Report: State of the Poudre — @fortcollinsgov

Click here to read the report. Here’s the executive summary:

Executive Summary
The purpose of this first State of the Poudre River (SOPR) is to provide a description of the current health of the Cache la Poudre River (Poudre) from approximately Gateway Natural Area to I-25. The Poudre is a complex natural system that has been altered by nearly two centuries of human influence. This has resulted in dramatic changes to the physical structure of the river, water quantity and quality, floodplain, forests, and wildlife communities. The human footprint continues to expand, placing additional pressure (or stresses) on the river ecosystem and the natural processes that sustain it. This river health assessment provides the City of Fort Collins with a new tool to track trends and benchmark progress towards its vision of sustaining a healthy and resilient Cache la Poudre River.

While the Poudre flows 126 miles from its headwaters to its confluence with the South Platte near Greeley this study focuses on a 24-mile reach from the lower canyon through Fort Collins. The study area was divided into four zones (Canyon, Rural, Urban, and Plains) and further into 18 study reaches based on natural changes on the landscape and human influences.

Overall Grade: For the 24-mile study area the Poudre River received an overall grade of C. This grade indicates the even though the Poudre has been altered and degraded by a suite of local and system wide stresses that impair its health, it continues to support basic elements of a functioning river ecosystem.

The framework for this baseline assessment includes nine indicators of river health which are informed by 25 indicator-specific metrics. Collectively these provide a thorough evaluation of how well the system is functioning. Metrics grades are developed by collecting and incorporating many types of data, which were then translated into an A-F grading system. Indicator and metric numerical scores and their corresponding letter grades were calibrated to categorical definitions relating to degree of functionality or impairment.

Recommended ranges developed for each metric (as established in the River Health Assessment Framework, City of Fort Collins, 2015) and were developed based on the City’s concept of working towards a functioning river ecosystem. The recommended ranges consider the contemporary real- world context and reasonable expectations for future change and the potential for improvement. They should, however, be used as a guide and aspiration rather than a directive. Also, when interpreting results for a comprehensive scientific assessment such as this, it is important to consider that uncertainty and variability exists across scientific disciplines, data sources, and river reaches. The methods and grading guidelines provide an explicit description of the analytical approaches used and can help the reader understand this variability.

This report is structured to allow the reader to understand the project approach (Sections 1 and 2) followed by identification of potential influences, or stressors, on river health in Section 3. The health assessment scores (Section 4) reveal the ramifications these anthropogenic stressors are having on ecosystem condition. Results indicate there is considerable variability across aspects of river health as scores vary widely (from A to F) at smallest unit of measurement (metrics scores by reach). In Section 5, the focus shifts to an overview of river health, describing the link between stressors and degree and type of impairment for each of the four zones. Poudre River health indicator grades for each zone are compared to the ranges recommended in the City’s Poudre River Health Assessment Framework (2015)—to highlight areas where there is the greatest gap between the City’s goals for the river and today’s conditions. This section also includes an analysis of the causes of impairment and explores which problems are tractable to practical solutions. Section 6 looks toward the potential future applications and improvements for the project.

From The Fort Collins Coloradoan (Jacy Marmaduke):

In their first-ever health assessment of a 24-mile stretch of the Poudre River, a group of Fort Collins water experts awarded the river an overall grade of a C.

In other words, the river is functional, the assessment’s authors said. But it could, and should, be better.

City officials aspire to a B grade for the river, which would mean the assessed stretch is considered “highly functional.”

The report was put together by a group of ecologists and resource managers from the city’s natural areas and utilities departments, Colorado Parks and Wildlife and several consulting firms. The goal was to develop a tool city officials can use to benchmark progress toward a healthier river.

The study focused on the Poudre from the lower canyon near Gateway Natural Area to Interstate 25 and used an A-F grading system. The spotlight was on six key indicators of river health:

  • Flows, the primary driver of river health
  • Sediment, a natural component of rivers that can be harmful if amounts are too much or too little
  • River channel, including shape, width and depth
  • Water quality
  • Aquatic life
  • Riparian corridor, including riverside forests, wetlands and grasslands
  • The overall grade of C “indicates that even though the Poudre has been altered and degraded by a suite of local and system-wide stresses that impair its health, it continues to support basic elements of a functioning river ecosystem,” the report states.

    The river’s lower canyon zone fared better than the urban, rural and plains zones, scoring an overall B-minus with high marks for riparian corridor health, water nutrients and land and channel erosion. The canyon zone scored poorly on habitat connectivity and water temperatures, the latter because warming water temperatures represent risks for aquatic life.

    The river’s urban zone earned a C grade with high marks for water nutrients, trout population and land erosion. The urban zone failed in riparian corridor health, habitat connectivity and river flows.

    Overall, river flows were an issue for most of the 24-mile stretch.

    “The Poudre is characterized by major changes in flow volumes and timing,” the report states. “Reductions have significantly altered peak and base flows, the effects (of) which are exacerbated the further one travels downstream. Diversions also cause unnatural fluctuations in flow volume, which likely affects critical habitat and reproductive needs of fish and insects in the river.”

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