ABSTRACT
Most of the world’s water is in the oceans, and the largest proportion of fresh waters is frozen in ice caps and glaciers or stored in reserves of groundwater. e water found in rivers, lakes and wetlands together constitute less than 1 per cent of all the planet’s fresh water (see Figure 1.7), yet their relative accessibility has given these sources a disproportionate importance to humanity. Since its earliest inception, human society has seen freshwater bodies as a vital resource, and entire ancient ‘hydraulic civilizations’ developed on certain rivers several thousand years ago, notably those of the Tigris-Euphrates, the Nile and the Indus, as irrigation agriculture played a formative role in the development of complex social organization. Society is no less reliant on this fundamental natural resource today, both directly and indirectly due to fresh water’s critical importance to the functioning of numerous environmental processes, which also provide further resources and ecosystem services on which we rely. Fresh water from lakes, rivers and wetlands is utilized directly for municipal, agricultural, industrial, fi sheries, recreational and power generation uses; it forms a convenient medium for transport and a sink for wastes.
