Many people assume that just because water comes underground it must be clean and pure. This is a very foolish assumption and it is one of the reasons why studying caves can be very important.

Consider what a cave is. In essence it is just like a pipe created by nature. If you pour water in one end it flows through very quickly. If that water is polluted then most likely, polluted water will flow out the other end of the cave. Most caves that have creeks in them get their water from rain and runoff from the surrounding country. Water picks up pollutants, including biological contaminants, and these can wash straight into fissures in the ground, contributing to the flow of underground streams. One way of thinking of a cave is that it is just like the stormwater drains that you see beside a road. All of these drains connect and runoff from roads and parks gets dumped into our rivers. You certainly would not drink water that had flowed straight off our roads so why then, do people assume that water from underground is pure?

The reason is that not all water that flows up from underground got there the way just described. Most people are familiar with thermal springs. Deposits of water can be found at great depth within the earth. These deposits are warmed by the rock around them and due to the structure of the rock around them, the water is forced to the surface. Since this water has been underground for a long time, and combined with the heat, most of the biological contaminants will have been destroyed. This still does not mean the water is safe to drink though. If the rock that surrounds the water contains toxic minerals, these will be present in the water and can cause harm.

Areas may also be encountered where the water has seeped through rocks such as sandstone. Due to the very small spaces between the particles making up the sandstone, much of the pollutants are filtered out. There is also the time aspect, where the water has taken so long to pass through the rock that the biological contaminants have died rendering the water safe. A good rule of thumb is that unless you can be assured that water is safe, assume that it is polluted.

In regard to the water at Jenolan, the catchment area for the underground streams occur within national parks and forestry areas. Consequently the water that enters the caves is reasonably pure and safe. Water is drawn from the stream that flows through the Imperial Cave and this forms the Jenolan water supply. Some of the homes at Jenolan receive the water untreated although all water supplied to visitors has received additional treatment as a safeguard. If you wish, you can turn on any tap at Jenolan and the water that flows from that tap is drawn from the underground river.

After the water is used at Jenolan it is passed to the sewage treatment works on site to ensure the water is properly treated before being released back into the river to continue its flow to the Pacific Ocean.