sustainable water use involves the rigorous assessment of all source of clean water to establish the current and future rates of use, the impacts of that use both downstream and in the wider area where the water may be used and the impact of contaminated water streams on the environment and economic well being of the area. it also involves the implementation of social policies such as water pricing in order to manage water demand. in some localities, water may also have spiritual relevance and the use of such water may need to take account of such interests. for example, the maori believe that water is the source and foundation of all life and have many spiritual associations with water and places associated with water. on a national and global scale, water sustainability requires strategic and long term planning to ensure appropriate sources of clean water are identified and the environmental and economic impact of such choices are understood and accepted. the re-use and reclamation of water is also part of sustainability including downstream impacts on both surface waters and ground waters.