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 Niño 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.
Highlights
The word lake comes from the Latin word lacus, which means a medium to large "hole" or "space" that is filled with water and surrounded by land (Day and Garratt 2006; Hutter et al 2010)
Lett. (2021) 8:21 (Williams 2012; Chesner 2012; Wagner et al 2013). This lake is geographically located in the middle of the northern part of Sumatra Island, North Sumatra Province, Indonesia
In accordance with the studies on the decrease and fluctuation of lake levels in different parts of the world that are significantly related to El Niño Southern Oscillation (ENSO), climate change, and human activities, the authors established the basis of this review on the decline and fluctuation of the water level of Lake Toba
Summary
The word lake comes from the Latin word lacus, which means a medium to large "hole" or "space" that is filled with water and surrounded by land (Day and Garratt 2006; Hutter et al 2010). (Williams 2012; Chesner 2012; Wagner et al 2013) This lake is geographically located in the middle of the northern part of Sumatra Island, North Sumatra Province, Indonesia. It stretches between 2°21′32′′–2°56′28′′ N and 98°26′35′′–99°15′40′′ E, with water surface and catchment areas of approximately 1124 km and 2486 km, respectively. According to Lukman and Ridwansyah (2011), the lake surface is 903 m above sea level, approximately 50 km in length and 27 km in width, and it has an average depth of 228 m. The Lake Toba area (see Fig. 1) has been recognized as being beneficial for tourism, agriculture, plantation, fisheries, and industry (Saragih and Sunito 2001; Nasution and Damanik 2009), with its discharge used by power plants to supply electricity in North Sumatra (Loebis 1999; Sianturi 2004; Sihotang et al 2012; Lukman 2017)
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