1.1 Changes of state: Chemical structure, weak hydrogen
bonds, high boiling point, liquid at temperatures when its
low molecular mass would make it a gas. Water at surface
evaporates. 100°C and 1 atmosphere pressure, all H bonds
break, turns to gas as it boils. Narrow temp range of state
changes allows the hydrological cycle to occur.
1.2 Anomalous expansion: Water molecules in ice less densely packs than as
liquid so ice floats. Water in lake cooled by cold air, as water is cooled below
4°C, molecules take up arrangement of solid, lowers density, water expands
and cold water floats. Expansion on water is unusual. Deeper, warmer water
unaffected as further cooling produces floating ice. Layer of cold water/ice
prevents water below from freezing allowing most the lake to remain unfrozen.
1.3 Solvent: 'General physiological solvent'
most biological reactions need dissolved
water. Plant nutrients only absorbed if
dissolved in water, materials transported
in blood/sap are dissolved in water.
1.4 High heat capacity: heats, cools slowly, maintains
climatic stability by moderating temperature changes.
2 Hydrological cycle
2.1 RT=Vol/average transfer rate.
2.2 Transfer rate: volume of material
moved between reservoirs.
2.3 Residence time: average time a
molecule remains in a reservoir.
2.4 Aquifer: underground rock
structure from which water
2.5.1 Inputs: Precipitation:
impacted by global climate
change, urban heat islands.
2.5.2 Throughflow: Interception: impacted by deforestation, afforestation, urbanisation.
Infiltration: impacted by soil compaction, urbanisation. Percolation: impacted by soil
compaction. Groundwater flow: impacted by groundwater abstraction, artificial aquifer
recharge, reduced infiltration/interception.
2.5.3 Outputs: Evaporation: impacted by reservoirs, increased temps.
Transpiration: impacted by vegetation changes. River channel
discharge: impacted by abstraction, flood drainage.