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4 IlIOLOGICAL HEPORT 29 Yakima River basin in Washington. focusing on Pacific salmon restoration, and the Truckee.Car. son River systems in Nevada, emphasizing endan. gered species and terminal wetland habitat recov- ery, were highlighted as examples of emerging multiple.use management. Assigning a reservoir water budget to the fisheries for downstream habi. tat management is now being seriously considered during the operations evaluation phase of many large federal water storage projects. The tradi- tional water user groups (for example, irrigated agriculture, municipal, and industrial) may prefer such reservoir water budget management because the fish water is treated the same as other water in the system, and the call for water must be decided by the fishery manager, relieving the reservoir operator and other users in the system from ha\;ng to decide how and when the instream flows are to be delivered, The shift from a set of minimum flow constraints to a water budget set aside specifically for fisheries purposes changed the role of the fisheries manager in river systems in the United States. From now on, to be most effective, the fishery resource managers must become water and habitat managers. Thus, natural resource agencies need to acquire a more interdisciplinary mix among their employees, These contemporary agencies must be prepared to decide about the delivery of water on a daily basis during particular seasons and to decide what por- tIOn of the river basin fishery resource will be favored (and conversely what part sacrificed) dur- ing droughts. By adopting water budgets, a mutual 'sharing' of storage in federal water projects across all user groups during droughts is facilitated, Un- der the traditional diversionary allocation philoso- phy of 'first.in-time-first-in-right' practiced under Western water appropriation doctrine, the fishery may have first priority during a water.short year (if flows are reserved by appropriation) or last pri- ority (if allocated a very junior water right). By gaining a 'seat at the management table' the in- stream-fishery interests get part of the water stored during high.flow periods for release when the most critical conditions occur downstream. Sharing the storage allows for delivery to relieve these critical conditions, Multiple Use Implies Interdisciplinary Analyses Multiple.use management of water at the river basin level is widely recognized 39 essential in the " United States A recent study by the National Re- search Council (1992) points out that management of reservoirs for single purposes such as irrigation or hydro-electric production is no longer socially acceptable. Efficient use of water must incorporate a multitude of instream and consumptive uses throughout a river basin. This management will require an interdisciplinary group of professional water managers to establish procedures for evalu. ating the water supply, distributing the water, and sharing the consequences of low supply, Resolving conflicts among states and user groups sharing the same river system calls for interjurisdictiona1 river boards or commissions to manage water stored in public reservoirs for instream and out~of-stream uses. Agency resource personnel will be asked to apply state-of-the.art tools, extensively tempered with judgement and experience, to day.to-day deci. sion making, Fishery and recreation agency man. agers will make recommendations on seasonal and monthly bases, dependent on forecasted water sup- ply and available storage. Stream ecologists have a substantial challenge before them to provide re. search data to enhance the ability ofresource man. agers to make these decisions. Research is needed to Improve and validate relations between fish, wildlife, and riparian vegetation and the stream flow regime, New research is needed for groups of organisms (guilds' and habitat variables that are not currently factored into the decisionrnaking process. Development of IFIM IFIM unfolded against the backdrop of minimum flow standards, quantitative impact analyses, water budgets, and interdisciplinary analyses. The specific impetus was the National Environmental Policy Act, which mandated all federal water re- source agencies to consider alternative water devel- opment and management schemes, This require. ment placed increased responsibility on natural resource agencies for methods, evaluations, and recommendations related to reservoir storage and release and stream channel depletions, IFIM was developed by an interdisciplinary team and was founded on a basic understanding and description of the water supply and habitats within stream reaches of concern. Historical analysis of the flow regime using a monthly or weekly timestep to de. scribe the reference or baseline hydrologic condi- tions was considered essential because this type of analysis was normal practice within the water reo