As the number of people increases in the world, we need to figure out how to protect our environment and to invent alternative methods to save our resources. 
Once such method would be to use hydroelectricity to power a plant that would be able to filter out salt water and clean the water so it would be drinkable and usable.  Hydroelectric power is a form of energy generated by the conversion of free-falling water to electricity.  If someone could use this power to create a machine that would be able to filter out the salt and chemicals, it would be a major development that would greatly benefit the world.  According to the National Geographic Society, the world is made up of approximately 70% water, only about 2.5 percent is fresh water, and only 1% of that is easily accessible.  If saltwater could be filtered, water could be more available to areas that lack fresh water.  This invention would not only be a game changer, but a life changer.