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catchment hydrology (processes of the water cycle) (Evaporation (the heat…
catchment hydrology (processes of the water cycle)
Evaporation
the phase change of liquid to vapour
the main pathway by which water enters the atmosphere
heat is needed to bring about evaporation (to break the molecular bonds)
the heat on the water released condensation into the atmo
allows huge quantities of heat to be transferred around the planet
interception
vegetation interception a proportions of precip, storing it temporarily on branches, leaves and stems
eventually this moisture either evaporates (interception loss) or falls to the ground
throughfall is rainwater that os briefly intercepted before dripping to the ground
stemflow- during intense or prolonged rainfall, intercepted rainwater may flow to the ground along brances and stems
infiltration, throughflow, groundwater flow and run-off
rain falling to the ground and not entering storage follows one of two flowpaths to streams and rivers:
infiltration
by gravity into soil and lateral movement or throughflow
overland flow
across the ground surface either as a sheet or as trickles and rivulets
two conflicting idea explain the flowpaths followed by rainwater
one relates overland flow to the soil's infiltration capacity or maximum rate it can absorb rain
rainfall, regardless of its intensity exceeds infiltration, always infiltrates the soil.
Overland only occurs when soul becomes saturated and the water rises to the surface- know as saturated overland flow
where soils are underlain by permeable rocks, water seeps, or percolates deep underground
this water then seeps migrates slowly though the rock pores and joints as groundwater flow, eventurally emerging at the surface
E.g. groundwater levels on the chalk in souther England follows a distinct pattern:
by late Oct the water table is beginning to rise as temps and evapotranspiration fall.
this recharge continues until late jan.
groundwater levels than decline throughout late winter, spring and summer, reaching their lowest point in early autumn
Cryospheric processes
Ablation is loss of ice from snow, ice sheets and glaciers due to a combination of melting, evaporation and sublimation
meltwater is an important component of river flow in high latitudes and mountain catchments in spring and summer
rapid thawing of snow in upland Britain in winter is a common cause of flooding in adjacent lowlands