在波特兰大都会区（俄勒冈州），27家市政供水商正在评估区域供水前景，包括长期需求、水资源可用性、水质和系统需求。一个关键的组成部分是确定布尔润河、哥伦比亚河、克拉卡马斯河、威拉米特河和特拉斯克河未来可用于市政用途的水量。作为整体综合资源规划项目的一部分，蒙哥马利·沃森进行了一项涉及旱年水文的水资源可用性研究；规划水平水库运行模型；考虑流内流动；列入或可能列入濒危或濒危物种标准的鱼类； 以及许多其他政治环境问题。本文总结了水资源有效性研究的方法和结果。西北部河道内的水流状况正处于快速变化时期，主要是由于对珍稀濒危鱼类的担忧。确定了11类河道内流量考虑因素，从经过认证的河道内水权到资源机构或环境组织提出的新建议或最新建议。这些考虑因素将对未来的用水产生重大影响。

In the Portland Metropolitan Area (Oregon), twenty-seven municipal water providers are evaluating the regional water supply outlook regarding long-term demands, water availability, water quality, and system needs. A critical component is the determination of how much water is available for future municipal purposes from the Bull Run, Columbia, Clackamas, Willamette and Trask rivers. As part of the overall integrated resources planning projects, Montgomery Watson performed a water availability study involving drought year hydrology; planning level reservoir operations models; instream flow considerations; fish species that are listed, or may be listed, under threatened or endangered species criteria; and numerous other political-environmental issues. This paper summarizes the methods and results of the water availability study. The instream flow picture in the northwest is in a period of rapid change, primarily due to concerns over rare and endangered fish species. Eleven categories of instream flow considerations were identified, ranging from certificated instream water rights to emerging or recent recommendations by resource agencies or environmental organizations. These considerations will impact future water use significantly.