A Collaborative Model Process to Examine Temperature TMDL's and Related Remediation Strategies for the Willamette Basin

Water managers in the Willamette River Basin face a number of difficult and closely interrelated challenges associated with the Endangered Species Act (ESA), the Clean Water Act (CWA), and other associated concerns. For example, under the CWA, the Oregon Department of Environmental Quality (ODEQ) has recently released a total Maximum Daily Load (TMDL) for temperature in the Willamette Basin. Considerable public planning has already been accomplished in the basin with much of the assessment and planning phases for solving some of the basin's problems codified in the temperature TMDL. Some of the major factors impacting temperature in the Willamette include operation of the multiple reservoirs, permitted industrial and municipal discharges, land-use types, and irrigation practices. Possible mitigation strategies include changes in land-use to increase shading along streams, installations to cool or store point- source discharges, changes in how and when water is released from the reservoirs, installation of multi-port withdrawal structures on the reservoirs, and remediation of riparian and hyporheic zones. Each of these strategies comes with ecological, economic, and/or social costs and/or benefits that must be weighed and understood before meaningful dialogue about how to best manage the basin can occur. To address this problem a collaborative team from Sandia National Laboratories, the Institute for Water Resources, David Evans and Associates, and the Portland District of the Corps of Engineers have been working with stakeholders in the basin to design and collaboratively develop an integrated temperature model of the basin to examine the linkages between the various strategies and their tradeoffs. The model consists of a series of systems dynamics lumped parameter models that provides real-time feedback and scenario testing capabilities, as well as the ability to link disparate systems such as hydrology, ecosystem services, recreation, and economics. This presentation will describe the collaborative process in which the model was developed as well as demonstrate the model itself and how it is being used to influence and inform policy decisions in the basin.