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ward, interior western, interior central, in- terior eastern, and Gulf of Maine) shows pronounced differences in cfsm mean val- ues and C.I. ranges. The C.I. overlap (Fig- ure 5) that exists among the mountain windward, Long Island Sound, and St. Lawrence regions is an artifact of high variability and small sample sizes charac- teristic of each of the latter two regions and not due to similarities in gage data. If more gages were present within these re- gions, the variability reflected in the ranges of cfsm values among these regions, es- pecially Long Island Sound, may be re- duced and might permit these groups to become statistically distinguishable. The mean August cfsm values and con- fidence intervals for the mountain wind- ward and the combined mountain lee- ward/interior and coastal regions are as follows: Mean August 95% C.I. 95% C.I. Region cfsm lower upper Mountain windward 0.62 0.58 0.67 Other regions combined 0.31 0.28 0.35 These two regional classes appear to be statistically representative of the hydro- logic regions identified during the study. It is noteworthy that the C.I. ranges around these means do not overlap, nor do they include the 0.5 cfsm value of the ABF pol- icy. In applying these values to a refined ABF recommendation, as discussed below, Mountain Windward (Class I) should be reasonably rounded to 0.6 cfsm, and the other regions (Class II) should be round- ed to 0.3 cfsm. IMPLEMENTING THE REFINED REGIONAL ABF POLICY The development of an Aquatic Base Flow (ABF) policy has been an accepted resource protection concept that provides necessary measures to protect aquatic hab- itat and expedites the resolution of in- stream water diversion issues in New En- gland. However, the implementation of a New England-wide ABF policy should take into account the varying hydrologic fac- tors which influence New England August streamflow, namely the effects of mean basin elevation and windward/ leeward mountain ranges. Therefore, the applica- tion of a policy-based flow recommenda- tion needs to recognize that streamflow is determined by basin characteristics. The above analysis establishes that the present 0.5 cfsm recommendation policy omits the variability of basin characteris- tics. A result of this omission is that the distinctions between basin types are less- ened, meaning that the current policy does not recommend enough flow for projects located in certain high elevation stream basins of New England and recommends more discharge than is necessary for proj- ects in other areas. In other words, the present ABF policy tends to fall short of its intent, which is to protect aquatic hab- itat by approximating unregulated August median flow. Based on the above analysis, a refined Regional ABF policy would establish a case-specific classification (Class I or Class II) for each river basin in question, starting at the point of interest and including all upstream drainage from that point, using the selected basin characteristics cited in Table 2. This requires classifying individ- ual basins and calculating basin drainage areas using USGS topographic maps. It is necessary to divide any drainage that is not entirely a Class I or Class II hydrologic region into sub-basins and to determine the proportional area of Class I and Class II drainages prior to computing the flow recommendation. Once the basin type has been classified as Class I, Class II, or a combination of the two, an appropriate cfsm value can be de- veloped and recommended to the project developer. Many New England ABF rec- ommendations, therefore, would be either 0.6 cfsm or 0.3 cfsm, depending on the hy- drologic region. In drainages that include both classes of hydrologic regions, the fi- nal flow recommendation would be pro- rated between 0.6 cfsm and 0.3 cfsm, based on the areal proportion of Class I and Class II sub-basin characteristics. This Regional ABF policy, utilizing basin characteristics as the foundation for IN- 20 Rivers • Volume 1, Number 1 January 1990