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<br />Executive Summary <br /> <br />Scenario III - Elkhead Enlargement . enlargement of Elkhead Reservoir <br />. Juniper rights converted to instream flow <br />. Juniper rights subordinated only to storage <br /> <br />Scenario IV - Stagecoach Enlargement . enlargement of Elkhead Reservoir <br />. enlargement of Stagecoach Reservoir <br />. Juniper rights converted to instream flow <br />. Juniper rights subordinated only to storage <br /> <br />Scenario V - Williams Fork Project . enlargement of Elkhead Reservoir <br />. development of Williams Fork Project <br />. Juniper rights converted to instream flow <br />. Juniper rights subordinated only to storage <br /> <br />Potential reservoirs at the East Fork and Elk Creek sites were not explicitly modeled. <br />These two reservoirs are functionally equivalent, in tenns of water deliveries and instream <br />flow regimes in reaches of interest, to the Williams Fork and Stagecoach Enlargement <br />alternatives which were modeled explicitly. <br /> <br />The "no action" scenario is functionally equivalent to simulation of the exercise of the <br />general subordination. This is true because the limits on the general and other subordinations <br />exceed the estimated consumption under all existing and future junior demands explicitly <br />represented in the basin model. Thus, subordination of the Juniper rights in the model would <br />make them the most junior right represented, and unable to influence the operation of any other <br />rights represented in the model. <br /> <br />Results from model scenarios were used in two ways. First, the model was used to test <br />the sensitivity of predicted demands shortages, reservoir contents and instream flows to various <br />operational constraints, new storage facilities and instream flow requirements. Second, model <br />results for each scenario were compared against results of the baseline scenario in order to <br />evaluate which scenario could best meet basin wide water demands while maximizing <br />recreational opportunities and helping to protect historical flow regimes in reaches potentially <br />containing endangered fish habitat. <br /> <br />Evaluation Results <br /> <br />Scenario I - No Action (Baseline) <br /> <br />Scenario I of the Yampa River Basin Model represents physical conditions and water <br />rights as they currently exist and are administered in the basin. Three reservoirs were operated <br />in this scenario including Stagecoach Reservoir, Steamboat Lake and Elkhead Reservoir. <br />Operations of several other reservoirs presently existing in the basin, such as Lake Catamount, <br />Yamcolo Reservoir and numerous small reservoirs, were not explicitly modeled. Depletive <br />effects of these projects, however, were implicit in the gage-based model hydrology or were <br />modeled as separate demands (this was the case with Lake Catamount). <br /> <br />Demands are met in the basin model according to assigned ranks; these ranks generally <br />correspond to the relative priorities of basin water rights. In all of the model-scenarios, the <br />demand increment to reflect existing senior demands (potential 1989 conditions) were met prior <br />to allowing existing reservoirs to fill. While existing reservoir storage decrees are generally <br />junior rights, historically they have been allowed to fill without administrative call by senior <br /> <br />S-19 <br />