Forest and Water

When it rains, water moves over the land and through the soil. It gathers to form water supplies. Some water supplies are on the land, such as rivers and lakes. Other water supplies are under the ground. A clean and reliable water supply is very important for health and the economy.

Water in Kalimantan

Kalimantan is home to many river systems and watersheds.
The forests are important for keeping the quality of water in these rivers good.

In many places, there is not enough water, because people use too much water or they waste water. Some water supplies are of poor quality because activities make the water dirty.

How can we get clean and reliable water supply?

To get a clean and reliable water supply, we must look after our watersheds. A watershed is the area of land where the rain water moves into a stream for the water supply. The way the land is used in the watershed affects the water quality. Usually, water from forested lands is very high quality.


How do forests make the water supply good?

Making high-quality water is the most important thing that forests do for our water supply. Forests keep water clean in several ways:

Why is sediment bad for water quality?

  • If a dam has a lot of sediment, it will hold less water.
  • If water has a lot of sediment, it is not good for drinking or other uses. Improving the water is then very expensive.
  • If water has a lot of sediment, it is not good for fish to live and breed.


  • Forests minimize erosion; that is, they stop soil from being washed away.
    Therefore, water from the forest does not have much sediment (sediment is soil that travels in water to other places). Sediment is bad for water quality. Water flowing through forests is usually very clear, because it doesn’t contain sediment.
  • Forests trap or filter other water pollutants.
  • Forest activities usually don’t use any fertilizer, pesticides or fuels, or other dirty liquids.

Forests also help balance the flow of water in the ground. Forests use a lot of water, but forest soil can store a lot of water too. This water is then slowly released into the ground.

Does clearing forest harm the water supply?

Like everything in nature, watersheds are very complex, so the water supply depends on many factors. However, logging can harm water quality.

Logging increases the risk of erosion and it can make more sediment. One way to reduce this risk is to practice selective logging or reduced impact logging.

Transporting the logs also increases the risk of erosion and makes more sediment. Fuels used for logging machinery and for trucks can pollute the water supply.