Contour Maps, Catchments & The Water Cycle Flashcards
what is a catchment?
a catchment is the area supplying the water (e.g rainfall, streamflow, runoff) to a designate point - think of a bowl with the rim defining the catchment
how do you define a catchment on a map?
look for the ridges of HIGH POINTS (highest elevation) because water flows downhill
the more closely spaced contour lines…
the steeper the slope
what does a V-shape in contour lines indicate?
a sloping ridge or a valley
what is a rule relating to catchment boundaries?
they should be perpendicular to the contour lines (as with streamflow)
what are the steps to define a catchment?
- identify the high points
- identify directions of water flow using arrows
- define the catchment (i.e the rim of the ‘bowl’) capturing ALL the water within the catchment ending at your chosen point
how does catchment hydrology affect us?
it affects our groundwater and the quality in the environment an hence the quality of our drinking water
is most of our water freshwater or saltwater?
saltwater
what are some land-use effects on our Water Cycle?
- sedimentation/soil erosion decreases water quality
- land use/construction has a negative impact
what is oxygen important in water quality?
oxygen depletion can lead to
- eutrophication
- decreased ecosystem health
- fish kills
- decreased drinking water-quality
what is groundwater?
groundwater fills the spaces between the soil particles and fractured rock beneath the Earth’s surface (it is the water stored between particles)
globally, how much of our freshwater is stored as groundwater?
30% - a considerable amount of our groundwater is used as our water supply
what is the saturated zone?
the region where the pores and fractures of the ground are saturated with water
what is the water table?
the upper surface of the zone of saturation (lies in between the saturated and unsaturated zone)
what is the unsaturated zone?
the region of sediment above the water table
what is an aquifer?
an aquifer is a underground layer of water-bearing rock or unconsolidated material, typically made up of gravel, sand, sandstone, or fractured rock like limestone - aquifers are where you find groundwater
how is water from aquifers brought up to the surface?
water is brought up to the surface naturally via springs, artisan wells, or discharged into lakes or streams
how is groundwater replenished?
by rain and snow melt (global water cycle)
how is groundwater extracted?
by wells - pipes drilled into the ground that fills with GW and pumps are used if needed
how can human activity pollute groundwater?
in permeable aquifers, pollutants can sink into GW supplies, GW can be polluted by landfills, leaky underground gas tanks, overuse of fertilisers and pesticides
why do we need water? give examples?
- for drinking
- general water supplies
- wastewater
- industry
- agriculture (irrigation)
what is the general water balance equation?
P = R + E + ΔS
where P = precipitation (rainfall, snowfall, etc)
R = runoff (streamflow, overland flow)
E = evapotranspiration (evaporation, transpiration)
ΔS = change in storage (pond water, groundwater etc)
what are tributaries?
a small river or stream flowing into a larger river or lake
what is the general flow equation?
Q = VA (Q is the volume of water that passes through a given point per unit time)
where Q = flow rate (m^3/s)
V = flow velocity (m/s)
A = cross sectional area (m^2)
what is Darcy’s Law?
Darcy’s law describes fluid flow through a porous medium (e.g groundwater through the subsurface)
Q = k x i x A
where Q = flow rate
k = permeability (hydraulic conductivity)
i = hydraulic gradient = [(h2-h1) / (L2-L1)] (see diagram in handout) - the change in h is the vertical drop and the change in L is the flow distance
what is the continuity equation/principle?
it is based on the principle of conservation of mass, the rate at which mass enters a system is equal to the rate at which mass leaves the system…
Q1 = Q2 so V1A1 = V2A2
