Outline how water is transferred through a drainage basin by:

(i) infiltration;

(ii) throughflow.

Suggest how a change in the balance of water stored in oceans and ice could result in:

(i) one environmental consequence with positive effects for people;

(ii) one environmental consequence with negative effects for people.

“The benefits gained from the construction of large dams outweigh any costs.” Discuss this statement with reference to one or more major dams.

(i)

Award [1] for a simple description and [1] for some development.

For example:
Infiltration is the downward movement of water [1] from the surface/into the soil [1] / may be influenced by vegetation cover/slope angle/human impact [1].

(ii)

Award [1] for a simple description and [1] for some development.

For example:
Throughflow is the sideways/lateral movement of water within the soil [1] where downward movement is restricted [1] / moves through pores/cracks/fissures or natural pipes in the soil [1].

(i)

Consequences include: retreat of glaciers and ice shelves / ice caps; accessibility to more land (for farming); new sea floor resources found; increased water supply; changes in tourism; new shipping routes.

Award [1] for the consequence and [2] for development and/or exemplification.

For example: Arctic ice melting [1] is allowing the discovery of previously unknown oceanic resources [1], eg oil [1].

(ii)

Consequences include: rising sea levels caused by ice melt; flooding in low-lying areas; drowned features on coastlines or emergent features; coastal inundation; increased river flows; water insecurity; changes in tourism; environmental refugees.

Award [1] for the consequence and [2] for development and/or exemplification.

For example:
Ice melt is causing rising sea levels [1] which are inundating coastal areas/low-lying islands, eg Pacific atolls [1] leading to migration [1].

At least one example of a major dam should be named and located. Both benefits and costs should be discussed.

Costs could include: biodiversity loss; increased siltation; changing river load downstream (and water temperature change with ecosystem impacts); loss of water through increased evaporation; increased chances of diseases (such as bilharzia); loss of nutrients due to flood control; salinization; seismic activity; increased landslides; forced migration/displacement of population; loss of farmland; loss of historic sites; drowning of settlements; disruption of transport links.

Benefits include: power generation; industrialization; economic spin-off; prestige, water supply; irrigation; transport/navigation; flood control; supplements low river levels; fishing; recreation and tourism.

Good candidates may question from whose perspective the statement is made or may apply concepts. Another approach may be to apply scale or timescale, ie many people benefit over a broad area while only local people lose their homes, or the benefits and costs may only become clear over time.

To access band D, there should be description of some costs and benefits – do not expect balance.

For band E, there should be either explanation of a greater range/depth of costs and benefits or some discussion of the statement (considers perspective, scale, time, etc).

For band F, expect both.

Marks should be allocated according to the markbands.

The meanings of the terms “infiltration” and “throughflow” were often imperfectly understood. The use of a diagram sometimes helped the answer, and due credit was given.

This was generally well answered. A variety of different consequences was acceptable, but answers were often not sufficiently developed to warrant full marks.

Some excellent responses, mainly using Three Gorges Dam, the Hoover Dam and Aswan Dams as examples. The best answers gave range/variety/detail of costs and benefits, in relation to the particular dams chosen, and were able to make some overall evaluation. Sometimes, however, answers were general and descriptive.