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.
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| Ephemeral: Typical |
Ephemeral: Atypical |
Effluent Dependent |