Nov 2003 Mark Scheme Geography HL and SL paper 2

Nov 2003 Mark Scheme Geography HL and SL paper 2 -...

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A1. Drainage basins and their management Either (a) Essay [20 marks] With reference to specific examples, explain how and why river discharge is modified by humans. Describe the consequences of these modifications. Definitions of what is meant by discharge are expected. The volume of water passing a point on a river’s course at a particular time (Q = A x V). An understanding of the fluvial system, and reference to case examples is also expected. There should be reference to a number of ways in which modification can occur. Emphasis should be placed on answering “why” and on using examples to substantiate responses. The following may be included as intentional: extraction of water for irrigation, domestic and industrial use and multi-purpose schemes, with examples such as the Colorado, the Nile; flood control schemes, construction of dams, weirs; the consequences of political control over river systems, such as River Jordan, the Nile; the canalization or diversion of channels. The following may be included as unintentional: afforestation reducing discharge and deforestation increasing discharge; deforestation in the Himalaya, resulting in an increase in the flood hazard in Bangladesh for example; terracing in SE Asia resulting in changes in the rates that water reaches channels; urbanization resulting in faster responses and greater overland / channel flow. The consequences may include an increase in the flood risk, sediment starvation downstream of dams, which may lead to greater erosion of channels and delta recession. Less discharge in the lower course may cause aggravation. Diversion of water on to terraces in the Himalaya can result in slope failure and landslides. Sediment supplies may no longer reach coastal systems, e.g. the damming of the Volta river in Ghana has resulted in serious coastal erosion in the Bight of Benin. The Colorado has been dammed in eight places resulting in a serious shortage of water downstream. The river no longer reaches the sea. A good response would include many of the points mentioned. It would also be acceptable if fewer examples are included but covered in greater detail. Allocate approximately [12 to 14 marks] for the first part of the essay and [6 to 8 marks] for the consequences. Although not explicitly, good responses may differentiate between intentional and unintentional modification. To obtain full marks responses would be expected to cover the intentional and unintentional changes. Given these considerations, marks should be allocated according to the markbands. – 3 –
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Nov 2003 Mark Scheme Geography HL and SL paper 2 -...

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