Human Disruptions to the Drainage Basin

Question 1

Give five examples of human disruptions to the drainage basin?

Answer 1

• Cloud seeding
• Urbanisation
• Dam construction
• Deforestation and afforestation
• Groundwater abstraction

Question 2

What is cloud seeding?

Answer 2

This is the attempt to change the amount or type of precipitation by dispersing substances (such as silver iodide pellets or ammonium nitrate) into the air that serve as cloud condensation nuclei (hygroscopic nuclei). New technology and research claims to have produced reliable results that make cloud seeding a dependable and affordable water-supply practice for many regions, but its effectiveness is still debated.

Question 3

How does urbanisation affect the drainage basin?

Answer 3

Urbanisation creates impermeable surfaces that reduce infiltration and increase surface runoff and throughflow through artificial drains; stream and river discharges often increase rapidly as a result.

Question 4

How does dam construction affect the drainage basin?

Answer 4

Dams increase surface water stores and evaporation and reduce downstream river discharge.

Question 5

How does deforestation affect the drainage basin?

Answer 5

Deforestation leads to a reduction in evapotranspiration and also an increase in surface run-off. This increases flooding potential, leads to a decline of surface storage and a decrease in the lag time between peak rainfall and peak discharge.

Question 6

What is the impact of afforestation on the drainage basin?

Answer 6

Afforestation reverses the impact of deforestation by lengthening lag times.

Question 7

How does groundwater abstraction affect the drainage basin?

Answer 7

In some locations groundwater is abstracted from aquifers faster than it is replaced, causing reduced groundwater flow and a lower water table. In other locations, reduced industrial activity or deforestation has increased groundwater storage, increasing the risk of groundwater flooding if the water table reaches the land surface.

Question 8

Which aspect of the drainage basin does cloud seeding impact upon?

Answer 8

Precipitation

Question 9

Which aspect of the drainage basin does urbanisation impact upon?

Answer 9

Interception and infiltration

Question 10

Which aspect of the drainage basin does dam construction impact upon?

Answer 10

Evaporation

Question 11

Which aspect of the drainage basin does deforestation and afforestation impact upon?

Answer 11

Interception

Question 12

Which aspect of the drainage basin does groundwater abstraction impact upon?

Answer 12

Groundwater levels

Question 13

Give a case study example of where cloud seeding has been implemented?

Answer 13

China used cloud seeding in Beijing just before the 2008 Olympic Games to create rain to clear the air of pollution.

Question 14

Give a case study example of the impact of urbanisation on the drainage basin?

Answer 14

Across the UK, urbanisation has increased the flood risk in many towns and cities such as Winchester and Maidenhead (2014 floods) and Carlisle, York and Manchester (2015 floods).

Question 15

Give a case study example of where dam construction has been implemented?

Answer 15

Lake Nasser, behind the Aswan Dam in Egypt, is estimated to have evaporation losses of 10 to 16 billion cubic meters every year.

Question 16

Give a case study example which indicates how deforestation impacts the drainage basin?

Answer 16

Research in deforestation in Nepal shows a range of negative impacts of deforestation; for example increased surface run-off and subsequent risk of flooding in Nepal and Bangladesh.

Question 17

Give a case study example of where groundwater abstraction has been implemented?

Answer 17

Groundwater is used to irrigate more than 40% of China’s farmland and provides about 70% of drinking water in the dry northern and north-west regions.