Variations In Runoff And The Water Cycle

Question 1

What do hydrographs involve?

Answer 1

River discharge is the volume of water that flows in CUMECS

Hydrographs show the river discharge over time.

TERMS:

Peak Discharge - When the river discharge is at its highest.

Lag time - The delay between peak rainfall and peak discharge.

Rising limb - The lead up to peak discharge.

Falling limb.

Flashy - Small lag time and rapid rising and falling limbs.

Question 2

What factors can influence a hydrographs shape?

Answer 2

Size of drainage basin, Larger drainage basins catch more precipitation so have higher peak discharge.

Shape of drainage basin, Circular basins have a more flashy hydrograph as all the water reaches the river at the same time.

Topography, Water flows more quickly down steep areas and has less time to infiltrate so lag times are reduced.

Rock and soil type, Impermeable rocks increase surface runoff increasing peak discharge.

Question 3

What physical factors can impact the water cycle?

Answer 3

STORMS AND PRECIPITATION
Intense storms generate more precipitation and greater peak discharges, runoff and stores increase in size, infiltration can often not keep up with storm levels of precipitation and hence increase runoff.

SEASONAL CHANGES AND VEGETATION
Summer is often drier than winter, in the winter the temperature can drop below zero and freeze water, increasing cryospheric storage and decrease flows, the flows can be much much larger when the ice melts.
As vegetation dies back in winter interception is lowest and in the summer it is highest which can slow flows. The higher the vegetation the lower the surface runoff and percolation due to evapotranspiration.

Question 4

What human factors can impact the water cycle?

Answer 4

FARMING PRACTICES
> Ploughing breaks up the surface increasing infiltration.
> Crops increase infiltration and interception as well as increasing evapotranspiration which can increase precipitation.
> Livestock, Such as Cattle trample soil preventing infiltration and increasing surface runoff.
> Irrigation, Increase runoff and decrease groundwater stores if extracted.

LAND USE CHANGE
> Deforestation, reduces interception, when forest floor is removed it decrease interception further.
> Construction of roads and buildings create impermeable surfaces that prevent infiltration, increasing runoff, increasing flood risk.

WATER ABSTRACTION
> Water is abstracted to meet demand reducing the volume of freshwater storage.
> During dry seasons groundwater is depleted further.