An Effluent Dependent Stream is generally a stream with ephemeral or intermittent flow that receives treated effluent. For some portions of the year, wastewater treatment plants may be the only source of water in such a stream for some distance below the effluent outfall. Treated effluent may also be discharged into a perennial stream, but this does not make the stream “effluent dependent”.
On the map in this article, the locations of large wastewater treatment plants with discharges to ephemeral stream channels are indicated by water drops. Rectangular pop-outs show in greater detail the measured extent of effluent flow from the discharge point or “outfall”. Wastewater treatment facilities that discharge to flowing streams are indicated by a purple dot with no pop-out, because the extent of effluent flow is coincident with the flow of the stream. Facilities that do not discharge effluent to an Arizona waterway are not shown.