water

What are open systems?

Have external inputs and outputs of energy and matter exchange at its boundaries

What are closed systems

No inputs occur from outside and nothing is lost. Only energy as its input and output and matter is contained within system boundary

What is the global hydrological system?

The continuous movement of water on above and below the Earths surface. It’s a closed system so no external inputs or outputs, no water lost or gained

Explain how water is recycled in the global hydrological system

1. The sun evaporates surface water into water vapour

2. The water vapour condenses to form clouds

3. Moisture is transported around the globe which drives atmospheric circulation and returns to surface as precipitation

4. When water reaches the ground, some water will evaporate back into atmosphere whilst some water may percolate the ground to form groundwater.

How does the hydrological cycle lead to local temperature fluctuations

Water evaporates using energy form its surrounding to do this process, which cools the environment. When water condenses, heat is released.

How is gravitational potential energy involved in the hydrological system

When a water droplets falls from high above sea level to the ground it has a high amount of gravitational potential energy. When it’s in motion GPE turn into KE so allows water to move over the surface.

What amount does freshwater make up in all of Earths water

2.5%

What amount of freshwater is locked away and how

1.6% is locked away and 68.7% of this is locked away as ice within cryosphere and the remaining 30.1% is groundwater.

How much of Earths freshwater is accessible to humans

1%

Why’s water stored unevenly around the globe

Water is stored unevenly because of the uneven spread of land to sea and permeable or porous rock which enables aquifers to form.

What are fluxes

Transfers of water in the hydrological cycle

What are annual fluxes

Variations in flows due to to temperature, seasons and location. Flows like evaporation will be greatest in warmer areas so higher rates of precipitation. Store like ice caps will get smaller due to climate change but ocean stores will increase.

What is global water budget

Difference between the inputs and outputs from the different stores

What is residence times?

Time water is held in a store.

What factors affect size of stores and water residence times

• Flows or transfers like evaporation

• Global factors like climate change

• Local factors like human activity on a hill slope

How do transfers affect size of water store and water residence time

More precipitation increases availability of water for storage. Or surface flow increases,allowing more infiltration.

What’s cryosphere

Water stored in solid form like glaciers and ice sheets

What’s hydrosphere

Water stored in liquid form like rivers and lakes, groundwater.

How has climate change affected how water is stored

1. During last ice age, third of earths surface was ice sheets and glaciers so increased cryosphere stores

2. This reduced hydrospheres stone and sea levels where 100m lower.

What’s the Inter tropical Convergence Zone

Area of low pressure that forms due to action of the Had,ey Cell, where the Northeast Trade Winds meets the Southeast Trade near the equator.

Explain what happens at the Inter tropical convergence zone

The equator receives more insulation so higher temperatures which leads to more evaporation

Warm moist air rises, cools and condenses and forms banks of towering clouds with heavy rainfall

Low pressure zone created called ITCZ

How is a positive feedback created when cryospheres melt

Melting of ice sheets adds water to hydrosphere like oceans. Ice shelves are destabilised so ice breaks off so they melt and hydrosphere store increases . This is positive feedback loop

What are drainage basins

Area of land drained by a river and its tributaries with a boundary known as the watershed composing of hills and mountains. An open subsystem in hydrological system

What’s a catchment area

An individual drainage basin is the area drained by a river and its tributaries

What features do drainage basin features have

Watershed, source, confluence, tributary,mouth

What’s confluence

Point where two rivers meet

What’s tributary

A smaller stream or river flowing into a larger stream or river

What’s the mouth and source of a river

Mouth- where river meets ocean or sea

Source-furthest point from mouth where river starts

What is orographic(relief) rainfall

Warm moist air formed by evaporation and carried by prevailing wind is forced to rise over high ground like mountains. Air cools, condenses , forming clouds so leads to precipitation. In the rain shadow,Dry air descends and warms so more moisture held in atmosphere.

What is a rain shadow

Region with little rainfall because it’s sheltered from prevailing winds by mountains

What frontal rainfall

Warm and cold air masses meet and warm air rises over cold air. Warm air cools and condenses to form clouds creating precipitation.

What’s conventional rainfall

Ground heats air above it and moisture from ground evaporates. Warm moist air rises rapidly which cools,condenses to form clouds so that precipitation occurs.

What’s interception

Precipitation that doesn’t reach soil because it’s intercept by vegetation and the forest floor. Reduces surface runoff and so reduces soil erosion and flooding

What’s infiltration

water on the ground soaking into the soil and porous rocks

What’s throughflow

Flowing of water within soil moving towards the river

What’s percolation

Movement of water through soil or underlying porous rocks

What’s groundwater flow

Flow of water through rocks towards river

What are the flows in a drainage basin

Throughflow, groundwater flow, infiltration,percolation, interception

What is river discharge

Volume of water passing a point in the river channel at a hives unit of time and expressed as cubic metres per second or cumecs

What are outputs of drainage basins

Evaporation, transpiration and channel flow

How does climate affect drainage basins

• It’s affect type and amount of precipitation

• Extent of evaporation

• Amount and type of vegetation

How does soil affect drainage basins

• Infiltration and through flow- the pores in soil affects rate of infiltration and through flow

• Impermeable , saturated or compacted or frozen soil means low infiltration rates and high surface runoff

How does vegetation affect drainage basins

• Amount and type of vegetations affects interception, infiltration

• Less or no vegetation means more surface runoff off and reduced interception and more infiltration

How does geology affect drainage basins

• Impermeable rocks reduces percolation so reduces groundwater flow

• Geology affects type of soil which impacts flows

How does relief affect drainage basins

• Flatter slopes means more infiltration so reduces surface runoff off , steeper slopes means infiltration is reduced and surface runoff is increased

• Upland areas experience more precipitation so affect flows in drainage basins

How does deforestation impact drainage basins

Clearance of trees reduces interception and infiltration rates. Increases surface runoff o, reduces evapotrAnspiratipn which reduces precipitation

How does urbanisation affect drainage basins

Tarmac and concrete are impermeable so reduce infiltration and increase surface runoff. Drainage system move water to rivers more rapidly so increases risk of flooding

How does agriculture impact drainage basins

Reduces amount of large vegetation so decreases interception and increases runoff

How does livestock farming impact drainage basins

Compaction of soil due to livestock trampling so soil is less porous so less permeable so reduces infiltration

How does abstraction affect drainage basins

Over abstraction leads to reduced through flow and groundwater flow in river and reduces groundwater storage

How do reservoirs affect drainage basins

Dams and reservoirs reduce water flow downstream. Increases evaporation as there’s greater surface area of water

What are water budgets

Annual balance between inputs like rain and outputs like evaporation and their impacts on soil water availability

What’s the water budget equation

Precipitation (P) = total runoff (O) + evapotranspiration(E)±changes in storages (S)

How do west seasons impact water budget

Precipitation greater than evapotranspiration which creates water surplus. Groundwater stores fill with water which increases surface runoff o, higher discharge and higher river levels. So positive water balance

How do drier seasons affect water budget

Evapotranspiration exceeds precipitation, plants absorb water so groundwater stores depleted so negative water balance

What’s the soil water budget

Shows the balance between impure and outputs of a soil store over a year. Dependent on soil depth, type, texture, and permeability

What is discharge

Volume of water moving past a point in a river per given time

How is discharge calculated

Q(discharge in cumecs)= A(cross sectional area in m2) x V(velocity m/s)

What factors influence discharge

Rate of precipitation snd how fast water transfers to the river across the drainage basin.

What are hydrographs

Used to measure discharge and they can be annual or storm hydrographs

What are annual hydrographs

Also called a rivers regime, shows the pattern of seasonal variation that takes places through a drainage basin to river discharge over a year. Measured in cumecs.

What are storm hydrographs

Shows changes in a rivers discharge during and after a storm. Drawn to show a river reacts to a storm. They compare to variables, rainfall during storm in mm and river discharge in cumecs

Describe the difference between how a flashy and a flat hydrograph is drawn

Flashy hydrographs have a short lag time with high peak discharge, steep rising limb. Flat hydrograph have longer lag time , low peak discharge and gentle rising limb.

How does rock type affect shape of hydrographs

• Impermeable rocks decreases percolation and increases surface runoff so flashy hydropgraph

• Permeable rocks allow percolation so lower surface runoff so flat hydrograph

How does soil types affect shale of hydrographs

• Clay soils means less infiltration sp increases surface runoff so flashy hydrographs

• Sandy soils have a high infiltration rate so decreases surface runoff so flat hydrograph

How does weather and climate affect shape of hydrograph

• Heavy or prolonged rainfall and rapid snow melt exceeds soil capacity so increased surface runoff so flashy hydrographs

• Steady rainfall and slow snow melt don’t exceed infiltration capacity of soil so flat hydrograph. High evaporation means less surface runoff off so flat shape

How does antecedent conditions affects shape of hydrographs

• Saturates soil so infiltration is low and surface runoff is greater so flashy shape

• Unsaturated soils so infiltration is high and surface runoff is low so flat

How does vegetation affect shape of hydrographs

Deciduous plants and trees means less interception in winter as they shed leaves so flashy

Trees means high levels of interception so flat

How does drainage basin size affect shape of hydrographs

• Smaller basins have steep rising limbs and short lag time as water reaches rivers more quickly

• Large basins have longer lag times and gentle rising limbs as water takes longer to flow through basin

How does deforestation affect shape of hydrographs

• Deforestation reduces interception, urbanisation increases impermeable surfaces, agriculture increases compaction of soil so increases surface runoff off so flashy shapes

• Afforestation increases interception so flat.

What are droughts

Extended period of time when there’s below average rainfall

What are meteorological droughts

Occurs when there’s a rainfall deficit and caused by changes in atmospheric circulation leading to lack of rain from short term or long term changes , lack of rainfall combined with high temperatures so increases evaporation

What is agricultural drought

Water deficiency in soil leading to crop failure and reduced biomass

What is hydrological droughts

Lack of water stored on surface and underground in lakes, rivers, reservoirs and aquifers

What’s socio economic drought

Water demand for socioeconomic means exceeds water supply e.g for crop irrigation and hydroelectric power. Could be because of lack of rainfall or overuse of available water.

What’s the El Niño Southern Oscillation(ENSO) cycle

Movement of warm water mass in the equatorial Pacific Ocean, due to changes in trade winds m atmospheric circulation and ocean currents. It includes phases El Niño and La Niña

What’s the El Niño phase?

• occurs when sea temp is 0.5 degrees above average so warmer average weather in eastern Pacific

• Peaks usually in December and occurs 2-7 years

• Can cause thermal expansion and sea level rise

Trade winds from East to west are weakened, so warm water travels east increasing sea temp in central and eastern pacific. Warm water heat air above so rainfalls occurs. Low pressure formed as air rises.Dry air travels west and sinks causing high pressure. Clear skies increases temp and lack of moisture causes droughts.

What is a La Niña event

Trade winds from east to west strengthen so warm water pushed to western Pacific. Warn water heats air causing thick clouds and heavy rainfall. Dry air moves east , cools and skunks in eastern Pacific. The sinking of dry air creates high pressure so drought in east.

What happens In the tropical Pacific during a normal year?

Tropical pacific experiences trade winds which pushes warm water from east ( South America ) to west ( Asia and Australasia) . In South America, cold water rises from ocean depth to replace warm water. This is called upwelling, creating a temp difference across the pacific. Warm ocean heat air above it which cools, condenses forming rain clouds. The dry air travels east in upper atmosphere which descends in eastern Pacific.

• How does drought risk increase from human activities

• Over abstraction from rivers and groundwater

• Reducing downstream supply of water by building reservoirs and water transfers

• Deforestation and overgrazing reduces vegetation cover so reduces evapotranspiratipn rates which reduces atmospheric moisture and precipitation

• Vegetation removal means less organic matter so reduces soils moisture retention. Organic matter like earthworms create pores for water drainage

• Compaction of soil so less porous so reduces soil moisture retention so reduces infiltration and increase surface runoff

Case study: Sahel Africa, drought back ground info

Semi arid region.

Since 1960s there’s been a decline in annual rainfall

What were the causes and impacts of Sahel droughts in late 20th century?

Caused by air pollution made from Europe and North America, which led to atmospheric cooling, changing global NEA budget and atmospheric circulation so that the tropical rains associated with the ITCZ didn’t arrive causing drought

A study showed that the droughts could have been from higher sea surface temperature caused by anthropogenic climate change . The rain bearing clouds seem to fall when sea surface temperature in the tropical Atlantic is warmer than usual.

What social factors are increasing the impacts of droughts in Sahel region?

Sahel as one if the worlds highest poverty rates

lowest development levels

Annual population growth rates of 2.5 to 4 %

What are the environmental factors that increase the risk and impacts of drought in Sahel region?

Population growth means greater demand for food and fuel wood so more natural ecosystems converted to farmland.

Land being over cultivated and overgrazed causing desertification

Reduced rainfall causes reduced vegetation and soil moisture.

What’s the Millennium Drought in Australia

Longest uninterrupted years with below median rainfall.

Annual rainfall between 1997- 2009 was 12.4 % below 20th century mean

What was the physical cause of Millennium drought in Australia

El Niño events - strengthening of high pressure belts known as sub tropical ridge accounts for 80% of rainfall decline. This ridge blocks storm tracks(depression) forcing them towards higher latitudes and thereby reducing frontal rainfall.

What is the human cause of Millenium drought in Australia

Climate models used suggest that high pressure belts are intensifying with increases in global temp due to greenhouse gas emissions. Anthropogenic climate change could be reducing temperature gradients between Equator and the Pole which reduces energy for mid latitude storm systems and polar front jet stream. Though insufficient evidence to support this theory.

How does drought impact wetland ecosystems?

Droughts reduce areas of open water so habitats are lost. Soil moisture is reduces which leads to soil erosion for example by the wind and a reducing ability to store water which increase risk of floods. Organic soils may oxidise releasing carbon into atmosphere . Water supply reduced so concentration of nutrients and pollutants increase.

How do droughts affect species?

Can remove species from food webs allowing other species to establish themselves in their place. Droughts destroy habitats while kills species. Species like snipe will be affected as they depend on soil invertebrates and droughts decrease soil moisture so soil will be less penetratabke to receive invertebrates.

How does droughts affect forest ecosystem

Foliage loss, impairment growth of drought stressed trees, increase in pests and diseases , damage to vascular tissues in trees which impacts water transport.

What is an example of droughts affects a forest ecosystem?

Piñon pines dying off in Mexico. Hot dry condition means the pine trees are more vulnerable to pine bark beetle attacks, contributed to warmer winters because beetles are able to survive through winter and reproduce.

Some areas had 90% of piñon die

How much carbon do forests hold?

0.73 tonnes of carbon per hectare per year

how much of the world is affected by freshwater flooding?

One third of the worlds land area

What’s flooding?

Result of surplus water in hydrological system

what’s a mid latitude depression.

Mid latitude depression - weather systema low atmospheric pressure. Each depression has two bands of rain, a warm front and cold front. Warm fronts are the first to pass over in a low pressure system. This is when warm air rises above cold air when they meet. Warm fronts bring steady continuous rain. Cold front passes over which brings heavy rains and . When cold fronts catches up with warm fronts it creates an occluded front which brings heavy rains.

What causes most river flooding

Mid latitude depression. Soil absorbs rainfall but when throughflow and groundwater flow can’t transfer water quickly enough, soil becomes saturated which increases surface runoff. This increases river discharge and when river capacity is exceeded , water flood floodplain

What’s a monsoon

Seasonal change in direction of prevailing winds of a region

How does snowmelt lead to flooding

Sudden rise in air temp increases snowmelt. Snow melts faster than water can infiltrate, surface runoff increases which can be due to frozen soil.

Example of snowmelt causing flooding

2008 in North Dakota 2009 foods

How does urbanisation increase flood risk?

Urbanisation- increase in impermeable surfaces like roads increases surface runoff. River lag times are reduced via urban drainage system which transfers water away from streets and into rivers. Bridges and culverts which are underground channels that are made to divert water under infrastructure which reduces river capacity