Water Balance Flashcards
Define water balance.
It’s the balance between inputs (precipitation) and outputs (run off)
Where do rivers get their water from ?
Direct precipitation.
Overland flow.
If stores can release water.
As river moves down stream they’re also fed by tributaries
River regime.
Difference in discharge throughout the year.
Showing annual pattern.
What will a river regime look like in uk?
Discharge greater in winter / autumn months.
Than in summer.
Water balance equation.
Precipitation = discharge + evapotranspiration +/- change in stores.
P = Q + E +/- S
What are the 2 most important parts of water balance.
Precipitation.
Potential evapotranspiration.
What factor is evapotranspiration close to ?
Temp
Higher temp=higher evapotranspiration.
What is potential evapotranpiration ?
Is the amount of water than could be evaporated or transpired from an area of sufficient water availability
What graph illustrates the relationship between precipitation and potential evapotranspiration over a year ?
Soil moisture graph.
How to soil moisture budgets vary?
Depending on climate.
Name the 4 components of soil moisture graph ?
Recharge
Utilisation
Deficit
Surplus
Utilisation
When potential ET exceeds precipitation.
Water store used up by plants
Surplus
Precipitation greater than ET.
All space in soil filled with water.
Ground water recharged.
Overland flow can occur - flooding.
Deficit
Potential ET exceeds precipitation.
No/ little water in soil.
Plants wilt (or have adaptations to survive dry conditions xerophytes)
Recharged
Precipitation exceed ET
Soil water is recharged now as soil fills.
Describe soil moisture graph for eastern England.
During summer ET exceeds precipitation meaning soil utilisation and deficit occurs.
Winter/spring precipitation exceeds ET meaning stores can recharge and gain a surplus
Describe soil moisture graph for equatorial region .
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.
Describe soil moisture graph for tropical wet/ dry climate.
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.
