State
of water quality and propose management plan for Ha Long bay, Vietnam
Do Trong Binh
Ha Long Bay, the "Bay of the descending dragons", is a UNESCO world heritage
site located in Quang Ninh which is the northernmost province of Vietnam. Due to
its great natural beauty and availability of natural resources the area has a
huge potential for economic development. As a result the Ha Long Bay area has
been designated as one of three focal areas for economic development in Vietnam.
The downside of this development potential is that economic activities are often
a cause of coastal and marine environmental problems. A number of studies
assessed that Ha Long Bay and its tributaries are threatened by pollution. The
goal of this investigation was to analyse these problems and propose a
management plan to improve the water quality in the Bay. Numerical simulation
modelling and a Geographical Information System (GIS) were used as main
approaches.
Results of this study show that the water quality of Ha Long Bay is affected
by human activities concentrated in Ha Long City. Untreated domestic and
industrial wastes are the main factors affecting the water quality in especially
the nearshore area of the Bay. A great number of pollution sources were
identified. These are responsible for the deteriorating water quality in the Ha
Long Bay area. Pollution sources were divided into two types, namely specific
and non-specific sources. Oil, SS and iron are the problematic variables in the
study area. Heavy metals that cause a deterioration of coastal water quality are
zinc and cadmium. Furthermore the concentration of oil in water was invariably
higher than the Vietnamese standard. During the rainy season BOD5, COD and SS
were found to be twice as high as during the dry season. Besides during the
rainy season transparency also showed around half of that during the dry season.
From 1995 to 2001 there has been an apparent increase of BOD5 and oil
concentration and a decrease in DO.
Another result of this investigation is a set of digital maps that show the
distribution of pollutants in January 1997, July 1997 and July 1998. These maps
were generated using a GIS and existing data. The pollutants that were mapped
are BOD5, DO, SS, coal-fragments, oil in water, total-phosphorus and
total-nitrogen. The numerical simulation model has been used as a tool for
environmental/water quality management planning. It has been applied to simulate
the hydrodynamics and water quality parameters (BOD5, DO) for Ha Long Bay at the
present as well as to predict future water quality in 2010 without the
implementation of a water quality management plan.
From the analysis of the present state of the water quality, prediction of
future water quality, a GIS analysis, water quality modelling and an analysis of
future economic development a water quality management plan has been proposed.
This plan includes: environmental zoning, a legal and institutional framework,
water quality monitoring and environmental measures for sanitation, mining,
tourism, natural resources.
