Appendix C 

 Happy Valley Hydrology 



Watershed and Hydrology Analysis 



FOR THE 



Happy Valley Timber Sale 



Introduction 



Water Quality 



The primary parameter of concern for water quality is sediment. Increased sediment delivery 

 and deposition can affect physical and biological water quality, channel stability and 

 geomorphology. Sediment yield can be affected by a number of activities. Timber harvesting 

 and associated road construction can increase sediment yield through exposure of bare soil. 

 These impacts can be mitigated through implementation of Best Management Practices (BMPs), 

 and other erosion control measures. 



Water Yield 



Timber harvesting and associated activities can affect the timing, distribution, and amount of 

 water yield in a harvested watershed. Similarly, effects of stand replacement wildfire also affect 

 water quantity and yield in a watershed. Water yields increase proportionately to the percentage 

 of canopy removal, because removal of live trees reduces the amount of water transpired, leaving 

 more water available for soil saturation and mnoff Canopy removal also decreases interception 

 of rain and snow and alters snoWpack distribution and snowmelt, which lead to further water 

 yield increases. Higher water yields may lead to increases in peak flows and peak-flow duration, 

 which can result in accelerated streambank erosion and sediment deposition. 



Analysis Methods 



Existing conditions for water quality and water yield were analyzed using field site visits and 

 visual inspection of the drainage features in the proposed project area. 



Analysis Area 



Water Quality 



The analysis area for water quality is the proposed project area, and all forest roads that lead into 

 the project area from other ownership. The primary focus of the sediment delivery analysis was 

 on the first order discontinuous stream and ephemeral draws located within the proposed project 

 area. 



Water Yield 



The analysis area for water yield is the first order discontinuous stream running through the 

 project area. 



Existing Conditions 



Page 1 of 4 1 



