CDS (I) 2022 General Knowledge · Question 100 of 120

Correct — B, water in usable condition. The stem asks for a resource that satisfies two conditions at once — it can run out, and it can be renewed — and only fresh water in a usable state does both. The hydrological cycle keeps returning water to the land as rain and snowmelt, so the stock regenerates on a human timescale; that is the renewable half. But at any given place and time the quantity fit to drink and irrigate with is finite, and it can be drawn down faster than it is replaced or spoiled by pollution until it is no longer usable; that is the exhaustible half. India's own aquifers are the standard illustration, with groundwater in parts of the north-west being pumped out far faster than the monsoon puts it back. This double character is why water sits in a category of its own between resources that can never be used up and resources that never come back.

• (a)Solar energy — Solar energy fails the first test rather than the second. It arrives continuously and human use makes no measurable dent in it, so it is classed as inexhaustible or perpetual, not as exhaustible. A resource has to be capable of running out before the question of renewing it arises.
• (c)Soil — Soil fails the renewability test on any timescale that matters to people. It can certainly be exhausted — eroded, salinised, built over — but the weathering and organic accumulation that build a soil profile work over centuries and millennia, which is why soil is grouped with the exhaustible resources that do not come back. Its fertility can be restored by management; the soil body itself cannot be regrown to order.
• (d)Landscape in its natural condition — A natural landscape is the clearest one-way case in the list. Once a valley is flooded by a reservoir, a hillside quarried or a wetland drained and built on, the original landscape is gone; what can be created afterwards is a new one, not a renewal of the old. It is exhaustible and non-renewable.

Natural resources are sorted first by whether human use can exhaust them. Those that cannot be exhausted — solar radiation, wind, tides, the atmosphere as a whole — are called inexhaustible or perpetual. Those that can be exhausted split again. Some are renewable, meaning natural processes replace them at rates comparable to the rates at which people use them: fresh water, forests, fisheries, wildlife. Others are non-renewable, meaning replacement is so slow that the stock is effectively fixed: minerals, fossil fuels, soil bodies and undisturbed landscapes. The question is built on that three-way scheme, and the phrase 'water in usable condition' is a giveaway that the scheme is what is being tested.

Two of the four options are decided by the word exhaustible and two by the word renewable, so it helps to apply the tests in order. Solar energy goes out on the first test. Soil and natural landscape survive the first but fail the second. Water is the only one left. Candidates most often stumble on soil, because school textbooks that use a simple renewable-versus-non-renewable split usually park soil on the renewable side along with water and forests. On the finer three-way scheme this paper is using, soil belongs with the slow-forming resources, and it is worth being honest that the two schemes give different answers for soil — the exam's option set, with 'water in usable condition' spelled out in exactly the phrasing the three-way scheme uses, tells you which one it wants. As a practical matter the distinction is what makes water policy urgent: a renewable resource can still be destroyed by using it faster than it returns.

• Inexhaustible or perpetual resources — solar energy, wind, tides — are not measurably reduced by human use.
• Exhaustible resources divide into renewable ones, which natural processes replace on human timescales, and non-renewable ones, which they do not.
• Fresh water in usable condition is the standard example of an exhaustible but renewable resource: the hydrological cycle replaces it, but a local stock can be drawn down or polluted beyond use.
• Soil profiles and undisturbed natural landscapes take so long to form, or cannot be recreated at all, that they are grouped with the non-renewable resources.
• A renewable resource stops behaving renewably once the rate of use exceeds the rate of replenishment, which is the condition of over-exploited aquifers.

• Choosing solar energy because it is the resource most often labelled renewable. Renewable is only half the test; solar is not exhaustible at all.
• Choosing soil on the strength of the simpler two-way classification used in school textbooks, which puts soil with the renewables.
• Reading 'water' rather than 'water in usable condition'. The qualifier is what makes the resource exhaustible.

As a which-one-belongs-to-this-category item, as a match between resources and their classification, or as a statements item on renewable and non-renewable resources.

No directly related past PYQ was found.

• practice — not a real PYQ

  Which one of the following is best described as an inexhaustible natural resource?

  • (a)Coal
  • (b)Groundwater
  • (c)Tidal energy
  • (d)Topsoil

  Answer(c) Tidal energy — it is driven by the Earth-Moon system and human use does not reduce it. Coal and topsoil are exhaustible and effectively non-renewable, and groundwater is exhaustible though renewable.

• practice — not a real PYQ

  A renewable resource behaves like a non-renewable one when

  • (a)it is found in only a few countries
  • (b)the rate of use exceeds the rate of natural replenishment
  • (c)its price rises sharply in world markets
  • (d)it is owned privately rather than in common

  Answer(b) the rate of use exceeds the rate of natural replenishment — an over-pumped aquifer or an over-fished stock is renewable in principle and exhausted in practice.