Variations in Runoff

Question 1

What is River Discharge?

Answer 1

The volume of water (in m3) that flows in a river per second. Measured in cubic metres per second, or known as cumecs.

Question 2

What is a Hydrograph?

Answer 2

Graphs of river discharge over time. Show how the value of water flowing at a certain point in a river changes over a period of time.

Question 3

What would you see on a Hydrograph?

Answer 3

Peak Discharge
Lag Time
Rising Limb
Falling Limb

Question 4

What is a flashy hydrograph?

Answer 4

Steep, roughly symmetrical rising and falling limb.
Short lag times and high peak discharge
The basin will have rapid runoff and not much storage capacity.

Question 5

Amount of runoff and hyrograph shape can be affected by what?

Answer 5

• Size of Drainage Basin
• Shape of Drainage Basin
• Ground steepness
• Rock and Soil type

Question 6

What Physical factors affect the Water Cycle?

Answer 6

Storms and Precipitation

Seasonal changes and Vegetation

Question 7

How do Storms and Precipitation change the Water Cycle?

Answer 7

• Intense storms generate more precipitation, greater peak discharges
• Larger input of water causes flows and stories to increase in size
• Flows may occur rapidly, increasing runoff

Question 8

How to Seasonal changes and Vegetation change the Water Cycle?

Answer 8

• Size of inputs, flows and stores varies with seasons
  E.g Winter, stores freeze, reduce flows, when it thaws flow through the drainage basin will be much larger.
• Seasonal variation of plants. Vegetation intercepts precipitation, slows movement. Highest when more trees, deciduous trees have their leaves.
• More vegetation, more water lost through evapotranspiration, reduce runoff and peak discharge.

Question 9

What Human activities affect the Water Cycle?

Answer 9

Farming Practices
Land Use Changes
Water Abstraction

Question 10

How do Framing Practices change the Water Cycle?

Answer 10

Will affect infiltration rates;

• Ploughing: breaks up surface, more water can infiltrate, reduce runoff.
• Crops: increase infiltration and interception, reduce runoff and more evapotranspiration.
• Livestock: trample and compact soil, decrease infiltration, increase runoff
• Irrigation: increase runoff as not all water can infiltrate. Ground water or river levels may fall as water is abstracted for irrigation.

Question 11

How do Land Use Changes change the Water Cycle?

Answer 11

• Deforestation: reduces amount of water intercepted by vegetation
• New buildings and roads: creates impermeable layer, prevent infiltration, increases runoff. Water will move through system rapidly and lead to flooding

Question 12

How does Water Abstraction change the Water Cycle?

Answer 12

• Water abstracted to meet demand in densely populated areas. Reduces water in stores.
• Dry seasons, water abstracted from stores for consumption and irrigation, deplete stores further.