The Ayung River is the longest river on the Indonesian island of Bali. It runs 68.5 km from the northern mountain ranges, passing the Bangli, Badung, Gianyar regencies and the city of Denpasar, before discharging into the Badung Strait at Sanur. The river is famous for white water rafting. Ayung river watershed area has an annual average temperature between 18.4 °C to 26.6 °C, depending on the altitude. The average annual rainfall at the upstream is high, around 1963–3242 mm.

Going downstream at an average inclination of 13.13%, the rainfall and the rainy days on the river decrease. In the middle area, the average rainfall is around 1998–3176 mm with 105 -128 average rainy days. At the downstream, near the city of Denpasar, the rainfall becomes low, around 1486 mm with 69 average rainy days.
The drainage basin has two types of topography: mountainous and flat. The water debit measured in 1973-1986 is around 6.6-14.2 m³/second with an average of 8.69 m³/second. The sedimentation level at Buangga shows the highest at 544.4 ton/day and the lowest at 2.8 ton/day, with the calculated total (SCS-USDA method) of 91,393.127 ton/year.