The effects of ENSO, climate change and human activities on the water level of Lake Toba, Indonesia: a critical literature review

TL;DR

This literature review examines how climate variability, climate change, and human activities influence Lake Toba's water levels, highlighting the need for further systematic research to identify the dominant factors and future trends.

Contribution

It synthesizes existing studies on Lake Toba's water level changes and emphasizes the necessity for comprehensive analysis to determine the primary causes and future projections.

Findings

Climate variability and human activities significantly impact water levels.

Simulations suggest potential water surplus until mid-21st century.

Future climate scenarios indicate possible drier conditions and water level decreases.

Abstract

This research quantitatively and qualitatively analyzes the factors responsible for the water level variations in Lake Toba, North Sumatra Province, Indonesia. According to several studies carried out from 1993 to 2020, changes in the water level were associated with climate variability, climate change, and human activities. Furthermore, these studies stated that reduced rainfall during the rainy season due to the El Nino Southern Oscillation (ENSO) and the continuous increase in the maximum and average temperatures were some of the effects of climate change in the Lake Toba catchment area. Additionally, human interventions such as industrial activities, population growth, and damage to the surrounding environment of the Lake Toba watershed had significant impacts in terms of decreasing the water level. However, these studies were unable to determine the factor that had the most significant effect, although studies on other lakes worldwide have shown these factors are the main causes of fluctuations or decreases in water levels. A simulation study of Lake Toba's water balance showed the possibility of having a water surplus until the mid-twenty-first century. The input discharge was predicted to be greater than the output; therefore, Lake Toba could be optimized without affecting the future water level. However, the climate projections depicted a different situation, with scenarios predicting the possibility of extreme climate anomalies, demonstrating drier climatic conditions in the future. This review concludes that it is necessary to conduct an in-depth, comprehensive, and systematic study to identify the most dominant factor among the three that is causing the decrease in the Lake Toba water level and to describe the future projected water level.