2. 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 runoff. 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. 



B. 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. 



C. Analysis Area 



1. 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 ownerships. The primary focus of 

 the sediment delivery analysis was on the discontinuous streams and draws 

 located within the proposed project area. 



2. Water Yield 



The analysis area for water yield is the ephemeral draws covered by the project 

 area. 



D. Existing Conditions 



1. Regulatory Framework 



a. Montana Surface Water Quality Standards : According to ARM 17.30.607 (1), 

 the Ashley Creek drainage above Smith Lake and its tributaries, including Ashley 

 Lake, are all classified as B-1 . Among other criteria for B-1 waters, no increases 

 are allowed above naturally occurring levels of sediment and minimal increases in 

 turbidity. "Naturally occurring," as defined by ARM 17.30.602 (17), includes 

 conditions or materials present during runoff fi^om developed land where all 

 reasonable land, soil and water conservation practices (commonly called BMP's) 

 have been applied. Reasonable practices include methods, measures or practices 

 that protect present and reasonably anticipated beneficial uses. These practices 

 include but are not limited to structural and non-structural controls and operation 

 and maintenance procedures. Appropriate practices may be applied before, 

 during, or after completion of activities that may impact the resource. 



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