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Rainwater Catchment and Soak Pits

Water Shortage, Rainwater Catchment and Water Table Replenishment

Absorption wells (soak pits) and how they can avert a water shortage. What is an absorption well, how does it work and an engineering construction drawing.

In many parts of the world a shortage of water is becoming and ever more serious problem. In Bali excessive removal of water from the water table combined with improved drainage that carries water directly to the sea is creating a looming disaster. What can we all do to use less water, replenish the water table and avert the impending water crisis?

Absorption well design, construction, design details and drawing download

A Growing Water Crisis

Bali Water Shortage

Bali is facing a major water crisis, there simply isn't enough. Water is being pumped out of the ground a lot faster than it can be replenished. PDAM, the government water supply company, is not able to keep up with demand to supply piped water and those many people on the island that get their water from bores are sucking up so much that sea water is being drawn into the water tables and is progressing further and further inland.

The worst offenders for sucking water out of the ground are, as we might expect, the hotels who, in their ever increasing demand for water are drilling bores deeper and deeper. It is also reported that the more prestigious the hotel the more water they use.

Overbuilding of Hotels in Bali

Here in Bali there has been an epidemic of hotel builidng which is taking a terrible toll on an infrastructure already creaking under the strain.

In 2001 there were around 550 hotels and 1.35 million foreign visitors to Bali, in 2015 it is estimated there are over 3,000 hotels not to mention thousands of private villas and expected foreign visitors of 4.3 million. The roads are turning into car parks, electricity supply can't cope, Bali is drowning under garbage, hotel occupancy rates are falling (64.52% in 2011, 46.02% so far for 2015) and price wars have (I am reliably informed) resulted in room rates in starred hotels falling as much as $40 per night below market rates. Already a major player in the industry has abandoned 2 new hotels which are up for sale. The hotel industry is in self destruct.

The tourism target is 30 million by 2029. In spite of appeals for sanity from the governor more hotels are being built.

In all this mess probably one of the most serious consequences we are facing is the most basic but essential need - water.

The construction of a sewerage system in the southern part of Bali is considered progress from a hygiene point of view. Unfortunately it has negative consequences for the state of the water table. The water we use in our houses (much of which is pumped out of the water table) runs into the sewer and eventually to the sea. Before the sewerage system was built most of our waste water went to our septic tanks and back into the water table.

Seawater Contamination of the Water Table

Once contaminated by sea water the water table cannot be cleaned out. Irrigating the land using saline water is a common cause of desertification as many West Australian farmers found out to their chagrin after they had cut down all the trees.

Many people don't give it a second thought, we don't even notice it but when you see steel water tanks and pipes rusting away as a result of chlorides from sea water contamination of the ground water and houses starting to crumble away from salt laden rising damp you start to understand what the fuss is about and believe me it is closer to home and far more serious than most of us realise.

Into the future where will we find water? Desalination is perhaps an option but removing salt from water is not easy. We can use distillation in which the water is evaporated into steam then condensed back into water. We can also use Reverse Osmosis in which the water is pumped under high pressure through a membrane. These are expensive processes both in terms of the cost of equipment and the high amounts of energy they use.

For more information you can contact the IDEP Foundation who have joined forces with Universitas Politeknik Negeri Bali and have started the "Bali Water Protection Program". I am sure they would appreciate any support or help they can get. You can contact IDEP through their website at

What Can We Do to Save Water?

The water crisis is, however, something we are all part of and we can all help in the solution by taking four simple inexpensive steps.

Reduce how much water we are using.

The first question is how much water are you using. It is assumed that in Bali the water consumption is 183 litres per person per day. It is estimated that in starred hotels each occupied room consumes 2,000 litres per day.

You can go to the water calculator you will find at to check how much your household is using. This will give you a breakdown of where you use water and so you can work out what you might do to reduce your consumption (take particular note of your swimming pool usage).

Plant trees

It is well recognised that trees improve the ability for the ground to absorb and retain moisture. Serious salination in Western Australia has been caused by removing the tree cover.

Get as much of the water around your property back into the ground.

The best defence is to allow as much non saline water (rainwater) to enter the water table in the fresh water zone and so keep the progress of saline sea water at bay.

Australia can teach us a lesson in how not to manage rainwater. A large proportion of land area in Australia's cities is covered by roads, car parks, pavements and buildings and, with very efficient flood drainage, much of the rainfall is prevented from replenishing the water table.

Here in Bali, drainage systems, flood drains, subaks and rivers collect much of our fresh rainwater and carry it directly to the sea preventing it from sinking into the ground and so bypassing the water table beneath.

Install an absorption well

To get the water back into the ground you can install a catchment well or soak pit (locally known as a "resapan"and also known as a rainwater catchment absorption well). An absorption well is a reverse well, a hole in the ground we put water into so it can seep away into the ground.

For more information see here Absorption well, soak pit or resapan

No Sewage in an Absorption Well

It goes without saying that you must NEVER put unprocessed sewage into an absorption well, it MUST go into a properly designed septic tank or into the government sewer.

Copyright © Phil Wilson May 2015
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