The situation relating to water supply can be summarised thus (Narayan Pandey et al. 2003, 54):

1) Over half of the accessible freshwater runoff globally is already appropriated for human use

2) More than 1 × 10⁹ people currently lack access to clean drinking water

3) Human population will grow but per capita availability of freshwater will decrease in the coming century

4) Climate change will intensify the earth’s hydrological cycle in the next 100 years, with generally increased precipitation, evapotranspiration, occurrence of storms and significant changes in biogeochemical processes influencing water quality.

There is, therefore, a pressing need to develop local systems that will secure water sources for the future. It is here where traditional ecological knowledge (TEK) – in particular the implementation of rain harvesting techniques - is being employed to great effect. http://www.rainwaterharvesting.org/