The Hydrosphere & Open Channel Flashcards
Hydrosphere
in the stream, runoff is the integrator of all factors which affect quantity, quality, and regimen, and is one of the factors of watershed ecology itself
Streams/Rivers
flow downhill due to gravity, encounters resistance along the way
Stream/River Resistance
changes in slope, rocks, roughness, bends
Miles of Stream in PA
86,000 miles
Bodies of Water
river (big), stream (small), brooke (airrated), run, creek, crick, branch, fork; get written into laws, regional, some states have definitions on them
Pond vs Lake
pond (smaller), lake (bigger)
Thalwag
deepest part of the channel
Stream Order
classification of drainage network (n)
1st Order
top of stream drainage system
2nd Order
second stream in drainage system
When Stream Order is Useful
if streams of same order have common features are proportional to “n”
Bifurcation Ratio
(Rb) = N n / N n+1
Law of Stream Numbers
relates the number of streams of order I (Ni) to the bifurcation ratio and the principle stream order (k)
Law of Stream Number Equation
Ni = Rb^k-1
Stream Patterns
bends, riffles, pools, meander
Sinuous
has many curves and bends; winding
Sinuousity
how far the body of water travels; stream length/valley length
Straightening a Body of Water (development)
increases velocity, increases slope, more erosion, would want to go back to original form
Sinuous Range
1.0 to 1.5
Meandering Range
1.5 to 2.1
“Tortuous” Range
> 2.1
Drainage Density
Dd=L/A
miles/square miles
Velocity of Channel
speed (ft/sec; length/time); constantly changes
Slowest Velocity of Channel
on edge; Eddy Current
Fastest Velocity of Channel
on top in the middle where it is the deepest
No Slip of Channel
along the bottom; slow
Riffles
increase velocity; more sediment picked up
Pools
decrease velocity; sediment settles
Flow Meter
quantify the rate or volume of moving water
Gaging Station
censor in water measuring pressure (depth)
Weirs
inline damn and measure depth crossing
Stilling Basin
provides a means to absorb or dissipate the energy from the spillway discharge and protects the spillway area from erosion and undermining
Water Surface
open to atmosphere, no pressure; deeper you go, more pressure
Water Gains Energy Through
potential and kinetic
Potential Energy
comes from depth
Kinetic Energy
comes from velocity
Energy Grade Line
elevation of energy head of water flowing in channel; can’t see it, stays constant above the surface
Velocity
characteristic of the flow, measure of water’s kinetic energy; units: ft/sec
Velocity Head
V^2/2g (height/depth)
g= 32.2
units: (ft/sec)^2 / ft/sec^2 = ft
Pool getting a hole in the side
4ft deep pool (potential) rushes out hold (kinetic); gains velocity
Slow Stream Meets Fast Stream
slow stream gains more energy (speed); slow stream increases in energy to meet the fast stream; back flow
Back Flow
slow stream keeps picking up speed back up in the stream
Headloss
something that slows the flow down; backs up water
Headloss Causes
old, corroded, gunk filled pipes; rocks and rough bottom of stream
Manning’s Equation
V= (1.49/n)R^2/3S^1/2
Optimal Channel Shape
semi circle; hard to create
Common Channel Shape Used
trapezoids; easier to make
V
velocity
n
measure of roughness; friction encountered
S
slope of energy grade line
R
hydrolic radius; A/P (area/perimeter)
Slope
ft/ft (rise/run); 100%=45 degree angle
n vs V
increase n = decrease V
decrease n = increase V
S vs V
increase S = increase V
decrease S = decrease V
Streamflow Equation
Q=AV
Relative Values of n
0.03 or 0.035 (average)
cast iron pipe: 0.015
poor natural channel: 0.06
stones & weeds: 0.035
Rectangle Channel
Q=AV
(Q=bhV)
Trapezoid Channel
A = 2 triangles + 1 rectangle
A = 2(1/2)bh + wh
Q=AV
Industry Standard
give ratio of triangle angle 1:2 (out 1, up 2)
Streamflow
measure of the watershed response; very nearly a direct measure; may miss the groundwater response on smaller basins; on large basins, groundwater may be hard to estimate during runoff event
CSM
flow per square mile (average daily/area); useful for basin comparisons; get them on USGS
Routing
technique used to predict changes in shape of hydrograph as water moves through a channel
Effects on Timing
not all areas contribute to the stream at the same time or place
Flow Entering Stream
must travel downstream; takes time and must fill storage areas
Timing Effect on Hydrograph
curve occurs later downstream; curve is not as steep and longer; some water moves faster than others, attenuation, geology
Attenuation
reduction of speed; due to storage, geology, blockages
Lag Time of Flow Depends on
velocity, slope, distance
Downstream of Levy
get water faster than before having levy
Eminent Domain
private land taken by gov to make dams and other things; paid compensation
