lesson 4- the drainage basin

Question 1

what is the drainage basin?

Answer 1

an area of land surrounding a river, from which the river receives water, and subsequently drains this water

Question 2

what is surface water?

Answer 2

consists of rivers, which are a store (wetlands, lakes, oceans) AND a transfer (of water from ground to soils etc)
e.g. largest lake= Caspian sea (thought of to be 5.5 million years old)

Question 3

what is soil water?

Answer 3

water held together with air in unsaturated upper layers of earth- fundamental to hydrological and biological processes
- affects climate, weather, soil erosion etc

Question 4

what is groundwater?

Answer 4

water that collects underground in pore spaces of rock, atleast 4000m deep BUT reducing rapidly d2 extraction from irrigation

Question 5

what is biological water?

Answer 5

water stored in all biomass, varies depending on vegetation type and cover
BUT if vegetation is destroyed, this store of water also becomes destroyed, lost to atmos= climate becomes dry

Question 6

why is atmospheric water key?

Answer 6

atmospheric water absorbs, reflects, scatters incoming solar radiation
e.g. a small increase in water vapour-> increase in atmospheric temperature= positive feedback (increase global temp-> rise in global water vapour levels)

Question 7

How does the drainage system work? (9 steps)

Answer 7

1. input (precipitation)
2. precip lands on vegetation surface, provides store (interception) e.g. needle leaves…
3. water captured by veg surface is evaporated back into atmosphere
4. Throughfall- water falls from leaves on trees to ground + water also flows down stems of grass/ trees (stemflow)
5. infiltration- water enters soil
6. BUT rate of infiltration declines d2 rainstorms (soil is saturated, size of soil pores reduce-> rain clogs particles, reducing water movement)
7. water is held in soil- if rainfall intensity is greater than infiltration (infiltration capacity)-> soil becomes saturated, water builds up on surface (surface storage)
8. lateral movement of soil water= throughflow- the more vegetated an area the faster tf
9. vertical movement of soil water- percolation->groundwater passes into saturated rock, moving vertically and laterally very slowly