Existing water yield increases in all of the watershed analysis areas are predicted to be well 

 below those levels normally associated with detrimental water yield increases. Detrimental water 

 yield increases are levels of water yield increase associated with increases in the magnitude and 

 duration of peak flows which might cause or contribute to channel down cutting, channel scour, 

 or other forms of channel instability. Water yield modeling results show low levels of water 

 yield increase in Bear Creek, Beaver Creek, Arbuckle Gulch and Slusser Gulch. Predicted levels 

 of existing water yield increase are less than 1 % over natural conditions in all of these watershed 

 analysis areas. Results indicate moderate levels of water yield increase in Hupeck Gulch (4.6%) 

 and the Unnamed Tributary in Section 17 (4.3 %) and Section 21 (2.7 %). However, these three 

 drainage areas contain ephemeral and discontinuous flow regimes with stable stream channels 

 and ephemeral draw bottom. 



Predicted water yield increases are also well below thresholds set for each watershed analysis 

 area by a DNRC hydrologist. Threshold levels were specifically established for each watershed 

 analysis area using a risk matrix. Under this process thresholds are determined by considering 

 acceptable levels of risk, watershed sensitivity (flow regime and channel conditions) and 

 downstream resource values (beneficial uses). Thresholds for allowable increases in water yield 

 were set at 8% for Upper Willow Creek, Beaver Creek and Bear Creek, and 12% for all of the 

 remaining watershed analysis areas. 



Existing cumulative watershed impacts appear to be largely associated with localized 

 sources of increased sediment delivery within Upper Willow Creek and the Sub-watershed 

 analysis areas. A DNRC hydrologist and soil scientist completed detailed sediment source 

 inventories for the State's ownership in these watersheds. The results of these surveys are 

 contained in the Hydrology Project files and are discussed in the section addressing "Water 

 Quality". 



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