Water Balance / Water Budget

Question 1

Define Water Balance / Water Budget

Answer 1

. Shows the balance between inputs and outputs of a drainage basin system

. The water balance affects how much water is stored in the basin

. Useful for explaining if there is a DROUGHT or a FLOOD

Question 2

Inputs in water balance

Answer 2

.Precipitation

Question 3

Outputs in water balance

Answer 3

.Evaporation
. Transpiration
. Evapotranspiration
. River Discharge

Question 4

What happens in wet seasons?

i.e. winter, autumn

Answer 4

. Precipitation exceeds evapotranspiration creating a water surplus.

.The groundwater storage fills with water so there’s more surface runoff and higher discharge so river levels rise

Question 5

What happens in dry seasons?

i.e. summer

Answer 5

. Precipitation is lower than evapotranspiration creating a water deficit

. Groundwater store are depleted as water is used by plants and humans and some flows into the river channel, but isn’t replaced by precipitation

. The ground stores are recharged in the next wet season (i.e. autumn.)

Question 6

Another name for water balance

Answer 6

Water Budget

Question 7

Equation for Water Balance / Water Budget

Answer 7

Precipitation = discharge + evaporation ± change in storage

Question 8

Define Potential Evapotranspiration (PET)

Answer 8

. The amount of water that potentially could be lost by evapotranspiration from an area if there was sufficient water available

Question 9

When do rivers occur?

Answer 9

. If the stores are able to release water or if there is direct precipitation

Question 10

Define River’s Regime

Answer 10

the annual variation in the discharge or flow of a river at a particular point

. Measured in cubic metre per second

Question 11

Parts of soil water budget

Answer 11

. Soil moisture recharge
. Soil moisture utilisation
. Soil moisture deficit
. Soil moisture surplus
. Precipitation
. Potential Evapotranspiration
. Field Capacity Attained

Question 12

What does the soil moisture graph show?

Answer 12

. It is a water Budget / Water Balance graph

. It also shows the relationship between precipitation and potential evapotranspiration for a place over a YEAR

Question 13

If the ‘potential evapotranspiration’ line is somewhat constant or close to linear, what does it mean?

Answer 13

. Temperatures vary very little over the year

Question 14

Define Soil moisture surplus

Answer 14

. Occurs when precipitation exceeds potential evapotranspiration

. the period, when all the SOIL STORE are full and fully recharged.

.When there is soil moisture surplus, water might percolate down into the water table, now recharging the GROUNDWATER STORE

. There is overland flow so potential for FLOODING

. Surface stores such as puddles, lakes and rivers fill up with water

Question 15

Define Soil moisture deficit

Answer 15

. Occurs when potential evapotranspiration exceeds precipitation

. There will be a DROUGHT

. Plants wilt or may have to adapt to dry conditions or be irrigated by humans

. Water levels of rivers and other surface stores fall.

Question 16

Define Soil Moisture Recharge

Answer 16

. Occurs when precipitation exceeds potential evapotranspiration, but water need to recharge the soil moisture levels

. Soil stores are recharged UNTIL there is a surplus

. There is refilling of water in the dried up pores of soil.

. Field capacity has not been reached

. Water table rises

Question 17

Define Field Capacity

Answer 17

. The maximum amount of water soil can hold.

Question 18

Factors that affect evapotranspiration

Answer 18

. The higher the temperature. the higher the rate of evapotranspiration.

. This means that during summer, there is high potential evapotranspiration.

. Potential Evapotranspiration peaks in summer

• Refer to previous flashcards

Question 19

Define soil moisture utilisation

Answer 19

. Occurs when potential evapotranspiration exceeds precipitation

. It is when the water stored is being utilised by plants and drawn to the surface through capillary action.

Question 20

Seasonal Variation of Soil Water Budget ⁠— Autumn

Answer 20

. In autumn, the greater input from precipitation than there is output from evapotranspiration

There soil moisture surplus

1. ) This is as deciduous trees begin to lose their leaves in autumn. There is also cooler temperatures in autumn.
2. )Cool temperatures and loss of leaves means less photosynthesis.
3. )If there is less photosynthesis, the stomata of plants remain closed.
4. )This means less transpiration, as less water vapour is loss through the plant
5. ) There is also less uptake from the capillaries from plants due to less photosynthesis. This means less soil moisture utilisation
6. ) There is also less evaporation from the surface and soil due to cooler temperatures

. This means that soil moisture levels increase and a soil moisture water surplus occurs

. There will be a decrease in vegetation storage and increase in soil storage

. There MAY be recharge (refer to graph)

Question 21

Seasonal Variation of Soil Water Budget ⁠— Winter

Answer 21

. Potential evapotranspiration from plants reaches a MINIMUM due to colder temperatures.

. There is soil moisture surplus

1. ) This is as deciduous trees being to lose their leaves in winter. There is also cooler temperatures in winter.
2. )Cool temperatures and loss of leaves means less photosynthesis.
3. )If there is less photosynthesis, the stomata of plants remain closed.
4. )This means less transpiration, as less water vapour is loss through the plant
5. ) There is also less uptake from the capillaries of plants, as there is less photosynthesis. This means less soil moisture utilisation. There is increased soil storage and decreased vegetation storage
6. ) There is also less evaporation from the surface and soil due to cooler temperature

. There MAY be recharge (refer to graph)

Question 22

Seasonal Variation of Soil Water Budget ⁠— Summer

Answer 22

. Hotter weather lead to utilisation of soil water, because evapotranspiration peaks and precipitation is at an MINIMUM

. Plants need to utilise their soil moisture for photosynthesis due to the warmer temperature

. Plants photosynthesise more due to warmer weather and leaves growing again of deciduous trees

. More transpiration as stomata of plants open due to photosynthesis

. There will be a water deficit as the output of potential evapotranspiration is greater than the input of precipitation. The soil water stores are depleting. There will also be increased vegetation storage.

Question 23

Seasonal Variation of Soil Water Budget ⁠— Spring

Answer 23

. Around February and March, plants being to grow

. This means photosynthesis increase, as deciduous trees grows leaves back and also temperatures increase

. This means that transpiration can be released as water vapour from the stomata

. This is also some soil moisture utilisation from plants, due to more photosynthesis

. Potential Evapotranspiration increase and there is a water surplus

. There is more vegetation storage and less soil storage

• They may be soil moisture recharge

Question 24

Why is there more precipitation in colder months (i.e winter) ?

Answer 24

. Cold air carries left water as the water vapour molecules are less likely to be in a gaseous state

. Warmer air carries more water as the water vapour molecules are more likely to be in a gaseous state

Question 25

KEY THING to remember about seasonal variation in the soil water budget

Answer 25

. Countries may have VERY DIFFERENT water budgets, depending on CLIMATE

. However, the SEASONAL water budget variations will be MAYBE similar. Use the previous flashcards but use in the CONTEXT of the soil water budget

. It is only the months of this season that differ

. For example, winter in UK is from December to March

. However, winter in Australia is from June to August

Question 26

What happens in Summer?

Answer 26

. More potential evapotranspiration

. Less precipitation

Question 27

What happens in Winter?

Answer 27

. Less potential evapotranspiration

. More precipitation

Question 28

EXCELLENT Exam question page

Answer 28

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