Exam 2 Flashcards
Lentic
nonflowing, standing water (small pools to Great Lakes)
Lotic
running/flowing water (seeps to larger and wets)
Base Flow
not influenced by precipitation; no rain, all water in streams right now from ground water
Seep
where water starts to come out from a hillside
Ephemeral
there is a stream right after a rain storm and then it disappears
Intermitant
flows for a while, then dries up
Perennial
stays flowing throughout the year during normal rainfall
What shapes a river?
- climate
- geology
- topography
- vegetation
- human land use
Climate
heat, precip/rainfall, drought, snowpack
Geology
chemical identity and buffering capacity; including influences based on ions and minerals leached from bedrock and surficial (topmost layer) material; limestone has lots of perculation and granite not much at all; determines pH of a river
Topography
influences stream morphology; flow velocity (how fast stream moves); whether stream is carrying or depositing sediment/ sediment erosion transfer or deposition; substrate: boulders, bedrock; habitat: step pools, meander pattern: riffles or rapid area: riffle - pool - run
High gradient areas
v-shape cross section; erosional; often find step pool, boulders, cobbles
Entrenched
measure of vertical containment in a channel; determined by bankfull width and flood prone width; FP (flood prone width):BF (bank full width)=entrenchment
Sinuosity
a bend; meander pattern
Moderate gradient area
in a valley start to see sinuosity: riffle - pool - run; smaller deposits: cobble, gravel, sand; not erosional, more depositional; water starts to slow down; slightly entrenched; larger flood prone area
Riparian zone
land along the river/ floodplain
Vegetation
best vegetation to have along a river is riparian forest
Instream habitat
instream wood, branches, etc creates important habitat and diversity for fish and other organisms
Bank stability
root systems of trees on bank holds the bank together especially during storms; just grass you would get a slumped bank when the bank falls in
Autumn leaves
major energy source of streams; in summer canopy of leaves overhanging causes “drops” (falling insects) (another energy source)
Trees
cool the stream and regulate temps; higher order streams cooling effect is not as apparent because the stream is wider so trees do not overlap
Pollutants
are absorbed through the vegetation; nutrients phosphorus and nitrogen as well as toxins get absorbed
Human Land Use
riparian forests getting replaced by impervious surfaces which causes a lot of runoff; increasing impervious surfaces 10-20% you double the amt of runoff; more flash floods; dams also changes the habitat and fragments populations
Colluvial
sediment and organic matter accumulates at base of the hill
Alluvial
sediment and organic matter has been carried down from upstream
Power of water
determined by slope and volume of water
Longitudinal Dimension
downstream; can see erosion, deposition and connectivity; dams disrupt connectivity; riverine (lotic) -> impoundment (lentic); transport of nutrients and sediments is disrupted; disrupts exchange downstream
Latitudinal Dimension
lateral connectivity involves the riparian zone; material exchange between river and riparian zone; sediments/ soil accumulates; lots of agriculture along rivers because that’s where soils are good for farming
Vertical Dimension
- groundwater seeps down from water table into river; you get chemicals and ions and dissolved organic carbon
- hyporheic zone: diversity of species; nutrient spiraling; nutrients in sediments then water column; fish eggs sweep their tail to remove fine sediments to make nests
Stream segment
between 2 tributaries; within it you can have a stream reach
Stream reach
riffle, pool, run; more homogeneous part of the segment
Stenotherm
narrow temp range (ie. slimy sculpin)
Eurytherm
wide temp range (ie. sunfish and bass)
Stream Gains
precip (P) and ground water seepage inflow (Gin)
Stream Losses
stream outflow (Q), evapotranspiration (ET), ground water seepage outflow (Gout)
Discharge (flow)
amount/volume of water flowing through a cross-sectional area of a stream per unit time (seconds); area*velocity= volume discharge
Thalweg
deepest point in channel
Hydrograph
discharge over time
Factors influencing flow
- slope (force of gravity)
- cross-sectional area of a stream
- roughness of bottom and banks which can cause friction and decrease flow
- wetted perimeter: boundary on bottom between streamwater and sediment; the smaller the wetted perimeter the less friction there is and increase flow
Laminar flow
slow, smooth flow
Turbulent flow
rough, fast; most always see turbulent flow
Intermediate/ transitional flow
in the middle of laminar and turbulent
Straight channel
fasted flow in center b/c less friction from along banks; flow faster the farther you are from the bottom
Meandering channel
slip off bank, sand point bar, thalweg
Abiotic Factors
- current
- sediment
- temperature
- chemistry
Current
flow meandering discharge; transports material/ resources; removes waste; high flows can displace organisms downstream/ downstream displacement; organisms have opportunity for dispersal
Entrainment
picked up by current and moved
Disturbance
event that effects the fitness of an organism
Microhabitat flow refuges
behind rocks where flow is slowed down
Inertia
Resistance to change in motion; big/heavy object has greater inertia
Viscosity
resistance to change in form (internal friction) due to mutual attraction of water molecules; viscosity changes over temperature
Reynolds Number
the ratio of inertial forces to viscous forces
Froude Number
how bulk fluids are moving; velocity based on gravitational forces; Fr=(gravitational forces)/(inertial forces)
Hydraulic Jump
- entrains air
- serves as a launch pad for fish moving upstream
- makes sound of water as air bubbles burst
- serves as habitat for aquatic organisms
Stream temperature
solar radiation is the primary heat source for aquatic ecosystems
Ice dam
sudden melting of ice in the spring mixed with wood/branches
Plunge pool
trout hangout; important in geomorphology
Sources of bed material
colluvial and alluvial; erosion of banks; stream acts as a sediment “sorting machine”
Wentworth scale of grain sizes
sediments classified by their size; boulders, gravel, cobble
Stream armoring
a stream with larger sediment overlaying finer sediment; stream less susceptible to changing
Stream transport
sand is the most easily entrained (carried and moved); silt and clay more cohesive so harder to pull those off the bottom
Contents of stream bed
dissolved load (ions), suspended load (what is picked up off the bottom and carried), and bed load (moved by velocity of water, tumbled down and rolled)
Erosion
- can cut new channels, banks and streambeds
- greater without riparian vegetation
- greater if you have impervious surfaces; causes flash flooding and rapid runoff
Competence
moving grains downstream; largest particle that can be moved at a particular flow
Critical erosion velocity
velocity needed to transport a particular grain size
Sheer stress
force of the water on the substrate/ stream bed; good way to analyze flow and velocity and its effect on organisms and stream bed
Bernoulli Principle
where velocity is high the pressure is low; where velocity is low the pressure is higher; air or fluids/water; relates to birds and their wings/flying when they aren’t moving as fast pressure is high
Pool tailout
lots of gravel coming out of the pool; lots of sorting
Downdwelling
area where water is drawn down through pool tailout; important spawning sigh because oxygenated water flowing through gravel bringing oxygen to eggs and waste products drawn away
Flood plains can change overtime due to
- climatic conditions: glaciers
- flow changes: not flowing as far or becoming incized/ cut deeper
- what was once a flood plain can become a terrace
- when you slow water silt can accumulate behind a dam
Avulsion
sudden divergence of a stream causing a new channel formation and dewatering of former channel
Glacial tilt
a lot of unsorted sediment left behind by a glacier; very heterogeneous
Headcut
sudden vertical drop in the stream bed that can form a ‘knickpoint’ which can migrate upstream b/c water is flowing and sediments get washed out (erosion going upstream)
Incision
scouring out of a channel making it deeper and the sides/banks are higher and less stable and more likely to fall in and sediments get washed downstream
Species abundance and richness are correlated with
- amt of detritus
- algal biomass
- substrate stability and complexity (roughness and crevices)
- depth (deeper water, less diversity)
- velocity
Suncook River Avulsion
- moved lots of sediment downstream
- banks slumping
- headcutting: knick point where there is a sudden drop and erosion
- out of balance, trying to get back to equilibrium; excavated a lot of material and sent it downstream
- bridge upstream threatened
