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~ A. J. DOUGLAS AND R. L. JOHNSON sportfishing, wading, swimming. canoeing, whitewater rafting, and kayaking. Water is a medium of transport for municipal, industrial, and agricultural wastes. Also, stream water may provide substantial aesthetic benefits. Some of these benefits are neglected in any particular instream flow benefits study. This reflects the competitive nature of some of the outputs; water that is used to transport industrial wastes is usually unsuitable for swimming or the provision of aquatic habitat. Diversionary uses of streamflows obviously compete with instream uses. Streams may be completely dewatered by agricultural diversions for crop irrigation.7 However, the competitive nature of instream uses and diversionary uses is often more subtle. Recreational instream uses are high quality water uses. Agricultural return flow is usually low quality water. Hence the competitive na ture of the two sets of demands for the water resource stems in part from the fact that agricultural diver- sions lower water quality. But seepage and evaporation in irrigation canals, and evaporation and evapotranspiration from fields and crops, also generate substantial consumptive losses. 6 These two factors-low quality return flows and consumptive losses-create competition between instream flow demands and irrigation demands. Municipal and industrial water uses also create major diversionary demands for the stream water. Finally, it is important to note that recreational streamflow demands may compete with market oriented instream flow demands. Goodman8 points out that hydropower facilities consume only a small quantity of water and usually have a negligible effect on water quality. But bottom release dams typically lower water temperature, while dams or reservoirs with release gates located near the top of the structure typically raise water temperatures. Maddux el al.9 note that these tempera- ture changes can impact fisheries adversely. Rapid flow alterations downstream from hydropower facilities supplying peak load electricity can also have major adverse fisheries effects.9 NONMARKET VALUATION METHODS Contemporary research deals with a remarkably broad range of water resource valu- ation issues. Thus it is not surprising that there are two broadly accepted methods for obtaining economic estimates of instream flow benefits, namely, the contingent value method (CVM) and the travel cost method (TCM). Clawson and KnetschlO use the travel cost method to estimate the social benefits conferred by an outdoor recreation site. The TCM can also be used to estimate benefits from an improvement in some site characteristic such as augmented streamflows.]O The survey instrument for a travel cost method study may be mailed out to a group of residents in some geo-. graphic area or it may be administered to recreationists who have recently used the site. 10,] ] The travel cost method solicits data from respondents about travel costs to estimate a demand curve for trips to the site. Clawson and KnetschlO use the travel cost method to estimate a relation between travel costs and the participation rate- trips to the site per annum per thousand residents-for each of several concentric regions around the site. This is the zonal variant of the travel cost method. Richards and Wood]] use a micro-data travel cost approach that estimates a relation between travel costs and trips to the site for recreationists who have used the site. This method produces estimates of per trip benefits, and must be combined with inde- pendent data on participation days to generate aggregate benefits conferred value estimates. The contingent value method also uses data from questionnaires. The contingent value method directly queries respondents with regard to the payment they would