Publications

Datta, S., Karmakar, S., Mezbahuddin, S., Hossain, M. M., Chaudhary, B. S., Hoque, M. E., ... & Baul, T. K. (2022). The limits of watershed delineation: implications of different DEMs, DEM resolutions, and area threshold values. Hydrology Research, 53(8), 1047-1062. https://doi.org/10.2166/nh.2022.126

Abstract

Identifying and demarcating watershed areas provides a basis for designing and planning for water resources. In this study, DEMs-based estimates of watershed characteristics of three rivers of Bangladesh – Halda, Sangu, and Chengi – were derived using eight Digital Elevation Models (DEMs) of 30 m, 90 m, and 225 m resolution in the Soil and Water Assessment Tool (SWAT). We have assessed watershed characteristics concerning DEMs, resolutions, and Area Threshold Values (ATVs). Though the elevation data differed, high correlation values among DEMs and resolutions confirm the negligible effect of elevation in the watershed delineation. However, the slope and watershed delineation vary for different DEMs and resolutions. The 90 m DEMs estimated larger areas for Halda and Chengi and lower perimeter values for all three rivers. In watershed delineation, the area near the mouth and flat terrain did not coincide with DEMs. The common intersected area by DEMs can be used as the focal area of watershed management. ATV ≤ 40 km2 significantly influences sub-basin counts and stream network extraction for these watershed areas. Though watershed size and shape were independent of the different ATVs, the DEM-based watershed delineation process in SWAT needs optimum ATV values to represent the stream network precisely.

Datta, S., Karmakar, S., Islam, M. N., Karim, M. E., Kabir, M. H., & Uddin, J. (2022). Assessing landcover and water uses effects on water quality in a rapidly developing semi-urban coastal area of Bangladesh. Journal of Cleaner Production, 336, 130388. https://doi.org/10.1016/j.jclepro.2022.130388

Abstract

We have studied the urbanization effect on water resources of a developing semi-urban area on the southeast side of Chattogram (Chittagong) city, enduring industrialization and subsequent urbanization. The landcover comprising water bodies, vegetation, and agricultural lands were 9.36%, 40.55%, and ∼37%, respectively. Domestic water demand was estimated by interviewing households, while water samples were collected using the grab sampling method from rivers, canals, ponds, and groundwater for laboratory analysis. Daily average water consumption increases with growing family size and income. 52.14 million liters per day (MLD) water is needed for households in the study area, with a per capita demand of 123.80 L per day. The daily maximum water demand range of households was 78.20 MLD – 104.27 MLD, with the peak hourly demand being 5.87 MLD. However, available aquifer recharge is estimated as low as 11 million m3 per year. Except for some points, the average pH, TDS, and Cl− values were acceptable, though EC, SS, and COD values were exceeding the water quality standards with a small amount of HCO3− and no CO3− values in the water samples, making the water of the study area less compatible for domestic purposes. The primary causes were waste disposals, saltwater intrusion, and a few instances of industrial discharge. The settlement landcover directly influences water quality parameters pH, TDS, and conductivity in compositional analysis. We believe that expanding the build-up area to the vegetated area will eventually induce water quality degradation, mainly saline water intrusion.

Hossen, S., Ali, Y., Chakma, S., Datta, S., & Hoque, A. S. M. R. (2025). Spatiotemporal analysis of land cover change, projection, and fragmentation: an application of Google Earth Engine and machine learning approach on Baraitali Forest, Bangladesh. Geology, Ecology, and Landscapes, 9(3), 907–920. https://doi.org/10.1080/24749508.2024.2359776

Abstract

Understanding the spatiotemporal dynamics of land cover/use change and forest fragmentation from 1981 to 2021 across the Baraitali Forest was very crucial for modeling future land cover, formulation of sustainable and robust forest/land-management strategies, and policy. The study adopted a mixed modern tool of Google Earth Engine platform, Machine Learning Algorithms, ArcGIS software, Land Change Modeller of TerrSet software, and FRAGSTATS programs. The study revealed that total land cover from 1981 to 2021 found a negative change in vegetative coverage, and a positive change in settlement which was more visible within the 6 land cover classes. Projections of future land cover for the next 10 years anticipate that vegetation coverage will be reduced by 65.96 ha, while settlement will be enhanced by 41.91 ha in 2031. The study also found conversions/transition of land cover throughout the research area. Overall change of spatiotemporal patterns was leading to substantial forest fragmentation. The overall accuracy and Kappa statistics for all the supervised land cover classifications were satisfactory. The study will fill an information gap by providing the revealed information at national and regional scales and may contribute to understanding of global change.

Haque, M. B., Karmakar, S., Datta, S., Sajid, A. P., Mamun, M. A. A., Hoque, M. E., ... & Alam, M. S. (2024). Discharge and sediment load modelling using rating curve-based missing data management. Hydrology Research, 55(10), 959-975. https://doi.org/10.2166/nh.2024.165

Abstract

Hydrological models are vital for water management to determine in-stream flow, irrigational water, domestic water supply, and biodiversity conservation. This study formulates a hydrological model with a novel approach for streamflow and sediment load in the QGIS-supported Soil and Water Assessment Tool for the Halda River catchment, a unique ecological habitat for natural carp spawning and freshwater sources. The daily simulation uses an innovative stage–discharge relationship technique from available 15-day interval flow data. The model evaluation parameters R2 values 0.80 and 0.62, and NS values 0.81 and 0.61 for calibration and validation of streamflow suggested excellent agreement in the seasonal cycle and most of the monsoon peak flow. The streamflow/precipitation ratio indicates a significant influence of groundwater through infiltration. The baseflow shows a decreasing trend. The sediment load based on suspended sediment concentration at a downstream location is 1,625 tons/day. On the contrary, the model prediction is 30 times lower. The scattered sediment load data support the model estimate by considering relatively lower intervention or land use change in its upstream. This model provides a baseline for daily flow and sediment load for scenario modeling (e.g., climate change, land use change) for environmental flow estimation of the fish habitat, freshwater supply, irrigation, and salinity intrusion.

Karim, M. E., Hoque, M. E., Islam, M. N., Hossain, M. M. Bhuiyan., Datta, S., & Karmakar, S. (2020). Land-use and Land Cover Characterisation and Spatial-temporal Analysis of the Matamuhuri River Watershed. The Chittagong University Journal of Marine Sciences and Fisheries, 1(1), 49-65. 

Link: https://cu.ac.bd/cujms/assets/paperfile/21_paperfile_LG3AESI77Z_(4)%20.pdf

Abstract

Changes in physiographic, meteorological, and biogeographic processes affect the river basin process. These natural processes are usually overridden by anthropogenic land use, and land cover changes henceforth affecting basin run-off and sediment load. The Matamuhuri River basin is one of the pristine watersheds of Bangladesh, where settlement density is among the lowest. During the last two decades, rapid land cover changes have become eminent in many regional watersheds of Bangladesh due to population growth and a changing perception of resources. Hence, we have studied the land cover change in the Matamuhuri River basin by selecting Landsat images from the Earth Explorer database managed by USDA for 1989, 2004, and 2019. Four land classes were selected for this study. This study revealed that during 1989 (the base year), the dominant land cover was forest or vegetation, which covered 138,526.29 ha (67.74%) and settlement covered 19,782.72 ha (9.67%). In 2004, the settlement controlled nearly 16.85% of the total land, and vegetation cover had decreased (59.22%). In 2019, the vegetation cover regained its stronghold (66.06%), which may be due to government policy to conserve forest land though a remarkable increase, in settlement also observed. Agriculture land is decreased in this case. It holds nearly 11.85% of the total land (24,231.87 ha). This data shows that as infrastructure development downstream of the watershed increases, the catchment becomes more vulnerable to change. Again, the upstream area's land-cover change is very rapid, requiring adequate conservation attention. The overall accuracy of the classification was calculated at 76.6%, 81.25% and 90.24%, with Kappa coefficient values of 0.69, 0.75 and 0.87, respectively, for 1989, 2004 and 209 image classification. The overall Kappa accuracy test shows the strength of the supervised classification performed in this study.

Datta, S., Nawaz, S., Hossen, M. N., Karim, M. E., Juthy, N. T., Hossain, M. L., & Kabir, M. H. (2023). Flood risk assessment in developing countries: Dealing with data quality and availability. In V. O. Oladokun, D. Proverbs, O. Adewale Adebimpe & T. Adedeji (Eds.), Handbook of flood risk management in developing countries (pp. 197–216). Routledge, Taylor and Francis. https://doi.org/10.1201/9781003160823-16

Abstract

Flood risk assessment (FRA) assists in formulating disaster management strategies for a country and identifies climatic and geographical factors of disaster with spatial and temporal variability and impact on society. Developing countries like Bangladesh, India, Nigeria and Indonesia are the top victims of floods. However, FRA studies in these countries were less noticeable before 2018. A systematic literature review approach is used to find the models and techniques employed in FRA studies of these countries. Additionally, required data and their sources, which were used for risk mapping, land use planning, flood mitigation and management, were also focused on with the approach. Most of the studies integrated statistical models, remote sensing and GIS models like the analytical hierarchy process and hydrological and watershed models. Though most of the data were available locally for the mentioned developing countries, global disaster and spatial databases were also significantly used in the studies.

 Karmakar, S., Hoque, Md. E., Mamun, M. M. A. A., Parvez, M. A., Datta, S., Islam, Md. N., Karim, M. E., and Alam, M. S.: Catchment land use and river morphological changes effect on flow and pollution load of Halda River: implication in integrated river management, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1109, https://doi.org/10.5194/egusphere-egu2020-1109, 2019

Abstract

Halda River originated and ends inside Bangladesh, is a unique natural carp spawning habitat that underwent a massive channel modification, intensive land use and land cover changes across its basin both in the upstream and downstream area over the decades. The carp fish breeding habited is heavily disturbed that marked by a significant reduction in fish spawning in recent years. The fish habitat of this river is reported as critically endangered in many studies. However, these problems are not studied in a hydrological perspective apart from fish spawning characterization and water quality nexus. We have studied the flow regime of the catchment for different seasons and its effects on water quality, siltation, and erosion of this river at 12 cross-sections at the upper course and middle course. Water level and discharge data that are available from the regulatory authority, Bangladesh Water Development Board for the last 40 years at an upstream cross-section and rainfall data at 4 stations of the catchment were studied and integrated to understand nutrient load using QSWAT. The upstream-downstream linkage is heavily regulated followed by the construction of an earthen dam and rubber dam on its major tributaries at upstream for irrigation to the agricultural land that was revealed from this study and field visits. Moreover, basin land-use and land-cover change would have a significant contribution to sediment dynamics eventually causing siltation and erosion in downstream cross-section. The increase in agricultural land that altered forest vegetation would affect runoff characteristics and water quality. We have reported that the change in sediment load and siltation in its downstream and at different hydraulic structure points (here sluice gate, irrigation canals, and embankments) would be attributed to land-use change and flow regulation. This study reports the relationship to the hydraulic response viz. discharge, the water level of this river system to the catchment land use and siltation. Floods are more likely to occur in the downstream region compared to the upstream region in the same hydro-meteorological regime in this basin as it revealed from the river section changes over time.

Shyamal Karmakar, Srijon Datta, Marjena Beantha Haque, Ayub Parvez, Mir Enamul Karim, Abdullah Al Mamun, M Shafiul Alama and M Mozzaffar Hossain

Link: https://doi.org/10.13140/RG.2.2.22918.45122

Abstract

Developing and testing hydrological models in data poor regions is vital to support water management facilities. Quantum-GIS was integrated to the Soil and Water Assessment Tool (SWAT) to simulating streamflow and sediment transport in Halda Basin using MERIT Digital Elevation Models (DEMs). This hydrological model used 1990-1992 as the observation and 1993-1997, 1999-2001 as calibration and validation period. The models evaluation parameters R2 value 0.85 and 0.80, NS value 0.84, 0.79 for calibration and validation using streamflow of Panchapukuria station suggested a very good agreement in seasonal cycle and most of the monsoon stream flow. The streamflow/precipitation ratio indicates significant influence to groundwater through infiltration. The baseflow is decreasing and significantly affected by the dam construction. This study could serve as a baseline for scenario modelling (e.g. , climate change), environmental flow estimation for fish habitat, freshwater supply, irrigation and salinity intrusion.

Shyamal Karmakar, Srijon Datta, Marjena B. Haque, Iftekhar S. Khan, Md. Abu Syed

Link: https://www.researchgate.net/publication/390944224_EFFECTS_OF_SRM_ON_THE_HYDROLOGY_OF_MEGHNA_RIVER_BASIN

Abstract

Meghna and Brahmaputra are two transboundary rivers that drain through Bangladesh to reach the Bay of Bengal, where the upper basins are shared by India, India and China, respectively, joined Ganges-Padma to become fifth largest river basin with highest inhabitation in planet earth. This two neighboring watershed share the most precipitation as monsoon (June-September) due to its orographic barrier. We have used QSWAT, a semi-distributed physical model using standard soil, land use, and elevation dataset of baseline 2010, to set a hydrological model for historical phase, 2001-2020, control phase (2020-2035), and three SRM phases, 2036-2050, 2051-2070, and 2071-2099. The daily river discharge of the Meghna River was calibrated at the downstream discharge point, Bhoirab bazar, Bangladesh where smaller sub-basin discharge also compared. Five ESMs (MPI-LR, UKESM, IPSL CESM2, and CNRM) simulated data of G6Sulfur SRM scenarios were compared with two emission scenarios, SSP245 and SSP585. Monsoon discharge varies significantly, followed by the post-monsoon discharge. Each sub-basin yearly mean surface runoff of hydrological simulation showed significant changes in four sub-basin during SRM phase III  compared to SSPs.