Please enable JavaScript.
Coggle requires JavaScript to display documents.
4.1. INTRODUCTION TO WATER SYSTEMS (Knowledge and Understanding…
4.1. INTRODUCTION TO WATER SYSTEMS
Knowledge and Understanding
hydrological cycle - system of water flows and storages that may be disrupted by human activity
solar radiation drives the hydrological cycle
fresh water = 2.6% of Earth's water storages
human activities such as agriculture, deforestation and urbanisation have significant impact on surface run-off and infiltration
Storages in hydrological cycle - organisms and various water bodies - oceans, ground water (aquifers), lakes, soil, rivers, atmosphere, glaciers and icecaps
Flows in hydrological cycle - evapotranspiration, sublimation, evaporation, condensation, advection, precipitation, melting, freezing, flooding, surface run off, infiltration
Earth's water budget
70% of earth's surface is water
97% is ocean water, around 2.6% is fresh
68.7% of fresh water is in polar ice caps and glaciers
30.1% fresh water is in ground water
0.3% on earth's surface - lake, river, swamps
0.001% - held in atmosphere
Human impact on the water cycle
Withdrawals
- for domestic use, irrigation in agriculture and industry
Discharges
- adding pollutants to water, e.g. chemicals from agriculture, fertilisers, sewage
Changing the speed at which water can flow and where it flows
e.g. in cities by building roads, canalising means water flows faster , dams making reservoirs
Diverting rivers or sections of rivers
many are diverted away from important areas to avoid flood damage, some towards dams to improve storage
Urbanisation and flash floods
rainfall or snowmelt can't infiltrate the soil so runs off on the surface - cities surfaces are usually impermeable
Ocean currents and energy distribution
ocean currents - movement of water both vertically and horizontally
surface currents (upper 400m of ocean) - moved by the wind, earth's rotation deflects them and increases their circular movement
deep water currents (thermohaline currents - make up 90% of ocean currents and cause oceanic conveyor belt)
Oceanic conveyor belt
due to differences in water density caused by salt and temperature
warm water can hold less salt than cold water so is less dense and rises
cold water holds more salt so is denser and sinks
when warm water rises, cold has to come up from depth to replace it - upswellings
when cold water rises - it too has to be replaced by warm water in downwellings
cold ocean currents: poles - equator, warm ocean currents: equator - poles
Ocean currents and climate
water masses heat up and cool down slower than land masses - land close to seas and oceans has mild climate with moderate winters and cool summers
ocean currents also affect climate e.g. warm gulf stream/ north atlantic drift moderates climate of northwestern europe which other wise would have a subarctic climate
El Nino southern oscillation