Physical Resources

When you have read this chapter you will have been introduced to:

• the hydrologic cycle


• the life cycle of lakes


• salt water, brackish water, and desalination


• irrigation, waterlogging, and salinization


• soil formation, soil ageing, and soil taxonomy


• soil transport


• soil, climate, and land use


• soil erosion and its control


• mining and processing fuels


• mining and processing minerals

22. Fresh water and the hydrologic cycle

In the sense used here, a ‘resource’ is a substance a living organism needs for its survival. There are
also non-material resources, such as social contact and status, which may be essential to a feeling of
well-being or even to survival itself, but these are not considered here.

Non-humans as well as humans make use of the resources available to them; animals need such
things as food, water, shelter, and nesting sites, all of which are resources, as are the sunlight and
mineral nutrients required by plants. Human biological requirements are similar to those of other
animals. Like them, we need food, water, and shelter, although we differ from other species in the
means we have developed for obtaining them. It is because human and non-human requirements
often coincide that sometimes we find ourselves in direct competition for resources with non-humans.
It is not only we who find crop plants edible and nutritious, for example, and before we can build
houses to shelter ourselves we must clear the land of its previous, non-human occupants.

Water is, perhaps, the most fundamental of the resources we require. Without water, as the cliché has
it, life could not exist on land. Our bodies are largely water (by weight), and if you add together the
ingredients listed on many food packets you will find they seldom amount to more than about half
the total weight: the remainder is water.

It is not any kind of water we need, of course, but fresh water. Sea water is of only limited use to us, and
out of reach for people living deep inside continents, and drinking it is harmful, although it can be rendered
potable by the removal of its dissolved salts. For the most part, therefore, we humans must obtain all the
water we need from rivers, lakes, and underground aquifers. In the world as a whole, it is estimated that
by the year 2000 we will be using about 4350 km^3 (4.35×10^15 litres) of water a year. Of this, almost 60 per
cent will be needed for crop irrigation, 30 per cent for industrial processes and cooling, and 10.5 per cent
for domestic cooking, washing, and drinking (RAVEN ET AL., 1993, p. 273).

Of all the water in the world, 97 per cent is in the oceans, so our freshwater needs must be met from
the remaining 3 per cent. It is not even that simple, however, because of all the fresh water, more than

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90 / Basics of Environmental Science