4.1 Introduction to water systems

what is the hydrological cycle

a system of water flows and storages

what is the role of solar radiation in the hydrological cycle

it drives the hydrological cycle

what is the hydrological cycle

a system of water flows and storages

what is the role of solar radiation in the hydrological cycle

it drives the hydrological cycle

how much of the earth's water stores are fresh water

2.6%

what do storages in the hydrological cycle include

oceans, groundwater, lakes, soil, rivers, atmosphere, glaciers, ice caps

what do flows in the hydrological cycle include

evapotranspiration, sublimation, evaporation, condensation, advection, precipitation, melting, freezing, flooding, surface run-off, infiltration, percolation

what are some human activities that have a significant impact on the surface run-off and infiltration

agriculture, deforestation, urbanization

what are ocean circulation systems driven by

differences in temperature and salinity

what is the water budget

a quantitative estimate of the amounts of water in storages and flows of the water cycle

how much of the earth's fresh water is in the polar ice caps and glaciers

about 68.7%

what percentage of the earth's fresh water is ground water

30.1%

what percentage of the earth's fresh water is actually on the earths surface

about 0.3%

how much of earth's water is in the atmosphere as water vapour

0.001%

what is the turnover time in the hydrological cycle

the time it takes for a molecule of water to enter and leave that part of the system

what is the turnover time of water in the ocean

37,000 years

what is the turnover time of water in the ice caps

16,000 years

what is the turnover time of groundwater

300 years

what is the turnover time of water in rivers

12-20 days

what is the turnover time of water in the atmosphere

about 9 days

what are two renewable sources of water

atmosphere, rivers

what is a middle ground renewable resources of water

groundwater aquifers

what are two non-renewable sources of water

oceans, icecaps

what are the two main factors that drive the hydrological cycle

solar radiation and the force of gravity

what are five transfers in the water cycle

advection, flooding, surface run-off, infiltration, percolation, stream flow, currents

what are three transformations in the water cycle

evapotranspiration, condensation, freezing

what are seven storages in the water cycle

oceans, soil, groundwater, lakes, rivers and streams, atmosphere, glaciers and ice caps

what are four ways in which humans can impact the water cycle

withdrawals, discharges, changing the speed water can flow, diverting rivers or sections of rivers

what are withdrawals in the water cycle

taking water out of stores for domestic use, irrigation in agriculture and industry

what are discharges in the water cycle

adding pollutants to water, eg chemicals from agriculture, fertilizers, sewage

how can the speed at which water flows and where it flows be changed

in cities by building roads and channelling rivers underground or in concreted areas, canalizing - straightening large sections of rivers in concrete channels to facilitate more rapid flow, with dams, barrages and dykes, making reservoirs

why are rivers or sections of rivers diverted

they are diverted away from important areas to avoid flood damage and some are diverted towards dams to improve storage

what are three examples of major changes in the water cycle caused by humans

Aral sea, Ganges basin, Run-of from urbanized areas causing local flooding

how was the Aral sea changed

intense irrigation has almost stopped river flow into the sea and lowered the sea's level (it has shrunk in area by 90% in the last 50 years)

how has the Ganges basin been changed by humans

deforestation increases flooding as precipitation is not absorbed by vegetation

where do flash floods occur

when rainfall or snowmelt cannot infiltrate the soil and runs off on the surface

what can flash floods be due to

land being hard-baked in hot areas and impermeable surfaces in cities

what happened to Manila in 2012

50% of the city was flooded

where are ocean currents found

both on the surface and in deep water

where are surface currents found

in the upper 400 m of the ocean

how do surface currents move

by the wind, the Earth's rotation deflects them and increases their circular movement

what are deep water currents also known as

thermohaline currents

what percentage of ocean currents are thermohaline currents

90%

what type of currents cause the oceanic conveyor belt

thermohaline currents

what are thermohaline currents caused by

differences in water density caused by salt and temperature

how do thermohaline currents work

warm water can hold less salt than cold water so it is less dense and rises, cold water holds more salt, is denser so sinks, when warm water rises, cold has to come up from depth to replace it, these are upwellings, when cold water rises, it too has to be replaced by warm water in downwellings, in this way, water circulates

give two examples of cold ocean currents

the Humboldt Current, the Benguela Current

what direction do cold water currents run

from the poles to the equator

what direction do warm currents flow

from the equator to the poles

give two examples of warm ocean currents

the Gulf Stream, the Angola Current

what is the effect of the Gulf Stream and North Atlantic Drift on the climate

moderates the climate of Northwestern Europe, which otherwise would have a sub-arctic climate

what is the effect of the Benguela Current on the climate

moderates the climate of the Namibian desert

what is the El Nino Southern Oscillation

the movement of warm water and air towards South America suppresses upwelling.

what do the trade winds to in the ENSO

blow the warm surface water westward

what are the local effects of el nino

collapse of anchovy fish stocks, massive death of sea birds and storms and flooding in the coastal plain of Peru

why is the anchovy fishery off the coast of Peru extremely rich

there is an upwelling where cold nutrient-rich waters come up from the ocean depths

what are some examples of changes in global weather due to el nino

droughts in Australia, Indonesia, the Pacific Northwest and Canada, Heavy storms often resulting in flooding is California and the Midwest of the US, Central Europe and eastern Asia, the absence of the monsoon in India, the Indian population depends on the monsoon rains from its food production

what is the Gulf Stream

a current in the Atlantic Ocean that comes from the Gulf of Mexico across the Atlantic

what is the size of the Gulf Stream (depth and width)

1000m deep and 100km wide

why does the Gulf Stream seen and return to the conveyor belt as it reaches the north of Britain and Scandinavia

as the water flows some evaporates so its saltiness increases, by the time it reaches these places, it is so much saltier and more dense than the surrounding water that it sinks

what is the North Atlantic Oscillation

a weather phenomenon in the Atlantic similar to ENSO

what happens in high index NAO years

there is low pressure over Iceland and high over the Azores so westerly winds blow and winters a mild and summers are cool and wetter

what happens in low index NAO years

the pressure differences are lower so the westerlies reduce and winters are colder and summers have heat-waves