Effluent-Dependent Waterways in the Southwest: Advancing Water Policy through Ecological Analysis

EPA Grant Number: F07C40598
Title: Effluent-Dependent Waterways in the Southwest: Advancing Water Policy through Ecological Analysis
Investigators: White, Margaret Susan
Institution: Arizona State University - Main Campus
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2007 through January 1, 2010
RFA: STAR Graduate Fellowships (2007) RFA Text |  Recipients Lists
Research Category: Water and Watersheds , Academic Fellowships , Fellowship - Ecology and Planning


Flow regimes of many rivers in the southwestern United States have been altered by anthropogenic actions. Today, a new hydro-dynamic is emerging as water consumption for growing urban development is increasing the amount of effluent generated and discharged into stream channels or aquifers. This research examines the increased generation of wastewater effluent and its integration into water policy frameworks. More specifically, it investigates the ecological outcomes of discharging wastewater effluent into streams with varying hydrologic regimes and analyzes the policy frameworks driving this current practice. Two fundamental questions frame this work: What are the effects of urban wastewater effluent on riparian ecosystem function and plant community structure as influenced by the degree of connectivity between surface water and groundwater in the receiving stream? What types of policy frameworks drive current practice and how can water resources managers integrate decision rules about wastewater into the complex water landscape?


The distribution of riparian communities is influenced by flood events as well as by groundwater levels and surface flow rates. Therefore, stream hydrology and other ecological factors should be considered when deciding to discharge effluent into a waterway. In this research, multiple approaches are used to facilitate the development of a set of guidelines for identifying waterways suitable for the release of wastewater effluent with riparian ecosystem recovery as an outcome. First, a regional spatio-temporal analysis of effluent and effluent-dependent waterways in Arizona since the mid-twentieth century will quantify hydrologic variability (e.g., surface flow regimes, surface water-groundwater connectivity, watershed size) across the landscape and categorize the types of waterways into which effluent is discharged. Next, the study focuses at both landscape and floodplain scales to contrast riparian vegetation dynamics between two rapidly urbanizing effluent-dependent stream reaches that differ in surface-groundwater interactions. These case study reaches will also be contrasted with non-effluent control streams that span a hydrologic gradient from ephemeral to perennial flow regimes. Finally, the scientific findings will be coupled with an assessment of existing water policy frameworks in Arizona to determine how scientific guidelines for wastewater effluent can be integrated into the decision-making process for riparian ecosystem management.

Expected Results:

Existing water policy frameworks are complex and fragmented; surface water, groundwater, and effluent are managed separately and have differing levels of management. Scientific studies offer a means for improving understanding of links among stream hydrology, water quality, and riparian plant communities, thereby informing policy and management. This work utilizes scientific analysis as a framework for informing regional planning and ecosystem management and contributes the first characterization of the spatial patterns and temporal changes of effluent-dependent waterways in Arizona. This research also presents the use of hydrologic studies on ecosystem structure and function to inform planning and policy models for effluent discharge points and reuse.

Supplemental Keywords:

Riparian, wastewater effluent, connectivity, southwest, policy, hydrology, groundwater, decision making, spatial scale, management, restoration, urban ecology,, Scientific Discipline

Progress and Final Reports:

  • 2007
  • 2008
  • Final