Lecture 2-Hydrology Intro Flashcards
% of water occurring as saline water in oceans
96.5%
% of water occurring as freshwater
2.5%
% of water occurring as saline groundwater
1%
% of FRESHWATER in the cryosphere
68.5%
% of FRESHWATER in land reservoirs (lakes, rivers, soil moisture)
1.2% living things - 0.2% rivers - 0.5% swamps - 2.5% soil moisture - 3.8% lakes - 20.9% ice & permafrost - 69%
% of FRESHWATER occurring in the atmosphere
3.0%
atmosphere water break down (water vapour vs suspended)
water vapour = 99.9%
suspended = 0.0%
% of FRESHWATER in groundwater
30.1%
key concepts for visualizing the hydrology
cycle
system
continuity (conservation of mass)
hydrological cycle
conceptualises the interdependence and continuous movement of all forms of water
issues with the hydrological cycle
- implies sequential movement but this isn’t always the case (precip can be evaporated, water can be trapped in groundwater zone)
- missing human element
- water movement is irregular and episodic (rainfall, evap, streamflow)
- limited practical value
3 types of human influence
+
examples of consequences of human interference with water cycle
land-use change, climate change, water use change
examples:
diversions, land conversion, deption, contamination, nutrient loading/dead zones, sea-level rise, scarcity, discharge from ice sheets and glaciers, extreme weather from climate change
hydrological system (flow chart)
- each catchment/drainage basin is an individual system
- inputs (precip) –> flow routes –> storage –> outputs (evap/runoff)
- each component can be quantified
- components can be ‘sub-systems’
- used to investigate perturbations, feedbacks, external impacts
examples of what the hydrological system could be used to study
land-use change, irrigation/land drainage, the abstraction of groundwater or surface water for human use
hydrological continuity (conservation of mass)
- hydrological storage and fluxes described by equations
- continuity means: change of storage over time = input - output
- in hydrological context: input=precipication and outputs=evaporation and runoff, so change in storage over time = precipitation - evaporation - runoff
calculate global water balance
global annual flux of water between precipitation and evaporation is approximately balanced
how is climate change changing the hydrological cycle?
melting from ice - changes in the cryosphere
even though it is a very small component, why is the atmosphere important?
Fluxes have a disproportional influence on the whole system because it is the driver of the system, water vapor transfers large masses of water around the planet and occurs in short time frames
rivers are also a small percentage, why are rivers important?
generally renewable, transports water between places, source to supply, water from rivers is easy for us to utilize
global water balance / hydrological cycle simplified description
precipitation (373) and evaporation (413) occur over the ocean, the difference (40) is water vapor that gets transferred over the land. Then over land precip (113) and evap (73) also occur. The remaining (>40) gets stored or becomes runoff (> because of melting from ice)
how to convert volume into a depth
divide by the area
water deficit
more water loss (evaporation) than input (precipitation)
water surplus
more input (precipitation) than water loss (evaporation) so surplus is water runoff
describe the water balance for tropical rainforest
high rainfall
input > 2000 mm
balance: some of the precipitation will be balanced by evapotranspiration, but there will be large runoff values
describe the water balance for sub-tropical hot desert
low precipitation
input < 250 mm (but can be much lower)
balance: high evaporation, very low runoff (typically ephemeral streams), will see more water stored in the ground which may be very old
describe the water balance for the high latitude (polar) region
precipitation relatively low
input around 300 mm (and a lot will occur as snow which changes dynamics of the system downstream)
balance: seasonal, snowmelt releases water to join the catchment, evaporation is low - not much water (or vegetation) because it is locked up in the snow, sublimation can occur
