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  • Arid West Water Quality Research Program (AWWQRP)

    Arid Region

    The Pima County Regional Wastewater Reclamation Department (PCRWRD), in Tucson, Arizona was funded by the U.S. Environmental Protection Agency (EPA) to conduct the Arid West Water Quality Research Project (AWWQRP). The objective of the project was to improve the scientific base for regulation of water quality, protection of species, habitats, and uses of watercourses, and designation of appropriate treated wastewater effluent controls in ephemeral and effluent-dependent watercourses of the arid and semi-arid western states.

    Five EPA regional offices are involved in regulating water quality in these seventeen states.

    Ephemeral and Effluent-dependent

    Ephemeral river and stream channels are dry for most of the year, carrying water only in response to rainfall events or spring snow melt. The Santa Cruz River a few miles downstream from Tucson, Arizona is an example of an ephemeral river.

    Stream segments that derive essentially all their flow from wastewater treatment facilities are termed effluent-dependent. Aside from considerations of the aquatic habitat that must be protected in these streams, the effluent contribution to a riparian habitat supporting amphibian and terrestrial communities must be considered.

    Thus there are not only multiple uses but sometimes competing uses associated with the quality and quantity of the water. The project was created to address concerns that the water quality criteria developed under the Clean Water Act - on which state water quality standards are based - may not be appropriate for arid and semi-arid ecosystems.

    Typical Atypical effluent
    Ephemeral: Typical Ephemeral: Atypical Effluent Dependent

    Pre-Research Survey of Municipal NPDES Dischargers

    The objectives of the Survey were to obtain information on water quality issues and problems faced by wastewater dischargers in the arid West and to gather basic data such as discharge rates, designated uses of receiving waters and the physical, chemical and biological characteristics of receiving waters.

    Habitat Characterization Study

    The objectives of this study were to (1) review existing physical, chemical and biological data for a selected group of ten sites throughout the arid West where treated effluents are being discharged into normally dry streambeds or streams that would have minimal flow during part of the year in the absence of effluent discharge; (2) characterize the habitats based on established protocols and protocols adapted for arid West conditions; (3) identify similarities and differences among the ten sites; (4) recommend a system for habitat classification and (5) recommend areas for additional study.

    Extant Criteria Evaluation

    This project evaluated the technical basis for national water quality criteria for specific chemicals from an arid West perspective. The evaluation included a technical review of exposure assumptions and the representativeness of species used to calculate water quality criteria. Also included in this project is an exploratory study to evaluate the relationship between hardness and metals toxicity at hardness values >400 mg/l CaCO3. This exploratory analysis evaluated copper, using Ceriodaphnia dubia as the test species.

    Additional Reports

    The AWWQRP has shared information about the Project and our research results through numerous public outreach efforts. Following are some of the presentations that have been given at various conferences.

    Arizona Water & Pollution Control Association

    Annual Conference

    Society of Environmental Toxicology and Chemistry

    Annual Conference (Nov. 15, 2005)

    American Water Resources Association

    Annual Conference (Nov. 7, 2005)

    Nevada Water Resources Association

    Annual Conference (Feb. 26, 2004)

    Colorado Water Quality Control Division

    Section 309 Study Advisory Group - Arid West "Extant Criteria Study" Symposium (Jul. 28, 2003)

    Western Governors' Association

    Western States Water Council Symposium on Arid Areas Issues (Dec. 11, 2002)


    Educational Institutions


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