Better management of current water sources would be a good start. Educating the public about water usage and how to conserve water instead of wasting it. People think that because we have water all over the earth there is no way it can ever run-out. What people don't realize is that only a tiny percentage of water on earth is suitable for drinking. Improved maintenance of city water supplies would save millions of gallons of water which is lost because of leeks. The government should make it mandatory for all new homes and businesses to have water saving appliances and faucets.
There are three ares of actions to avoid water shortage. The first one is the very obvious one of cutting down on the use of water by changes in our lifestyle and by technological innovations. For example, we can reduce the frequency of watering our lawn or washing our car. This involves change in lifestyle. We can also use technology to cut down on water usage. For example, we may use the washing machines that require less water.
The second measure to avoid water shortage is to ensure that maximum of the water received on land through rain, which is also the ultimated source of water in lakes, rivers, and underground sources, is collected and used for human purposes. For example, instead of letting rain water flow in to drains, we can make arrangement to collect and store it for later use.
Finally we need to avoid wastage of water, including various kinds of avoidable pollution of water. For example, instead of letting all the water used for domestic purposes, we can segregate use of water in such a way that some of it can be used for gardening. Particularly industrial use of water in some industries can be cut down substantially by treating the water discharged from industrial processes and reusing it. This also reduces land and water pollution by contaminated water discharged by industries and other sources.