The southwest coastal region of Bangladesh, being under tidal
influence and dependent on sweet water supplies from upstream, has a unique
brackish water ecosystem. The region, having vast low-lying areas enclosed by
man-made polders, is considered to be highly vulnerable to climate change
induced hazards. In this study, linear trends in hydro-climatic variables, such
as temperature, rainfall, sunshine, humidity, sweet water inflow and tidal
water level in the region are assessed using secondary data and following both
parametric and nonparametric statistical techniques. Correlation between the
sweet water flow from the Gorai River, a major distributary of the Ganges
River, and the salinity level in the Rupsa-Pasur River near Khulna, a southern
metropolis, is also investigated. The results reveal that the temperature in
the Khulna region is increasing at a significant rate, particularly in recent
years. The number of extremely cold nights is decreasing and the heat index is
increasing. The sunshine duration has a decreasing trend and the humidity has
an increasing trend. Rainfall is increasing in terms of both magnitude and
number of rainy days. However, the annual maximum rainfall and the number of
days with high intensity rainfall have remained almost static. The annual
maximum tidal high water level is increasing and the annual minimum low water
level is decreasing at a rate of 7 - 18 mm and 4 - 8 mm per year, respectively.
There is a negative correlation between the Gorai flow and the river water salinity
around Khulna. Dredging of the Gorai during 1998-2001 resulted in an
improvement of the salinity situation in the Khulna region. The variation in
water salinity, tidal water level and sweet water flows in different time
periods indicates that the human interventions through upstream diversion and
coastal polders have contributed more in hydro-morphological changes in the
southwest than the climate change. However, there are some evidences of climate
change in the meteorological variables at Khulna.