Beel Dakatia located in the northeastern part of khulna district and falls within the Ganges tidal deltaic plain. The area has been experiencing waterlogging and drainage problems for more than 15 years as a result of creating polders and ignoring morphological, hydrological and tectonic conditions. This has resulted in crop failure and environmental degradation. The balance that existed between sedimentation and subsidence was totally disrupted by polders, causing very rapid sedimentation in the tidal channels, and very limited sedimentation and rapid subsidence of the tidal flats. In the Khulna and jessore regions, polders 1, 3, 4, 5, 6, 8, 15, 24 and 25 have been experiencing waterlogging and among these the most serious problem is observed in polder 25, the waterlogged part of which is known as Beel Dakatia. It lies between longitudes 89'20'E and 89'35'E and latitudes 22'45'N and 23'00'N under the administrative boundaries of dumuria and phultala upazilas of Khulna district. The total area of this polder is about 19,430 ha of which 9,000 ha or about 50% are usually under 0.5m to 2m water.
The climatological conditions of Beel Dakatia are characterised by sultry summers and moderate winters. The area also suffers heavily from tropical cyclones, tidal inundation, heavy rainfall and salinity. The maximum and minimum temperatures usually range from 40'C to 29'C and 5'C to 25'C respectively. The average annual rainfall during 1965-1990 was about 1,750 mm. The average relative humidity in the dry season ranges from 64 to 75 percent and in the wet season from 75 to 87 percent. The area is drained by the Solmari, Hamkura, Hari, Salta, bhadra and bhairab rivers.
Beel Dakatia and its surrounding areas have marsh clay, peat and deltaic silt deposits. Peaty clay, clayey peat and peat constitute the major part of the area. In fact, the organic rich and fine-textured materials are common except in the slightly raised area, where clayey silt, silty clay and clay are common. Different geological deposits of Beel Dakatia are tidal-channel deposit, natural levee (kanda) deposit, intertidal-plain deposit and subtidal-plain deposit.
Before polders were created in the area, crop failure due to saline inundation and monsoon flooding occurred every two or three years. To overcome this problem, zamindars since the 17th century constructed temporary low dikes and wooden sluices around the area to protect the arable land from natural hazards. After the abolition of the Zamindari system, the problems of land management became serious and crop failure occurred frequently due to irregular and inadequate maintenance of the dikes. To overcome the problem, a programme to create permanent polders was undertaken by the government in 1959. After Beel Dakatia became waterlogged, attempts have been made by the bangladesh water development board and local people to de-water the beel. The attempts were mainly related to excavation and re-excavation of Solmari and Hamkura rivers, and their feeder channels. The channels silted up soon after re-excavation. Attempts to de-water Beel Dakatia by small power pumps failed. During 1989-1992 the local people tried to convert it into a tidal basin to allow sedimentation inside Beel Dakatia. In 1995 the government started dredging Solmari river, and this made about 5,000 ha out of 9,000 ha water free. But still 4,000 ha of land are under permanent waterlogging. Lately the government has taken up the Khulna-Jessore Drainage Rehabilitation Project (KJDRP) of which Beel Dakatia forms a small part.
The main causes of the problems are related to sedimentation in the tidal channels and subsidence of the tidal flats. Other causes include sudden decrease of upland flow of different rivers in the area, improper maintenance of embankments and sluices, and wilful diversion of water by influential shrimp farmers.
Tectonically, Beel Dakatia is part of the Faridpur Trough. Subsidence of this area has been reported since 1927, at a rate of about 1.5 to 2.5 cm/year. Beel Dakatia is principally a peat basin and all the processes of subsidence are active here. Before polders were created, subsidence was compensated by the sedimentation over the tidal flats. The present situation of Beel Dakatia is the result of sedimentation in the adjacent riverbeds and simultaneous subsidence of the tidal flats. Hence, the riverbeds are becoming higher than the adjacent tidal flats. This situation is creating further inundation of arable land and permanent waterlogging.
Waterlogging has caused serious environmental degradation and suffering to the people of Beel Dakatia. It affects people, agriculture, infrastructures and water resources. Villages, roads, bridges, culverts have either become isolated or gone under water. Six villages are completely isolated from other villages, about ten villages are more or less detached from the mainland and about 9,000 ha of arable land are now under water together with all the sweetwater ponds and even some tubewells. diarrhoeal disease, dysentery, gastric and skin diseases are common here. Waterlogging, increased salinity and siltation in and around the area have affected the flora and fauna. Trees, birds and domestic animals like cows and goats are also disturbed due to waterlogging and salinity.
An agro-based economy and a colourful socio-cultural life have suffered decline. About 55 percent of farming families have turned fishermen. A sizeable number of local people have already migrated to other places.
The following options can be considered to resolve the waterlogging and drainage problems of Beel Dakatia: (i) the area can be converted into a tidal basin by modifying existing structures and allowing sedimentation under controlled system; (ii) water management by constructing and maintaining new and old embankments, sluice gates, culverts, etc; and (iii) pumping out excess water by power pumps or windmills. An alternative proposed suggests introducing pisciculture, duck farming and shrimp culture. [Sifatul Quader Chowdhury]