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<br />Comment, Mr. Fredrich: Although I agree with the need for models that <br />can be adjusted to reflect the effects of potential changes in the <br />physical system, I'm not certain that what is needed is a runoff <br />model that more closely simulates the physical processes involved <br />in the rainfall-runoff transformation. I think that perhaps we <br />should study more closely the process that we have modelled so that <br />we can identify the factors that are important. in changes and the <br />degree of change in a factor necessary to produce a change in output. <br />1'm not sure that more "sophisticated" models are warranted, given <br />the data availability usually encquntered in planning studies. <br /> <br />Reply, Mr. Benn: Viable solutions in regional planning studies are <br />obtained by estimating the impact of alternatives. To properly <br />study alternatives it is often as important to understand what is <br />happening to water in the transformation from rainfall to runoff <br />as it is to determine time history of runoff itself. For example, <br />a method under consideration for wastewater disposal is to apply the <br />water periodically to the land surface. This scheme envisions the <br />soil and its organisms fixing or degrading contaminants before the <br />water is conducted to streams and/or groundwater. The feasibility of <br />this system for a given area can only be evaluated by considering the <br />rates of water acceptance, retention, and migration, which, of course, <br />are functions of site properties and the hydrology of the area. Many <br />other problems can be cited in both the civil and military areas where <br />predictions of the state-of-the-ground are critical to the design and <br />successful performance of an activity or item of hardware, i.e., <br />battlefield surveillance, munition effectiveness, cross-country <br />locomotion, forest harvesting, agricultural soil preparation, etc. <br />Thus, I believe the need for better analytical tools is undeniable. <br />The problem of data acquisition and manipulation for the improved <br />models is indeed a monumental one. The terrain analysis techniques <br />developed at WES rely heavily on the ability to acquire and manipulate <br />large volumes of environmental data. I feel these procedures or <br />similar ones can be applied to the hydrologist's data acquisition and <br />manipulation problems. <br /> <br />39 <br />