Why should you save water?

You must have heard it umpteen times through your newspapers, tv channels, conservationist friends - Save Water. Have you ever thought why you should save water? I used to ask this question myself. If you put some thought into it you will understand the reasons why you should save water and this understanding will make you save water more effectively than the barrage of "Save Water" messages you see.

Water is one of the most abundant natural resources that we have. More than three quarters of the earth's surface is covered with water. Besides you can't just destroy water like that normally. You change it from one form to another and also cycles through different physical processes and biological processes. On an average the total available water content on planet earth remains almost constant.

However most of the water that we have on earth is not directly in potable form. Seawater is not, neither is water locked in marshes, swamps, salty lakes. So that leaves rivers, fresh-water lakes, ponds, wells and ground water table. Now for clarity of reasoning we can divide people into those who depend on public water supply systems (city and town dwellers) and those who depend on natural water sources directly.

Public water supply systems become necessary when people cannot practically get all the water they need on their own from nearby natural water sources. This happens when population densities rises and the local natural water bodies cannot sustain year long the water requirements of the people. So naturally this process happens in towns and cities where water is pumped from faraway and larger natural water bodies. Additionally this centralized distributions also opens the possibility of filtering and purifying the water at source and reduces the possibilities of water borne diseases. So, off late, this facility is being extended to rural areas as well.

Of the natural sources of water mentioned above, public distribution of water has to come from reasonably perennial sources and from where water can be drawn in volumes without causing too much of an imbalance in the ecosystem. So that leaves only large lakes and perennial rivers available as public water supply sources. More often than not these water bodies end up being reasonably far away from the city and it costs energy to pump the water to the city and to bring it to the homes of the inhabitants.

In a rural area where there is no public water supply, people normally depends on wells, ponds and to some extend rivers for their water supply needs. Wherever electricity is available it will be used to power pumps to draw and supply water to the homes. Also, both ponds and wells depend on ground water tables. So using water from these sources puts a pressure on the ground water table.

So we have seen two distinct reasons why we should save water
1) In both cases, where we use water from public water supply systems or directly from natural bodies, saving water will save the energy required to filter, purify and bring the water to the end user.
2) Saving water will reduce the pressure on the natural water bodies and will help in ensuring year round supply of water and also availability of water for agricultural purposes.
3) There is again a third and not so evident reason as to why we should save water. This applies only to towns and cities that depend on public water supply systems. All these systems depend on an underground network of pipes for distributing the water. The pipes only can supply a certain maximum quantity of water. If there are n users in that town/city and this maximum capacity is W liters per year, then a person using more than W/n liters of water per year will reduce the ability of other people in the same town/city to enjoy an equal amount of water as him. So saving water will help in equitable distribution of water in towns and cities. This is especially relevant in places where the topography of the land leads to unequal availability even under sub-maximal usage limits.