Bali has a long and rich history of agriculture, with the traditional Subak water irrigation system dating back over a thousand years. However, the intensive use of agrochemicals in conventional rice farming has led to significant damage to the soil, environment, and broader ecological system, as well as making farmers highly dependent on chemicals. The excess agrochemicals are carried downstream by the Subak water and into the ocean, destroying offshore corals.

The Water Filter System: A Sustainable Solution for Balinese Rice Farming

To combat this problem, Begawan has committed to a regenerative practice of agriculture. One way we are achieving this is through an efficient and well-functioning water filter system. In September 2022, the foundation invested in a complex water filter for the Subak to irrigate the farmers’ rice fields.

The water filter system includes sedimentation tanks with floating water hyacinth, which absorb and digest pollutants in the Subak water. As the water flows slowly through the system, suspended particles are filtered, and a layer of accumulated solids, called sludge, forms at the bottom of the tank and is periodically removed.

The water then flows into a volcanic rock filtration tank, which acts as a natural filter for bacteria. Lava rock has a rough textured surface that holds bacteria, and has a large surface area for the bacteria to colonise. From the volcanic rock tank, the water flows into two filtration tanks with gravel and natural plants like vetiver, bulrushes and pteris vittata. These plants absorb heavy metals and chemicals in the water, with pteris vittata being known as an arsenic hyperaccumulator.

Finally, the filtered water flows into fish ponds, which serve as a biological indicator that the water is safe from chemicals. The fish also feed on mosquito larvae, providing a natural way to control their population. The fish ponds are stocked with suckermouth/janitor fish, tilapia, and nyalian bali (rasbora baliensis) and are surrounded by floating lotus, water lily, and water hyacinth. These plants also feed the fish, developing plankton for them to feed on.

Regenerative Agriculture as a Sustainable Solution for Balinese Rice Farming

The water filter system has been carefully designed to ensure that the water entering the rice fields is as unpolluted by chemicals as possible. It is an ongoing monitoring task, with water tests conducted regularly to monitor the effectiveness of the system. After running the filter for three months, water tests will be conducted on both the raw Subak water and again in the ponds before it reaches the rice fields. These tests will be carried out on a regular basis.

Overall, the Begawan’s water filter system is a sustainable and innovative solution to the problem of agrochemical pollution in Bali. By using natural filtration methods, such as water hyacinth, volcanic rock, and natural plants, and incorporating fish ponds as a biological indicator, the foundation is able to ensure that the water entering the rice fields is safe for both the environment and the farmers. The system plays an important  role in the creation of clean water for chemical free agriculture, and one that should be replicated in other areas facing similar challenges. (Adrian)

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