Hydrologic monitoring and analysis in the Sundarbans mangrove ecosystem, Bangladesh Shahriar Md. Wahid a, * , Mukand S. Babel a , Abdur Rahman Bhuiyan b a Water Engineering and Management, Asian Institute of Technology, P.O. Box 4, Khlong Luang, Pathumthani 12120, Thailand b Institute of Water Modelling, House 476, Road 32, New DOHS, Dhaka, Bangladesh Received 28 July 2005; received in revised form 20 July 2006; accepted 25 July 2006 Summary The unique habitat of the Sundarbans mangrove ecosystem is dependent upon the hydrological regime. Therefore, a comprehensive study to understand the hydrologic behaviour and the changes that have taken place due to anthropogenic activities in and around the area is fundamental to the management of natural resources and environment. In the past, ad hoc and uncoordinated efforts were made due to the inherent inaccessibility and high cost of data col- lection. The present article documents the results of the hydrologic monitoring, modelling and analysis in the Sundarbans. The study results show that the annual maximum tidal range has increased by about 0.75 m in the eastern and central parts during the last two decades. About 60% area remains in higher salinity condition (>20 ppt) for at least 1.5 months in a year. Organic pollution in the waterways is within the Environmental Quality Standard (EQS) of Bangladesh with the average Dissolved Oxygen (DO) of 5.99 mg/L. Total Ammonia, Nitrate (NO 3 –N) and Phosphate (PO 4 –P) level are present in sufficient quantity for the aquatic life to survive and are within EQS limit. Lead and Chromium occasionally exceed EQS limit especially along the large barge routes in the western part. The data and information presented in the paper will serve as a baseline for future hydrological and environmental studies. ª 2006 Elsevier B.V. All rights reserved. KEYWORDS Hydrological monitoring; Mangrove ecosystem; Mathematical modeling; Sundarbans; Bangladesh Introduction The mangrove-dominated Ganges delta – the Sundarbans – is a complex ecosystem comprising one of the three largest single tract mangrove forests of the world (Blasco, 1975). Shared between two neighboring countries, Bangladesh and India, the larger part (62% of the total mangrove ecosys- tem) is situated in the southwest corner of Bangladesh be- tween latitudes 21°27 0 30 00 –22°30 0 00 00 North and longitude 89°02 0 00 00 –90°00 0 00 00 East (Fig. 1). The western boundary of the Bangladeshi Sundarbans follows the Harinbhanga– Raimangal–Kalindi river system and abuts with the Indian 0022-1694/$ - see front matter ª 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhydrol.2006.07.016 * Corresponding author. Tel.: +662 524 5561; fax: +662 524 6431. E-mail addresses: swahid@gmail.com (S.Md. Wahid), msbabel@ ait.ac.th (M.S. Babel). Journal of Hydrology (2007) 332, 381– 395 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/jhydrol