W - 1.5 -> 1.7 Flashcards
1
Q
Confined aquifer:
A
- The water is in porous rock
- It’s surrounded by impermeable rock
- Water can’t flow away, but can’t be replenished either
2
Q
Unconfined aquifer:
A
- The water is in porous rock
- It’s surrounded by permeable rock
- Water can percolate in, and flow away
3
Q
Rocky Mountains:
A
- Colorado river basin flows to the west, into Mexico
- The great plain is to the east, including the Ogallala Aquifer
4
Q
inputs
A
- Mainly rainfall (air temperature cools, air is saturated, condensation occurs around nuclei, clouds form)
- Location of rainfall is determined by the rain shadow features (e.g. mountains), or proximity to the ocean (e.g. cold ocean current and Pacific frontal air masses)
5
Q
Climate:
A
- Amount and timing of rainfall
- Temperature – determines evapotranspiration out
- Freezing conditions – flow is suspended
6
Q
geology:
A
- Porosity / perviousness of rocks – aquifer storage, so water is released steadily
- Impermeability: quick response to rainfall as water flows quickly through after heavy rain
7
Q
soils
A
- Deep soils store water – slow release means a steadier river regime
- Permafrost can inhibit percolation and melting can increase water supply
8
Q
complexity:
A
- large basins have complex regimes and cross climate zones, e.g. Blue Nile / White Nile
- Mountains make for more complexity – e.g. in hot environments, glaciated mountains store water (e.g. Andes)
9
Q
river regimes
A
- river regimes are defined as the annual variation in the discharge (flow) of a river at a particular point.
- Global patterns of precipitation and evapo-transpiration have a bearing on these fluxes of ‘overland channel flow’ (i.e. rivers).
- The global water budget means that rivers can have distinct annual flow rates (regimes) depending on latitude and topography.
- Whilst seasonal climate is usually the most important factor; geology, soil, vegetation cover and human activities also play a key role.
10
Q
The global pattern of water budgets varies with
A
latitude - compare tropical temperate and polar
11
Q
yukon:
A
- Generally has a small change in water budget owing to limited evaporation and precipitation
- River regime is dependent on glacial melt from Llewellyn Glacier in spring
- permafrost covers large area – means largely impermeable
- Spring Thaw – saturated overland flow contributes to rapid rise in river levels (steep spike, which gently declines – still limited evapotranspiration compared to Nile)
12
Q
amazon:
A
- river regime varies between Equatorial with no dry season and heavy convectional rainfall all year.
- Laterite clays and granites mean larger channel flows over whole basin.
13
Q
nile:
A
- Drainage basin is tropical with a distinct drier season
- No rainfall at all in northern margins (Sahara) means negative water balance.
- Ethiopian Highlands (largely impermeable geology) = large amounts of runoff transferred downstream
- Rapid fall owing to large evapo-transpiration rates
14
Q
Global Hydrological System
A
- Closed system on a global scale, but regional drainage basins are open to transfers in and out.
- Freshwater accounts for only 2.5% of total amount, of which only a 1/3 is available for human use and is unevenly distributed – this leads to conflict over this “finite resource”.
15
Q
Stores, Fluxes & Processes
A
- Size and residence times depends on a number of factors which vary spatially and over time.
- Factors include: soil, geology, climate (latitude & altitude), topography, vegetation, and human land use.
- Consider whether they are predominantly an input to a local system (e.g. precipitation) or an output (e.g. evapo-transpiration, channel flow).
