reservoirs and aquifers

sources of fresh water

• surface stores

• aquifers, rainwater

• sea water stores via desalination

• artificial stores

factors affecting the siting of reservoirs

• topography

• geology

• catchment area

• water supply

• existing land use

• pollution risk

• sedimentation

• infrastructure

topography- perfect for reservoirs

a valley with a large volume and a small surface area

geology- perfect for reservoirs

the rock should be impermeable with no unstable faults, fissures or seismic activity

catchment area- perfect for reservoirs

the river that has been dammed should have a large catchment area to allow maximum water volume reaching the reservoirs

water supply- perfect for reservoirs

there should be reliable, regular rainfall and low evapotranspiration rates

existing land use- perfect for reservoirs

the land should be of low value, so therefore not used by any important land use

pollution risk- perfect for reservoirs

there should be no urban, industrial or agricultural activity within the catchment that might cause a risk of the water becoming polluted

sedimentation- perfect for reservoirs

little sediment - the water arriving in the reservoir would become clogged with sediment and the dam may become stressed

infrastructure- perfect for reservoirs

near to supplies of construction workers and materials, the reservoirs should not be too far from an area of high water demand

effects of reservoirs

• sedimentation

• habitats change

• microclimate changes

• reduced river flow

microclimate changes

• local temp will change, they will be cooler in the day and warmer in the night

• wind speed will be increase as friction over the water is low

• wind speed will be increase as friction over the water is low

reduced river flows

• rivers downstream from dams can start to dry up

• water quality is often poorer in rivers downstream for example they might have reduced dissolved oxygen levels

• rivers downstream will flow less which will affect nutrient levels of floodplain ecosystems

effects of over abstraction

• subsidence

• salinisation

• reduced river flow

• ecosystem changes

salinisation

• in coastal areas, if the water table is lower than sea level, the sea water will enter the aquifer

• The salt will make the aquifer unsuitable for irrigation, as it will kills the crops by osmotic dehydration

subsidence

• Water in the interstitial spaces of the rocks helps provide structural support

• Without this water, the rock particles are compacted by the weight of the material above