Hydrosphere Flashcards
1.Global hydrological cycle
•Closed system~97% Ocean ~2% ice ~1% aquifer
•Sun heats surface of ocean causing evaporation where water molecules turn to gas and rise, as rising higher into atmosphere, cool and condensation takes place forming clouds. Precipitation follows.
•Alternatively, clouds blow onto land (advection). As they move over land, heated by sun, more evaporation takes place from rivers and lakes. In addition vegetation uses water in soil and can lose this through transpiration (sits on leaf and is evaporated. EVAPOTRANSPIRATION
•Clouds continue to blow over land, as altitude increases so too does precipitation. Falls as snow over high land and stored as ice for long periods before melting and returning to oceans
OR
•Falls as rain, three things can happen:
1. Makes way over saturated ground via gravity to nearest tributary stream, (surface runoff- fastest way of returning to ocean
2. Through flow - water infiltrates non-saturated soil and via gravity travels slowly through soil to nearest tributary stream
3. Groundwater flow - water percolates deeper into saturated rocks and travels very slowly to nearest tributary stream like a sponge releasing water. Water can be stored here for long periods of time before returning to sea
2.Drainage basin (4 elements - inputs, stores, transfers, outputs)
INPUTS
•driven by energy from sun (driving force). Causes clouds to be continually fed by evaporation (rivers/lakes) and transpiration (vegetation). Precipitation is main input in drainage basin
•amount of precipitation falls is related to - form of precipitation(rain, sleet, hail, snow), regularity, duration and intensity of precipitation.
STORES
•stored in rivers and lakes(0.01%) and on surface in vegetation and soils: trees INTERCEPT rain droplets which can be stored temporarily on leaves before either evaporating or falling onto the ground/running down branches. When water reaches ground can be stored as SOIL MOISTURE or vegetation can take it up THROUGH ROOT SYSTEMS where it will be stored INSIDE VEGETATION.
•Water also stored for longer periods of time in ice(2%) and below surface as groundwater(1%). The porosity permeability of soil and rock in area will dictate how much water can be stored in soil or rock(groundwater). Porous soil(sand) and rock(chalk) allow water to pass through fairly easily compared to more impermeable soil(clay) and rock(gneiss)
TRANSFERS
•Precipitation can land directly in river channels themselves. Surface run-off -water flows across surface because surface is a)saturated or b)impermeable. Also if c)torrential rain, rain can cause rain splash which is when relatively dry soil pores are blocked by bombardment of intense rainfall, stopping infiltration for short period of time
•Through flow - when water infiltrates surface and moves through lower soil by gravity towards rivers. Speed at which it moves will be slow if soil is saturated or pore spaces have been compressed by machinery/livestock
•Groundwater flow - when water percolates deep below surface, in pores, joints and bedding planes of permeable rocks. This transfers water very slowly to rivers often taking weeks, or even years - an important long term supply of water for rivers during dry periods.
OUTPUTS
•Water exits drainage basin. Can be evaporated from rivers/lakes or from soil and vegetation through transpiration from leaves. Water is lost from basin by river flowing into sea/ocean(river mouth)
3.Impacts of human activities
DEFORESTATION
•lowers storage in vegetation. Less interception by leaves, decreasing amount of storage of rainwater on leaves and in vegetation itself. Outputs will decrease as transpiration rates fall due to lack of vegetation, this will mean storage as condensation will also decrease, which may in turn lower precipitation rates.
•Any precipitation that does fall will cause erosion of soil as there are no roots holding it together. As soil thins it will store less water and become saturated more quickly resulting in increased amounts of surface runoff, which will lead to steep rising limb and short lag time in rivers. Soil may be gradually washed into rivers, which will decrease river/lake storage capacities.
DAMS
•Allow large valleys to be flooded, as a result, this increases the overall storage capacity of lakes and rivers. Large surface area of water can then lead to increased outputs of evaporation - as the sun heats some of the water and changes it from a liquid to a gas causing it to rise into atmosphere. As it rises, cools and changes back into a liquid as condensation, which increases the storage of clouds, which can also increase precipitation.
•dam will regulate how much water is allowed into the river downstream on a daily basis, resulting in artificial river hydrograph and consequently will affect the amount of water reaching the mouth of the river as an output. The Colorado river used to dry up 20 miles before it reached the river mouth because so much water had been stored in all of the dams and reservoirs upstream.
URBANISATION
•impacts transfers as lots of impermeable surfaces such as concrete prevent rainwater from being able to infiltrate down into the soil which results in increased surface runoff. Urbanised areas also have drainage systems which also funnel rainwater quickly into rivers, both of which cause steep rising limbs and short lag times
•since lots of surface water after rainfall event, outputs can increase as the energy of the sun shines and causes evaporation from impermeable surfaces, which as mentioned will increase storage in clouds and possibly increase precipitation as an input.
IRRIGATION
•irrigation of farmland can cause change in storage. If the soil is permeable like sand and the rocks below are also permeable like chalk, then increased amounts of water at the surface due to irrigation infiltrate and percolate down through the soil and rock, increasing water storage in aquifers. Could also affect transfers as more water may travel due to gravity through the pore spaces in soil and rock as through and groundwater flows
4.Differences in discharge between urban and rural hydrograph
URBAN
•shorter lag time and steeper rising limb because impermeable surfaces lead to rapid surface runoff and urban drainage systems also transfer water quickly to rivers
•large proportion of water that falls in urban area will make its way to river in this way (very little water lost from outputs or water stored in vegetation/soil) meaning high peak discharge
RURAL
•Interception by vegetation stores rainfall on leaves and takes it up through root systems in soil. Tree roots bind soil together, which promotes deep soil meaning more water can be stored in the soil. This delays the transfer of water to the river meaning a gentler falling limb/longer delay in returning to base flow
•water caught by leaves or been transpired by tree are affected by the heat of the sun and transpiration takes place where water is heated, turns into gas and rises into the atmosphere where it condenses to form clouds, it is therefore lost from the rural drainage basin resulting in a lower peak discharge
•rural areas with permeable soils like sand and rock such as chalk can store water and then release it slowly over hours or days after it has finished raining which leads to a gentler falling limb/longer delay returning to base flow
•likely to have much more infiltration and percolation, this means more water makes its way by the slower transfers of through flow/groundwater flow and with much less surface runoff, the result is a gentler rising limb/longer lag time
TRANSFERS = RISING LIMB
STORAGE = FALLING LIMB
OUTPUTS = PEAK DISCHARGE
5.River valency
•base flow discharge of river valency is about … cumecs. There is precipitation between … and … hours which causes the discharge to increase. It takes approximately … hours for discharge to rise after it started raining because very little rain falls in the main channel, it takes time for rain to reach river from drainage basin(transfers)
•heavy rainfall at … causes steep rising limb. Between … and … hours rainfall decreases and therefore rising limb becomes more gentle. From … to … hours heavy rainfall once again causes a steep rising limb. Peak discharge is about … cumecs at … hours with a short lag time of … hours.
•water reaches the river quickly because:
-BASIN SHAPE could be circular as opposed to elongated in shape which would transfer water quickly, also there could be a high DRAINAGE DENSITY in the basin, which would quickly funnel surface runoff into river channels leading to a short lag time and steeper rising limb
-perhaps there are STEEP VALLEY SIDES which would cause faster runoff resulting in short lag time and steep rising limb
-THIN SOIL would become saturated easily, which would cause rapid surface runoff short lag time and steep rising limb
•could be IMPERMEABLE ROCK which means very little water would infiltrate and percolate down through the rock to be stored as groundwater (slowing the transfer of water to the river), therefore lots of surface runoff would take place which delivers water to river rapidly meaning short lag time and steep rising limb
•may also be lack of vegetation in basin, which means that very little water is being intercepted by vegetation and stored on leaves, as soil moisture or soaked up by vegetation root systems leading to high peak discharge
•this means less water would be lost through evapotranspiration and therefore storage as condensation leading to a high peak discharge
•discharge falls at around … hours as it has completely stopped raining at … hours and the river returns to base flow where fed by groundwater
6.River wyre
•base flow discharge of river valency is about … cumecs. There is precipitation between … and … hours which causes the discharge to increase. It takes approximately … hours for discharge to rise after it started raining because very little rain falls in the main channel, it takes time for rain to reach river from drainage basin(transfers)
•peak rainfall at … there is a steep rising limb and peak discharge of first storm is … with short lag time.
•water reaches the river quickly because:
-BASIN SHAPE could be circular as opposed to elongated in shape which would transfer water quickly, also there could be a high DRAINAGE DENSITY in the basin, which would quickly funnel surface runoff into river channels leading to a short lag time and steeper rising limb
-perhaps there are STEEP VALLEY SIDES which would cause faster runoff resulting in short lag time and steep rising limb
-THIN SOIL would become saturated easily, which would cause rapid surface runoff short lag time and steep rising limb
•could be IMPERMEABLE ROCK which means very little water would infiltrate and percolate down through the rock to be stored as groundwater (slowing the transfer of water to the river), therefore lots of surface runoff would take place which delivers water to river rapidly meaning short lag time and steep rising limb
•may also be lack of vegetation in basin, which means that very little water is being intercepted by vegetation and stored on leaves, as soil moisture or soaked up by vegetation root systems leading to high peak discharge
•this means less water would be lost through evapotranspiration and therefore storage as condensation leading to a high peak discharge
•discharge falls at around … hours as it has completely stopped raining at … hours and the river returns to base flow where fed by through flow and groundwater flow
