Model Development Methodologies to Support Resource Management Decisions on the Willamette River

Water managers on the Willamette River in the state of Oregon are facing a new biological opinion and potentially strict TMDL regulations for temperature that will require actions by various stakeholders over the next few decades. Considerable public planning has already been accomplished in the basin with much of the assessment and planning phases for solving the basin's problems codified in a TMDL that was issued in 2006. Various alternatives have been proposed to meet the TMDL requirement, including operational changes at US Army Corps-operated reservoirs, projects that increase stream shading or restore the floodplain or hyporheic zone, and operational or technological changes at point sources such as waste water treatment plants and pulp and paper plants. To help meet the TMDL in a shorter time horizon, a collection of stakeholders formed the Willamette Partnership to develop an ecosystem marketplace where water quality and conservation credits can be traded. The marketplace will develop currencies in temperature and other environmental goods and services, and requires tools to describe linkages between credit trades, water operations, and other management changes (e.g. increases in stream shading) that control water temperature. These tools will link basin hydrology to temperature, water quality, and other concerns using a systems dynamics approach to provide real-time feedback to policy decisions. For these tools to be useful at the policy level, they must have short execution times, be able to capture the important dynamics of the problem, and be able to display the output in a manner that is meaningful to the stakeholders. This paper will present the development methodology of those tools, concentrating on the assumptions and comprises that were needed at the model level for the tool to meet those requirements.