Water And Carbon Cycles Flashcards
What are systems and what are they composed of?
Inter-related components connected to form a working unit:
* Inputs
* Transfers
* Stores
* Outputs
What is an open system?
Allows energy and mass to pass system boundaries
What is a closed system?
Energy is transferred into and out the system but all matter is enclosed
What is negative feedback?
A sequence of events that brings a change back into dynamic equilibrium, making something less than it was before
What is positive feedback?
A sequence of events that amplifies or increases change in a system
The water cycle on a local scale:
hill slope
inputs, outputs, stores, flows
Inputs
* solar energy
* precipitation
Outputs
* transpiration
* evaporation
* river discharge
Flows
* surface runoff
* infiltration
* percolation (movement through ground)
* throughflow (fast)
* interflow (medium)
* channel flow
* ground water flow (very slow)
* base flow (slow)
* stem flow
* throughfall
Stores
* interception
* vegetation storage
* channel storage
The water cycle on a regional scale:
drainage basin
definition, inputs, flows
A drainage basin is the area of land that is drained by a river and its tributaries. The edge of a river basin is maarked by a boundary called the watershed. Case study = Amazon drainage basin.
Inputs
* precipitation
Flows
* groundwater flow
* infiltration
* throughflow
* percolation
* baseflow
* overland flow
Outputs
* evapotranspiration
* river discharge
* runoff
What is precipitation?
Input
Any water that falls to the surface of the earth from the atmosphere including rain, snow and hail.
What is evapotranspiration?
Output
Compromised of evaporation and transpiration.
Evaporation occurs when water is heated by the sun, causing it to become a gas and rise into the atmosphere.
Transpiration occurs in plants when they respire through their leaves, releasing water they absorb through their roots, which then evaporates due to heating by the sun.
What is streamflow?
Output
All water that enters a drainage basin will either leave through the atmosphere, or through streams which drain the basin. These may flow as tributaries into other rivers or directly into lakes and oceans.
What is infiltration?
Flows
This is the process of water moving from above ground into the soil.
Grass crops and tree roots create passages for water to flow through from the surface into the soil, therefore increasing the how fast infiltration can occur. If precipitation falls at a greater rate than the infiltration capacity then surface runoff will occur
What is percolation?
flows
The movement of water through the soil under gravitational forces
What is throughflow?
flows
Water flowing from soil towards a river channel
What is surface runoff?
flows
Where water flows directly over the surface, occurring when the soil is saturated.
What is groundwater flow?
flows
Transfer of water very slowly through rocks. Ensures there is water in rivers even after long periods of dry weather
CASE STUDY
Amazon drainage basin
Changes in the watercycle over time (human activity vs natural variation
Amazon carries the largest volume of water contributing 20% of global riverine runoff to the ocean (209,000 cumecs)
Natural variation
The South American monsoon plays a vital role in changing the size of major water stores in the Amazon drainage basin due to the heavy rainfall which increases water levels in rivers and floodplains, replenishing water stores in the region or increasing their overall size.
Human activity
Cattle Ranching - Agriculture
Raising grazing cows for meat, dairy, leather and other cow-based products. Extensive cattle ranching is the number one culprit of deforestation in virtually every Amazon country, and it accounts for 80% of current deforestation.
Amazon among the top meat exporters in the world. In 2019 alone, over 74,000 wildfires burned in the Amazon, many of which were connected to ranching and the government’s renewed efforts to expand cattle production.
Logging
The business of cutting down trees and transporting the logs to sawmills. Illegal logging is widespread in Brazil and several Amazon countries. Logging is often not carried out sustainably, damaging habitats, diminishing levels of biodiversity and food sources, degrading the soil, polluting rivers and lands, and causing areas to dry out affecting the overall productivity for the peoples and animals that live there.
About 80% of the rainforest’s nutrients come from trees and plants. That leaves 20% of the nutrients in the soil. The nutrients from falling leaves are instantly recycled into the plants and trees. When an area of rainforest is clear-cut, conditions change very quickly. The soil dries up in the sun. When it rains, it washes the soil away. The rainforest never fully recovers. When land is cleared for grazing and plantations, it quickly becomes infertile, leading to further forest clearance.
Settlements (Urbanisation)
In the Brazilian Amazon rainforest, about 80% of the deforested areas are within 30 km of official roads. Populations are growing within the Amazon forest and along with them settlements. Many people are migrating to the forest looking for work associated with the natural wealth of this environment. Settlements like Parauapebas, an iron ore mining town, have grown rapidly, destroying forest and replacing it with a swath of shanty towns. Due to the rapid population increase there is more strain on agriculture and demand for crops increasing each year with the population as there are more mouths to feed. This leads to an increase in deforestation for more farmland and settlements, harming the rainforest even further and increasing emissions due to more cattle ranching being required.
What is afforestation?
The opposite of deforestation, the rehabilitation of forests
What is a monsoon climate?
A monsoon climate is a seasonal prevailing wind characterised by a dramatic seasonal change in direction of the prevailing winds of a region which brings a marked change in rainfall
What is the water balance?
The balance between inputs and outputs in the water cycle. It is expressed as:
P = Q + E (+/- change in storage)
P= precipitatoin
Q= run-off/streamflow/discharge
E= evapotranspiration
The water balance is more likely to be imbalanced on local scales compared to global.
What is the soil moisture budget?
Used by famers and water providers, describes the changes in the soil water store during the course of a year. Can be used to work out if there is a water shortage or excess leading to drought or flooding.
Water companies can calculate sustainable yield (maximum extraction of water that can be maintained in definitely)
