Quantifying Whitewater Recreation Opportunities

American Whitewater has developed a framework to better understand flow-recreation relationships through a series of study progressions, and to establish study outputs that can inform decision-making at the basin-wide, watershed, or stream reach level. This framework was developed by our Colorado-based stewardship team and has been utilized to identify river recreational needs in major river basins around the State of Colorado. The resulting study method establishes standardized terminology and analysis, providing the best available data for flow-dependent river recreation needs. Quantifying river recreation needs and opportunities can inform water management decisions at the local, state, and federal level and help develop collaborative solutions that support paddling and river health.

Assessing water needs for recreational attributes identified at the watershed, river, or river segment level requires an assessment of streamflow and how variable flow rates affect the quality, quantity, and timing of river-dependent recreation, such as whitewater boating or float-fishing. American Whitewater’s study progression first defines flows that support recreational uses along a range of ‘acceptable’ and ‘optimal’ flow conditions. These flow ranges are developed using web-based flow evaluation surveys. Subsequent quantification of recreation opportunities (e.g. ‘Boatable Days’) is completed by assessing the number of days within a period of study, when defined acceptable and optimal flows are present in the study’s stream reach. American Whitewater developed ‘Boatable Days’ as a quantitative metric most relevant to 1) describe current flow-dependent recreation opportunities and 2) evaluate how future flow conditions may affect existing recreational opportunities.

The Boatable Days study framework is a tool that water managers can use to quantify and describe current flow-related recreational attributes, and to measure how a change in current conditions may influence the quantity and quality of recreational opportunities. The study outputs do not prescribe management targets or represent desired mitigation and enhancement thresholds in any scenario where flow regimes can be managed. Rather, the Boatable Days framework aims to standardize recreational needs data and can assist with unique water management planning efforts being considered at the local and state level.

To account for highly variable annual flow conditions, the Boatable Days assessment sorts a study period into hydrologic year types (e.g., wet, wet-typical, dry-typical and dry) by ranking the total annual flow in acre-feet at a given stream gage. After hydrologic data is organized by year type, the daily average streamflow is evaluated against preferred flow ranges defined through previous flow evaluation surveys. When streamflow, as measured by gage data for the study reach, meets defined recreational flows on a particular day, for a particular experience class (e.g. the range of acceptable or optimal flows), the opportunity is counted as a ‘Boatable Day’. This same analysis is completed for every day of the study period for all year types, and for each acceptable and optimal flow range. The output of Boatable Days within each flow range is then totaled by month for comparison with other months and year types throughout the study period (See Figure 1).

Figure 1. Summary of Boatable Days results on the Rio Grande River between Creede and Wagon Wheel Gap. A) Number of Boatable Days across three different hydrological years types, B) Hydrological year types overlaid on acceptable and optimal flow ranges, and C) Number of Boatable Days per month in each different year type. Boatable Days occurring between November and March are outlined in purple, representing winter months when actual use is unlikely to occur.

Figure 1 is an example of Boatable Days results from American Whitewater’s assessment completed for the Rio Grande Basin Stream Management Plan process. These results quantify a baseline of existing river recreation opportunities using the Boatable Days metric and can be used to inform management decisions regarding local recreational resources. In addition to quantifying a baseline of existing opportunities, the Boatable Days framework can be used to assess how future hydrological scenarios may impact recreation.

The Boatable Days tool allows for several sensitivity analyses to help determine the impacts on recreational attributes from future hydrological scenarios, Identified Projects and Processes, changes in diversion decrees, or changing supply forecasts. These sensitivity analyses can be performed with user-provided annual hydrograph time-series or by estimated percent reductions or additions to historic flows (Fey, Stafford. 2016). This approach can assist in identifying when a noticeable change in recreation opportunities on a targeted study reach might occur, as well as the general magnitude of changes in flow that cause losses or gains to Boatable Days. This study progression can be useful for a variety of water planning processes and project level analyses. In Colorado, the Colorado Water Conservation Board identifies American Whitewater’s flow preference and Boatable Days methodologies in their Nonconsumptive Toolbox and as a resource for Stream Management Plans around the state.

In 2015, Colorado adopted a statewide Water Plan to guide the future of water management in Colorado under increasing pressure from population growth and climate change. A primary directive of the Water Plan is to develop Stream Management Plans (SMPs) for 80% of locally prioritized stream reaches by 2030. To meet this goal, Colorado’s Basin Roundtables and local water managers are working to develop these Stream Management Plans, identifying needs and opportunities for environmental and recreational values. American Whitewater’s Boatable Days framework has been and continues to be used to meet data gaps for river recreation in Stream Management Plan efforts around the state. A list of past and current river recreation assessments is located below. If the American Whitewater’s Boatable Days framework could be useful in your local river basin or for a management planning process in your area, you can contact Hattie Johnson at hattie@americanwhitewater.org.

Previous Studies:
Rio Grande Basin
• Colorado River Basin
• Yampa River
Lower Dolores River
• St. Vrain
Cataract Canyon
San Miguel River Basin
Gunnison and Taylor Rivers

Current studies:
• Roaring Fork & Crystal Rivers
• Cache la Poudre River

Additional resources:
Colorado Water Conservation Board Nonconsumptive toolbox
Colorado's 2015 Water Plan
Stream Management Planning in Colorado

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