MOHAMMAD AZIZUR RAHMAN1, JACKSON ROEHRIG2
1Georg-August-Universität Göttingen, Applied Geology, Germany
2University of Applied Sciences Cologne, Institute for Technology in the Tropics, Germany
The study area is in the Northwestern part of Bangladesh, which is one of the driest parts of Bangladesh. The Bangladesh government has decided to increase the crop coverage in this part and thus is looking for sustainable agricultural practices and appropriate management approaches for this area. In this study, hydrological and hydro-chemical investigations have been carried out to determine the basic parameters required for the development of a groundwater model.
About 1233 bore-hole logs have been collected for hydrological analysis and model preparation. On the basis of subsurface lithological information, a regional (Manda, Raninagar, Naogaon, Bagmara and Mohanpur `Upazila') and two local scale hydrostratigraphic models, fence diagrams and cross"=sections have been prepared using rockworks software 2004. The Hydrostratigraphic model and the fence diagram show the presence of two major aquifer systems in the study area, which is separated by a thin aquitard layer. Model cross sections show that in some places the upper aquifer merges with the lower aquifer. The model cross sections also show that the thickness of the upper aquitard is not uniform in the study area. It shows that in the southwestern part the thickness of the upper clay is about 30m higher than in the northeastern part. On the other hand, the thickness of the main aquifer (lower aquifer) is higher in the northeastern part of this area than in the southwestern part.
A thickness map of the aquifer was constructed using the sounding interpretation results for the `Manda Upazila' block. This map shows the maximum thickness of 125m for Chak Siddesshwari and Talpatila areas and this gradually decreases towards the surrounding areas. Comparing the sounding results with the available water quality data, reveals that the aquifer in the lower part bears saline water. Depth contours along the upper surface of the saline zone show that the maximum depth to the saline zone occurs at Talpatila and Chok Siddesshawari areas reaching 114m.
Hydro-chemical investigations show no remarkable aquifer contamination with arsenic. For better management of crop production in this area, the information of the study will assist to prepare an interactive information system and a dicision support system for the government.
Keywords: Aquifer system, Bangladesh, hydrostratigraphic model, irrigation, rockware 2004