Bz471 Exam One

Front 1

What does a hydrograph show?

Back 1

discharge variability

Front 2

What are the three dimensions of movement and exchange of organisms, materials and nutrients

Back 2

two way, longitudinal(upstream/downstream), lateral(channel/margins), and vertical (surficial/underground) exchanges

Front 3

What are some characteristics of lotic systems that lentic don't have?

Back 3

*Unidirectional Flow
*Width
*Depth
*Turbulence
*Mosaic Habitat Structure
*Dynamic, disturbance driven
*Longitudinal Connectivity
*Geologic Permanence

Front 4

Watershed

Back 4

Area that contributes water to a point on a stream
Also known as:
Catchment
Drainage basin

Front 5

Inputs

Back 5

Precipitation (rain, snow)

Front 6

Outputs

Back 6

Evapotranspiration
Stream Runnoff:
*Infiltration to groundwater (slow path)
*Overland flow (fast path)

Front 7

Hydrograph

Back 7

time series record of streamflow at a stream cross-section: discharge plotted against time

Front 8

Discharge

Back 8

=streamflow=*volumetric* flowrate
Units: Q=L^3/T
e.g. m^3/sec, gallons/day
Q(m^3/s)= A(m^2) * U(m/s)
will remain constant as channel shape changes, but velocity will not

Front 9

baseflow

Back 9

groundwater contribution?

Front 10

streamflow (runoff) is a balance between what two things?

Back 10

the inputs and outputs:
precipitation and ET

Front 11

What 5 Factors influence the Shape of a Hydrograph?

Back 11

*lithiology and soils (infiltration to groundwater vs. overland flow
*topography
*vegetative cover
*type of precipitation
*stream size

Front 12

flashy stream

Back 12

one whoose hydrograph responds quickly to changes in precipitation (little groundwater)

Front 13

stable stream

Back 13

one with more sluggish response (more groundwater flow)
-less variable environment (temp, nutrients, and physical disturbance)

Front 14

current velocity

Back 14

*linear* flow rate
units: U or V =L/T
e.g. m/sec

Front 15

Flow

Back 15

can either represent velocity OR Discharge
(Q or U)

Front 16

Why is current velocity (U) important ecologically?

Back 16

1)erosional force on organisms
2)erosional force on sediment
3)delivery of nutrients, gases, food, removal of wastes

Front 17

shear stress (τ)

Back 17

=the force per unit area on the streambed or object on the streambed
the force exerted as one "layer" of water moves past another
it is proportional to velocity gradient, which is measured as ΔU/Δy:
τ ~ μ * ΔU/Δy (μ = viscosity) where Y is distance from bottom SEE Picture on lecture 2
*the faster velocity changes above the bed surface, the higher the shear stress

Front 18

What 4 physical forces act on benthic organisms?

Back 18

1)Shear stress
2)Lift
3) Form Drag
4) Skin friction drag
See diagram in lect 2

Front 19

Lift

Back 19

Upward force caused by
pressure difference created
in vertical dimension (ΔU
vertical, i.e. Umax - Umin)
-reduced with claws

Front 20

Form Drag

Back 20

Force caused by pressure
difference in longitudinal direction (ΔU longi), influenced by body’s shape)
-reduced with fusiform (torpedo) shape to minimize flow seperation

Front 21

Skin Friction Drag

Back 21

Drag due to friction between
moving water and surface of
object (mucus reduces)

Front 22

Turbulence

Back 22

the norm in rough beds:
Turbulence occurs when the inertial force of moving water exceeds the cohesive force among molecules, causing “random” movement
• something breaks up flow coherence (obstacle in water)

Front 23

near-bed flow environments for benthic organisms are:

Back 23

Turbulent – velocity fluctuates around an average value at a given point on the bed (Umax may be far from average velocity).

Front 24

fluvial geomorphology

Back 24

there is a dynamic balance between Flow Regime (Q) and Sediment Regime (Qs)
-maintains the shape of the channel
-Depends on 'transport capacity' of the channel (fxn of how steep channel slope is)
*water moves sediment during higher flows
*sediment gets stored during lower flows
*Ecological Perspective
-habitat structure
-sediment size distribution
-channel form
-habitat dynamics
-sediment movement

Front 25

3 ways to view channel form

Back 25

-cross section of stream (local transect scale)
-planform (reach scale)
-longitudinal (whole basin)

Front 26

controls on channel geometry

Back 26

-discharge
-bed mobility
-bank stability

Front 27

"Graded stream"

Back 27

current discharge (Q) and sediment (Qs) regimes are 'in balance"
-Aggradation (Qs>Q)
-Degratation (Qs<Q)

Front 28

Critical erosion velocity or critical shear stress:

Back 28

velocity (shear stress) that is sufficient to move the particles on the bed (varies with particle size)

Front 29

Stream Competence

Back 29

the largest particle that may be moved as bedload (for a given Q)

Front 30

Stream power

Back 30

Q x Slope: How does competence change with slope?

Front 31

What is the most erodible particle type? Least?

Back 31

sand: low cohesion, small grain size
Clay: high cohesion, resists erosion

Front 32

What is the most transportable particle type?

Back 32

Clay: small grain size,