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West Branch at 9N

Watershed Description

This sampling location is at the mouth of the West Branch just before the confluence with the East Branch in Au Sable Forks. The watershed includes the towns of North Elba, Wilmington, and a portion of Black Brook. The West Branch is a world-class trout river and a popular fishing destination

  • Sampling Location: NYS Route 9N bridge over the West Branch in Ausable Forks. Latitude: 44.441149, Longitude: -73.675757
  • Watershed Size: 
  • Land Cover:
  • Road Network: 

Water Temperature

Water temperatures exceed 18°C (64°F) during July and August. These temperatures are result in high mortality rates for hatchling Brook Trout but are tolerable for adults. Actual daily maximum temperatures may exceed 25°C (77°F) which is above the tolerance for adult Brook Trout. Temperature are also above the preferred limit for Brown Trout (20°C or 68°F) and may exceed the upper tolerance of 26°C (80°F).

* Water temperature data are from spot sampling and may not be representative of the minimum or maximum temperature.

Dissolved Oxygen

Sufficient levels of dissolved oxygen is important to fish and other aquatic invertebrates. Many factors influence the amount of dissolved oxygen in water, such as temperature, wind, bacterial decomposition, plant growth, and dissolved ions.  Dissolved oxygen at this location are greater than 7 mg/L throughout the year, high enough to support trout and aquatic macroinvertebrates. The decline in dissolved oxygen from May through October is primarily the result of water temperature. Warm water cannot hold as much oxygen as cold water.


Chloride concentrations in rivers and streams that do not have significant road influences are on average 0.24 mg/L1. Concentrations at this site range from 4.5-21 mg/L indicating that this site is moderately impacted by road salt. Certain species of aquatic macroinvertebrates and fish may be stressed by concentrations from 10-100 mg/L. The rise in concentration in the summer months suggests that the groundwater feeding the river has been contaminated. 


This site is circumneutral to slightly basic with a pH ranging from 7-8.5. These values are typical for a higher order (downstream) site within the Ausable River watershed. The lower pH values in the spring may be the result of acidic runoff from snow melt. pH values are not low enough to threaten fish or other aquatic life.


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