Instream Flows for Recreation: A Handbook on Concepts and Research Methods

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Table 2 Some examples of flow - related "trip attributes" used to define various recreation experiences. Developing a specific list of trip attributes is a critical step in the process because attributes define the conditions for which flows are needed. Category Examples of Attributes Category Examples of Attributes Boatability No major portages Camping Scenic views of river Few hits in boulder gardens Open and flat areas for tents Clear channel through riffles Access (eddies for take -outs) No engine damage due to Sandy beaches groundings Lack of insects Whitewater Major rapids are Class III /IV Fishing Open bars for casting Long reaches of Class II rock- Clear water (low turbidity) dodging Wadable depths & velocities Large standing waves at Good fishing water (holes or constriction rapids riffles -- depends upon the Keeper holes at two major species, type of lure, etc.) rapids Variety/abundance of fish Rate of Boat Trips require less than 2 days Scenery/ Open views Travel given 4-6 hours /day on General River Active geological processes river Aesthetics Few traces of human use Variety of wildlife Sound /smell of river Power of waterfalls /rapids Hiking Access to side canyons Open point bars for Water clarity hiking and views Step 4: DESCRIBE HYDROLOGY Hydrology is the quantity and timing of water availability in a river system. Quantifying a river's annual hydrologic regime is an essential element in defining the range of flow management options — in the conceptual model, it is the "faucet" from which all other elements in the framework originate. Information about current or potential flow regimes is the starting point for an instream flow analysis. In describing hydrology, researchers need to consider not only the river's natural hydrology (how much water naturally flows in a river through a period of time), but also the ways in which that hydrology may be altered by dams, diversions, or withdrawals. On highly regulated streams, hydrologic regimes may be permanently affected by these structures, imposing severe constraints (or opportunities) on 12 flow management options. There are a variety of techniques for exploring the hydrology of a river, many of which are discussed in greater detail in Chapter 4, Exploring the Effects of Flow on Resource Conditions. In almost any study, however, researchers will need to demonstrate a basic understanding of the river's hydrologic regime through a brief summary. Information generally included in this summary (which should be a summary, not an infinite appendix) includes: ❑ Representative hydrographs, showing how average flows change over the course of a year (or the season of interest). ❑ Low -flow and high -flow analyses that show when and how often low or high flows (including peak flows) are likely to occur. ❑ Pre- and post- project flow regimes when the