Laserfiche WebLink
<br />; <br /> <br />Wetted Perimeter <br />Several states also use the Wetted Perimeter method to formulate instream flow e <br />recommendations. In fact, the biological principles which form the basis for both the Wetted <br />Perimeter methodology and CDOW's % WP criteria are quite similar (Skinner, pers. comm.). The <br />R2CROSS staging table contains the information that is required to produce a wetted perimeter <br />versus discharge plot. This plot could be used to compare R2CROSS and Wetted Perimeter <br />recommendations. As with Tennant, the Wetted Perimeter methodology should be used to verify <br />R2CROSS recommendations but it should not be used as the sole basis for an instream flow <br />recommendation. <br /> <br />Summary <br /> <br />Choosing an instream flow quantification technique can be a difficult and controversial task. <br />McKinney and Taylor (1988) state that the choice should be based on the technical merits of each <br />methodology and not the political issues surrounding a particular instream flow recommendation. <br />They state that standard setting approaches are most appropriate on streams with limited instream <br />value or where potential impacts of proposed water development projects are relatively benign and <br />that incremental methods should be used on streams with high instream value or where water <br />development projects may severely impact stream habitat quality. They believe that selection of a <br />particular flow quantification methodology should occur on a case-by-case basis with consideration <br />given to both standard setting and incremental approaches. <br /> <br />e <br /> <br />Similarly, Reiser et al. (1989) suggest that guidelines be developed for determining when a <br />technique or methodology is most appropriate rather than choosing a particular methodology for all <br />streams in all situations. They suggest that the selection of a given method should be based upon <br />the nature of the problem, time, fmancial, and logistic constraints, and the reliability and legal <br />acceptability of the method. <br /> <br />Lamb (1993) suggests that selection of an appropriate instream flow quantification technique <br />is driven by the need to address political and environmental problems and the ability of a specific <br />technology to meet certain scientific standards. He also states that political and environmental <br />problems fall on a continuum between long-range planning and project bargaining, with most <br />projects falling in a "mid-range" category and that the choice of an appropriate instream flow <br />quantification technique often depends on the anticipated complexity of the problem. <br /> <br />Stalnaker et al. (1995) indicate that "there is simply no best way. The choice of method or <br />methodology depends on the circumstances." They state that simple methods, like Tennant and the <br />Wetted Perimeter method, are Widely used and are important "first-cut analytical tools." They also <br />suggest that "IFIM is appropriate for the most controversial projects." <br /> <br />Most recently, Castleberry et a1. (1996) suggested that "no scientifically defensible method <br /> <br />15 <br /> <br />e <br />