentrated in urban areas. The state population is projected to grow to almost 13 million by 2050, with more than 60 percent of that growth predicted by 2020 (USEPA, 2007). These patterns underscore the need to identify more sustainable approaches to water management in Arizona (Eden and Megdal, 2005). As municipal growth increases and freshwater demands continue to intensify and strain existing water supplies, water resources policy and management are topics that increase in both complexity and consequence. Historic management of rivers has been aimed at creating or maintaining water supplies through engineering and political lenses focused on ensuring reliable water supplies, limiting flood damage, and reducing pollution (Karr & Chu, 2000). 7 One consequence has been the modification of watercourses, with more than ninety percent of riparian areas altered or degraded in the western United States (Gibbs, 2000; Patten, 2006). While these strategies have been deemed successful in the past, the critical discourse of sustainability questions how much these approaches should be continued (Gleick, 2010). Realizations that riparian and wetland ecosystems provide many beneficial services have shifted thinking in science and policy circles toward more “socioecological” (or “socionatural”) frameworks (Medema et al., 2008). Through this framing, complexity, variation, and uncertainty are accepted as inherent properties of linked social and natural processes (Gunderson and Holling, 2001; Naiman et al., 2005; Brauman et al., 2007). In response, a number of management frameworks (e.g., adaptive management, integrated water resources management) have emerged in the last thirty years. These frameworks have been organized to serve as testable premises, or prescriptions, designed for knowledge production and feedback loops to achieve specified desirable outcomes and manage uncertainty (Medema et al., 2008). However, integration of these frameworks into practice has proved difficult to achieve. Nowhere is this conflict more apparent than in the arid and semi-arid southwestern United States, a region with growing populations and limited water supplies highly dependent upon annual variability. During the twentieth century, the development of dams, storage reservoirs, delivery infrastructure, and improvements in groundwater withdrawal added to the reliability of water supplies and encouraged population growth (BRP, 2010). Freshwater consumption for urban and agricultural practices has led to significant declines in groundwater levels and the loss of approximately 35% of perennial surface flows in Arizona 8 (Turner and Richter, 2011). Paradoxically, rapid urbanization has also led to the production of large volumes of municipal wastewater often discharged into nearby channels propagating the development of effluent-dominated riparian ecosystems (Tellman, 1992). Despite progress in recognizing the need for sustainable water supplies, water policy and management in Arizona remain fundamentally driven by uncertainty over water scarcity, calling for alternative water supply and water reuse options. Consequently, policy makers and resource managers face a new challenge: create distribution systems that balance water for human consumption with environmental needs. Decision makers must determine how and how much to change management frameworks and water development strategies to meet the goals of sustainability. There are several ways in which they may do so. One approach is by integrating ecological information into decision frameworks with the overall goal of linking release, recharge, and overall renewability of water supply. A second way is by more deliberately engaging and reconciling the value of water used for human development and water for the environment. For example, there is value in releasing water as environmental flows, as well as reusing it to support direct human uses. These uses are in increasing opposition to each other as policy makers look to increase water supply, and managers need ways to consider and balance economic value of ecosystem services. A third method is using an integrated water resource management (IWRM) approach that encourages more reflexive, adaptive styles of decision making, which leading thinkers suggest are needed to manage critical resources in the 21 century (Holling, 1973; Gunderson and Holling, 2001; Medema et al., 2008).