The study looked at the water quality and sediment in the Rajang River at the Pelagus area to understand how a future dam might affect it. They found that oxygen levels in the water increased as you moved downstream. The amount of organic matter in the water was higher in certain areas, influenced by weather and dam discharge. Tributaries had higher levels of certain substances compared to the main river, affecting overall water quality. The water discharge from the dam affected oxygen and organic matter levels in the river.