Geography and Environment

The study identifies decadal landuse and landcover (LULC) changes during 1988-2017 in north-eastern Dhaka conurbation of Bangladesh. Driving forces behind the changes in the study area have also been investigated.In this study, LULC changes were studied using two Landsat sensors. GIS post-processing technique was used for satellite image classification, while an in-depth literature review was conducted to identify the drivers of land cover change. Accuracy for the classified maps ranged from 79percent to 86percent. It was found that agricultural land decreased 47.02 percent while homestead vegetation land cover has increased about 88 percent in the last thirty years (1988-2017).The in-depth analysis result indicates that Dhaka metropolitan area expansion, increased population, internal migration, ongoing housing development projects, and lack of proper landuse and land management implementation are the main drivers of LULC changes in the study area. The development control approach ...

In marine ecosystems, both living and non-living organisms depend on “good” water quality. It depends on a number of factors, and one of the most important is the quality of the water. The water quality index (WQI)
model is widely used to assess water quality, but existing models have uncertainty issues. To address this, the authors introduced two new WQI models: the weight based weighted quadratic mean (WQM) and unweighted based root mean squared (RMS) models. These models were used to assess water quality in the Bay of Bengal, using seven water quality indicators including salinity (SAL), temperature (TEMP), pH, transparency (TRAN), dissolved oxygen (DOX), total oxidized nitrogen (TON), and molybdate reactive phosphorus (MRP). Both models
ranked water quality between “good” and “fair” categories, with no significant difference between the weighted and unweighted models’ results. The models showed considerable variation in the computed WQI scores, ranging from 68 to 88 with an average of 75 for WQM and 70 to 76 with an average of 72 for RMS. The models did not have any issues with sub-index or aggregation functions, and both had a high level of sensitivity (R2 = 1) in terms of the spatio-temporal resolution of waterbodies. The study demonstrated that both WQI approaches effectively assessed marine waters, reducing uncertainty and improving the accuracy of the WQI score.

Groundwater resources around the world required periodic monitoring in order to ensure the safe and sustainable utilization for humans by keeping the good status of water quality. However, this could be a daunting task for developing countries due to the insufficient data in spatiotemporal resolution. Therefore, this research work aimed to assess groundwater quality in terms of drinking and irrigation purposes at the adjacent part of the Rooppur Nuclear Power Plant (RNPP) in Bangladesh. For the purposes of achieving the aim of this study, nine groundwater samples were collected seasonally (dry and wet season) and seventeen hydro-geochemical indicators were analyzed, including Temperature (Temp.), pH, electrical conductivity (EC), total dissolved solids (TDS), total alkalinity (TA), total hardness (TH), total organic carbon (TOC), bicarbonate (HCO3 −), chloride (Cl−), phosphate (PO4 3−), sulfate (SO4 2−), nitrite (NO2 −), nitrate (NO3 −), sodium (Na+), potassium (K+), calcium (Ca2+) and magnesium (Mg2+). The present study utilized the Canadian Council of Ministers of the Environment water quality index (CCME-WQI) model to assess water quality for drinking purposes. In addition, nine indices including EC, TDS, TH, sodium adsorption ratio (SAR), percent sodium (Na%), permeability index (PI), Kelley’s ratio (KR), magnesium hazard ratio (MHR), soluble sodium percentage (SSP), and Residual sodium carbonate (RSC) were used in this research for assessing the water quality for irrigation purposes. The computed mean CCME-WQI score found higher during the dry season (ranges 48 to 74) than the wet season (ranges 40 to 65). Moreover, CCME-WQI model ranked groundwater quality between the “poor” and “marginal” categories during the wet season implying unsuitable water for human con- sumption. Like CCME-WQI model, majority of the irrigation index also demonstrated suitable water for crop cultivation during dry season. The findings of this research indicate that it requires additional care to improve the monitoring programme for protecting strategic planners in order to protect groundwater resources during the any emergencies associated with RNPP groundwater quality in the RNPP area. Insightful information from this study might be useful as baseline for national strategic planners in order to protect groundwater resources during the any emergencies associated with RNPP.

With a total population of 278000, Sandwip has long been facing severe land erosion and accretion problems because of its geographical setting in the coastal area of Bangladesh. This research aimed to assess the erosion and accretion status along with the shoreline movement of this island based on multi temporal Landsat imagery and hydrological data from 1974 to 2014. The results revealed that water discharge and water level data are positively correlated with erosion and negatively correlated with accretion data. The results also indicate that the island has lost around 90 km 2 of its stable and gained around 17 km 2 of new land. The erosion activity is mostly happening in the northwestern, western, and southern banks whereas accretion has been occurring at a slower rate in the northern and eastern banks of the island. Because of this dynamic erosion-accretion activity the shoreline of the island has been moving towards the northeast side. This 40 years' data analysis solemnly affirms that maximum shoreline movement towards the land was 4004 meter in the southern bank with annual rate of approximately 100 m per year. At the same time interval, maximum seaward movement of the shoreline was observed in the northeastern portion (NSM >2247 m) at a maximum net rate of around 56 m per year (EPR = 55.85 m per year). Because of this idiosyncratic characteristic Sandwip's total land area was reduced to 73 km 2 during 1974 and 2014.