Danau Segara Anak is a volcanic lake formed in the caldera of Mount Rinjani, sitting over 2,000 meters above sea level. Spanning 11 square kilometers and reaching depths of up to 230 meters, this lake is located on the west side of Mount Rinjani in Lawang Sembalun village, Lombok, East Indonesia. The mystifying blue color of the lake gives Segara Anak its name: "Small Ocean."

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The Trek to Danau Segara Anak

The trek to Danau Segara Anak begins in Senaru Village and takes two days and a night to complete. The journey starts with a hike through a lush, tropical rainforest, ascending the mountain to the rim of the crater. The climb to the Senaru rim is challenging, with steep terrain and high cliffs, but the effort is rewarded by breathtaking panoramic views. At the top, hikers are greeted with the sight of the sun setting over Mount Rinjani, Bali, and the Gili Isles, with the dazzling blue waters of Segara Anak glistening hundreds of meters below. The crater rim is a popular campsite for both foreign and domestic tourists, providing a perfect spot to spend the night and catch the magnificent sunrise from atop Rinjani. From the crater’s rim, it is a sharp descent of about 600 meters to Danau Segara Anak.

Part of Segara Anak flows down a steep ravine, forming one large waterfall and several smaller ones. There are also four natural hot springs in the lake, believed to have magical healing powers, attracting many climbers for medicinal purposes.

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Geological and Ecological Significance

Despite its high altitude, the lake's surface water is unusually warm, ranging from 20-22 degrees Celsius, well above the mountain’s average temperature of 14-15 degrees Celsius. Between 2008 and 2009, researchers from Volcanology and Geological Hazard Mitigation and Universite Libre de Bruxelles conducted a study on Segara Anak. The tests revealed several leaks in the volcanic system of Gunung Baru, the cone in the center of the lake. These leaks from the magma chamber seep a large supply of hot water into Segara Anak, indicating a direct relationship between volcanic activity and the lake’s high temperature.

The geochemical composition of the hot water includes elements such as chloride, sodium, potassium, and sulfate. Although rich in elements, rainwater that enters the lake helps dilute its chemical content. The excellent water circulation maintains the lake’s neutrality, making it suitable for breeding fish.

Lake water circulation occurs when the surface water density is higher than that at the base. Rainwater, being denser than hydrothermal water, moves downward, while hydrothermal water moves up. This ongoing process provides well-mixed water and neutralizes the lake’s acidity, supporting fish life.

Human Impact and Conservation

In 1969, volcanologists from the Directorate of Geology recommended fish cultivation in the lake. At that time, there were no fish in Segara Anak. In 1985, the Nusa Tenggara Barat provincial government began breeding fish in the lake. The fish population grew rapidly, making Segara Anak a popular fishing spot. Some locals even make a living from fishing in the lake.

In the 1980s, the areas surrounding Segara Anak were rich in wildlife, including grouse, hornbill, barking deer, and several monkey species like the rare black ebony leaf monkey and the black crested macaque. However, human intervention has drastically changed the lake’s ecology. Increased human activity has led to the decline of many species. Initially, people only caught fish, but later, they began hunting grouse and deer. Now, few grouse remain, and the deer are no longer found along the route. It is estimated that only about a hundred deer remain.

Cultural Significance and Conclusion

In 1998, Danau Segara Anak was immortalized on the ten thousand rupiah bill, highlighting its cultural importance. Like other crater lakes around the world, Danau Segara Anak has a violent past, a brilliant present, and the potential for a catastrophic future. Yet, we remain fascinated by its origin, splendor, and unique existence. The trek to Danau Segara Anak is a journey into nature’s marvels, blending adventure, beauty, and a touch of mysticism.