2.1
What physical factors determine the supply of water?
•
Climate•
Relief•
Geology2.1 What physical factors determine the supply of water?
• In this section students should have a good background
on the part of the water cycle involving precipitation,
evapotranspiration, runoff and groundwater transfers. Although each of
these can be considered in isolation, it is often the interconnections
between them that determine supply. Areas of high precipitation and
plentiful water supply often do not coincide with areas of demand.
Katse case study below
Water Supplies in England and Wales
and map and document
Transfer water to SE England?
• Precipitation varies greatly from place to place in amount, seasonal distribution, variability and reliability. Similar amounts under different temperature regimes may result in quite different availability of supplies.
Botswana
• High relief may promote rapid runoff, but may also provide greater
opportunities for storage. Low relief may reduce precipitation and make
storage difficult. A combination of high relief and suitable geology can
create lakes that provide natural storage.
Katse case study below
• Impermeable rocks are likely to produce rapid runoff, but they may
also help retain water in storage schemes. Porous rocks may naturally
provide underground storage, and give an even supply throughout the
year, despite uneven distribution and variability of rainfall.
Difficulties of obtaining water in a difficult climate can be found at
http://www.slcgov.com/Utilities/NewsEvents/pdf/salt_lake_city_gis_waterwrites_05.pdfWater supplies from an aquifer are well documented in
http://www.environmentagency.gov.uk/commondata/acrobat/gw_report_june2007_1831580.pdfRainfall and water supply in Norway can be viewed at
http://www.un.org/esa/agenda21/natlinfo/countr/norway/waterNorway04f.pdf