The Looming Water Crisis
In many areas, a shortage of water is becoming an increasingly serious problem. In places like Bali, the excessive removal of water from the water table, combined with improved drainage that sends water directly to the sea, is creating a looming disaster. It’s essential to consider ways to reduce water usage and replenish the water table to avert a potential crisis.
Understanding Absorption Wells
An absorption well, also known as a soak pit or “resapan” in Indonesian, serves multiple crucial functions. These include:
- Providing effective drainage for areas prone to flooding.
- Acting as a septic tank soak away when a drain field isn’t feasible.
- Replenishing the water table by absorbing rainwater into the ground.
An absorption well is essentially a reverse well, a hole in the ground where water is directed to seep into the earth.
How to Build an Absorption Well
Low-Cost Construction
An absorption well can be built easily and affordably. Here’s a simplified method:
- Dig a hole in the ground, typically around 3 meters deep.
- Line the hole using 1-meter diameter concrete rings.
- Ensure the depth reaches permeable ground so the water can effectively soak away.
- The well can be covered with a concrete top and buried.
Rainwater Collection
Rainwater is considered pure and can be directed into the absorption well. A simple, 1-meter diameter empty pipe can hold a large volume of water. If one well isn’t sufficient, you can install multiple wells. Simple drainage systems can be used to collect rainwater from your property and direct it to the absorption well.
Filtration for Grey Water
You can also use absorption wells for lightly contaminated water like grey water from washing machines, washbasins, and showers. In this case, filtration is necessary.
For an effective filtration system, consider the following layers:
- 80 cm of batu kosong (loose stones) at the bottom.
- 20 cm of pasir (sand) on top of the stones.
- 20 cm of lapisan ijuk (coconut fiber) on top of the sand.
- 30 cm of kerikil (coral stone) as the top layer.
Important Note: Never put unprocessed sewage into an absorption well. It must go into a properly designed septic tank or the government sewer system.
Space-Saving Solutions
Even if you think space is an issue, an absorption well can be installed underneath the floor of your house. Although it can be buried, it is wise to have an access manhole for maintenance purposes, in case filtration layers become blocked.
Addressing Clay Soil Issues
Many properties are built on former rice fields, which often have a clay lining designed to hold water. In these cases, it’s crucial to dig through the clay layer to ensure the water can soak into the water table below.
By implementing rainwater harvesting and absorption wells, we can collectively contribute to replenishing the water table and preventing a water crisis.
