water extraction case study

Question 1

where is this case study?

Answer 1

RIVER KENNET, in SOUTHERN ENGLAND
drains 1200km2 area in WILTSHIRE + BERKSHIRE

Question 2

why is water extracted?

Answer 2

several urban areas close to the catchment rely on the Kennet basin to meet PUBLIC SUPPLY- also provides for local industries and agriculture
e.g. SWINDON (population of 200,000)

Question 3

who extracts it and how?

Answer 3

THAMES WATER abstracts GROUNDWATER from upper catchment from BOREHOLES- non of this water is returned to this river as waste water

Question 4

impacts on REGIONAL WATER CYCLE

Answer 4

• rates groundwater extraction EXCEED RATES OF RECHARGE + FALLING WATER TABLE has decreased flows of River Kennet by 10-14%
• 2003 drought (flows decreased 20%)
• changes in where water is stored- less flows means less flooding, so less water stored on wetlands on flood plain
• decreased WATER TABLE results in SPRINGS and STREAMS DRYING UP- threatens ECOSYSTEMS
• can extract FOSSIL WATER which has been underground for hundreds of years and is DIFFICULT TO REPLACE (NON-RENEWABLE RESOURCE)

OVER-ABSRACTION LEADS TO DECREASED WATER FLOW IN THE KENNET BY 10-14%, DECREASING WETLAND WATER STORAGE/ FLOODPLAIN INUNDUATION

Question 5

what is water extraction?

Answer 5

water extracted from surface + groundwater to meet PUBLIC, INDUSTRIAL, AGRICULTURAL DEMAND
- direct HUMAN INTERVENTION in the WATER CYCLE- changes the DYNAMIC OF RIVER FLOW and GROUNDWATER STORAGE

Question 6

where is 2nd case study?

Answer 6

LONDON

Question 7

London context

Answer 7

• located in centre of an SYNCLINAL STRUCTURE which forms an ARTESIAN BASIN; groundwater in the chalk trapped between London Clay
• rainwater enters where it outcrops at edge of basin- groundwater than flows by gravity through chalk to centre of basin
• so, under natural conditions, the WELLS and BOREHOLES in London are under ARTESIAN PRESSURE

Question 8

impacts of water extraction in London?

Answer 8

• groundwater from the chalk is an important source of water for the capital
• but OVER-EXPLOITATION in 19th Century + beginning 20th Century caused DRASTIC DECREASE in level of groundwater (decreased 90M IN CENTRAL LONDON)

Question 9

how have the impacts changed in London?

Answer 9

past 50 years: DECREASED DEMAND for water by industry in London + decreased rates of abstraction allowed water table to recover
in early 90s: INCREASED GROUNDWATER STORAGE, threatening buildings and underground tunnels as INCREASING 3M PER YEAR of water table
- now risen and stable