Global warming and water sustainability

Water is a primary element in the human diet and a necessary resource for the agriculture. In addition, industrial practices need a growing amount of water. Since human population is continuously growing at a quasi-exponential rate, water demand, for domestic, agricultural and industrial uses, is increasing too. However, considering that the water resources on the Earth are finite, even disregarding the potential threats due to the climate change, this situation appears as one of the biggest challenges of the current era. Actually, one-third of the world's population is water-stressed, of which 12% severely: in these nations, a large portion of the population lives below the minimum threshold judged permissible for a decent life. In practice, almost every nation deals with problems related to water sustainability. In some countries, the water supply is ensured only thanks to the extraction of fossil water, which is a limited resource that will not last indefinitely. The impact on water quality has also dramatically increased. The scarcity of water resources is expected to spread to wider areas in the near future, mostly in developing countries, if the actual trends of development and population growth do not change. The rapid urbanizing rate will also create additional stress. Climate change can in turn alter both water supply and demand: increasing temperatures will reflect in increased evaporation and decreased stream flows. Rising seas could contaminate groundwater resources, and increasingly variable precipitation will likely mean more frequent high-intensity droughts and floods and less available rainfall in arid and semiarid regions. The effects of these changes will increase the natural variability of the climate, exacerbating the extreme climatic phenomena (drought and flood events), increasing the difficulty of managing water resources, especially in the most vulnerable regions, and affecting water availability even in regions that are not usually subjected to water shortage.