A weir is a hydraulic structure built across the river. Usually smaller than conventional reservoirs, a weir is used to uplift the water level and then let the water flow by itself. In other words, a weir can be used to guide the direction of water flow for different usages. It can also control and regulate the water volume, especially for preventing flooding during the flood season. Between 1994 and 1998, seven weirs were constructed in Taiwan, including the Longen Weir (隆恩堰) in Xinzhu. Currently under construction are six weirs, such as the Jiji Weir (集集攔河堰) in Nantou, the Kao-Bing Weir (高屏攔河堰) in Kao-Bing region, and the Ailiao Weir (隘寮堰) in Bingdong.