Bali's crater lakes are vast reservoirs of stored rainwater, but they have no river outlets. Instead, the water from these lakes seeps into the landscape and gradually emerges from hundreds of springs on the slopes of the volcanoes. As rainwater accumulates and flows into streams and rivers, it carries mineral nutrients from the paras rock into the paddy fields, nurturing the growing rice.
Every local irrigation system begins with a spring or a dam in a river. The farmers who share water from the same local source, like a canal or a spring, form a subak. Irrigation canals divide the water into branching channels that bring water to every field, ensuring that downstream farmers receive their fair share of water. Farmers cannot buy or sell water. Instead, they make offerings in shrines and water temples to give thanks to Dewi Danu, Goddess of the Lake, for her gift of water.