Hydrosphere 1 Flashcards
Human water uses
Agriculture - 70%
industry - 22%
Domestic uses - 8%
Global demand for water increasing because
- Increase population
- Increase per capita use w increased affluence
- Increase irrigation of farmland
- industrialisation
Natural hydrological cycle
Dynamic equilibrium- processes in balance
97% water in oceans
2% land ice
Importance of reservoir not just quantity also transfer rate
Residence time equation
Residence time = vol h2o in reservoir/ mean transfer rate
Human impacts in hydrological cycle - upset dynamic equilibrium
Extent and direction of change vary spatially.
Rates of change also vary
Changes to large reservoirs often more obvious.
Main impact - pollutants from domestic and industrial water use.
Human impacts on hydrological cycle
List
1Deforestation 2Agriculture- soil compaction, crop irrigation increase evap and loss soil biota reduce water retention by soil. 3Urban dev 4GCC - melting evap condensation wind patterns. 5 Water abstraction - \+river \+reservoirs \+ aquifer
Water abstraction ricer effects
Less impact if returned to river clean.
If used to carry away wastes - reduce downstream flow
Water abstraction env impacts of reservoirs
-Habitat change
-Wildlife barriers - dam can be barrier to specie eg salmon - may prevent recolonisation of other areas river
- river regime down stream of dam —> change flow rate down stream by holding water - slow flow long periods time needed for river turtle egg nest, fast flow needed wash sediment from gravel beds where salmon and trout lay eggs.
- sedimentation - not able fertilise floodplain down stream and don’t build riverbanks and coastline to counteract erosion.
- Microclimates - large body water may change local climate - high heat capacity reduce temp fluctuations and water less friction increase wind speed.
More humidity, cloud cover, ppt downwind of reservoir
Water abstraction example of over exploited river
River Nile - flow through 10 countries disagreement over abstraction for irrigation, dams regulating flow, HEP and water source. As pop increase demand h2o increase possibly leading to conflict between countries
Water abstraction aquifers
For an aquifer to form in rock, rock must have:
- porosity (chalk, limestone, sand better)
- permeability
- associated geological structures - rock below water bearing rock must be impermeable and some rock above permeable allow for recharge
Water abstraction aquifers
Aquifer recharge
Natural amount h2o aquifer in dynamic equilibrium w amount recharge h2o.
Abstraction> recharge —> aquifer decline — may take long time to b obvious but has serious consequences.
Most recharge infiltrating percolates ppt. If abstraction
impacts of over exploited aquifer
5
+Changes in surface hydrology - many water bodies fed by aquifers - land dry
+ ecological impacts water table lowered plants w high water requirements die and aquatic animals/ wetlands dry and those dependent on them die.
+salt water incursion- osmotic dehydration
+ subsidence - buildings pipelines
+ reduced supplies - nearly 1/2 world pop live where aquifers being over exploited
Monitoring aquifer depletion
Check water table in wells/ boreholes
GRACE satellites orbit affected by force gravity which influenced by mass of water in aquifers below flight path
Entire earth surveyed every 30 days
Example of overexploited aquifer
High plains aquifer USA over 450,000km2 in midW states - major agricultural regions depend on it.
Recharged during last ice age - long term abstraction rates> recharge rates
Exploitation of new water sources
- Rainwater collection
- rivers usefulness determined by:
+ total annual water flow
+ flow fluctuations
+ level natural containment’s
+ pollutants from human activities - reservoirs
- estuary barrages - fewer land use conflicts, important inter-tidal habitats and obstacle for shipping and polluted by activities anywhere in river catchment.
- seawater - desalination
Factors affecting reservoir site selection
- Topography - barrow exit from large deep basin —> small dam lots water
- Geology - Rock beneath reservoir impermeable and strong enough to hold water w out seismic activity
- catchment area
- water supply - reg and large vol and not too hot to cause excessive evaporation
- pollution risk
- sedimentation - soil erosion —>!sedimentation and reduce volume h2o reservoir can hold.
- infrastructure - nearer area of demand
- existing land use and land use conflicts
Sustainable management of water
Artificial recharge of aquifers with surplus water from high rainfall
River regulation reservoirs
Inter-basin transfers from areas of surplus to area deficit canal and pipe
Unexploited aquifers
Afforestation
Water conservation
+ low volume uses - low h2o appliances, xeriscaping (planting plants need less h2o), drip irrigation (lower evap)
+ recycling used water (grey water)
+ pollution control (oil, sewage treatment, acid mine drainage, control heavy metal waste etc)
+ reduced wastage - 20% lost to leakage UK. Repairs and gd maintenance, water meters match payment to vol h2o used - encourage conservation
Water treatment - quality meet requirements for use
See table txt book
Water treatment process
12
Sedimentation (suspended solids settle)
Screens
Aeration ( bubbles air ensure high dissolved o2 content. Toxic metals removed and stop anaerobic hydrogen sulfide)
Flocculation/ coagulation and clarification (neutralise electrostatic charges of clay by adding flocculants - mixed w water passed into clarifier tank where particles allowed to settle)
Filtration (remove suspended solids and bacteria involve gravel and sand)
Activated C filters (remove organic chem. ie pesticides which absorb onto c filter)
Sterilisation (addition Cl, O3, or exposure to UV, Cl should keep h2o sterile during distribution but gradually lost - chloramine keep h2o sterile longer as break down to gradually release chlorine)
PH control (crushes lime make less acidic)
Fluoridation (improve dental health)
Ion exchange (toxic ions eg lead, mercury and arsenic removed by adding ion exchange resins. Iona absorb onto polymer beads or zeolite particles, ion exchange can remove Ca and Mg ions produce soft H2O)
Reverse osmosis - desalination only carried out if no other water source.
Saline h2o filtered v high pressure through partially permeable membrane/ v small polyamide tubes. Fresh water collected 1/2 og volume. Salty water returned to sea. v high pressure v expensive
Distillation- boiled and steam condensed and collected
