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4.1 Introduction to Water System, Deforestation, Agriculture, Urbanization…
4.1 Introduction to Water System
Solar radiation drives the hydrological Cycle
Insolation adds energy to liquid water, transforming it to a gas through evaporation
Uneven surface heating creates wind, transferring water vapor horizontally within the atmosphere
Vapor loses energy as it moves, condensing and eventually falling as precipitation
Outline how energy drives the hydrological cycle
primary source of energy driving hydrological cycle is solar energy
solar energy causes changes of state in water, such as evaporation
Condensation of water releases(latent) heat energy causing air to rise/hurricanes
Solar energy causes the temperature differences that create winds/ cause movement of water vapor
Kinetic / wind energy moves clouds
Fresh water makes up only a small fraction of the Earth's water storages
Diagram of the Water Cycle
Storages in the hydrological cycle include organisms, soil and various water bodies, including oceans, groundwater, lakes, rivers, atmospheres, glaciers and ice caps
Renewable or non-renewable?
Depends on where it is found in the cycle
Ocean circulation system
Salinity
Concentration salts higher in warm seas due to high evaporation rates
Runoff from most river reduce salinity of ecean
Thawing of large iceberg decrease salinity of ocean
Temperature
In tropical and subtropical areas, sea surface temperature in excess of 25 *C are caused by insolation
From 300 - 100m, temperature decline steeply about 8-10*C
Below 100m, temperature decrease unform 2*C in the ocean depth (thermocline)
Density
Temperature increase, water become less dense
Salinity increase, water become more dense
Cold, highly saline, deep mass of water is very dense
Warm, less saline, surface water is less dense
When large water mass with diff. densities meet, the denser water mass slips under the less dense mass -> drive the ocean conveyor belt
Deep water current (thermohaline current): make up 90% of ocean currents and cause the oceanic conveyor belt
There are 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 arise)
Cold water holds more salts, is denser (sink)
When warm water rises, cold has come to up from depth to replace it. (Upwelling)
When cold water rises, it has to be replaced by warm water. (downwellings)
Human Activity
Impact on:
Infiltration
- precipitation that soaks into soil
Surface runoff
- precipitation that does not soak into the soil but instead moves toward streams
Deforestation
Local Climate
deforestation
⬆️ light intensity, temp, wind speed & moisture at ground level
consequence:
⬆️ organic matter decompose at faster rate - so masa first2 deforestation, soil fertile
⬆️
raindrop impact
(force when raindrops impact the ground. other name: splash erosion)
⬆️ surface runoff, ⬆️ river sedimentation. river more murky, high turbidity
deforestation
⬇️ evapotranspiration, recycling of water slow down
⬇️ annual rainfall
Soil Compaction
deforestation
⬇️ trees to trap rainfall
⬇️
interception
(precipitation intercepted by the leaves/branches of plants/forest floor. if not intercepted, reach soil)
raindrop compacts the soil
⬇️ infiltration, ⬆️ surface runoff
Grazers
deforestation
new vegetation grow (grass)
encourage grazers to eat
grazers compact the soil
⬇️ infiltration, ⬆️ surface runoff
Ground Water Resources
deforestation
thin soil exposed to direct sunlight. lose moisture through evaporation
⬇️ ground water resources
Agriculture
Irrigation
(addition of water to areas where there is insufficient for adequate crop growth)
⬇️ earth albedo (dark green crops replace sandy surface)
⬆️ evapotranspiration, ⬆️ rainfall. + hail storms & tornadoes become more common
Land use
Grazers compact soil, ⬇️ infiltration
Ploughing loosen soil, ⬆️ infiltration
Poor drainage cause waterlogging & salinization
Urbanization
Convert permeable vegetated surface with impermeable concrete, brick, tiles, etc.
⬇️ infiltration, ⬆️ surface runoff
Lots of sewers & drainage channels. Move more water away to river, quickly. ⬆️ surface runoff
Increase risk of flooding &
flash flood
urban vs natural
view image clearly at:
https://resinbondedaggregates.com/blog/uk-flooding-what-is-causing-it-and-what-is-being-done-about-it
