Ground Water Level and Flood Risk
In big and highly-populated cities like Jakarta, flooding is not something new. In addition to the high amount of rainfall, flooding in the capital city is often worsened by the lack of water catchment area. According to Sutopo Purwo Nugroho, Head of Data, Information, and Public Relations in Indonesian National Board for Disaster Management (BNPB), as much as 85% of the rainwater that fell is converted into surface water instead of ground water. This is due to the fact that most of the land surfaces are covered with either concrete or cement, thus making the rainwater unable to be absorbed into the soil. Moreover, Mr. Sutopo also stated that Jakarta’s ground surface can only absorb 15% of the puddles that are formed into the ground.
Furthermore, during dry season, such condition might cause citizens to suffer from water scarcity due to lack of water reserves inside the ground. To make matters worse, ground water scarcity will cause yet another problem, which is subsidence or ground sinking. In fact, according to World Bank, approximately 40% of Jakarta area is already below sea level.
Now here comes the important question: is there anything that can be done to prevent those problems from happening? Or at least to mitigate the damage?The answer is yes, there is, and it’s even better because every person can do it at home, which is to make biopore filtration holes.
What is Biopore Infiltration Hole?
The term biopore itself refers to holes or small tunnels that are formed underground and resulted from the activities of organisms such as worms, termites, plant roots, etc. This concept of biopore is being replicated through the biopore infiltration hole. The biopore infiltration hole is a cylindrical hole (usually coated with plastic pipe) that is planted in the ground vertically. Biopore infiltration holes usually has a diameter of 10 cm and is planted with a depth of 100 cm.
Benefits of Biopore Infiltration Holes
Biopore infiltration holes possess multiple benefits such as:
- Help in reducing organic waste .Kitchen waste such as fruit and vegetables scraps can be put inside the biopore infiltration holes,which later on will be converted into compost. This activity can help in reducing the amount of waste that would end up in the soon-to-be-overload landfills. Moreover, the process of filling the biopore holes with organic waste will indirectly train people to sort their waste into at least two categories: organic and inorganic.
- Fertilize the Soil. Biopore holes will make the soil friable because it comprises of both air and water. In addition, organic waste that are put inside the biopore holes will stimulate microorganisms activities that will decompose the waste into compost. The compost will then increase the fertility of the soil and can also be used to fertilize plants.
3. Prevent Flooding and Increase Groundwater Reserves. With the existence of biopore holes, it will be easier for rainwater to be absorbed into the soil, since biopore infiltration holes will increase the area of infiltration up to 40 times as much. Consequently, groundwater reserves will increase, which also helps to reduce the risks for both flooding and drought.
4. Reduce the forming of puddles during rainy season. This is important because puddles are an ideal breeding ground for mosquitoes, which carry many diseases such as malaria and dengue fever.
Placement of Biopore Infiltration Holes
The first thing that needs to be done before making biopore infiltration holes is to decide the right spot for the biopore holes. Biopore infiltration holes should be made in areas where water will naturally gather. That being said, biopore infiltration holes can be made at the bottom of a gutter, near trees, in lower grounds of house yards, or in park boundaries. Also, biopore holes should be made in areas where only few people would pass to prevent them from being mired into the holes, and consequently, to prevent the biopore covers from being damaged.
How to Make Biopore Infiltration Holes
The tools that need to be prepared in order to make biopore holes are as follow:
- Ground drill or crowbar
- Plastic pipe with a diameter of 10 cm along with the pipe cover that has been perforated
- Organic waste
And here are the steps:
- Wet the soil using water. This will help to soften the ground and make it easier to be dug into.
- Start digging the hole using ground drill or crowbar. If you are using the ground drill, after the drill bit have been completely planted underground, pull the drill while rotating it to the right. After that, lift the drill and clean it from the remaining soil. Repeat the process. Make sure that the hole is perpendicular. If the digging becomes difficult due to the ground being hard, wet it further with water. Also, if along the process you stumble upon gravel and rocks, make sure to take them all out so that it will not hinder the biopore holes.
- Put the plastic pipe into the hole that has been dug. To make it more firm, you can reinforce the pipe by cementing its surroundings.
- Fill the plastic pipe that is already planted underground with organic waste such as dry leaves or fruit and vegetables scraps. The organic waste will help to stimulate the activities or organisms such as earthworms, since it will become their food source.
- When the holes have been filled, close it with the perforated lid.
Regarding the number of biopore holes that need to be made, you can follow this formula:
Number of biopore infiltration holes = Rainfall intensity (in mm/hour) x are of infiltration (in m2) divided by the rate of water absorption per hole (in litre/hour).
Example: An area with 50 mm of rainfall per hour (heavy rain), with water absorption rate of 3 litres per minutes (180 litres per hour) on a 100 m2 area of infiltration will need (50 x 100) / 180 = 28 biopore infiltration holes.
In addition, the minimum distance between biopore infiltration holes is 50 cm.
Types of Waste For Biopore Infiltration Holes
The types of waste that can be put inside the biopore infiltration holes are organic waste such as garden waste (dried leaves, tree twigs, plant remnants, cut grass), kitchen waste (vegetable and fruit scraps, chicken and fish bones), as well as pulp materials such as cardboard and paper. Inorganic waste such as cans, glass, metal, and plastic should not be put inside the biopore holes because it cannot be decomposed.
Maintenance of Biopore Infiltration Holes
Maintaining the biopore holes can be done by filling it with organic waste. A biopore hole with a diameter of 10 cm and a depth of 100 cm can be filled with around 7.8 litre of organic waste. Therefore, every hole can be stuffed with organic waste for 2-3 days. As time passes, the organic matters inside the biopore holes will dwindle, and we can stuff the hole with even more organic waste. After around 3 months, take the compost from the biopore hole and repeat the process of filling the hole with organic waste.
To minimize the possibility of unpleasant odors from inside the biopore hole, place the kitchen waste, such as meat or bones, in the bottom part of the hole. Then, put the garden waste on top of it until the biopore hole is full. Even if the biopore still reeks of unpleasant odors, it will only last temporarily.
Other Alternatives for Making Compost
Apart from the biopore infiltration holes, organic waste processing can also be done using other methods such as Takakura composting, Windrow Composting, Vermicompost (utilizing worms), as well as one other method that might sound less familiar, which is BSF. BSF stands for Black Soldier Flies, a type of flies that is bigger in size compared to the usual flies, and is known for their abilities to decompose organic waste. To know more about BSF, please visit bit.ly/W4CBSFsolusi
- Soeparwan Soeleman & Donor Rahayu. Halaman Organik. AgroMedia. ISBN 9790064810 via https://id.wikipedia.org/wiki/Biopori#cite_note-soeparwan-25