Water and Carbon Flashcards
What are systems composed of?
- inputs: matter or energy that is added to the system
- outputs: matter or energy that leaves the system
- flows: matter or energy that moves in a system
- boundaries: limits to the system (e.g. watershed)
What are open systems?
Systems which have inputs and outputs of both energy and matter.
What are closed systems?
Systems which have inputs and outputs of energy only.
What are isolated systems?
Systems which have no inputs or outputs of energy or matter.
What is the balance of a system?
The difference between the inputs and outputs.
What is a positive balance?
When inputs exceed outputs.
What is a negative balance?
When outputs exceed inputs.
When is a system in equilibrium?
When inputs and outputs are equal.
What are some characteristics of systems?
- systems are a generalisation of reality - often more complex than the system makes out
- they have a structure that is defined by its parts and processes
- systems tend to function in the same way, involving inputs and outputs of material that is then processed causing it to change in some way
- the various parts of a system have a relationship with each other
- the fact that functional relationships exist between the parts suggest the flow and transfer of some type of energy/matter
What is positive feedback?
A chain of events that amplifies the original event.
What is an example of positive feedback in the water cycle?
Water evaporates from the ocean, water vapour is a greenhouse gas so atmospheric greenhouse gas increases, this leads to warming, leading to more evaporation.
What is an example of positive feedback in the carbon cycle?
Permafrost begins to melt in the arctic tundra, transferring methane from the lithosphere to the atmosphere. As methane is a greenhouse gas, the enhanced greenhouse effect will become more pronounced, leading to more permafrost melting.
What is negative feedback?
A chain of events that dampens the impacts of the original event, leading to a dynamic equilibrium.
What is an example of negative feedback in the water cycle?
As ice sheets melt, there is more water vapour in the atmosphere, leading to increased cloudiness. Because clouds reflect 1/3 rd of incoming solar radiation, there will be less energy absorption on the earth’s surface, decreasing the rate of ice sheet melt.
What is an example of negative feedback in the carbon cycle?
An increase in atmospheric carbon dioxide leads to a faster rate of photosynthesis, expanding the biosphere and decreasing atmospheric carbon dioxide.
What is dynamic equilibrium?
A systems tendency to restore equilibrium state after a change.
What is an example of dynamic equilibrium in the water cycle?
Water evaporates from the hydrosphere’s surface, it rises and cools condensing into clouds. When these clouds are large enough, the water will be returned to the hydrosphere through precipitation.
What is an example of dynamic equilibrium in the carbon cycle?
Humans burn fossil fuels, increasing global temperatures. This encourages more plant growth, which takes in more carbon dioxide, reducing global temperatures.
What is the largest store of water?
The oceans, which contain 97% of global water.
What percentage of water stores are fresh water?
2.5%
What percentage of freshwater is found in the cryosphere?
69%
What percentage of freshwater is groundwater?
30%
What percentage of freshwater is made up of surface and other freshwater (permafrost, lakes, swamps, marshes, rivers, biosphere)
1%
How long do deep/shallow aquifers store water for?
Shallow - up to 200 years
Deep fossil aquifers - 10,000 years
Aquifers are underground water stores and are unevenly distributed on a global scale.
How long do glaciers store water for?
20-100 years
What is evaporation?
The process whereby liquid water changes into a gas when it absorbs heat energy.
How does evaporation drive change in the magnitude of water stores?
- approximately 90% of the atmospheric water store is from evaporation from the oceans and seas. The remaining 10% comes from plant transpiration.
- high levels of evaporation can occur in some tropical and desert areas. These are regional scale changes. Increased global changes are likely to occur due to climate change and increased atmospheric temperature.
- The level of evaporation on a global scale ocean and sea level is minimal, but within a drainage basin evaporation can have a large regional scale impact. Lakes or rivers in an area with a high maximum summer temperature will experience high levels of evaporation and hydrospheric storage will reduce significantly in this area.
What is condensation?
The process whereby the gaseous water vapour changes back into liquid water within the atmospheric water store.
How does condensation drive change in the magnitude of water stores?
Tiny, microscopic water molecules that develop around dust and smoke particles (aka aerosols) will be carried invisibly in the air. Where they combine into larger molecules of liquid ware or ice they may be seen as mist, fog, or clouds. This occurs on a global scale but could alter as climate change increases global atmospheric temperature.
How does cloud formation drive change in the magnitude of water stores?
Clouds form when water molecules aggregate. They are frequently noticed at the altitude where air temperature has fallen to a point where condensation of invisible water vapour occurs (condensation - or dew point), or where the humidity content has risen such that water cannot remaining in that state and condenses. As the molecules grow, clouds form with the tiny water or ice particles kept aloft by rising air currents (thermals).
What are cryospheric processes?
Processes that affect the total mass of ice at any scale from local patches of frozen ground to global ice amounts.
How do cryospheric processes act at hill slope?
Ice forms from the compression of falling snow. As layer upon layer of snow is added it can exert a pressure on the snow at the base, compressing that snow and forcing air out of it. This will slowly form a denser substance called Névé and eventually ice. Melting and refreezing of previously fallen snow can also assist in this process.
How do cryospheric processes act in a drainage basin?
Cryospheric changes affect hydrological processes not only in the increase or decrease of runoff, but also in its seasonal distribution, thereby affecting the use of water resources.
How do cryospheric processes act globally?
Cryospheric changes cause global sea-level change and also global water-cycle processes. Cryospheric changes impact the ocean–freshwater balance, which drives the ocean thermohaline circulation, and thus global ocean circulation.
What is precipitation?
Any water that falls to the earth’s surface from the atmosphere including rain, snow, and hail.
What causes convectional rainfall?
Due to heating by the sun, warm air rises and then cools and condenses at higher altitudes, then falls as rain.
What causes orographic rainfall
Warm air is forced upwards by a barrier such as a mountain, causing it to condense at a higher altitude and fall as rain.
What causes frontal rainfall?
A warm air mass rises over a cooler, denser air mass. It condenses at a higher altitude and falls as rain.
What are the outputs to the drainage basin?
Evapotranspiration and streamflow.
What is evapotranspiration?
Composed of evaporation and transpiration, it occurs in plants when they respire through their leaves, releasing water they absorbed through their roots when it evaporates from their leaves.
What is streamflow?
Water leaving the basin in streams. They may flow as tributaries into other rivers or directly into lakes and oceans.
What are the flows in the drainage basin?
- infiltration
- overland flow
- percolation
- throughflow
- groundwater flow
- streamflow
- stemflow
What is infiltration?
The process of water moving from above ground into the soil. The infiltration capacity refers to how quickly the infiltration can occur.
What is overland flow?
When precipitation falls at a greater rate than the infiltration capacity, water flows above ground as sheetflow (lots of water flowing over a large area) or rills (small channels similar to streams that are unlikely to carry any water when there is not any rainfall).
What is percolation?
Water moving from the ground/soil into porous rocks or fractures. The percolation rate is dependent on the fractures present and the permeability of the rock.
What is throughflow?
Water moving thorough the soil into streams and rivers. The speed is dependent on the type of soil. Sandy soils drain quickly because they have a low field capacity, large pore spaces, and natural channels from animals such as worms.
What is groundwater flow?
Water moving through the rocks.
What is stemflow?
Flow of water that has been intercepted by plants down a stem, leaf, branch, or other part of a plant.
What are the stores in a drainage basin?
- soil water: water which is stored in the soil and utilised by plants
- groundwater: water which is stored in the pore spaces of rocks
- river channel: water that is stored in a river
- interception: water which is intercepted by a plants branches and leaves before it reaches the ground
- surface storage: water stored in puddles, ponds, lakes, etc.
What is the water balance equation?
Precipitation = Total runoff + evapotranspiration + change in storage
Water balance is used to express the process of water storage and transfer in a drainage basin.
What is discharge in a hydrograph?
The volume of water passing though a cross-sectional point of a river at any one point in time, measured in cubic metres per second (CUMECS). It is made up of the base flow and stormflow.
What is the rising limb of a flood hydrograph?
The line on the graph which represents the discharge increasing.
What is the falling limb of a flood hydrograph?
The line on the graph which represents the discharge falling.
What is lag time?
The difference between peak rainfall and peak discharge.
What is baseflow?
The level of groundwater flow.
What is stormflow?
Overland flow and throughflow.
What is bankfull discharge?
The maximum capacity of the river. If the river exceeds this then it will burst its banks and be in flood.
What are the characteristics of flashy hydrographs?
- short lag time
- steep rising and falling limb
- higher flood risk
- high peak discharge
What are the characteristics of subdued hydrographs?
- long lag time
- gradual rising and falling limb
- lower flood risk
- low peak discharge
What natural factors make a flashy hydrograph more likely?
- High intensity rainfall - higher discharge potential from river as it is more likely for the soil to reach its field capacity, increasing runoff and decreasing lag time
- Prior rainfall - increased surface runoff as soil is already saturated/reached field capacity
- Impermeable bedrock - decreased percolation leading to more throughflow
- Many tributaries - increases speed of drainage, decreasing lag time
- Small basin - water reaches the river quicker, decreasing lag time
- Low temperature - less evapotranspiration leading to greater peak discharge
- Vegetation cover - forested areas intercept rainwater, decreasing lag time
What human factors make a flashy hydrograph more likely?
- Urbanisation - more impermeable surfaces, increasing runoff and reducing infiltration and surface storage
- Pastoral farming - ground trampled so less interception and more surface runoff
- Deforestation - less interception by trees, so water reaches ground and river quicker
What does the soil water budget show?
The annual balance between inputs and outputs in the water cycle and their impact on soil water storage/availability. The budget is never the same due to varying conditions year on year and the process is affected by how much rainfall their is in the previous year.
What does the soil water budget depend on?
Type, depth, and permeability of the soil and bedrock.
What is the soil field capacity?
The maximum possible level of storage of water in the soil.
Once the field capacity is reached, any rainfall after this will not infiltrate the soil and is likely to cause flooding.
What is the soil water budget like in the autumn?
There is a greater input form precipitation than there is an output from evapotranspiration as deciduous trees lose their leaves and the cooler temperatures mean that the plants photosynthesise less. Soil moisture levels increase and water surplus occurs.
