EQ1 5.3 WATER BUDGETS AND RIVER SYSTEMS

Question 1

what is the water budget

Answer 1

there is usually a natural rhythm that balances out times of surplus with times of deficit.

Question 2

what is the best place to observe and measure the water budget

Answer 2

a drainage basin because factors within the basin control the amount of water available at any givern time

Question 3

what is water surplus

Answer 3

precipitation is greater than evapotranspiration

Question 4

what is soil moisture utilisation

Answer 4

soil moisture starts to be used up by plants

Question 5

what is soil moisture deficit

Answer 5

evapotranspiration is greater than precipitation and any previously available moisture has been used (in soil moisture utilisation)

Question 6

soil moisture recharge

Answer 6

recharge occurs when water is replaced after a drier period

Question 7

field capacity

Answer 7

the maximum amount of water soil can hold

Question 8

what inputs affect the water budget

Answer 8

precipitation, water diversion into the area, groundwater flow,surface flow, surface runoff

Question 9

what outputs affect the water budget

Answer 9

evapotranspiration,water diversion out of the area,groundwater flow, surface water flow, surface runoff, , industrial or residential use

Question 10

what is a river regime

Answer 10

the annual pattern of of discharge

Question 11

what is a simple river regime

Answer 11

river experiences a period of seasonally high discharge followed by low discharge- typical of rivers that rely on glacial melt water or seasonal storms

Question 12

what is a complex river regime

Answer 12

when larger rivers cross various relief or climactic zones eg. mississippi or are subject to human factors

Question 13

what is a storm hydrograph

Answer 13

a hydrograph is a graph showing the discharge of a river at a given point over a period of time.

Question 14

what does a hydrograph show

Answer 14

how a river responds to a particular storm

Question 15

what is the rising limb

Answer 15

water makes its way down valley sides and into the river, the discharge increases (rising limb)

Question 16

what is the lagtime

Answer 16

the gap between the peak rainfall and peak discharge is called the lagtime

Question 17

what is the water budget

Answer 17

The balance between water being evaporated from the oceans and precipitated onto the land

Question 18

what is fossil water

Answer 18

non-renewable, untouched, ancient freshwater stores

Question 19

where can we find fossil water

Answer 19

beneath deserts and in polar areas

Question 20

what is the impact of new technology on fossil water

Answer 20

New technology is now allowing us to access more of this water. For example, the extension of oil drilling technology and the use of satellite imagery can increase use of these fossil aquifers.

Question 21

what is another examples of a non-renewable store of water

Answer 21

The cryosphere (glaciers and ice caps) is another non-renewable store as it continues to melt.

Question 22

polar hydrology

Answer 22

The Polar area is also referred to as the cryosphere (ice-sheets and glaciers).
There is very little vegetation due to low temperature and limited light, so the ability for plants to grow is reduced.

Question 23

polar hydrology in winter

Answer 23

During the winter, the ground, lakes and rivers are frozen in the cryosphere. Winter snow and ice mean that 85% of solar radiation is reflected.
Permafrost is soil that is permanently frozen.

Question 24

polar hydrology in summer

Answer 24

In the spring and summer frozen water thaws in the cryosphere causing rapid surface runoff, resulting in increased evaporation.
As ice and soils thaw, biogenic gases (gases produced by or used by organisms e.g. methane) are released into the atmosphere.

Question 25

tropical hydrology

Answer 25

In the tropical rainforest, there is little seasonal variation due to the consistent temperature, high rainfall and consistent sunlight.
There is a high density of vegetation that collects the majority of precipitation.
Around 50% of the precipitation is returned via evapotranspiration.
Rainforests are able to generate their own water cycle due to convectional rainfall.
Convectional rainfall is when the forest floor is warm and so the air on the surface heats up and expands. This air rises and condenses, forming rain clouds.

Question 26

tropical rainfall deforested

Answer 26

Deforestation reduces evapotranspiration which in turn reduces precipitation levels and water supply as less water is being put back into the cycle via plants. It instead will have to flow through streams and rivers, taking longer to cycle through.
Vegetation is crucial for the area’s convectional rainfall.
Rainfall is essential for all rainforest life, so severe deforestation would have devastating knock-on effects on the rest of the ecosystem.

Question 27

rainfall in tropics

Answer 27

The tropics receive a high concentration of solar radiation so there is a lot of ocean evaporation, resulting in high rainfall.

Question 28

where does the yukon river flow through

Answer 28

it flows through alaska

Question 29

what are the weather conditions in alaska

Answer 29

Conditions in Alaska are highly variable across the seasons. In the winter, conditions are near polar, but temperatures soar in the summer.

Question 30

what climates does the yukon river flow through

Answer 30

different types of climates including the tundra and mountain

Question 31

In winter, precipitation is frozen how does this affect the flow

Answer 31

This causes the Yukon’s flow to be low.

Question 32

In summer, there is precipitation that does not freeze and also snowmelt of the winter’s precipitation. how does this affect flow

Answer 32

this causes the Yukon’s flow to be high

Question 33

is there human influence on the river yukon

Answer 33

As the area is a largely natural landscape, there is very little human influence on the river’s flow.

Question 34

what is the climate like in the amazon

Answer 34

The Amazon River flows through the Amazon rainforest where the climate is tropical.
Although the Amazon has a relatively consistent high temperature and rate of precipitation, there is some seasonal precipitation that leads to a lower river discharge.
The temperature and high biodiversity lead to very high levels of evapotranspiration.

Question 35

seasonality in the amazon affecting flows

Answer 35

consistent temperatures and rainfall create a largely consistent river flow. Some lower rainfall in September and December leads to a lower river flow.
La Niña and El Niño years also produce changes in rainfall, which affects river discharge levels.

Question 36

human influences affecting flows in the amazon

Answer 36

Deforestation affects interception, infiltration and surface runoff increasing the flow.
Large dams used by Brazilian cities for both hydroelectric power and irrigation can cause more discharge above the dam and a reduced flow below the dam.

Question 37

the murray-darling river climate

Answer 37

The Murray-Darling is in Australia where the climate is seasonal sub-tropical.
Most of the Murray-Darling’s basin is in a rain shadow.
This means that the basin is surrounded by mountains that collect most of the region’s rain. This can cause periods of prolonged drought.
The tributaries to the north experience a monsoon climate, whilst the southern tributaries experience temperate climate.
There are wet (Aug-Nov) and dry (Jan-Apr) seasons that cause high and low river flows respectively.

Question 38

seasonality in the murray-darling river

Answer 38

There is a high seasonal variability for the Murray-Darling’s discharge because of the clear wet and dry seasons.
The river is also impacted by the changes in rainfall patterns during La Niña and El Niño years.
La Niña brings cooler than normal sea surface temperatures and wetter weather to Australia.
El Niño brings the opposite; less rainfall.

Question 39

human influence in the murray-darling river

Answer 39

Water is drawn from the Murray-Darling for use in Australia’s cities and also to irrigate farms.
The natural flow paths of the river have been altered for human access, which has led to loss of habitat for local animals and a decline in quality of water.

Question 40

hydrographs

Answer 40

Hydrographs show how river discharges changes over time at a particular point in a river.

Question 41

how does increased runoff affect a hydrograph

Answer 41

Increased runoff leads to a reduced lag time and greater discharge, producing a steep hydrograph because more water gets into the river channel quicker.

Question 42

what is river discharge

Answer 42

River discharge is the volume of water flowing in a river each second and is measured in cumecs (m3/s).

Question 43

peak discharge

Answer 43

maximum discharge in the period of time.

Question 44

peak rainfall

Answer 44

maximum rainfall in the period of time.

Question 45

lag time

Answer 45

the interval between peak rainfall and discharge.

Question 46

rising limb

Answer 46

when the discharge is rising

Question 47

falling limb

Answer 47

when the discharge is falling

Question 48

how does permeable rock and soil affect the hydrograph

Answer 48

If the rock and soil is permeable (i.e. Limestone), precipitation will be able to infiltrate and percolate which lengthens the lag time and reduces the peak discharge.

Question 49

how does impermeable rock and soil affect the hydrograph

Answer 49

Impermeable rocks and soils (i.e. clay) stop precipitation infiltrating so surface runoff increases. Lag time is reduced and peak discharge is increased in these circumstances.

Question 50

how does saturated or frozen soil affect the hydrograph

Answer 50

If the soil is fully saturated or frozen by antecedent conditions, there will not be any infiltration leading to increased surface runoff, increasing the peak discharge.

Question 51

how does the steepness of the land affect the lagtime

Answer 51

The steeper the catchment of the river basin, the quicker the water reaches the river which increases peak discharge and reduces lag time.

Question 52

how does the level of vegetation affect the hydrograph

Answer 52

River catchments with high levels of vegetation will see high interception and evapotranspiration.

Question 53

how does the tree roots affect the hydrograph

Answer 53

Tree roots help to promote infiltration and results in catchments with more vegetation having a lower surface runoff, and reduced peak discharge.

Question 54

how does the shape of the catchment affect the hydrograph

Answer 54

The larger the catchment area of the river basin, the higher the peak discharge but the longer the lag time.
The more circular the catchment area shape, the shorter the lag time.

Question 55

how does the drainage basin affect the hydrograph

Answer 55

Denser drainage networks transport water more efficiently, increasing the flow and peak discharge.

Question 56

how does the land use affect the hydrograph

Answer 56

Areas that remain forested or as their natural habitat will see reduced peak discharge due to an increase in infiltration and interception of precipitation by vegetation.
There will be less interception in areas that have been deforested. This will increase the peak discharge.
Ploughing of agricultural land increases surface runoff. This causes lag time to reduce and peak discharge to increase.

Question 57

how does the urbanisation affect the hydrograph

Answer 57

Urbanisation leads to an increase in the number of impermeable surfaces (tarmac, concrete and tiles).
Impermeable surfaces lead to a decrease in infiltration, an increase in surface runoff and ultimately a reduction in the lag time. A shorter lag time means a greater peak discharge.

Question 58

how does the water management affect the hydrograph

Answer 58

Dams and reservoirs can be used to regulate the flow of the river by storing water and choosing when to release it downstream.
Abstraction of aquifers lowers groundwater levels and increases percolation and infiltration when rainfall happens.