SAF Water Quality & Management 3 — Questions and Answers
Question 1: Which stream order classification system is most commonly used in watershed analysis for forestry applications?
- Horton-Strahler ordering system (Correct answer)
- Pfankuch channel stability index
- Rosgen stream classification system
- Leopold-Wolman bankfull method
Correct answer: Horton-Strahler ordering system
The Horton-Strahler ordering system assigns numerical orders to stream segments based on tributary junctions and is standard for watershed analysis.
Question 2: Thermal pollution in streams adjacent to harvested areas is primarily caused by:
- Increased decomposition of logging slash in the water
- Loss of riparian canopy shade allowing solar radiation to heat water (Correct answer)
- Increased sediment load raising stream bed temperatures
- Root decomposition releasing heat into the water table
Correct answer: Loss of riparian canopy shade allowing solar radiation to heat water
Removal of riparian canopy exposes stream surfaces to direct solar radiation, causing significant temperature increases that stress cold-water fish species.
Question 3: What is the recommended minimum width for a riparian buffer zone on perennial streams in most state forestry BMP guidelines?
- 10 feet on each side
- 25 feet on each side
- 50 feet on each side (Correct answer)
- 100 feet on each side
Correct answer: 50 feet on each side
Most state BMP guidelines recommend a minimum 50-foot buffer on each side of perennial streams, though wider buffers are recommended on steeper slopes.
Question 4: The parameter 'biochemical oxygen demand' (BOD) in water quality testing measures:
- The concentration of dissolved oxygen in surface water
- The amount of oxygen consumed by microorganisms decomposing organic matter (Correct answer)
- The rate of photosynthesis by aquatic plants
- The oxygen required to oxidize inorganic minerals in solution
Correct answer: The amount of oxygen consumed by microorganisms decomposing organic matter
BOD measures the oxygen consumed by microbial decomposition of organic matter over 5 days at 20°C, indicating the degree of organic pollution in water.
Question 5: Skid trails should be located to minimize water quality impacts by:
- Running directly downslope to drain water quickly
- Following contours or at grades less than 10% with frequent water bars (Correct answer)
- Maximizing use of existing stream channels as haul routes
- Concentrating traffic into single lanes to limit disturbed area width
Correct answer: Following contours or at grades less than 10% with frequent water bars
Contour or low-grade skid trails with water bars prevent concentrated flow and reduce erosion by diverting runoff before it gains velocity.
Question 6: Which type of stream crossing causes the least aquatic habitat disruption when properly installed?
- Slab ford across the stream channel
- Culvert with undersized diameter
- Bridge with no in-stream footings (Correct answer)
- Temporary log stringer crossing
Correct answer: Bridge with no in-stream footings
Bridges with no in-stream footings span the entire channel, preserving stream hydrology, fish passage, and aquatic substrate without channel modification.
Question 7: What is the primary purpose of a water bar on a forest road or skid trail?
- To provide drinking water access for firefighters
- To intercept and divert runoff off the road surface before it gains erosive velocity (Correct answer)
- To mark stream crossings on topographic maps
- To measure water table depth along the road corridor
Correct answer: To intercept and divert runoff off the road surface before it gains erosive velocity
Water bars are diagonal drainage structures cut across roads and trails to intercept concentrated runoff and redirect it into vegetated areas before erosion occurs.
SAF Water Quality & Management 3
Which stream order classification system is most commonly used in watershed analysis for forestry applications?