Water Abstaction From The Chalk Of Southern England Flashcards
(18 cards)
Where does the water come from that supplies the chalk aquifer?
Rainfall that lands on the chalk hills of the North and South Downs and the Chilterns.
When does recharge take place?
During winter months when potential évapotranspiration is low and soil moisture deficits are negligible.
How do groundwater amounts vary?
Seasonally
Levels rise from autumn through winter into spring.
What happens to évapotranspiration and rainfall during the summer months?
Potential évapotranspiration generally exceeds rainfall.
What happens to soil deficits and percolation in the summer?
Soil moisture deficits build up and little percolation takes place.
Where does water abstraction happen?
At boreholes.
Why is the pattern of water transfer not constant?
It varies overtime and location.
What can rivers fed by groundwater from chalk aquifers have?
Intermittent sections.
What are the intermittent streams known as?
Bournes
What are bournes a natural characteristic of?
Chalk downlands
What aspect of the springs that feed the rivers changes each year?
The positions change
Greater altitude at winter and spring
What can happen if there are one or more dry winters?
The effective rainfall available for recharge is low and therefore these rivers can dry up altogether.
Where have some of the most acute problems with over abstraction been found?
In chalk stream systems
What percentage of flow for chalk stream systems is derived from underground aquifers?
95%
What do the catchments of chalk stream systems provide?
Underground reservoirs of high quality water that can be abstracted for public supply.
What has dramatically reduced the flow in many chalk streams?
Abstraction for public water supply and industry
When is public water demand the highest?
During dry summers
What are the human problems associated by overabstraction?
Inability to fish
No river views due to encroaching vegetation
No recreational activities
