World Physical and Regional Geography

Of the earth's total water, about 97.5 per cent is saline and about 2.5 per cent is fresh. Within that fresh fraction, roughly 68 to 69 per cent is locked in ice caps, glaciers and permanent snow, and roughly 30 per cent is groundwater. Those two together account for about 99 per cent of all freshwater. The question removes the ice and asks what dominates the remainder, and the answer is groundwater by a very large margin, so option (c) is correct.

• Option (b) is incorrect: surface freshwater in lakes and rivers is about 0.3 per cent of freshwater, which makes it the most visible and most used store but a very small one, and rivers alone are a vanishingly small fraction of that.
• Option (d) is incorrect, soil moisture being about 0.05 per cent of freshwater, and option (a) is incorrect, atmospheric water vapour being about 0.04 per cent, the smallest of the four despite its central role in the hydrological cycle because its residence time is measured in days. The governing principle, and the reason this is easier than it looks, is that stores with long residence times hold large volumes: ice and groundwater turn over in centuries to millennia, while the atmosphere turns over in about nine days.

The passage carries three tests and only one region satisfies all three. Extreme climate means a large annual range of temperature, which requires continentality. Scanty rainfall points to a semi arid regime. Nomadic herding as the traditional way of life points to a grassland too dry for settled cultivation and to a pastoral society. The Central Asian steppe of Kazakhstan, Mongolia and southern Russia satisfies all three: it lies deep in the interior of the largest landmass on earth, with bitter winters and hot summers, rainfall of roughly two hundred and fifty to five hundred millimetres, and a pastoral nomadic tradition running from the Scythians through the Turkic peoples to the Mongols, which is why option (b) is correct.

• Option (a) fails on two counts: the African savannah lies in the tropics and has no extreme annual range, and its rainfall is substantial though strongly seasonal, in the region of five hundred to fifteen hundred millimetres; its pastoralists, the Maasai and the Fulani, are real but the climate description does not fit.
• Option (c) fails on the human criterion above all: the North American prairie is a temperate grassland with a genuine continental range, but its inhabitants were bison hunters rather than herders and it became the wheat belt of the continent, no pastoral nomadic tradition being associated with it.
• Option (d) fails because the Siberian tundra is a cold desert of permafrost, moss and lichen rather than a grassland, and though reindeer herding is practised there the vegetation and the temperature regime do not answer to the description of a grazing steppe. The elimination route is the herding tradition, which is what the word nomadic is doing in the passage.

• Option (c) is correct. Seasonal reversal of the prevailing wind direction is the defining property of the monsoon, and the word itself derives from the Arabic mausim, meaning season. The reversal arises from the seasonal migration of the thermal equator and the Inter-Tropical Convergence Zone, the differential heating of land and sea and, in the South Asian case, the crossing of the equator by the south-east trades and their deflection to the right by the Coriolis effect to become the south-west monsoon. In winter the pressure pattern reverses and the flow is offshore from the continental high.
• Option (a) is incorrect: the equatorial climate is characterised by convergence, convectional afternoon rainfall throughout the year, low pressure and light variable winds, and there is no seasonal reversal.
• Option (b) is incorrect: the Mediterranean climate arises from the seasonal shifting of pressure belts, giving westerly cyclonic rain in winter and offshore trade wind influence with drought in summer, which is a seasonal change of regime but not a reversal of wind direction in the monsoon sense.
• Option (d) fails once either of the first two is rejected. The item is decided by holding the word monsoon to its own meaning.

• Option (b) is correct. The passage describes the diurnal convectional regime of the equatorial climate. Intense insolation on a nearly vertical Sun heats a humid surface, air rises in strong convection currents through the day, towering cumulonimbus builds by early afternoon, and a violent but short lived thunderstorm follows, often called the four o'clock rain, after which the sky clears. The decisive words are each day is more or less the same: the equatorial belt has small annual range of temperature, rain in every month and effectively no seasons, only a daily rhythm, and the writer describes a day rather than a season for that reason.
• Option (a) is wrong: the savannah has a sharply marked wet and dry season, so no day can stand for the year.
• Option (c) is wrong for the same reason, the monsoon being defined by seasonal reversal of wind and a long dry season.
• Option (d) is wrong: the Mediterranean regime has dry warm summers and wet mild winters, and its summer is the season of drought, not of daily thunderstorms. The governing principle is that a passage describing a typical day rather than a typical year can only describe a climate without seasons.

• Statement 1 is correct. The Aral Sea is the standard textbook case of anthropogenic desiccation. Soviet era diversion of the Amu Darya and Syr Darya for cotton irrigation from the 1960s onward cut off the inflow to an endorheic basin, and with evaporation continuing unchecked the lake lost the great majority of its area and volume and split into separate remnant water bodies, leaving the salt and pesticide laden Aralkum desert behind.
• Statement 2 is incorrect. The Black Sea is a large marine basin connected to the Mediterranean through the Bosporus and Dardanelles and fed by the Danube, Dnieper and Don; it has serious pollution and anoxia problems in its deep water, but it has not shrunk or dried up.
• Statement 3 is incorrect. Lake Baikal is the deepest and most voluminous freshwater lake on Earth, holding roughly a fifth of the world's unfrozen surface fresh water; it faces pollution and species pressure but no desiccation. Elimination route: the governing distinction is hydrological, between a closed basin with no outlet, where any diversion of inflow translates directly into loss of area, and an open or connected basin, where it does not. Only the Aral Sea is endorheic among the three, so only statement 1 can be correct and (a) follows without any need for further recall.

Hence (a).

• Pair 1 is incorrect. The Mekong rises on the Tibetan plateau, runs through China, Myanmar, Laos, Thailand and Cambodia and empties through its delta in southern Vietnam into the South China Sea; the Irrawaddy and Salween are the rivers that reach the Andaman Sea.
• Pair 2 is incorrect. The Thames flows eastward through London and enters the North Sea through its estuary, the Irish Sea lying to the west of Britain and receiving the Mersey and the Severn by way of the Bristol Channel.
• Pair 3 is correct, the Volga being the longest river in Europe and draining into the Caspian, an inland basin, which is why it is a river of internal drainage.
• Pair 4 is correct, the Zambezi crossing southern Africa past the Victoria Falls and reaching the Indian Ocean through Mozambique. The answer is 3 and 4, giving (c).

The question tests the ranking of freshwater reservoirs. Of all water on Earth roughly 97 per cent is saline ocean and about 3 per cent fresh. Within that freshwater fraction, glaciers and polar ice hold approximately 68 to 69 per cent, groundwater approximately 30 per cent, and surface water in rivers and lakes barely 0.3 per cent.

• Statement 1 is therefore incorrect by a very wide margin, rivers and lakes holding far less than groundwater.
• Statement 2 is correct, ice exceeding groundwater. Hence (b). The ordering to memorise is ice, then groundwater, then surface water, and it explains why groundwater depletion is so consequential: it is the largest reservoir of fresh water actually accessible for human use.

Lake Faguibine lies in northern Mali, in the Sahelian floodplain fed by the Niger through a system of channels near Timbuktu. Successive droughts from the early 1970s, compounded by reduced flood inflow and silting of the feeder channels, dried the lake, and its bed has since been colonised by sand and scrub, so that a formerly extensive water body now presents a desert landscape.

• Option (a) is wrong on location before anything else: Lake Victoria is in East Africa and remains the continent's largest lake by area.
• Option (c) is wrong because Lake Oguta, in Imo State in southeastern Nigeria, is a small natural lake that has not dried.
• Option (d) is wrong because Lake Volta in Ghana is not a natural lake at all but one of the world's largest reservoirs by surface area, impounded by the Akosombo Dam, and it holds water.

Hence (b).

The Levant is the historic name for the lands along the eastern shore of the Mediterranean, covering Syria, Lebanon, Israel, Palestine, Jordan and the adjoining coastal fringe of southern Turkey, with Cyprus sometimes included. The name derives from the rising of the sun in the east, which is the sense in which the region was seen from western Europe.

• Option (a) states this and is correct.
• Option (b) describes the Maghreb, the western North African belt from Egypt through Libya, Tunisia, Algeria and Morocco, which lies on the opposite side of the Mediterranean basin.
• Option (c) conflates two distinct regions, the Persian Gulf littoral and the Horn of Africa, neither of which touches the Mediterranean at all.
• Option (d) is wrong by overextension: the Levant is one segment of the Mediterranean coast, not the whole of it, and taking the entire littoral would absorb southern Europe and North Africa into the term.

Hence (a).

The Canada United States border is the longest international boundary in the world at roughly 8891 kilometres, including the Alaska Yukon and Alaska British Columbia sections, and it is also the longest undefended border.

• Option (d) is the closest competitor and the intended trap, since the Kazakhstan Russia border at about 7644 kilometres is the longest continuous land border without a maritime interruption, but it is still shorter overall.
• Option (b) is wrong because the Chile Argentina border along the Andes runs to about 5300 kilometres, long but well short of the leaders.
• Option (c) is wrong because the disputed China India boundary is roughly 3488 kilometres by the Indian reckoning, not remotely in contention. A candidate who recalls only that the answer is a very long northern hemisphere boundary must still separate Canada United States from Kazakhstan Russia, which is what the question is testing.

• Statement 1 is correct, since Lake Turkana is the largest permanent desert lake and the largest alkaline lake in the world, fed mainly by the Omo river and having no outlet, so that it loses water only by evaporation.
• Statement 2 is incorrect and is the eliminator on two separate counts. The lake lies in northern Kenya with its northern tip extending into Ethiopia, not in South Sudan, and it occupies a basin of the Great Rift Valley in East Africa, which is thousands of kilometres from the Sahara.
• Statement 3 is correct, since the Lake Turkana National Parks are inscribed on the World Heritage List, partly for the hominin fossil record of Koobi Fora, and the lake is popularly called the Jade Sea from the blue green colour imparted by algae.

Hence 1 and 3 and (b) is correct, while (c) and (d) accept the misplacement of the lake and (a) drops the World Heritage and Jade Sea facts.