ACA Hydrology & Water Reading Flashcards
6 cards from real ACA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 ACA Hydrology & Water Reading flashcards as text
What is 'helical flow' in a river bend, and how does it affect paddling?
Answer: A flow pattern where water spirals in a corkscrew-like motion, pushing surface water toward the outside of the bend and bottom material toward the inside
Helical flow in river bends moves surface water toward the outside of the curve (where it is deeper and faster) and sweeps material along the bottom toward the inside (the shallow gravel bar side).
What does 'CFS' stand for, and what does a reading of 500 CFS versus 5,000 CFS indicate about a river?
Answer: Cubic Feet per Second; a measure of volume flow rate — 5,000 CFS is ten times more water volume than 500 CFS, generally indicating a significantly more powerful and potentially hazardous river
CFS (Cubic Feet per Second) measures the volume of water flowing past a point per second — higher CFS means more powerful currents, bigger waves, and more severe consequences for swims.
What is a 'rooster tail' on the water surface, and what does it indicate to a paddler?
Answer: A plume of water erupting upstream of a submerged rock, indicating a shallow obstacle just beneath the surface
A rooster tail is an upward jet of water where current hits a submerged rock — it marks the downstream side of the rock and is a warning to steer around it.
How does a dam release affect river conditions downstream for paddlers?
Answer: Controlled releases can rapidly and dramatically raise water levels, increase current speed, and change hazard profiles downstream with little warning
Dam releases can raise water levels rapidly over a large distance, dramatically increasing current velocity, strainer hazards, and hydraulic power — paddlers must check release schedules before and during trips.
What is a 'confluence' and what hazards should a paddler anticipate at one?
Answer: The point where two waterways meet — paddlers should anticipate conflicting currents, increased turbulence, debris loads, and possible wave trains from combined flows
At a confluence, two currents meet and can create turbulent mixing zones, debris jams, powerful boils, and wave features that are not present on either upstream section alone.
What is the significance of 'flood stage' and 'action stage' in USGS river gauge readings for paddlers?
Answer: Flood stage indicates water has left its banks and is inundating surrounding land — paddlers should avoid rivers at or near flood stage due to extreme currents, debris, and strainers
When a river reaches flood stage, it has overflowed its banks, introducing catastrophic currents, floating debris, and newly formed strainers that make paddling extremely dangerous.