Storm hydrographs-83

Question 1

what do hydrographs show?

Answer 1

variation in a rivers discharge over charge

Question 2

what is discharge?

Answer 2

the volume of water passing through a river at a given time

Question 3

what is shown by the bars?

Answer 3

precipitation

Question 4

what is shown by the line?

Answer 4

discharge of the river

Question 5

what is lag time?

Answer 5

time between peak rainfall and peak discharge

Question 6

what happens when it starts to rain?
(stage 1)

Answer 6

rain is absorbed by the soil, which saturates the river as its pores fill with water, so discharge isn’t increased

Question 7

what happens when the soil is saturated? (stage 2)

Answer 7

all rainfall cant infiltrate soil, so it increases discharge
creates the rising limb

Question 8

what happens on the falling limb

Answer 8

water evaporates, and runoff makes it fall off the drainage basin system, and away,decreasing discharge

Question 9

what effect does the size of a drainage basin have?

Answer 9

Lag time is shorter and peak is higher in a small basin
-as water reaches the river channel quicker due to a shorter distance to travel

Question 10

what effect does the relief of a drainage basin have?

Answer 10

lag time is shorter and peak is higher in a steeper basin
-as water reaches the channel quicker when it is travelling downhill

Question 11

what effect does the intensity of precipitation have?

Answer 11

lag time is shorter and peak is higher after intense rainfall
-more water falling than water infiltration

Question 12

what effect does the type of precipitation have?

Answer 12

lag time is slower and peak is lower after snowfall
-as snow takes time to melt

Question 13

what effect does the urbanisation have?

Answer 13

lag time is faster and peak is higher in an urbanised area
-as surface runoff is higher in areas with concrete and tarmac, so water reaches the river basin quicker

Question 14

Case study- river Ribble- Lancashire
-during intense storms, the hydrograph has a ____ lag time and a ____ peak.
-upper course is made of _________, stores ____water and slows down discharge increase. _____ river basin. Flows through _______ areas such as ______.

Answer 14

during intense storms, the hydrograph has a short lag time and a high peak.
-upper course is peat soil, stores groundwater and slows down discharge increase. Large river basin. Flows through urbanised areas such as Burnley.