Contour Maps, Catchments & The Water Cycle

Question 1

what is a catchment?

Answer 1

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

Question 2

how do you define a catchment on a map?

Answer 2

look for the ridges of HIGH POINTS (highest elevation) because water flows downhill

Question 3

the more closely spaced contour lines…

Answer 3

the steeper the slope

Question 4

what does a V-shape in contour lines indicate?

Answer 4

a sloping ridge or a valley

Question 5

what is a rule relating to catchment boundaries?

Answer 5

they should be perpendicular to the contour lines (as with streamflow)

Question 6

what are the steps to define a catchment?

Answer 6

1. identify the high points
2. identify directions of water flow using arrows
3. define the catchment (i.e the rim of the ‘bowl’) capturing ALL the water within the catchment ending at your chosen point

Question 7

how does catchment hydrology affect us?

Answer 7

it affects our groundwater and the quality in the environment an hence the quality of our drinking water

Question 8

is most of our water freshwater or saltwater?

Answer 8

saltwater

Question 9

what are some land-use effects on our Water Cycle?

Answer 9

• sedimentation/soil erosion decreases water quality

- land use/construction has a negative impact

Question 10

what is oxygen important in water quality?

Answer 10

oxygen depletion can lead to

• eutrophication
• decreased ecosystem health
• fish kills
• decreased drinking water-quality

Question 11

what is groundwater?

Answer 11

groundwater fills the spaces between the soil particles and fractured rock beneath the Earth’s surface (it is the water stored between particles)

Question 12

globally, how much of our freshwater is stored as groundwater?

Answer 12

30% - a considerable amount of our groundwater is used as our water supply

Question 13

what is the saturated zone?

Answer 13

the region where the pores and fractures of the ground are saturated with water

Question 14

what is the water table?

Answer 14

the upper surface of the zone of saturation (lies in between the saturated and unsaturated zone)

Question 15

what is the unsaturated zone?

Answer 15

the region of sediment above the water table

Question 16

what is an aquifer?

Answer 16

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

Question 17

how is water from aquifers brought up to the surface?

Answer 17

water is brought up to the surface naturally via springs, artisan wells, or discharged into lakes or streams

Question 18

how is groundwater replenished?

Answer 18

by rain and snow melt (global water cycle)

Question 19

how is groundwater extracted?

Answer 19

by wells - pipes drilled into the ground that fills with GW and pumps are used if needed

Question 20

how can human activity pollute groundwater?

Answer 20

in permeable aquifers, pollutants can sink into GW supplies, GW can be polluted by landfills, leaky underground gas tanks, overuse of fertilisers and pesticides

Question 21

why do we need water? give examples?

Answer 21

• for drinking
• general water supplies
• wastewater
• industry
• agriculture (irrigation)

Question 22

what is the general water balance equation?

Answer 22

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)

Question 23

what are tributaries?

Answer 23

a small river or stream flowing into a larger river or lake

Question 24

what is the general flow equation?

Answer 24

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)

Question 25

what is Darcy’s Law?

Answer 25

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

Question 26

what is the continuity equation/principle?

Answer 26

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