Abstract
Rapid urbanization, industrialization, and development activities are posing numerous threats to the rivers of Bangladesh. In the recent decade, Turag River has been exposed to severe threats due to anthropogenic activities. The present research deals with the evaluation of water quantity–quality, landuse and landcover (LULC), and land surface temperature (LST) of Turag River and its floodplain by using an integrated approach of field study, laboratory analysis, and geospatial techniques. LULC mapping of the study area has been done using multi-temporal Landsat satellite images by unsupervised method, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index indices (NDWI) approach. From LULC classification, the study shows that the average reduction of water bodies from 1989 to 2019 is about 60–66%, and the rate of reduction is about 14.25 ha per year. Due to anthropogenic activities and rapid urbanization, a large number of water bodies have been depleting. The average temperature of the river water from filed observed data is 30.23 °C and from image processed data is about 28.32 °C. The minimum and maximum values of pH, EC, TDS, and Eh are 6.87–8.44, 808–1192 μs/cm, 406–739 ppm, − 31 to – 150 mV, respectively. The concentration ranges of cations (Na, Ca, Mg, K, Fe, and Mn) are 85.43–247.60, 28.59–39.47, 11.1–13.58, 5.21–13.26l, .07–1.14, .006–.47 mg/l consecutively. The ranges of anions concentration (HCO3−, Cl−, SO42−, NO3−) are 165.45–388.87, 54.81–194.07, 52.49–289.63, l9.63–126.93 mg/l, respectively. It is evident that HCO3−, NO3−, and Mn exceed the standard limit of Bangladesh Water Quality Standard (BWQS) and World Health Organization (WHO), indicating that the water of the Turag River is deteriorating that is not safe for human consumption and aquaculture purposes. The study will assist to take some effective measures to control the pollution and uphold the water quality and natural riparian processes. So, the outputs of the study will contribute to the future urban landuse planning in the river floodplain area to mitigate ongoing alarming pollution and unplanned industrialization.
Highlights
Bangladesh is a riverine country with its major Ganges, Brahmaputra, and Meghna (GBM) river system
The prime objective of this study is to investigate and monitor the changes of water bodies, landuse and landcover (LULC) surrounding the Turag River, and land surface temperature in and around the river both the quality and quantity of the Turag River using multi-spectral Landsat satellite images from 1989 to 2019
A total of five LULC classes of the study area have been classified such as water bodies, vegetation, bared, and urban area
Summary
Bangladesh is a riverine country with its major Ganges, Brahmaputra, and Meghna (GBM) river system. Numerous small tributaries and distributaries of this major river system are draining throughout the country. River has a vital role in civilization, but unplanned urbanization has been playing a negative impact on the natural processes of rivers. Rivers in Bangladesh serve people by providing waterways, energy sources, and agricultural activities. Turag River is a vital channel flowing through the northwestern part of the megacity Dhaka that is geologically located on the south-central region of Madhupur tract and drains toward the southern part of the country [1]. The major landuse along the banks of the Turag River has been
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