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8000 7000 6000 ....... ~ ~ 5000 <5 ~ S 4000 C<:l v t: '" Natural Flow Hydrograph __ 2000 Conventional Stair-stepped InstreamFlow Water Right 3000 1000 o Oet Nav Dee Jan Peb Mar Apr May Jun JuI Aug Sep FIGURE 2. Conventional Stair-Stepped Instream Flow Water Right Another improvement is to add one differential flow to a constant year-round base flow amount. In protecting the Little Bighorn River bordering the Little Bighorn National Monument, the State of Montana and the NPS agreed to a year-round instream right of 51 cfs in addition to a IS-day spring peak flow of 950 cfs (Mont. Code Ann. 9 85-20-501, Art. II, S F). The result is a single, dramatic step up and then down from the base flow value that may still not protect all of the river's hydrologic variation. Conventional instream flow water rights can be crafted to protect a complex or dynamic range of flows with the amounts increasing as the streamflow increases, varying day-to-day and year-to-year, thereby more closely simulating natural flow patterns. Though never implemented, the U.S. Forest Service (USFS) and the Colorado Water Conservation Board (CWCB) proposed to appropriate such a complex and variable conventional instream flow water right for the Piedra wilderness area in southwestern Colorado (USFS and CWCB 1992).2 Figure 3 illustrates this type of conventional instream flow water right. 2TIle Piedra wilderness area was proposed for designation in the Colorado Wilderness Act of 1991, which was never passed by Congress. The proposed Piedra wilderness was located downstream of a number of previously established water rights, so any recognized federally reserved water right could potentially limit the development of these upstream rights. In attempt to avoid this conflict, the 1991 Colorado Wilderness Act called for the USFS to protect the Piedra River where it flowed though the proposed wilderness area with an appropriative water right established under state law in conjunction with the CWCB. 5