RRI.CO.ID, Jakarta - Lake Toba in North Sumatra has experienced a significant decline in water levels over the past few decades. Recent research reveals that the cause is more complex than simply climate change.

Hendri, a researcher at the Center for Climate and Atmospheric Research (PRIMA) at the National Research and Innovation Agency (BRIN), discussed the results of his research on the dynamics of Lake Toba's water level from 1957 to 2020 to determine the true cause. The results show that declines have indeed occurred, but the pattern differs between the periods before and after 1984.

1984 was a significant turning point because it coincided with the start of operations of dams and hydroelectric power plants in the area. Since then, the pattern of lake water level decline has changed drastically compared to the previous period.

From 1957 to 1984, the decline was quite sharp and was dominated by weather factors, particularly the El Niño phenomenon, which reduced rainfall. After 1984, the rate of decline slowed significantly, although annual fluctuations persisted.

Some years recorded extreme declines due to the combination of El Niño and a positive Indian Ocean Dipole phenomenon. These fluctuations demonstrate that climate factors still play a role, although they are not the sole cause.

After 1984, human activity became increasingly significant in influencing the lake's condition. Water use for power generation is said to have a greater impact than the household activities of the surrounding community.

Land use changes in the water catchment area also contribute to the lake's water reserves. Satellite imagery even shows a drastic reduction in natural forests around Lake Toba in recent decades, while settlements and agricultural land continue to expand.

The reduction in natural forests is thought to reduce the area's ability to absorb and store rainwater. This condition ultimately exacerbates the lake's water level fluctuations from year to year.

These findings emphasize that maintaining the sustainability of Lake Toba is not enough simply to adapt to climate change. Wiser land use management and water resource utilization are considered equally important for the lake's future sustainability.