The river basin - hydrosphere

Question 1

Inputs of water

Answer 1

rainfall
rivers and streams flowing into the sea
groundwater seepage into the soil
evaporation from the sea and rivers

Question 2

outputs of water

Answer 2

water is lost from the drainage basic either by the rivers and its tributaries carrying it out into the sea
or by evapotranspiration (water being lost directly from vegetation, water surfaces and from the ground.

Question 3

questions to answer on a hydrograph

Answer 3

• when did the precipitation start?
• how long did it precipitate for?
• when it started was it heavy or light?
• did it stop suddenly or tail away?
• how long was it after the highest peak precipitation until the river was at its highest?
• how quickly did it return to base (normal)?
• what was the peak river flow?`

Question 4

Things to refer to in the hydrograph:

Answer 4

rising limb
recession limb
lag time 
rainfall intensity 
peak flow compared to base flow
recovery rate, back to base flow

Question 5

Human activities and influences

Answer 5

• mining: opencast mining results in silting up of lakes, reservoirs and rivers reducing storage capacity. Reduced vegetation cover
• deforestation: results in increased run-ff. Plant roots reduce through flow by taking up water from the soil
• Climate change: can cause alterations in river discharge. There will be an increase in rainfall with more storms in some areas
• Over-grazing: leave areas with less vegetation’s, resulting in similar outcomes as deforestation (increased run-off)

Question 6

Physical activities and influences

Answer 6

-geology: rocks can be permeable (allowing water to flow through), impermeable (not allowing water to flow through) or Porous (allowing water to soak through and be stored); impermeable means faster surface run off; permeable or porous absorbs water which slows down run off and increases lag time.
- vegetation: intercepts precipitation and slows movements of water into river channels which increases lag time; water is lost through evaporation and transpiration reducing the peak discharge of a river
- Drainage density: basin’s with more streams drain more quickly, so have shorter lag time.
- Temperature: low temperatures means water stored as snow/ice which reduces run-off; melting when temperatures rise increases run-off; higher temperatures increases evapotranspiration reducing surface run-off
(hard baked or frozen soils are impermeable)