Sun Moon Lake is the most famous scenic spot on Taiwan Island. Located in Nantou County in the west, it is the second largest lake in Taiwan Province and the largest natural lake lying on the hilltop between Yushan and Alishan. The lakeshore is 35 kilometers in circumference, 7.7 2 in area and 230 meters in depth. The water surface is slightly larger than the famous lake, Hangzhou West Lake, but the water depth is more than 10 times that of the West Lake. Riyuetan Lake is a beautiful "Tianchi" in Taiwan, China. There is a small island in the Sun Moon Lake, which looks like a pearl floating on the water. It is called Lalu Island. It is bounded by the island. The northern half of the lake is like a circle, while the southern half is like a crescent moon. Therefore, the Sun Moon Lake is named after it. The beauty of Sun-Moon Lake lies in the mountains and peaks around the lake, the vast surface of the lake and the clear water of the lake. The morning and evening scenery varies from season to season. The average temperature in July is not higher than 22 C and in January is not lower than 15 C. The summer is refreshing and pleasant. It is a summer resort. There is a small island in Riyuetan Lake. The lake to the north is like a sun wheel and to the south is like a crescent moon. So it is called Riyuetan Lake. Now the lake is shaped like a maple leaf because of the construction of a power plant with water storage. The dam is 91 meters long, 48.5 meters high and has a water storage capacity of 147 million cubic meters. The discharge of the reservoir is injected into Riyuetan Lake through a 15 km long tunnel, which plays the role of supplementing the water source when the water is dry. Before the hydropower station was built, the lake area of Riyuetan Lake was 4.4_2, the average water depth was about 4 meters, and the lake surface was 726.8 meters above sea level. After the completion of the hydropower station, the water level has been raised by more than 30 meters, the lowlands near the lake have been flooded, the lake area has expanded by 70 (%) to 7.73 2, the average water depth has reached 19.1 meters, the lake circumference is 35 kilometers, and the maximum water depth is 40 meters.