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. . FEB 05 .00 l7:3~ p.1S JUSTIFICATION FOR RESEARCH DISCHARGES The Research Plan presents a series of null hypotheses that should be tested through collection of data about the driving variable and response variable. These relationships can also be interpreted by developing a set of resconse curves. Response curves are commonly used in ecol09ical ri~k a~geggments. The ~ Glen Canyon Environmental Studies are, in part, a risk assessment in that they attempt to evaluate the level of risk each resource in the Canyon may be exposed to under a particular perturbation. In this case, the perturbations are the discharge regimes that operation. of the dam create, as well as other human activities. A response curve relates the variable (y) at ~~Sk, for example, beach face topography or sedimene volume to some perturbation (xl. for example, magnitude of discharge fluctuation or human camping activity. In order to develop a minimal "curve" and to have sufficient data to test the null hypotheses ~resented in the Research Plan, the perturbation (x) axis should have a minimum of three points and the sample size should be sufficient to allow adequate statistical tests. In some cases it may be impossible to collect a sufficient number of samples to ensure the statistical reliability of the pattern observed. In this case, the statistical tests and the response curves with regression lines and variances may just show trends, a level of analysis probably sufficient for management decisions. Response by a Canyon resource to a perturbation must be determined over time. One day of a particular fluctuating discharqe or one day's camping activity is insufficient to develOp a pattern or repetition of response. There is a periOd in which the system must reach an "eqUilibrium" with a particular perturbation, especially with discharges. After this, the response of a resource can be measured. If the perturbation variea in an unpredictable and random fashion, as is the case with discharqes and human activity, there is a need for experimental conditions as well as a control. For fluctuating discharqes, the experimental conditions are controlled research discharges that will equilibrate within the system, and the controls are constant discharges with the same daily volume as the fluctuating discharges. Responses of resources to normal operation fluctuating discharqes, which are highly variable, will be compared with responses to controlled fluctuating discharges and constant discharges. Human activity will always be random at any of the tests sites, thus establishment of control sites is essential. Paired control sites will have no human activity. This will be the equivalent to no fluctuations (constant discharge) in fluctuating discharge studies. 1