4.1: Water Systems

Question 1

What is the hydrosphere?

Answer 1

Incudes all of the earths water such as oceans, rivers, lakes, atmospheric moisture

Fresh water: around 2.5% by volume
-> of this 69% is stored in glaciers and ice sheets
-> 30% stored in groundwater
-> 1% is in rivers, lakes, reservoirs, streams

Question 2

What are surface freshwater and groundwater?

Answer 2

surface freshwater: found in rivers, lakes, reservoirs, streams
groundwater: water stored underground in aquifers

Question 3

What forces drive the hydrological cycle?

Answer 3

Solar radiation:
sun’s heat causes water to evaporate from oceans, lakes, rivers
water vapour cools -> condenses into clouds, releasing heat

Gravity:
pulls condensed water to Earth via precipitation
causes water runoff and drain through soil
rivers flow downhill due to gravity -> move water from inland -> ocean

Question 4

What is the hydrological cycle?

Answer 4

A series of processes in which water is constantly recycled through the system
-> shapes landscapes, transport minerals and is essential to life on earth

Closed system

Question 5

What are the main stores of the hydrological cycle?

Answer 5

Oceans

Glaciers and ice caps

Groundwater and aquifers

Surface freshwater (rivers and lakes)

Atmosphere

Question 6

What are the main flows in the hydrological cycle?

Answer 6

Transformations: process where the state or form of water changes
Transfers: movement of water from one location to another

Evaporation:
Transformation

Transpiration:
Transformation
(Plants absorb water from soil through roots and release it as water vapor)

Evapotranspiration:
Transformation

Sublimation:
Transformation

Condensation:
Transformation

Melting:
Transformation

Freezing:
Transformation

Advection:
Transfer
(Wind-blown movement of water vapor/condensed droplets (clouds))

Precipitation:
Transfer

Surface run-off:
Transfer
(Movement of water over earths surface where ground is saturated/impermeable -> excess water)

Infiltration:
Transfer
(Process of water seeping into the soil from the surface -> groundwater)

Percolation:
Transfer
(Downward movement of water through soil and underlying rock layers -> aquifers, reservoirs)

Streamflow:
Transfer
(Movement of water in streams/rivers/water bodies driven by gravity -> ocean/lakes)

Groundwater flow:
Transfer
(Movement of water through pores in underground soil/rock laters -> oceans/rivers/lakes)

Question 7

What are the types of human activities that impact the hydrological cycle?

Answer 7

Withdrawal:
Domestic use, irrigation, industry

Discharge:
Adding pollutants (sewage/fertilizers)

Changing flow speed:
Rivers channeled underground
Canalizing/straightening
Dams/barrages/dykes

Diverting rivers:
Away from important areas to avoid flood damage
Towards dam to improve storage

Question 8

What is the impact of agriculture and irrigation on the hydrological cycle?

Answer 8

Irrigation - artificially watering crops
-> modifies water distribution and availability in the region

Increased irrigation =
-> artificially high evapotranspiration rates (more water supplied to plants than natural)
-> increased atmospheric moisture levels
-> localized increase in precipitation downwind of irrigated areas
-> increased run-off (water faster than soil can absorb -> water flow carry sediment/fertilizers/pesticides -> water pollution and nutrient imbalances)

Question 9

What is the impact of deforestation on the hydrological cycle?

Answer 9

Déforestation - clearing and removal of forests
-> mostly for agriculture, logging or urban development

Forest are important because:
-> natural sponges
-> absorb rainfall and facilitate infiltration (recharge groundwater and maintain stream flows)

When no forest:
-> no tree canopy/vegetation intercepting rainfall -> more water reaches ground -> increased run-off
-> no trees -> less transportation and evaporation -> reduces evapotranspiration rates -> reduce atmoshpereic moisture

OVERALL:
Deforestation disrupt balance between run-off and infiltration -> increase erosion -> reduce groundwater rechange -> alter flow patterns

Question 10

What is the impact of urbanization on the hydrological cycle?

Answer 10

Urbanization - transformation of natural landscapes into urban areas

Increased urbanization =
-> less permeable surfaces -> less infiltration -> reduced groundwater recharge + increased run-off -> flooding and diminished water in dry periods

Urban areas usually have efficient drainage systems:
-> accelerates surface run-off -> overload natural water stores -> downstream flooding
-> urban areas experience high temps = urban heat island effect (concentration of buildings + paved surfaces -> increased evaporation rates -> alter local precipitation)

Question 11

What is the steady state of a water body?

Answer 11

Having a balance between inputs and outputs -> ensures water level remains constant over time
E.g. 180 water units in -> 180 water units out

Question 12

What is sustainable water harvesting

Answer 12

taking waters from a water body at a rate that does not exceed the rate of natural replenishment

Ensures harvested water amounts doesn’t disrupt the steady state

Question 13

What happens when inputs < outputs?

Answer 13

If inputs < outputs then water bodies decrease in size

Unsustainable water harvesting for agriculture or domestic/industrial purposes -> water extracted faster that it can replenish