Teesta Research Articles

The Role of Sulfuric Acid in Continental Weathering: Insights From Dissolved Major Ions and Inorganic Carbon Isotopes of the Teesta River, Lower Brahmaputra System

AbstractChemical weathering in the Himalayan river basins plays a key role in the global carbon cycle that controls the climate. In this contribution, the spatial distribution of dissolved major ions and (inorganic) carbon isotopic compositions of the Teesta River, a major tributary of the Brahmaputra River, has been investigated to constrain solute sources, weathering patterns, and acids involved in these processes. Mixing diagrams and piper plots of major ions indicate a dominant solutes supply by weathering of silicates and carbonates. The average sulfate concentration of the Teesta samples (92 ± 47 µM) is significantly higher than that reported earlier for atmospheric deposition (∼5 µM) in this basin. The carbon isotopic compositions of the dissolved inorganic fractions (δ13CDIC) of the samples vary between −11.87‰ and −3.82‰ (mean: −7‰ ± 2‰). Comparison of δ13CDIC – SO4/(SO4 + HCO3) – HCO3/(Ca + Mg) trends with their corresponding values expected for H2SO4 and H2CO3 acid‐mediated weathering indicates that both these acids contribute to chemical weathering in the Teesta river catchment. Inversion modeling of major ions and δ13CDIC data have been used to quantify the impact of carbonic (H2CO3) and sulfuric acids (H2SO4) on the Teesta water chemistry. On average, the fractions of cations derived from H2CO3‐mediated weathering of carbonates (0.27 ± 0.14) and silicates (0.20 ± 0.09) are comparable with H2SO4‐mediated carbonate (0.38 ± 0.18) and silicate (0.15 ± 0.11) weathering in this basin. These results show that the amount of CO2 uptake (via H2CO3‐mediated silicate weathering) and release (via H2SO4‐mediated carbonate weathering) are in balance for the Teesta River.

Modeling fragmentation probability of land-use and land-cover using the bagging, random forest and random subspace in the Teesta River Basin, Bangladesh

Land-use and land-cover (LULC) changes have become a crucial issue that urgently needs to be addressed due to global environmental change. Many studies have employed remote sensing data for assessing LULC changes, however, the investigation of fragmentation probability modeling is still scarce in the existing literature. Thus, the coupling of bagging, random forest (RF), random subspace (RSS), and their ensemble model with multi-temporal datasets within the GIS environment makes it possible to model the fragmentation probability of LULC in the Teesta River Basin (TRB), Bangladesh. The number of patch (NP), edge density (ED), largest patch index (LPI), contagion index (%) (CONTAG), aggregation index (AI), perimeter area ratio (P/A ratio), the class area (CA), percentage of landscape (PLAND), patch density (PD), total edge (TE), largest shape index (LSI) and total core area (TCA) were the landscape and class matrices, which were derived from the LULC maps using FRAGSTATS software. The machine learning-based sensitivity models, such as decision tree and support vector machine-based feature selection techniques were implemented to explore the influence of the parameters for fragmentation probability modeling. The results showed that water bodies and barren land were substantially decreased by (6.21%), and (14.59%) respectively while the built-up areas increased by 1.45% from 2010 to 2019. Results revealed that the dominance of the agricultural area has been increased as human interference has been elevated in the TRB. However, twelve class-level and landscape matrices were used to delineate the fragmentation probability zone with the aid of bagging, RF, and RSS algorithms. LULC images and fragmentation probability models were validated using the kappa coefficient and the area under curve (AUC) of the receiver operating characteristics (ROC). The validation outcomes depicted that the three models such as bagging (AUC = 0.864), RF (AUC = 0.819), RSS (AUC = 0.859), and ensemble model (AUC = 0.912) have a good capability to appraise the fragmentation probability, and ensemble model has the highest precision level among three models. Nearly 49% (1789 km2) of the LULC was under a high to very high fragmentation potential zone that requires to be protected with direct measures. The results of sensitivity analysis showed that the number of patches significantly influenced the fragmentation probability model, while the largest patch index was the least sensitive parameter for modeling.

Drought dynamics of Northwestern Teesta Floodplain of Bangladesh: a remote sensing approach to ascertain the cause and effect.

Drought is an affliction for a region that primarily depends on agriculture as economic activity. Commonly monitoring and characterizing of drought is performed by only analyzing the meteorological aspect, assuming precipitation as the primary source of water. However, in riverine Bangladesh, this can lead to an erroneous conclusion, as there is a multitude of available water sources. Consequently, in this study, vegetation condition (Standard Vegetation Index), soil moisture (Soil Moisture Index), and precipitation (Standard Precipitation Index) are separately investigated from 2003 to 2019, in the Northwestern Teesta floodplain. Subsequently, statistical regression analysis is performed to determine the relationships between different aspects of drought. In addition, information obtained from field visits and expert opinions has also been assimilated. Analysis of vegetation and soil moisture condition presents a progressively improving scenario. However, SPI shows an incessant decline in meteorological drought conditions, especially after 2007. Evidently, regression analysis does not provide any indication of an interrelationship between the studied agricultural and meteorological parameters. Presumably, this absence is instigated because the study area is highly irrigated as the groundwater table is suitably near the surface and the existence of nearby Teesta river allows for the utilization of surface water. Moreover, the cropping pattern is shifting toward crops that require much less water and to places where soil moisture is scarce. Thus, this study addresses the gap in knowledge regarding the nature of agricultural drought and the dynamics of different aspects of drought which will be invaluable for the water management and agricultural policy in the study area as well as other regions with a similar backdrop.

Ecotourism and Sustainable Community Development: A Case Study of Sillery Gaon, West Bengal

Ecotourism has a significant role in community development in the host areas through alternative but sustainable livelihood. This tourism practice meets the needs of the tourists and hosts together, protecting the natural environment. Nowadays, this tourism involves visiting new areas to learn about various landscapes, environment, habitats as well as the cultural activities of an individual community. It also expands the possibilities for future. So, ecotourism can be an effective method for sustainable rural development in the Himalayan tract of West Bengal. In Darjeeling and Kalimpong districts of West Bengal, ecotourism is still a community-based activity which involves local people and their culture. Most of the ecotourism sites in this part of West Bengal are within forest and hilly tract. Here growth of ecotourism has been phenomenal during the last decades with the influx of tourists that boosted the local economy. Sillery Gaon, a small village, in ‘Silk Route Circuit’ of West Bengal, is a new addition to it and a perfect example of this scenario. It is situated in Kashyone, gram panchayat of Kalimpong District. This pictorial village is surrounded with the dense forest of Pankhasari range and blessed with the panoramic view of Tista River and Kanchenjunga. In the last ten years, the villagers have developed ecotourism facilities and activities which transformed their traditional agrarian economy to tourism-based livelihood. This paper is based on a case study that analyses the symbiotic relationship between the ecotourism practice and sustainable community development of Sillary Gaon village. It also deals with the prospects and challenges of ecotourism sector of this village.

An assessment of snow-glacier melt runoff under climate change scenarios in the Himalayan basin

In this study, a coupled and improved snow-glacier runoff modeling framework has been presented, which aims to separate the snowmelt runoff from glaciated and non-glaciated areas. To fulfil the above objective, the two hydrological models such as the conceptual Glacier-hydrological Model (GSM-SOCONT) and Soil & Water Assessment Tool (SWAT) have been used over the Teesta river Himalayan catchments. The temperature index model (TIM) based degree-day approach (DDA) in GSM-SOCONT model has been modified and radiation components were added. The R2 values computed between observed and modeled discharge (1991–2005) was improved from 0.55 to 0.63 after adding the radiation components. Initially, SWAT model has been used for the simulation, calibration, and optimization of the various snowmelt hydrology parameters. Then, SWAT model based optimized parameters and outcomes were used as inputs to set up the GSM-SOCONT model. After simulating/separating snow melts from glaciated and non-glaciated areas, the optimized snow-glacier parameters from the improved GSM-SOCONT (1991–2005) were re-input to the SWAT for the projection of snowmelt scenarios (2008–2100) utilizing the downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5) Global Circulation Models (GCMs) datasets. The snow water equivalent (SWE) reconstructed for the year 2005 from the MODIS satellite snow covers (i.e. ranges from 80 to 138 mm) found comparable to the SWAT generated SWE (i.e. ranges from 86 to 115 mm). Based on the future projections of snowmelt, the earlier snow-melting or shifts have been observed in extreme high and low elevation areas of the Sikkim Himalaya.

Comparative Assessment of Vulnerability to Drought and Flood in the Lower Teesta River Basin: A SWOT Analysis

People repeatedly confronted by natural catastrophe in almost every year such as drought and flood in the lower Teesta Basin area. After the construction of two barrages in Gozaldoba and Dalia on Teesta River drought and flood occurs almost every year. Intensity and frequency of these calamities are also increasing in an alarming rate, which caused serious damage to livelihoods and economy of this area. The objective of this paper is to find out the drought and flood induced vulnerability in the study area through Strength Weakness Opportunities Threat (SWOT) analysis. By this we can summarize the current state of a space and helping to devise a plan for the future, one that employs the existing strengths, redresses existing weaknesses, exploits opportunities and defends against threats. The study is conducted in Charkharibari village of Tepakharibari union of Dimla upazilla in Nilphamary district and Jigabari village of Tepamadhupur union of Kaunia upazilla in Rangpur district, taking the locational advantage, flood and drought proneness, topographic nature and population diversity under consideration. The study population is finite and sample size was determined by using Kothari’s formula. Sample size for Charkharibari and Jigabari is 200 and 85 respectively; samples were drawn through Simple Random Sampling (SRS) procedure. The relevant data and information used in this study have been collected from both primary and secondary sources. Primary data has been collected through a questionnaire survey and couple of Focus Group Discussions (FGD’s) with a view to collect quantitative as well as qualitative data. Results from Strength Weakness Opportunities Threat (SWOT) analysis shows that, between the two villages severity of drought and flood is higher in Charkharibari village. After comparing the strengths Jigabari is ahead; comparing weakness, opportunities and threat Charkharibari is ahead. Based on the analysis and the findings, it is evident that in terms of vulnerability Charkharibari is more vulnerable than Jigabari. But there are more opportunities for Charkharibari than Jigabari. However, it is evident that proper dissemination of information regarding early warning and assistance from government as well as non-government organizations can significantly improve the coping capacity of people.

Genetic diversity and population structure of Barilius barna (Hamilton, 1822) in the sub-Himalayan Dooars region of West Bengal, India through Mitochondrial Cytochrome Oxidase I Sequence analyses

The genetic diversity and the population structure of Barilius barna (Hamilton, 1822) wild population from the Teesta River were assessed through mtDNA cytochrome oxidase I (COI) sequence analyses. The haplotype and nucleotide diversity analyses revealed low level of genetic diversity in the B. barna wild populations, especially in the lower reaches of Teesta (Bholarhat). The genetic differentiation and gene flow between the two study sites were 0.08434 and 2.71, respectively. Tajima’s D , Fu and Li’s D and Fu and Li’s F analyses were used to assess population differentiation in the two study sites. Haplotype networking and phylogenetic analyses clearly distinguished the two populations from each other, as well as from other populations from other parts of the country. Nature and implications of the genetic and haplotype diversities among the populations are discussed. Phylogenetic analyses also indicated that the Gajoldoba population is genetically closer to north Indian river populations, than that to Bholarhat population.

Livelihood Improvement of Farmers through Agroforestry Practices in Teesta and Jamuna River Basins

Agroforestry is one of the most sustainable land management systems practiced around the world due to the socioeconomic benefits to farmers. In Bangladesh, farmers practice agroforestry, applying indigenous knowledge. The objectives of the study are to explore the dominant agroforestry systems and species preferred by and to assess the socio-economic impact of agroforestry technologies on their livelihoods of farmers of the Char dwellers in Jamuna and Teesta river basins. The study was conducted at four Char Upazillas such as Kazipur, Shariakandi, Kaunia and Dimla. A total 120 farmers were surveyed during the research period using structured questionnaire with both open and closed ended questions. The majority of the respondents (56.67%) having low score in adoption of traditional agroforestry practices. Most of the farmers (94.17%) in Teesta and Jamuna river basins are practicing traditional homestead agroforestry system. The most frequent strategy was boundary tree plantation (44.17%) followed by scattered tree plantation technique on composite planting system, and the alley of cropland. A total of 41 tree species are abundant in Char areas of Teesta and Januna basins. Eucalyptus (Eucalyptus camaldulensis) is widely adaptable in Bangladesh including Char areas followed by Mango (Mangifera indica) in homestead besides, Mahagony (Swietenia mahagoni) is another abundant species planted in croplands boundaries of Char areas along with Akashmoni (Acacia auriculiformis). The farmers mentioned different problems they were facing in practicing agroforestry but ‘shade cast by trees’ was the major problem. Majority farmers of Char areas plant trees in homestead for fruits (63.33%) and in cropland for fuel wood (95.83%) and timber production (82.50%). Farmers’ livelihoods improved enormously by practicing agroforestry as they have more access to food, fodder and fuel wood which is reflected by greater access to livelihood capitals except social capital. However, the farmers have experienced increased incidences of pests and diseases to annual crops and trees. Agroforestry practices increases species diversity, ensure economic return and sustain farmers’ livelihoods. The respondents, local leaders and experts suggested the constrains of adopting agroforestry in Char areas are lack of awareness, education, technical skills, capital, technical assistance, interest, marketing and transportation facilities at the study areas . The government should initiate some agroforestry focused projects, especially in the Char areas for the capacity building of the farmers and equip them with the new farming techniques through trainings and orientation workshops. The farmers should be provided scientific guidance about suitable tree species grown on agricultural land with field crops, their silvicultural operations and tree management practices along with free services and inputs including seeds, seedlings and loan schemes for promoting agroforestry.

Development of potential map for groundwater abstraction in the northwest region of Bangladesh using RS-GIS-based weighted overlay analysis and water-table-fluctuation technique.

The increasing trend of population growth along with the rapid groundwater-based agricultural expansion and decreasing trend of mean annual rainfall in the Northwest region of Bangladesh has been exacerbating the declination of groundwater for further expansion. Therefore, the present study attempts to demarcate the potential groundwater abstraction zones from the assessment of potential recharge and available recharge. Potential recharge was obtained with commonly used geospatial-based weighted linear combination (WLC) technique. Here, WLC analysis was based on eight factors related to physiographic (e.g. drainage density, lineament density, slope), geomorphologic (e.g. geomorphology, lithology, soil), land use and land cover (LULC) and hydrology (i.e. rainfall). Available net recharge was assessed for the period 1993-2017 by employing the water table fluctuation method. Finally, the resultant map on potential abstraction was characterized into five different classes, viz. 'very low', 'low', 'moderate', 'high' and 'very high'. The derived map reveals that 'very high' potential zone is distributed along the Teesta river floodplain, especially the northeastern part. In contrast, the Barind Tract (i.e. the southwestern and the southcentral parts) area shows 'very low' groundwater prospect. Such fused interpretations are expected to contribute to the planning of integrated management of water resources.

Study on the Present Status of Endangered Fishes and Productivity of Teesta River Closest to Barrage Region

This study was conducted to monitor the present condition of endangered fishes and productivity of Teesta river closest to Teesta barrage situated in the Lalmonirhat district of Bangladesh. Water and sediment samples were collected twice in a month during the study period from six different (3 upstream and 3 downstream) sites with three replications for each. Required information about threatened fishes was collected from the sampling region associated fishermen and fish markets. The study disclosed over 50 threatened fish species in Teesta river including several threatened fishes namely Bagarius bagarius, Sisor rabdophorus etc. The commonly available endangered fishes were Macrognathus aculiatus, Mastacembelus armatus, Barilius tileo, Raiamas bola, Botia dario, B. lohachata etc. which are rarely available in nationwide. Planktonic flora and fauna determination revealed that comparatively higher density of plankton (n >11500 per liter) as well as more number of planktonic flora (>21 nos.) and fauna (>9 nos.) were monitored in the early monsoon and monsoon season (April-September) and comparatively lower planktonic density (n<10000 per liter) and less number were found in premonsoon season (January-February). The investigation of benthic fauna showed that the riverine ecosystem near to barrage contained 16 species of macro-benthos from different groups. Lastly, it can be noticed that it is very essential to take all effective necessary actions to provide good productivity and conserve the ichthyo diversity of Teesta river that will help to conserve the commonly available endangered and critically endangered fishes of Teesta river.
 Res. Agric., Livest. Fish.7(3): 577-589, December 2020

Determinants of Household-Level Coping Strategies and Recoveries from Riverine Flood Disasters: Empirical Evidence from the Right Bank of Teesta River, Bangladesh

Although recurrent floods cause detrimental impact for the people living in riverine floodplains, households are taking up various risks management strategies to deal with them. This paper examined household’s post-disaster coping strategies to respond and recover from riverine floods in 2017. Data were collected through a questionnaire survey from 377 households from the right bank of Teesta River in Bangladesh. Households employed different coping strategies including borrowing money, assets disposal, consumption reduction, temporary migration, and grants from external sources, to cope with flood. Results from logistic regression models suggested that increasing severity of flood reduced households’ consumption. Exposed households were more likely to borrow money. Consumption reduction and temporary migration were mostly adopted by agricultural landless households. Income from nonfarm sources was found to be an important factor influencing household’s decisions on coping. Furthermore, households that recovered from the last flood disaster seek insurance through their own savings and available physical assets, highlighting the role of disaster preparedness in resilient recovery. This study calls for the policy intervention at the household-level to enhance the adaptive capacity of riverine households so that people at risk can cope better and recover from flood disaster using their resources.

Inventory and GLOF hazard assessment of glacial lakes in the Sikkim Himalayas, India

Glacial Lake Outburst Floods (GLOFs) are a recurring hazard in the Himalayas, posing significant threat to downstream communities. The North Sikkim district of India, comprising the upper reaches of the Teesta River in the Eastern Himalayas, has experienced past GLOF events. The identification of lakes susceptible to this phenomenon is therefore paramount. Using multi-temporal satellite images, this study tracks lake growth in the region, revealing that 203 new lakes had developed herein during the observation period (2000–2018). Of these, 82 lakes had formed during 2011–2018 alone; indicating marked glacial retreat and consequent lake area growth, alongside a rising temperature trend. Using various weighted geometric and geomorphic parameters, the 36 most hazardous lakes were identified, from which the 10 lakes posing the greatest GLOF threat were discerned. These lakes are mostly situated along the main snowline and Great Himalayan water-divide in the north-eastern part of Sikkim and should be monitored continuously.

The factor analysis of groundwater quality data of the Tista floodplain and the Dharla floodplain, Kurigram, Bangladesh: Siderite dissolution is a source of iron in groundwater

The present research work deals with the hydrochemical nature of the groundwater samples of the Dharla and the Tista River floodplains of Kurigram district, Bangladesh. The mechanism of groundwater chemistry was studied from the Gibbs plot and it can be summarized that precipitation and rock-water interaction are the major factors that influence the groundwater chemistry. The first four factors comprise 83.243% of the total variability of the groundwater samples of the Dharla floodplain aquifer whereas in case of the groundwater of the aquifers of the Tista floodplain first five factors constitute the 81.298% of the total variability of the original data. The study shows the dominance of HCO3-1 in the anionic part of the groundwater. More than 73.68% of the groundwater samples of the aquifers of the Tista floodplain exceed the maximum permissible limit of WHO for arsenic. The groundwater samples from the Tista floodplain especially from some parts of Rajarhat have high concentrations of iron. The first factor of the Dharla floodplain is dominated by iron and HCO3-1 ions which suggests the derivation of iron in the groundwater of the study area from the chemical weathering of siderite (FeCO3).

Upstream downstream divergence and hydro‐socioeconomic distress in South Asia

AbstractThe issue of transboundary river management is highly pertinent to South Asia with conflicts emerging in water resource management and utilization which indeed affect the beneficial uses of downstream states. The paper considers the situation of the Teesta river basin to assess the water unavailability driven agricultural shock, cost of loss and damage of the downstream region, identify the mutual benefits of water collaboration, and suggest potential adaptation options for water unavailability. The study found during 1995–2010, the annual mean discharge in the upper Teesta floodplain was 707 cumec, where the downstream discharge was 140 cumec and during 2005–2010 the downstream region received less than 8% of the mean annual discharge which may be attributed to reduced flow from the upstream region due to the intense operation of dams and barrage. Consequently, the water reliant 5,000 villages and 12 sub‐districts of lower Teesta basin of Bangladesh were found to be experiencing immense hydro‐socioeconomic impairment and food insecurity. The study estimates that in the Rangpur region, total loss and damage of Boro rice production is 15,08,020 metric tons during 2006–2015, and in the Nilphamri total loss and damage is estimated 9,83,054 metric tons during the same period. Here, the total computed economic loss for both the region is $564 million from 2006–15 FY, which remarkably trims down the overall agricultural production and socio‐economic situation in the lower Teesta region of Bangladesh and fuel the hydro‐economic and political tension between the close riparian.

Living with Recurrent Flooding Risks in Bangladesh: Understanding Household Perception of Riverine Flood Disaster Risks and its Determinants

Riverine people are often affected by floods because of their proximity to the riverbank. Numerous studies were conducted on the physical characteristics of floods; however, there is still inadequate knowledge on the perception of flood risk of riverine households in Bangladesh. The present study explores the risk perception of riverine households to recurrent flood disaster and its associated determinants. Using systematic random sampling technique, 377 members from 377 households (one person from each household) were interviewed from the right bank of the Teesta River, Bangladesh. The results revealed that the sex of respondents, household’s income, house location, and extents of damage to the houses significantly influenced respondent’s ris perception. ale and female had a different perception of flood risk. Respondents whose houses were destroyed completely were found to be more fatalists to report their concern about the future flood. The majority of the respondents underestimated the likelihood of future flood occurrence. The findings of this study offer important implications for the risk managers to provide training to the riverine people to raise their awareness and perception about flood risk.

An assessment of vital water quality parameters of Teesta River closest to barrage region in Lalmonirhat district of Bangladesh

This study was conducted to monitor the key water quality parameters of Teesta river ecosystem closest to Teesta barrage from July 2018 to April 2019 (10 months) situated in the Lalmonirhat district of Bangladesh. Water samples were collected twice in every month from different six sampling sites selected from the upstream and downstream regions of the barrage. Monitored minimum temperature (21.67 ºC) was recorded in the month of January and it was maximum in the month of July (32.03 ºC). Gradual increase of temperature was recorded from March to July (early monsoon) indicated that water temperature was normally uplifted according to the seasonal change. The observed dissolve oxygen level showed relatively in the month of July (6.5 mg/l) and higher in the month of January (8.1 mg/l). Average temperature and dissolved oxygen fluctuations were significantly (p< 0.05) varied among different sampling months. Inverse relationships were observed between water temperatures and dissolve oxygen level. It is important to note that downstream region of barrage had slightly higher DO level than the upstream region that might the impact of barrage water flow. The recorded pH revealed that slightly alkaline pH level found in all the year round (7.1 to 7.7). Besides, both nitrate-nitrogen and phosphate-phosphorous levels were observed little higher in the late monsoon. The findings of this study suggested that better ecosystem health (temperature, pH and abundance of plankton) was observed in early monsoon season.

The geological setting of arsenic enrichment in groundwater of the shallow aquifers of the Tista Floodplain, Rangpur, Bangladesh

Arsenic is present in water samples within the studied active floodplain areas of the Tista river, Rangpur Division, Bangladesh. All the water samples contain less arsenic than the WHO prescribed limit of 10 μg/L. 93.33% groundwater samples have higher Mn content than the permissible limit of 0.01 mg/L of WHO. The heavy metal concentrations of water can be expressed as Fe&gt;Mn&gt;Zn&gt;As on the basis of their mean content. The heavy metals are negatively correlated with the well depth which is indicative of the influence of the anthropogenic activities on the concentrations of heavy metals. The arsenic concentration in water samples is higher in the central part of the study area. The coarser grain size, dominance of physical weathering, elevated topography and the effective flushing of groundwater resulted low concentration of arsenic in the groundwater. The EDS study reveals that arsenic occurs as coating materials of the silicate minerals. The river waters also have arsenic content lower than WHOs permissible limit. The factor analysis reveals that the iron and arsenic is released by the chemical weathering of arsenic bearing minerals like pyrite and arsenopyrite. The Fe and Mn derived in the groundwater by the chemical weathering of iron and manganese bearing minerals such as iron rich clay, silicate minerals and iron sulfides. Â

Marginal value of sub-watershed treatment on profit in Darjeeling district, India

Continuous soil erosion if unchecked would have adverse consequences on agricultural productivity. Of the many soil conservation measures in place to address this issue, those that are large-scale can not only limit soil erosion but also restore soil cover. In the Teesta River Watershed in Darjeeling district in the Eastern Himalayas, the government has undertaken soil conservation interventions at the sub-watershed level. This study assesses whether farm profits are significantly different between treated and untreated sub-watersheds, using data from a primary survey conducted in Darjeeling in the year 2013. The major problem in estimating the impact was identification and hence we used instrument variable. We estimated a farm profit function using the two-stage least square method and found that overall profits were higher in treated sub-watersheds than in untreated sub-watersheds.

Flood susceptibility modelling using advanced ensemble machine learning models

Floods are one of nature's most destructive disasters because of the immense damage to land, buildings, and human fatalities. It is difficult to forecast the areas that are vulnerable to flash flooding due to the dynamic and complex nature of the flash floods. Therefore, earlier identification of flash flood susceptible sites can be performed using advanced machine learning models for managing flood disasters. In this study, we applied and assessed two new hybrid ensemble models, namely Dagging and Random Subspace (RS) coupled with Artificial Neural Network (ANN), Random Forest (RF), and Support Vector Machine (SVM) which are the other three state-of-the-art machine learning models for modelling flood susceptibility maps at the Teesta River basin, the northern region of Bangladesh. The application of these models includes twelve flood influencing factors with 413 current and former flooding points, which were transferred in a GIS environment. The information gain ratio, the multicollinearity diagnostics tests were employed to determine the association between the occurrences and flood influential factors. For the validation and the comparison of these models, for the ability to predict the statistical appraisal measures such as Freidman, Wilcoxon signed-rank, and t-paired tests and Receiver Operating Characteristic Curve (ROC) were employed. The value of the Area Under the Curve (AUC) of ROC was above 0.80 for all models. For flood susceptibility modelling, the Dagging model performs superior, followed by RF, the ANN, the SVM, and the RS, then the several benchmark models. The approach and solution-oriented outcomes outlined in this paper will assist state and local authorities as well as policy makers in reducing flood-related threats and will also assist in the implementation of effective mitigation strategies to mitigate future damage.

Mechanism of elevated radioactivity in Teesta river basin from Bangladesh: Radiochemical characterization, provenance and associated hazards

This work presents a river basin (Teesta River, Bangladesh) which possesses significantly higher radioactivity compared to other freshwater basins around the globe. A total of thirty sediment samples were collected to determine the naturally occurring radionuclides (226Ra, 232Th, and 4 K)and elemental abundances using the HPGe gamma spectrometry and instrumental neutron activation analysis (INAA), respectively. To understand the provenance of higher radioactivity, the compositional elements (Sc, Ti, V, Fe, La, Ce, Sm, Eu, Dy, Yb, Lu, Hf, Ta, Th, and U) of heavy minerals are thoroughly studied, where ∑REEs (rare earth elements), Hf, Ta, Th, and U are ∼2 times higher than the crustal values with negative Ce and Eu anomalies. Mechanism to co-occurrence among radioactivity concentrations and REEs has been explored in this work. Enrichment of light rare earth elements ( × 2.01 UCC) and thorium ( × 2.8 UCC), and Th/U (=5.54 ± 1.05), 232Th/4 K ratio and statistical analyses demonstrate the presence of heavy minerals with monazite predominance. Accumulations of these minerals are most likely due to the fluvial suspended sediments transported by the hydrodynamic forces from up-stream. Elemental ratios including La/V, Th/Yb, Th/Sc, and Hf/Sc confirm the dominance of felsic-source over the mafic-components and the source of sediment has experienced major recycling and sorting during transportation. Evaluation of radiological risks invokes ionizing radiation related hazards to the local inhabitants and the householders residing in the buildings comprised with sandy river sediments. However, minute probability of REEs, Th, and U entrance to the human body through food chain can cause trivial health risks.