The Red River is formed by the confluence of the Da, Thao and Lo Rivers at Viet Tri upstream of Ha Noi. The Chay and Gam Rivers are tributaries of the Lo River, all rising in China. The Day River is the first of several distributaries that form the Red River Delta. It branches downstream of Son Tay and flows south of Ha Noi. The Cau, Thuong and Luc Nam Rivers are tributaries of the Thai Binh River. They rise within Vietnam, where rainfall is lower, and discharge to the Gulf of Tonkin. The Duong and Luoc Rivers, distributaries of the Red River, discharge to the Thai Binh River.
Administratively the Red River Basin comprised 26 provinces now. The Red River Delta (RRD) Region consists of 11 provinces and covers 17% (15,000 km2) of basins in Vietnam. The upper basin covers about 70% of the Northern Highlands (NH) Region including 8 complete provinces and parts of 7 more. Parts of Cao Bang, Bac Kan and Lang Son Provinces drain north into China through the Bang Giang, Ky Cung and other small rivers. Most of Quang Ninh Province drains direct to the Gulf of Tonkin. In the south parts of Lai Chau, Son La and Hoa Binh Provinces are in the Ma River Basin. The total population of the RRB was about 25 million in 2000 of which 10 million (40%) were poor compared with the national average of 37%. Furthermore poverty is essentially a rural affliction and, although the incidence of RRB poverty is higher in the highlands (55% vs 37%), there are 25% more poor people in the densely populated rural delta (5.5 vs 4.4 million).
The RRB has a monsoon climate with pronounced wet and dry seasons. More than half the delta is less than 2 m above mean sea level. It is protected from flooding and typhoon storm surge by 3,000 km of river dykes and 1,500 km of sea dykes forming about 30 main polders. Rice is the main crop and intensive production relies on a combination of gravity and pumping for both irrigation and drainage. While development potential is limited the scope to improve the agricultural production performance of existing systems is thought to be significant. Provincial Irrigation and Drainage Management Companies (IMC’s), District Irrigation Enterprises (DIEs) and Commune Agricultural Cooperatives (CACs) manage the polder irrigation and drainage systems except the inter-provincial Bac Hang Hai system where the IMC reports to MARD.
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.
In various previous projects diagnostics studies have been made of the water resources issues in the basin (Red River Delta Master plan study 1996, Water Resources Sector Review 1996, Red River Basin WRM study 2001, Day River Water Resources Development study 2002, etc). Nevertheless, no consensus exists about the real problems and the priority management options related to water resources in the basin. The Red River Delta study concluded that there is generally ‘a favorable waterbalance’ and major WRM issues are: (i) flooding, (ii) the performance of irrigation & drainage systems, and (iii) groundwater quality due to municipal and industrial pollution. The Sector Review estimated the 85% reliable flow at Son Tay to be 1,367 m3/s versus a present peak demand of only 660 m3/s in January. The reported mean annual flow of 137 BCM represents nearly 5,500 m3/capita/annum. This compares favorably with international norms as countries are only considered water stressed when the renewable water supply drops below 1,700 m3/capita/annum and water scarce when it drops below 1,000 m3/capita/annum. The Sector Review did not, however, consider the considerable spatial and temporal variation in water availability.
The Thai Binh Sub-basin and its tributaries, including the Cau River, are relatively short of water reflecting smaller basins and lower rainfall. While local estimates predict demand for water will increase by as much as 100% over the next 40 years the Sector Review did not envisage any increase in view of limited potential for irrigation expansion. While water shortages have occurred in dry years, the Sector Review attributed the problem to limited irrigation system capacities and poor management performance rather than insufficient water at intakes. In the Orientation phase of the subject study, however, it has been concluded that apart from the Cau basin, also some other subbasins are under water stress during particularly the dry season. Thus the performance of existing irrigation and drainage systems is likely to prove a priority issue. Improved agricultural production performance is likely to require a combination of system management and agricultural improvements as well as provision of infrastructure subprojects.
While there is general consensus that flooding poses the greatest risk to development in the RRD a recent flood study found that Hanoi is currently protected against the 450-year flood. Thus structural dyke failure is considered the main risk rather than overtopping.
The six Cau River Provinces set up a committee to manage water quality reflecting local demand for municipal and industrial pollution control. The Sector Review was concerned by the risk of groundwater contamination, as the main source of domestic water supplies, but the impacts of municipal and industrial pollution remain to be determined. Recent research indicates arsenic, occurring naturally in groundwater, poses a greater health risk. Hai Phong is reported to obtain municipal water from surface sources with associated risk of saline intrusion.