Linking Reclaimed Water Consumption with Quantitative Downstream Flow Impacts

Although reclaimed water - municipal wastewater treatment plant effluent - can serve as a locally sustainable alternative water resource, this additional consumptive use of reclaimed water may cause impacts downstream. This paper seeks to quantitatively assess these impacts by employing scenario analysis coupled with a two-sample t-test to evaluate the statistical significance of streamflow alteration. Further, the potential for lower volumes of streamflow is linked to impacts on downstream stakeholders through the use of stakeholder performance metrics. To demonstrate the applicability of this approach, two diverse regions are evaluated: (1) the Illinois River downstream from the greater Chicago, Illinois, area, and (2) the Middle Rio Grande River downstream from Albuquerque, New Mexico. In Illinois, impacts to barge transportation are marginal and decrease with distance downstream of effluent consumption. In the Rio Grande, impacts to the Rio Grande silvery minnow worsen downstream such that a proposed consumption would be unlikely to be established under federal regulations. The extent of downstream impacts is important in legal and policy contexts regarding the sustainability of reclaimed water projects.