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21 <br />equal to the August MMF or 0.015 m3/s/km2 (crosk). The ABF is assumed <br />to be adequate for all periods of the year, unless additional releases <br />are necessary for fish spawning and incubation (U.S. Fish and Wildlife <br />Service 1981). Instream flow releases recommended during the spawning <br />and incubation periods are presented in Table 2-1. Like the Montana <br />Method, the NEFRP relies on flow statistics which can be obtained <br />without extensive field surveys. <br />The ABF which is calculated by this procedure is recommended as <br />the minimum instantaneous discharge immediately below the dam during <br />normal runoff conditions. During low-flow periods when inflow to the <br />reservoir is less than the ABF, minimum releases equal to the inflow <br />are requested. The NEFRP is unique in that alternative proposals for <br />the flow release locations, schedules, and supplies can be submitted <br />by the developer. Provided that such proposals are supported by <br />biological justification and are found to afford adequate protection <br />to aquatic biota, USFWS personnel may incorporate all or part of such <br />proposals into their recommendations (U.S. Fish and Wildlife Service <br />1981). Thus, the NEFRP supports the ABF as sufficient to maintain <br />aquatic life but does not preclude the same maintenance (or level of <br />protection) at lower flows (W. Knapp, personal communication). <br />Other variations of methods that use a constant yield factor as <br />the basis for determining instream flow needs have been proposed by <br />Robinson (1969) for the Connecticut River and by Chiang and Johnson <br />(1976) for streams in Pennsylvania. Robinson's recommendations were <br />somewhat lower than the present New England Flow Recommendation <br />Policy: 0.091 m3/s/km2 (crosk) or 1.24 ft3/s/sq mile (cfsm) for <br />maximum fishery values and 0.026\crosk (0.36 cfsm) for moderate fishery <br />values. The recommendations of Chiang and Johnson (1976) were based <br />on an even lower set of stream flow statistics, either _the__7Q10 <br />(minimum flow which persists for seven days once every ten years) or a <br />yield factor of 0.011 crosk (0.15 cfsm). These differences in minimum <br />flow requirements reflect the lack of a general consensus on what <br />flows satisfy the needs of aquatic ecosystems as well as differences <br />in basin runoff characteristics.