These processes are essential to the functioning of the natural environment and as a result, water stress can arise when the amount of water in the environment is insufficient for natural environmental processes to function and deliver the services on which people, flora and fauna depend. Typically, “environmental water requirements” are treated as a residual (King and Brown 2011), and as a result, the lack of water available for environmental needs is creating serious environmental problems. For instance, due to extensive water extractions, some large rivers in semi-arid locations, such as the Colorado and the Murray, only intermittently reach the sea (King and Brown, 2011), and the reduced flows in rivers and water volumes in lakes and wetlands has had a major negative impact on ecosystems. This transformation has also greatly reduced the water quality of the remaining water making it much more saline.