4) Water Movement and Groundwater

movement of water, small scale, large scale, convection

what are examples of small scale water movement?

diffusion
convection and advection
laminar and turbulent flow
surfaces and flow

explain diffusion

net movement of molecules or atoms from a region of high conc to a region of low conc
no movement of water itself

explain convection and advection

convection: flow arising from density diffs
advection: transport of substance by the bulk movement of a fluid
convection will move molecules and orgs in a lake that can’t resist that current
convection impacts dissolved oxygen in the water

explain laminar vs turbulent flow

laminar flow: low velocity, flow path of water is unidirectional
turbulent flow: higher velocity disordered flow that leads to mixing
affected by velocity, density, viscosity

what are details about surfaces and flow?

water velocity slows when it interacts with a surface
occurs at bottom of river, rocks, shoreline of lakes

flow boundary layer

outer edge of where water changes from laminar to turbulent
algal mats and many invertebrates use the boundary layer

thickness of boundary layer increases with

less water velocity
more roughness
more distance from upstream edge of object
more size

What are examples of large scale water movement

lake water movement
surface travelling waves
standing waves/surface seiche
langmuir circulation cells
ekman spiral
internal seiche

what is lake water movement?

waves: rise and fall of water involving oscillation
currents: net unidirectional flow water

currents build ___ than ___ but eventually ___

more slowly than waves, but eventually contain most of lake’s kinetic energy

what are surface travelling waves caused by?

wind, friction between air and water
doesn’t have a huge impact past surface of water, but does have impact near shore

what are standing waves (seiches)

wind pushes whole water body to be at an angle, sloshing effect like a bath

what are langmuir circulation cells?

happens in light wind, disappear in strong winds
upwelling and downwelling of water
as water moves down, it needs to be replaces by water closer to the surface
zones with spirals moving towards each other, causing accumulation of water, air, orgs, oil, debris, etc

what is an ekman spiral?

effect of wind, coriolis effect
large lakes and in ocean
N hemisphere movement to the right of wind
Pushing in one direction but also earth spinning, causing water to spiral
We see water move in a curve

what is an internal seiche?

can have different nodes of oscillation, 1 is like seesaw,
influenced by bathymetry = more complex with more nodes
can be caused by landslide, wind, rain event

explain combo of waves and currents

big lake has internal seiche but also impacted by coriolis
focusing on one point, it moves up, up to max, down, back to start, down, down to min, up, back to start
whole surface moves like a balance board

explain thermocline as related to cyanobacteria?

thermocline depth and intensity varies, an internal wave moves, and cyanobacteria will move with it because it’s a more favourable environment

explain difference between internal and surface seiche

internal seiche is much slower than surface, and is a wave moving on the thermocline

explain overland flow vs interflow vs groundwater flow

overland flow = surface
interflow = subsurface
groundwater flow = deeper lateral movement

what is the hyporheic zone?

zone of groundwater and river water intermingling, dynamic movement
important for gas-nutrient exchange (and contaminants)
river is moving faster than groundwater, so different speeds and differe characteristics of water
supports biodiversity

difference between vadose zone and phreatic zone

vadose: infiltration and unsaturation
phreatic: capillary fringe, water table, aquifer

how might water flow in different directions on surface vs below?

Hill slopes east, vs slope below surface water flows north

what is unconfined aquifer?

layer of permeable surface above, impermeable surface below
under atmospheric pressure
wells need a pump
water levels vary, more impacted by drought

what is confined aquifer?

impermeable surface above and below
heavily under pressure, from ground and atmosphere
artesian wells don’t need pump
below water table

water stays in aquifers for ___?

variable amounts of time
some hold water for thousands or millions of years
if we use that water, it took hundreds of years to accumulate so its not sustainable

what determines how fast water percolates into groundwater?

soil texture and composition

impermeable surfaces can ___ flow into groundwaters, ____ recharge and ___ flooding

decrease
reduce
increase

explain this

1942: vegetation are able to get food water source
overtime, sustained groundwater use, we lowered the water table, so the vegetation died off after not getting good water supply
1989: now there is a large riparian zone and a smaller river, very little vegetation in that area

groundwater depletion

overuse of groundwater
too much agriculture
smaller river
industrial and community use

pesticides will runoff and enter groundwater easily through ___

sandy soils