Variations in Runoff and the Water Cycle

Question 1

what is river discharge? and how is it measured?

Answer 1

it is the volume of water that flows in a river per second, it is measured in cumecs (m3/s)

Question 2

how can river discharge be increased?

Answer 2

high levels of run off increases it because more water enters the river so the volume is increased

Question 3

what is peak discharge?

Answer 3

this is the highest point on the graph when river discharge is at its greatest

Question 4

what is lag time?

Answer 4

this is the delay between peak rainfall and peak discharge, a shorter lag time can increase peak discharge and vice versa

Question 5

what is a rising limb?

Answer 5

this is the amount of water from lowest point to peak discharge, river discharge increases as rainwater flows into the river

Question 6

what is a falling limb?

Answer 6

this is the part of the graph after peak discharge, river discharge is decreasing because less water is flowing into the river

Question 7

how does the size of drainage basins affect runoff?

Answer 7

larger drainage basins catch more precipitation so they have a higher peak discharge, smaller drainage basins have shorter lag times because it has less distance to travel and reaches the channel quicker

Question 8

how does the ground steepness affect runoff?

Answer 8

water flows more quickly downhill in steep-sided drainage basins which shortens lag time, water also has less time to infiltrate the soil so runoff is higher

Question 9

how does rock and soil type affect runoff?

Answer 9

impermeable rocks and soil don’t store water or let it infiltrate which increases surface runoff, peak discharge also increases as more water reaches the river in a shorter period