Stretching west of Hoa Binh is the Song Da Reservoir (Ho Song Da), Vietnam’s largest. The flooding of the Da River has displaces a large number of farmers for about 200km up stream, and is part of a major hydroelectric scheme that generates power for northern Vietnam. In 1994, a 500kV power line was extended from this area to the south, feeing Ho Chi Minh City (HCMC) from the seasonal power shortages that often blacked out the city for up to three days at a time.
Easiest access to the reservoir is by taking a spur road that cuts off from Hwy 6 at Dong Bang Junction (60km west of Hoa Binh and just outside Mai Chau). From Dong Bang Junction it’s about a 5km drive to Bai San Pier. There’s no obvious jetty here – hang around and someone will come out from one of the houses and ask where you want to go. You’ll need a Vietnamese speaker to help make arrangements.
One of the trips you can take is to the Ba Khan Islands. The islands are the tops of submerged mountains and the visual effect is like a freshwater version of Halong Bay. The return trip to the islands takes three hours and costs 150,000d per boat )each boat can seat 10 passengers).
Another possible boat trip is to Than Nhan village, home to members of the Dao tribe. The two-hour return trip costs about 100,000d. The boat leaves you at a pier from where it’s a steep 4km uphill walk to the village. If you’d like to stay in the village, you can take the boat one way for 50,000d and get a rutrun boat to Bai San Pier the next day.
The last option is to charter a boat from Bai San Pier to Hoa Binh (400,000d, six hours).