How Does Nature Filter Water?

The water on Earth has been existing for millions of years and will exist for the next millions of years. Its the same water that rained down upon our ancestors that we use today, and it will be the same water that our future generations will use thousand years from now. Nature has been working extremely hard to use this water over and over and over through its hydrological cycle. 

I think that most important thing to remember is that - Nature does not offer us polluted water. 

Nature has created a brilliant water filtration system for the water that falls on the ground. Water is naturally filtered through the natural filter pads of dense, deep layers of dirt, gravel and sand.When the raindrops fall through various forests, deserts, wetlands, and many such "living filters", they absorb excess minerals,  nutrients and impurities from the water. The remaining water then seeps in the ground. As the gravitational force pulls the water deeper, it passes through layers and layers of gravel and soil. 

Soil is an awesome natural filter which performs three very significant tasks- 

1. Restore the PH balance of the water- sands help stabilize acidic particles in waters and restore its natural balance. 

2. Filtration of the solids- air gaps between the sand particles literally trap the solids allowing only water to seep through. Some soil particles or clays have an electrochemical attraction to water and can lock up some of the chemicals on their surface through this electro-chemical reaction. 

3. Biological treatment - As water seeps deeper, the soil layer becomes very dense , the air gets thinner.Oxygen gets lesser. This loss of oxygen  kills any biological contamination surviving in the water and sterilizes it off unwanted bacteria.

By the time water seeped in the ground reaches its destination water source, it is filtered by the ground it passes through. And without giving a thought to this delicate system nature created for us, we engage in various activities that destroy living filters such as forests and wetlands, degrade and contaminate the soil structure, contaminate the water sources with our non biodegradable, hazardous, chemical wastes. And makes the natural water purification process that much harder!!!