Impact of Water Logging in South Western Coastal Zone of Bangladesh: A Case Study

Abstract

An integrated drainage path is an important component for tropical countries. If heavy rainfall occurred with lacking of drainage path, water logging is the consequence of the surroundings. Three southwestern coastal districts of Bangladesh namely Satkhira, Khulna and Jashore are the worst hit areas and experiencing severe prolonged water logging and remain submerged in every year for long periods. Mostly affected Tala upazila has been selected for this study. The Coastal Embankment Project (CEP) disconnected the wetlands from the rivers and disallowed sedimentation inside the wetlands which gradually caused the drainage congestion of the rivers as the sediment deposited on the river bed. In many places the river bed became higher than the wetlands in the surrounding basins. The aim of this study is to illustrate the impact of water logging, investigate the salinity related variables (Chloride, EC and SAR) and acidic conditions in soil solution (pH and sulfate) related to plant nutrients (Nitrogen, Potassium, and Phosphorus) in soils after prolonged water-logging and propose suggestions for future work. To obtain this aims necessary information were collected through house hold survey, field visit and key informant interviews. Most of the laboratory investigation of soil and water sample was performed from environmental laboratory, KUET and Soil Resource Development Institute (SRDI), Regional Laboratory, Khulna. Secondary data were also collected for comparing with the experimental results. The study results that due to prolonged water logging of the study area the agricultural land price are not increased as the residential or commercial land price. Because both types of agricultural land become ideal and the land can’t use for cultivation. Presently only 16% of people are alive taking farming as the main occupation and about 60% of people living with day laboring occupation. The structures of the study area has affected seriously due to prolonged water logging. The brick foundations losses its longevity by corrosive effect of salinity and damping. Water logging causes the damage to roads in the rainy season every year leading to the movement problem and interrupts the journey. The educational institutions of the study area became flooded for long time and the students can’t continue their learning. Crop production also hampered due to prolonged water logging, especially the Amon rice production. From the laboratory investigation of the soil and water sample the average value of sulfate (SO4-2) concentration was found within the optimum range 25-200 mg/L. The nitrate (NO3-) concentration of the soil sample was lower than the optimum range for all location, water sample result found within the optimum range 0 -10mg/L. Nitrogen content was found less than the optimum limit. Potassium, Calcium and Magnesium content was exceed the optimum limit. Phosphorus content in Kumira and Gopalpur union exist within the limit but in the Tala and Tentulia union excess than the optimum limit. The maximum chloride concentration of soil was found .080g/kg, 0.315g/kg, 0.356g/kg and 0.490g/kg of Tentulia, Tala, Islamkathi and Kumira union respectively. Paddy can grow with maximum soil Cl- concentration of 1g/kg without any yield loss. Therefore, rice production has not affected by chloride concentration, salinity related variables or plant nutrients of the study area. It is only affected by prolonged water logging. To safe the study area from the water logging the main drainage path of the study area anyhow need to make smooth to carry the upstream rain water.