Some Environmental Issues Accompanying the Rapid Expansion of Shrimp Farming in Tam Giang Lagoon, Central Viet Nam: An Environmental Assessment Based on an Analysis Using High-resolution Satellite Images

Abstract

Tam Giang Lagoon, lying along the coast of Hue Province in Central Viet Nam, has undergone a rapid expansion of shrimp aquaculture over the last dozen years. Intensive shrimp farming has expanded not only in and along the littoral zone of the lagoon, but also over lowland paddy fields and on coastal sand dunes. In this research, the authors studied three areas that include the coastal sand dune area southeast of Tam Giang Lagoon, classifying shrimp farming into six types in terms of aquacultural facility and operational management, while identifying their geographical distributions and processes of development during the period 1999-2009 through on-site survey and interpretation of multi-temporal high-resolution satellite images of Landsat7-ETM, QuickBird and ALOS-AVNIR-2. Some environmental issues accompanying the development of the respective types of shrimp farming are schematized to make an assessment of lagoon environments from the perspective of sustainable resource management in this area. In the results, the following three conclusions are presented.(1) Overcrowded installation of aquacultural facilities in and along the littoral zone has deteriorated water quality in the lagoons, and such facilities may have increased recent flood levels during times of flooding.(2) Intensive aquaculture spreading over the lacustrine lowlands has caused further water pollution in the lagoons and outbreaks of shrimp diseases, and this type of aquaculture may lead to saltwater intruding into the groundwater under adjacent paddy fields.(3) Recent development of large-scale intensive shrimp farming on coastal sand dunes may cause a shrinkage of the freshwater lens existing under the sand dunes, as well as leakage of saltwater from shrimp ponds into the freshwater lens.