Water Balance

Question 1

Define water balance.

Answer 1

It’s the balance between inputs (precipitation) and outputs (run off)

Question 2

Where do rivers get their water from ?

Answer 2

Direct precipitation.
Overland flow.
If stores can release water.

As river moves down stream they’re also fed by tributaries

Question 3

River regime.

Answer 3

Difference in discharge throughout the year.

Showing annual pattern.

Question 4

What will a river regime look like in uk?

Answer 4

Discharge greater in winter / autumn months.

Than in summer.

Question 5

Water balance equation.

Answer 5

Precipitation = discharge + evapotranspiration +/- change in stores.

P = Q + E +/- S

Question 6

What are the 2 most important parts of water balance.

Answer 6

Precipitation.

Potential evapotranspiration.

Question 7

What factor is evapotranspiration close to ?

Answer 7

Temp

Higher temp=higher evapotranspiration.

Question 8

What is potential evapotranpiration ?

Answer 8

Is the amount of water than could be evaporated or transpired from an area of sufficient water availability

Question 9

What graph illustrates the relationship between precipitation and potential evapotranspiration over a year ?

Answer 9

Soil moisture graph.

Question 10

How to soil moisture budgets vary?

Answer 10

Depending on climate.

Question 11

Name the 4 components of soil moisture graph ?

Answer 11

Recharge
Utilisation
Deficit
Surplus

Question 12

Utilisation

Answer 12

When potential ET exceeds precipitation.

Water store used up by plants

Question 13

Surplus

Answer 13

Precipitation greater than ET.

All space in soil filled with water.

Ground water recharged.

Overland flow can occur - flooding.

Question 14

Deficit

Answer 14

Potential ET exceeds precipitation.

No/ little water in soil.

Plants wilt (or have adaptations to survive dry conditions xerophytes)

Question 15

Recharged

Answer 15

Precipitation exceed ET

Soil water is recharged now as soil fills.

Question 16

Describe soil moisture graph for eastern England.

Answer 16

During summer ET exceeds precipitation meaning soil utilisation and deficit occurs.

Winter/spring precipitation exceeds ET meaning stores can recharge and gain a surplus

Question 17

Describe soil moisture graph for equatorial region .

Answer 17

Temps vary very little through year.
PT stays constant.
High rainfall which exceeds PT.
High rainfall fills stores so they’re in surplus.
In short times when ET exceeds Precipitation, soil water doesn’t go into deficit so plants / rivers have store all year round.
High precipitation between Feb-June and August to November.

Question 18

Describe soil moisture graph for tropical wet/ dry climate.

Answer 18

During rainy season (July-Oct) soils recharge until surplus.
Surplus doesn’t last long when rain stops - short utilisation period.
December to July soil is dry as ET exceeds precipitation.
Vegetation has adapted to seasonal water supply so survive drought.