Geography · 2003 · November · Paper 2 · HLSL · Markscheme

MARKSCHEME November 2003 GEOGRAPHY Higher Level and Standard Level Paper 2 24 pages N03/320/HS(2)M+ INTERNATIONAL BACCALAUREATE BACCALAURÉAT INTERNATIONAL BACHILLERATO INTERNACIONALc SECTION A 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-pur pose schemes, with examples such as the Colorado, the Nile; flood control schemes, c onstruction of dams, weirs; the consequences of political control over river systems, such as River Jo rdan, the Nile; the canalization or diversion of channels. The following may be included as unintenti onal: afforestation re ducing 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 increas e 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 cau se aggravation. Dive rsion 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 th e 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