Electricity Vietnam (EVN) has two hydropower facilities in the RRB; Hoa Binh Reservoir on the Da River (live storage 5.65 BCM) and Thac Ba Reservoir on the Chay River (2.06 BCM). During the wet season these large reservoirs and the Day River Barrage are operated by MARD to control flooding. Nine main irrigation reservoirs (total 0.7 BCM) serve 60,000 ha. Existing storage capacity presently regulates only about six percent of mean annual flow and there is considerable potential for further storage development, especially on the Da and Lo-Gam Rivers. The GOV is now considering several dams, and has decided already upon construction of the Son La Multi-purpose Reservoir on the Da River upstream of the existing Hoa Binh Reservoir.