By Dyah Susanti Nur Chasanah, M.Sc. – (Thesis M.Sc Unesco-IHE, Delft, Netherland, 2014), Supervised by Prof. Charlotte de Fraiture Ph.D., M.Sc. Prof.Dr.Ir. Robiyanto H.Susanto, M.Agr.Sc. and F.X. Suryadi,M.Sc,PhD
The fisheries area which has the source of water supply from Banyuasin River which closes to the Bangka Strait up to now still have not received the optimum production of fish and shrimp commodities. They often face a crop failure mostly for shrimp commodity. The growing period of shrimp and also milkfish are very slowly and the worst problem is the mortality of shrimp mostly in the dry season. The problems which are encountered by the farmers in this area are due to the physical problem and also the chemical problem. The physical problem is related to the insufficiency of water supply to fill the pond in dry season and flooding occurrence when in rainy season and usually takes place in month December. The chemical problem is due to the chemical characteristic of the soil which has high acidity, resulting the acid water if the water cannot adequate to fill the pond.
The methodology of the research is field observation and study literature of aquaculture practices. The first field observation was that the soil analysis which involve; pH, organic content, texture and pyrite content. The second one was the water level observation for 24 hours which has been conducted in 2 until 3 September 2013 in several Sites of secondary canal and also two fish ponds.
The physical problem was analyzed using DUFLOW modelling in order to analyze the source of the problems encountered by analyzing the water level in the pond and discharge of the water flowing from the canal into the pond. The secondary canal and also inlet/outlet channel of fishponds discharge have been analyzed; therefore it can be obtained the losses of water supply. From the discharge analysis, it can be planned purposed improvement due to dry season which can be implemented on the field.
The shortage of water can be solved by deepening the canal into 2 m and also widening the canal into 11.4 m width area for several sections in Site 2 and Site 3. The deepening canal after Site 3 is also 2 m of deep but the top width of the canal is 10 m. The improvement in inlet or outlet of the pond is also should be conducted by widening the bed width of the channel. The deepening and widening the canal avoid the reflection wave of tide when it flow towards the canal, therefore the rising tide can be utilized efficiently and optimally utilized to supply the water pond.
The other purposed improvement is the improvement of culvert which initially has 0.3 m of diameter size into 0.4 m of diameter size for the pond which has 2 ha or 2.5 ha of areas, and for the pond which has 3 ha of area the diameter size of culvert should be 0.5 m and it is necessary also the using of flap gate to assure the quickly inflow to the pond and the fast flushing from the pond.
The result of this purposed improvement is that in the dry season, water from estuary can flow into the pond and adequate for supply thirty ponds which the assumption have 2.5 ha of areas. The flushing water and also fulfill water for the first time after preparation stage can be conducted in this season through the purposed improvement, though the water level of pond depth is less than in the normal season but it still can be accepted which is 1 m of water depth for the maximum depth maintained in the pond.
Keywords: Duflow modelling, water management, aquaculture, Shrimp, Milkfish, Aquaculture Best Management Practices