Dajia River is a river in north-central Taiwan. It flows through Taichung City for 124 km. The sources of the Dajia are: Hsuehshan and Nanhu Mountain in the Central Mountain Range. The Dajia River flows through the Taichung City districts of Heping, Xinshe, Dongshi, Shigang, Fengyuan, Houli, Shengang, Waipu, Dajia, Qingshui, and Da'an before emptying into the Taiwan Strait.
The Deji Reservoir, formed by Techi Dam, is a 592-hectare reservoir in Dajia District. The reservoir provides municipal water, generates hydroelectric power, is used for recreation and prevents flooding. Techi and a cascade of five other dams on the Dajia produce up to 1,100 megawatts of hydroelectric power and generate more than 2.4 billion KWh per year. The other five dams in sequence from top hill are Qingshan Dam
, Kukuan Dam
, Tienlun Dam
, Ma'an Dam and Shihgang Dam
Taiwan's Central Cross-Island Highway runs along the Tachia River from Heping to Dongshih. The Taichung Beltway begins in Fongyuan and follows the Tachia through into Cingshuei.
The Dajia experiences frequent earthflows during typhoons and heavy rain, damaging homes and breaking up roads, sometimes permanently.In September 2008, rains from Typhoon Sinlaku resulted in storm-swollen waters which washed away supports for a section of Houfeng Bridge (which links Houli Township and Fengyuan City), leaving six people dead. In June 2010, the bridge finally reopened to vehicular traffic after over NT$1.4 billion of reconstruction work.