ABSTRACT
This chapter illustrates developments in water use and societal evolution by placing water in the context of such factors as quantity, quality, technology, complexity of organisation and return on investment. There are different possible approaches to impending water problems. One approach is through conventional engineering, which tends to be complex and expensive, and requires finite fossil fuels. A high-gain system can extract resources and organise itself with minimal explicit effort. The steep energy gradient does the work of organisation. In a low-gain human system, the society must provide some of the work formerly provided by a steep gradient. The chapter also illustrates how low-gain resources must be collected and aggregated to perform useful work at the system or societal level. The transition from high- to low-gain resource extraction is characteristic of human economic activity. It is also evident in the foraging behaviour of other species, and in the emergence of species with similar subsistence strategies.
