Water is a renewable resource in the sense that it replenishes itself through rain. However, it is possible to use water in ways that render it a non-renewable resource.
A renewable resource is any natural resource that replaces itself given enough time. The rate of replenishment must be equal to or faster than the rate of usage. As water continuously evaporates from the Earth's surface, it collects in the atmosphere to later come back to the Earth as rain. On the Earth itself surface water replenishes groundwater, and groundwater replaces surface water. With careful management and responsible usage, water is a renewable resource.
There are increasing concerns about water scarcity in many parts of the world, particularly in developing nations or regions of high population density. Only 3 percent of the Earth's water is fresh water, and only one-third of that amount is usable for drinking water. The rest of Earth's fresh water is part of ice caps and glaciers. In many of the world's most populous regions, potable water is a scare commodity because of overuse, mismanagement and pollution.
Hydroelectric power is one important use of water as a renewable resource. Water power is efficient, produces very little waste comparative to other energy sources and the water is reusable.