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Water Resource Management Options in the Seawater Irrigation Project in Kung Krabaen, Thailand
Dissertation Abstract:
The purpose of this study was fourfold as follows: (1) to elucidate problems related to shrimp culture in Kung Krabaen Bay, (2) to study trends in water quality in the Kung Krabaen Bay, (3) to determine the perception of the shrimp farmers on a number of matters about Seawater Irrigation Project, and (4) to determine the most appropriate methods for managing the new water resource associated with the Seawater Irrigation Project.
The methodology for the study consisted of field observation, questionnaire surveys, sampling and analysis of water and wastewater, and discussions with some relevant authorities and NGOs connected with the project. Fieldwork was carried out from September 1996 to September 1997 in Kung Krabaen Bay. The social survey involved 88 respondents. Data were analyzed for frequencies, means, standard deviation and percentage. Sampling of water in the shrimp ponds was carried out over two cropping seasons with each crop consisting of 10 ponds. Each water sample was analyzed for dissolved oxygen, biochemical oxygen demand, nitrite, nitrate, ammonia, pH, salinity, water temperature, and suspended solids. In addition, t-test and one-way ANOVA were employed to compare water quality values.
The following conclusions were based on the findings of the study:
1. The main cause of failure in the shrimp farms in Kung Krabaen Bay was due to poor environmental conditions and weaknesses in the farm management system that allowed for infection of the shrimps by yellow head bacuvirus.
2. The major problem of water quality deterioration in Kung Krabaen Bay occurs mainly in the canals and in the inner coast region. The lack of separate fresh seawater resource and wastewater discharge canal exacerbated the problems of obtaining good quality water for efficient shrimp farming.
3. The trend in water quality variations indicated improvement from 1995 to 1997. This may be attributed to the change in the shrimp farming system from an intensive system to a closed system. Nonetheless, this improvement is still not adequate to provide a suitable water resource for shrimp farming in the future. A new fresh seawater resource will be required to rejuvenate the shrimp industry in Kung Krabaen.
4. The Seawater Irrigation Project being developed by the KKBC promises a suitable new water resource for shrimp farming. However, local participation in the project planning and development is poor and appropriate management systems for the new water resource needs to be identified.
5. The water resource management system proposed by the project proponent has some inherent weaknesses especially with respect to the rate of water supply and the duration of supply. Depending on the type of shrimp farming system being practiced, the water demand may exceed the supply capacity. In addition, the schedule for pumping seawater would cause a lot of inconvenience to the farmers.
6. The “Arrange Supply” system is a suitable system for managing the new seawater resource in the short-term because this system is based on the expected water needs of the crop and is technically simple to operate. However, it places some constraints on the farmer in terms of the type of shrimp farming system that may be practiced and scheduling of shrimp farming activities. The system which is suitable for operating the seawater resource in the long-term is the “Semi Demand Supply” system which is more flexible but still environment friendly. However, it requires more careful planning and operational expertise.
7. The important criteria for the success of the Seawater Irrigation Project are (a) the mode of shrimp culture being practiced, (b) the water resource management system, (c) preservation of the water quality in the Gulf of Thailand, and (d) research and extension activities of the KKBC. Some recommendations are presented for each of these criteria aimed at augmenting and supporting the success of the new water resource management system to ensure successful shrimp farming operations in the future.