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INTRODUCTION The Big Thompson Watershed, HUC 10190006, (Figure 1) is a tributary to the South Platte River located approximately 50 miles northwest of Denver, Colorado. The natural, topographical Big Thompson River basin collects water from approximately 900 square miles including portions of Larimer, Boulder and Weld counties. Additionally, the Colorado-Big Thompson (C-BT) project creates a virtual tributary linking the Big Thompson with the headwaters of the Colorado River in Grand County. This watershed encompasses many resource issues typical of the wildland-urban interface and faces increasing challenges in maintaining water quality to support designated uses. Population growth on the Colorado Front Range exceeded 35% during the 1990's, compared to 13% nationally. The associated changes in water use from agricultural to recreation and municipal water supplies place tremendous demands on water and land managers to ensure high quality water supplies. Managers and citizens in the Big Thompson watershed recognize the need for a comprehensive watershed management plan, and have established the Big Thompson Watershed Forum to coordinate the process as described in this proposal. Several Big Thompson water bodies are listed on Colorado's 2006 303(4) list or monitoring and evaluation list. Horsetooth Reservoir, one of our largest terminal reservoirs and a primary drinking water supply for the north Front Range was placed on the 2006 303(4) list for dissolved oxygen. Additionally, three years of comprehensive water monitoring and data analysis have led to the development of a list of 72 water quality issues of concern. From this list, the Big Thompson Watershed Forum (the Forum) has identified nutrients (phosphorus and nitrogen) as our priority pollutants of concern. Nutrients are an emerging pollutant of concern and EPA has mandated states to develop nutrient standards. Focusing the Big Thompson Watershed Management Plan on nutrients will prepare affected interests, such as the regulated and recreation communities, for changing standards. Publishing a management plan with recommended nutrient thresholds prior to the promulgation of regulations also increases the public's awareness of local nutrient issues. Currently, the Big Thompson River segment downstream of the City of Loveland, has a Total Phosphorus geomean of 698 micrograms per liter and a recommended EPA value of 67 micrograms per liter. Researching other stream segments and lakes and reservoirs will identify areas where nutrient standards compliance may be difficult. Providing stakeholders with this information now will increase the likelihood that pollution controls can be implemented prior to standards adoption. -4-