Bangladesh is one of the largest deltas in the world having a very flat topography. Three major rivers, the Ganges, the Brahmaputra and the Meghna having a total catchment area of about 1.7 million km2, provides drainage to 1,660,000 km2 of the combined catchment, pass through this country. 93% of the catchment area of these rivers lies outside the country in India, China, Nepal and Bhutan. The country has an average rainfall of about 2300 mm, ranging between 1500 and 5000 mm. Bangladesh has also a unique coastline, conical in shape, which causes a higher sea level during monsoon months. Bangladesh is a disaster-prone country and almost every year, the country experiences disasters like tropical cyclones, storm surges, coastal erosion, floods, droughts and saline water encroachment in the coast. Due to the low elevated topography, river system and rainfall pattern, flood occurs in almost every year.Because of its geographic location and low-lying topographic condition, Bangladesh is likely to be in extreme vulnerable situation under the current scenario of changing in climatic condition, especially the water sector and water dependent agriculture are the most sensitive amongst anticipated impacts. To assess the current trend of hydrologic conditions for overall water resources development and management and to predict future changes due to human activities and climate change impacts, generation of adequate data and information by appropriate monitoring network is utmost important.
The successive floods of 1954 and 1955 caused extensive damages to the livelihood, properties and infrastructure. Floods and flood damages were not unknown in this country but during these floods the damages were so alarming that the Government created a new organisation “Flood Control Organisation” and also sought International help for institutional development and capacity building. As a result under the recommendation of Krugg’s Mission Report East Pakistan Water and Power Development Authority (EPWAPDA) was created by the Ordnance No. 1 of 1959, for the exploitation, management and utilization of the water resources of the country and to develop power supply sector. Immediately after creation of EPWAPDA, Hydrology started working as the Directorate Planning and Investigation under Chief Engineer Planning. By the mid 1960’s, Hydrology was placed under Chief Engineer Hydrology and projects were undertaken to establish monitoring network for hydrological, hydrogeological, morphological data collection and processing.
Hydrographic System in Bangladesh is characterized by the Himalayan to the north, Bay of Bengal to the south, Flood plains of the Ganges (Padma)-Brahmaputra (Jamuna)-Meghna (GBM) River System, Tertiary Hills to the east and southeast and consists of
a. The three major river systems
1. The Ganges-Padma
2. The Brahmaputra-Jamuna
3. The Surma-Meghna.
b. Fifty seven trans-boundary rivers(includes the three major rivers and their tributaries and distributaries).
c. Seven independent riversdraining Chittagong and Chittagong Hill Tracts directly into the Bay of Bengal.
d. Inland water bodies 9wet lands) of haor, baors and beels.
e. A coastline of over 700 km and 10 large estuarine watersin the coastal districts