Deltaic Region Research Articles

Improving River Bathymetry and Topography Representation of a Low-Lying Flat River Basin by Integrating Multiple Sourced Datasets

Topography represented in the form of Digital Elevation Models (DEMs) has profound applications in hydrological modeling. DEMs can be generated from several sources including satellite products, contours, survey data, and LiDAR, each with their own merits and demerits. Where high resolution, accuracy, and spatial extent are concerned, it is often found that a DEM from one source alone is not able to represent the topography of the target area with full accuracy. Upon comparing different DEMs, it was found that most were able to successfully represent mountainous regions but failed to represent flat deltaic regions. Therefore, in this research with Bago River basin, Myanmar as a study area, a new methodology to combine multiple sources of data with different data types is developed. The inputs are: (a) a 10 m DEM, developed using contour data, point elevation data, and UTM topographic maps; (b) a 5 m Digital Surface Model (DSM) acquired by the Advanced Land Observation Satellite (ALOS); and (c) 168 sets of multiple-point elevation data representing a cross-sectional survey along the Bago River and the Bago-Sittaung canal. The output is a 10 m resolution Enhanced DEM (EnDEM) which is able to preserve the merits of all the input data, i.e., upper mountainous region, lower flat deltaic basin, and the river bathymetry. This paper provides a novel approach to DEM integration and burning of the river cross-section onto the DEM.

Primary productivity connects hilsa fishery in the Bay of Bengal

Tropical hilsa shad (Tenualosa ilisha) contributes significantly to the society and economy of Bangladesh, India and Myanmar, but little is known about their habitats across the life cycle and their relationship with environmental drivers. This study describes spatial and temporal variability of productivity in the Bay of Bengal (BoB) relating to hilsa fishery. Decadal data on net primary productivity, nutrients (i.e. nitrate, phosphate and silicate) and zooplankton were collected from Aqua MODIS, world ocean database and COPEPOD respectively with spatial resolution 1°×1°. Moreover, monthly abundance of phytoplankton, hilsa catch and long-term catch dynamics were analyzed to determine the associations between variables. The present study was extended over 3.568 million km2 area, of which 0.131–0.213 million km2 area characterized as the most productive with net primary production of >2,000 mg C/m2/day, 0.373–0.861 million km2 area as moderately productive with 500–2,000 mg C/m2/day, and 2.517–3.040 million km2 area as the least productive with <500 mg C/m2/day which were consistent with field verification data. In case of nutrients, the Ganges-Brahmaputra-Meghna (GBM) delta was rich in nitrate and phosphate than that of the Ayeyarwady delta, while silicate concentration persisted high all over the northern BoB including the deltas. A peak abundance of phytoplankton was observed in GBM delta during the months of August-November, when ~80% of total hilsa are harvested in Bangladesh annually. Variations in seasonal productivity linked with nutrients and phytoplankton abundance are important factors for predicting hilsa habitat and their migration patterns in the deltaic regions and shelf waters of BoB. These results can be useful in forecasting potential responses of the hilsa in BoB ecosystem to changing global ocean productivity.

Developing an Integrated Nuclear Waste Management Strategies on Aggregate Orphan Source Radioactive Materials in the Oil and Gas Sector.

Orphan sourced radioactive waste materials associated with oil and gas exploration, exploitation and production have been identified as causal factors in environmental health risks of operation personnel and the host communities in the Niger Delta. These Technologically Enhanced Radionuclides such as 14C, 40K, 87Rb, 232Th, 288U and some low frequency radioactive heavy metals constitute potential dangers to environmental health assay. Highly Sensitive Radiation Detection Tracers (HSRDT) were deployed for tracking and analysis of ionized leakages in the coastal marine offshore and shallow offshore areas in in a typical deltaic region. The inverse determination technique of the generalized half-life period was integrated into the model equations 1 – 12. Table 1 is a survey from 1992 t0 2015, showing that some identified radionuclides are reactive and contaminants to the surrounding environment from oil and gas processes. However, inadequate strategic decommissioning activities are responsible for severe occupational and environmental hazards to flora and fauna. This paper is fundamental to developing an integrated orphan waste management system as remedial techniques to minimize radiation waste burns and other harmful environmental effects on personnel and the environment. Its application is useful for decision-making on radioactive waste material management strategy. Furthermore, possible conceptual legal framework and standards for the disposal system of orphan sourced radionuclides in the petroleum sector could be explored. Keywords: Radioactive Waste Materials; Aggregate Orphan–Sourced Radionuclides; Environment Management; Waste Disposal Systems; Oil and Gas Sector etc.

Coastal inundation due to tropical cyclones along the east coast of India: an influence of climate change impact

Coastal inundation due to storm tides is computed using ADvanced CIRCulation (ADCIRC) model along the east coast of India. Inland inundation due to storm tides is calculated every 10 km along the coast by using synthetic tracks as described in Rao et al. (Nat Hazards, 2019. https://doi.org/10.1007/s11069-019-03804-z). The cyclonic winds are computed using a maximum pressure drop of the cyclone based on a 100-year return period. The coast is mapped for the maximum possible extent of inland inundation with water levels at the district level. The influence of climate change impact as a result of global warming on the coastal inundation is evaluated by enhancing the intensity of the cyclones. Peak water levels of about 10–12 m are found along the north of Odisha coast. The most vulnerable region in terms of coastal inundation in the present scenario is found in the districts of West Bengal; however, they are the least affected by about 5–6% due to climate change scenario (CCS). The most affected inundated districts by more than 50% due to CCS are observed in the Godavari deltaic region in Andhra Pradesh. Though the water levels in the Ramanathapuram District in Tamil Nadu reach more than 8 m in any scenario, the region is unaffected by the coastal inundation due to high local topography. By examining the inundated area of different water levels, it is revealed that more than 75% of the total area is inundated with greater than 2 m water levels in the northern districts of Odisha and Ramanathapuram District in Tamil Nadu.

Processes and characteristics of hydrogeochemical variations between unconfined and confined aquifer systems: a case study of the Nakdong River Basin in Busan City, Korea.

This study is to assess the hydrogeochemical characteristics of groundwater at the deltaic region of the Nakdong River Basin in the Busan Metropolitan City of Korea. The study area is covered by the Quaternary sedimentary deposits and the Cretaceous granites associated with unconformity. The thick sedimentary deposits consists of two aquifers, i.e., unconfined and confined aquifers on the basis of clay deposit. Groundwater samples were collected from seven boreholes: two from unconfined aquifer and five from confined aquifer systems during the wet season of 2017year. ORP and DO indicates thatthe groundwater of the unconfined aquifer exists in the oxidization condition and that of the confined aquifer pertains in the reduction condition. Piper's trilinear diagram shows CaSO4 type for groundwater of the unconfined aquifer, and NaCl type for that of the confined aquifer. Ionic concentrations of groundwater increase in the confined aquifer because of direct and reverse ion exchange processes. Carbonate weathering and evaporation are other mechanisms in the water-rock interaction. Saturation indices of dolomite and calcite are observed as oversaturated, while halite reveals undersaturation. Hierarchical cluster analysis (HCA) exhibitsthat cluster 1 and cluster 2 represents the properties of groundwater in unconfined and confined aquifers, respectively. Factor analysis shows that groundwater of the confined aquifer is much influenced by seawater, and includes heavy metals of iron and aluminum. Groundwater samples in unconfined and confined aquifers are located at the rock weathering and evaporation zones in the Gibbs diagram. Inverse geochemical modeling of PHREEQC code suggests that carbonate dissolution and ion exchange of major ions are the prevailing geochemical processes. This comprehensive research provides the distinguished hydrogeochemical characteristics of groundwater in confined and unconfined aquifer systems of the Nakdong River Basin in Busan City, Korea.

Optimal interventions for flood control, drainage and irrigation project improvements

ABSTRACTA Mixed-Integer Nonlinear Programming (MINLP) model is formulated and solved in this study to optimize environmental sustainability of flood control, drainage, and irrigation (FCDI) projects in the deltaic regions of Bangladesh. The model optimizes the value of integrated resource benefit, a dimensionless variable defined to measure the environmental sustainability based on the water, agricultural and ecological resources, with a set of project interventions being the major drivers. The resource benefits were evaluated with the help of several indicators, such as flood, navigability, salinity, waterlogging, cropping intensity, land loss and vegetation. The solution of MINLP model provided optimal values of the decision variables, which are the quantities of project interventions (e.g. length and height of dike, number of sluices and drainage inlets, lengths of drainage canals, erosion protection and afforestation works). The approach and the MINLP formulation presented in this study can be used for any real-life FCDI project improvements.

Application of water quality index, synthetic pollution index, and geospatial tools for the assessment of drinking water quality in the Indus Delta, Pakistan.

Seawater intrusion into the Indus Delta, Pakistan, has spoiled groundwater aquifers in the area. In the delta, the groundwater is widely used by residents for drinking. Considering the gravity of the problem, and concerns expressed by affected communities, the present study was conducted to assess and map the quality of groundwater, based on the physico-chemical properties of 180 samples, using two standard numerical indices, geospatial and statistical techniques. The analysis of water samples revealed that several parameters exceeded the drinking water quality guidelines suggested by the World Health Organization (WHO). The water quality index (WQI) identified that about 1.7%, 1.1%, 27.8%, 42.8%, and 26.6% of the water samples were excellent, good, poor, very poor, and unsuitable for drinking purposes, respectively. However, the synthetic pollution index (SPI) ranked the quality of 2.8%, 2.2%, 23.9%, 41.7%, and 29.4% as suitable, slightly polluted, moderately polluted, highly polluted, and unsuitable, respectively. Though the numerical model's input is different, the proportionate ranking revealed a fair correlation (R2 = 0.75) between the outcomes of both indices. The results of the numerical indices and the interpolated geographical information system (GIS) mapping revealed that the quality of groundwater in most of the delta does not meet WHO guidelines for potable water. Hence, it is recommended that the groundwater of the delta should be properly treated before its use for domestic purposes. The study highlights the significance of using numerical indices and geospatial techniques for water quality evaluation in the Indus Delta and similar deltaic regions throughout the world.

Wetland Biomass and Productivity in Coastal Louisiana: Base Line Data (1976–2015) and Knowledge Gaps for the Development of Spatially Explicit Models for Ecosystem Restoration and Rehabilitation Initiatives

Coastal Louisiana hosts 37% of the coastal wetland area in the conterminous US, including one of the deltaic coastal regions more susceptible to the synergy of human and natural impacts causing wetland loss. As a result of the construction of flood protection infrastructure, dredging of channels across wetlands for oil/gas exploration and maritime transport activities, coastal Louisiana has lost approximately 4900 km2 of wetland area since the early 1930s. Despite the economic relevance of both wetland biomass and net primary productivity (NPP) as ecosystem services, there is a lack of vegetation simulation models to forecast the trends of those functional attributes at the landscape level as hydrological restoration projects are implemented. Here, we review the availability of peer-reviewed biomass and NPP wetland data (below and aboveground) published during the period 1976–2015 for use in the development, calibration and validation of high spatial resolution (&lt;200 m × 200 m) vegetation process-based ecological models. We discuss and list the knowledge gaps for those species that represent vegetation community associations of ecological importance, including the long-term research issues associated to limited number of paired belowground biomass and productivity studies across hydrological basins currently undergoing different freshwater diversions management regimes and hydrological restoration priorities.

Spectral Wave Characteristics over the Head Bay of Bengal: A Modeling Study

Information on spectral wave characteristics is an essential prerequisite for ocean engineering-related activities and also to understand the complex wave environment at any given location. To the best of our knowledge, there are no comprehensive studies attempted so far to study the wave spectral characteristics over the head Bay of Bengal, a low-lying deltaic environment. The present study is an attempt to describe the spectral characteristics of wave evolution across different locations over this deltaic region based on numerical simulations. Therefore, it implements a multi-scale nested modeling approach using two state-of-art wave models, WAM and SWAN, and forced with ERA-Interim winds spanning the year of 2016. Model-computed integrated wave parameters are validated against wave rider buoy data as well as remotely sensed SARAL/AltiKa and merged altimeter data. Analysis of the monthly averaged one-dimensional spectrum reveals a single peak during the southwest monsoon and existence of double peaks from November to January, and occasionally up to March. Variance energy density undergoes inter-seasonal variation and attains its maxima during the month of July. Transformation of swell wave energy as a function of depth is found to be mostly associated with physical processes such as wave-bottom interaction and attenuation by opposing winds during the northeast (NE) monsoon. Fetch restriction for the evolution of wind seas (from the NE), modification in wind shear stress by opposing swells, and bottom effects remarkably contribute to the reduction in wind sea energy at shallow water depths. This study indicates that the influence of swells is higher along the eastern side of the basin as compared to the western side, and marginally higher variance is also observed over the east except during February–April. The two-dimensional wave spectra exhibit differential wave systems approaching from various directions attributed to a reflected swell system from the south-southeast throughout the year, southwest swells, reversing wind seas following local winds, and reflected wind seas from the land boundary.

Scale effects on land loss modeling in the Mississippi River Delta

Abstract. In complex natural-human system modeling, often times a first step is to examine the relationships between a dependent variable and a number of independent variables at their locations. The neighborhood effect, also known as a scale effect, has seldom been considered in the analysis. Previous research has shown that scale effects affect the reliability of analysis results, and rigorous scientific studies should take an extra step to examine the scale effects for more accurate analysis and modeling. However, detecting the neighborhood effects of various variables and then incorporating them into a holistic modeling system posts a serious challenge because of the fundamental difference in properties between variables from the human component (e.g., census data) and variables from the natural component (e.g., landscape properties). Moreover, uncertainties involved in data, data scale, algorithms, and scale of analysis make the findings and the interpretations of the findings unreliable. A major issue of modeling neighborhood effects is the determination of appropriate neighborhood size, also known as the spatial context scale or the operational scale. It has been shown in the literature that neighborhood effects vary with the neighborhood size used to compute the effects. Thus, research on how to determine the neighborhood size that best captures the scale of operation of a phenomenon is very much needed so that we can have more confidence in the modeling results.This study examines the use of variogram in detecting the appropriate neighborhood size of the variables involved in land loss modeling in the Mississippi River Delta. The goal is to find out the best combination of variables and their neighborhood sizes that best explain the variation of land loss patterns in the Deltaic region. The Mississippi River Delta has been suffering substantial land loss during the past several decades. Land loss has been a subject of intense research by many researchers from multiple disciplines, aiming at mitigating the land loss process and its potential damages. However, a majority of land loss projections were derived solely from the natural processes, such as sea level rise, regional subsidence, and reduced sediment flows. Very few studies have incorporated human-induced factors such as land fragmentation, urbanization, energy industrialization, and marine transportation. Even fewer have studied the scale effects. A study that captures and quantifies both natural and human factors as well as their neighborhood effects would help uncover the complex mechanism of land loss and provide a more accurate spatiotemporal projection of land loss patterns and probability.The analysis procedures are as follows. (1) First, the study area is rasterized into 1-km by 1-km grids. (2) A set of natural and human variables related to land loss in the deltaic region are collected. (3) Variogram analysis of each variable is conducted to identify the spatial neighborhood size of each variable, and a neighborhood variable for each independent variable is created. (4) Elastic Net regression analysis is applied to test and select the significant variables that affect land loss. Regression results between the model with and the model without neighborhood variables are compared. Through this study, we should be able to derive a more accurate land loss model for detailed analysis and future projections.

Assessment of regional-level long-term gridded rainfall variability over the Odisha State of India

Odisha State is located in eastern part of India which is blessed with sufficient amount of rainfall. Major part of the state is covered by Mahanadi river basin; Mahanadi river basin originated from Sihawa town and disposed out to Bay of Bengal near Sambalpur, Odisha State. The distribution pattern is erratic and uneven due to climate, topography, hydrology and geomorphology of the state. Catchment area of the Mahanadi is vast; therefore, drainage order is also high (about six); due to these features large amount of water has generated, and it will be appeared as flood at downstream through deltaic region to Bay of Bengal. In this connection, water resources planning and management are one of the crucial issues. For any hydrological study, it is necessary to identify the characteristics and climatic variability of the catchment. In the present study, long-term (1901–2013) rainfall time series has been utilized for rainfall variability analysis using nonparametric tests, viz. Mann–Kendall (MK), modified Mann–Kendall (MMK) and Theil–Sen’s slope. The average annual rainfall of the Odisha State is to be found as about 1438 mm; out of them, about 78% occurs in the monsoon season. In the present study, it was found that the maximum and minimum rainfalls occurred at Bhadrak and Puri districts, respectively. As per change point detection, it was found to be as 1945 is shift change year. Further, it was noticed that most of the districts are showing positive trends before change point and vice versa. Similar results are estimated in the monsoon season because most of the rainfall has occurred in the monsoon season. Both positive and negative trends have been found in Odisha State; detailed study has been carried out for rainfall behavior identification of the state. The present study is useful for agricultural and water resources planning and mitigation.

Caracterização Fotoestratigráfica e Petrofaciológica dos Cordões Arenosos Litorâneos do Delta do Rio Paraíba do Sul, RJ

O estudo do delta holocênico do rio Paraíba do Sul (RJ) a partir da interação de dados fotoestratigráficos, texturais e de minerais pesados, permitiu a delineação de petrofácies relacionadas a diversas rochas-fonte e processos sedimentares. A região do delta foi separada em planícies norte e sul, tendo o rio como referencial. A planície sul foi dividida em setores Sul 1, adjacente ao rio, e Sul 2, no extremo sul do delta. Os atributos fotoestratigráficos permitiram a identificação na planície norte de quinze fotossequências com onlaps S-N e poucos truncamentos erosivos. Na planície sul foram identificadas trinta fotossequências com onlaps dominantemente N-S e truncamentos erosivos SW-NE. O setor Sul 2 apresenta onlaps de direções variadas, truncamentos erosivos NW-SE e fonte sedimentar diferenciada, possivelmente relacionada a áreas ao sul do delta, enquanto a planície norte e o setor Sul 1 foram alimentados principalmente pela ação do rio e sua interação com correntes de deriva litorânea. Uma importante feição aproximadamente N-S é visível em todo delta e reflete um evento erosivo maior associado a um possível processo regressivo. Também foi possível delinear a ocorrência temporal do predomínio de contribuição de diferentes rochas-fonte e agentes deposicionais, sintetizadas nas petrofácies estabelecidas.

A social-ecological analysis of drinking water risks in coastal Bangladesh

Groundwater resources in deltaic regions are vulnerable to contamination by saline seawater, posing significant crisis for drinking water. Current policy and practice of building water supply infrastructure, without adequate hydrogeological analysis and institutional coordination are failing to provide basic drinking water services for millions of poor people in such difficult hydrogeological contexts. We apply a social-ecological systems approach to examine interdisciplinary data from hydrogeological mapping, a water infrastructure audit, 2103 household surveys, focus group discussions and interviews to evaluate the risks to drinking water security in one of 139 polders in coastal Bangladesh. We find that increasing access through public tubewells is common but insufficient to reduce drinking water risks. In response, there has been a four-fold growth in private investments in shallow tubewells with new technologies and entrepreneurial models to mitigate groundwater salinity. Despite these interventions, poor households in water-stressed environments face significant trade-offs in drinking water quality, accessibility and affordability. We argue that institutional coordination and hydrogeological monitoring at a systems level is necessary to mitigate socio-ecological risks for more equitable and efficient outcomes.

Sameness and difference in delta planning

Triggered by an increased awareness of the possible effects of climate change, many deltaic regions around the world are undertaking planning initiatives to address the problems they expect to face in the future. Dutch delta planning knowledge and expertise figure prominently in some of these initiatives. We use this article to ask why this is so. What makes Dutch delta knowledge special, and how does it become generic enough to travel to other places? The pertinence of these questions stems from the realization that deltas do not pre-exist human interventions, but are as much the effect of different planning cultures, trajectories and objectives, as they are their cause. Through a discussion of some telling anecdotes of delta planning, our analysis shows that while the Dutchness of delta planning expertise is a powerful branding, this expertise can only travel through a conscious and simultaneous process of un-Dutching: by packaging and scientizing Dutch Delta planning to turn it into a more generic Adaptive Delta Management approach.

Impact of river erosion on livelihood and coping strategies of displaced people in South-Eastern Bangladesh

Bangladesh is situated in riverine and deltaic region in South Asia where riverbank erosion is a catastrophic climate induced disaster in Bangladesh. The present study has been undertaken to investigate the impact of riverbank erosion on lives and livelihoods of the displaced people in the South-Eastern Bangladesh. Both quantitative and qualitative data have been used through in-depth interviews, focus group discussion and questionnaire survey. The study reveals that riverbank erosion is addressing displacement, hidden hunger and poverty, loss of land and identity of coastal people. Besides, displaced persons face social, economic, cultural stigma in their community. People have used different types of indigenous knowledge to reduce the sufferings of the affected people. The findings of this study are vital for policymakers to articulate and implement effective approaches and programs to reduce vulnerability and to increase the local adaptation processes in order to improve such households' livelihood all over Bangladesh.

Impact of river erosion on livelihood and coping strategies of displaced people in South-Eastern Bangladesh

Bangladesh is situated in riverine and deltaic region in South Asia where riverbank erosion is a catastrophic climate induced disaster in Bangladesh. The present study has been undertaken to investigate the impact of riverbank erosion on lives and livelihoods of the displaced people in the South-Eastern Bangladesh. Both quantitative and qualitative data have been used through in-depth interviews, focus group discussion and questionnaire survey. The study reveals that riverbank erosion is addressing displacement, hidden hunger and poverty, loss of land and identity of coastal people. Besides, displaced persons face social, economic, cultural stigma in their community. People have used different types of indigenous knowledge to reduce the sufferings of the affected people. The findings of this study are vital for policymakers to articulate and implement effective approaches and programs to reduce vulnerability and to increase the local adaptation processes in order to improve such households' livelihood all over Bangladesh.

The Role of Reactive Iron in the Preservation of Terrestrial Organic Carbon in Estuarine Sediments

AbstractTo better understand the role of reactive Fe (FeR) in the preservation of sedimentary organic carbon (SOC) in estuarine sediments, we examined specific surface area, grain size composition, total OC (TOC), lignin phenols, FeR, FeR‐associated OC (Fe‐OC) and lignin phenols (Fe‐lignin), and δ13C of FeR‐associated OC (δ13CFe‐OC) in surface sediments of the Changjiang Estuary and adjacent shelf. An estimated 7.4 ± 3.5% of the OC was directly bound with FeR in the Changjiang Estuary and adjacent shelf. Unusually low TOC/specific surface area loadings and Fe‐OC/Fe ratios in mobile muds suggest that frequent physical reworking may reduce FeR binding with OC, with selective loss of marine OC. More depleted 13CFe‐OC relative to 13C of TOC (13Cbulk) in deltaic regions and mobile muds showed that FeR was largely associated with terrestrial OC, derived from extensive riverine OC and Fe inputs. A higher proportion of hematite in the mobile muds compared to the offshore samples indicated that Fe oxides are likely subjected to selective sorting and/or become mature during long‐term sediment transport. When considering the percentage of Fe‐OC to SOC and SOC burial rates in different marine environments (e.g., nondeltaic shelf, anoxic basins, slope, and deep sea), our findings suggest that about 15.6 ± 6.5% of SOC is directly bound to FeR on a global scale, which is lower than the previous estimation (~21.5%). This work further supports the notion of a Rusty Sink where, in this case, FeR plays an important role in the preservation and potential transport of terrestrial OC in the marine environment.

Coupling land use evolution and subsidence in the Po Delta, Italy: Revising the past occurrence and prospecting the future management challenges

The Po River delta is characterized by a large system of shallow lagoons, wetlands, and reclaimed lands. Like many other deltaic regions, the Po Delta has largely subsided due to natural processes and anthropogenic activities, with a strong impact on its geomorphological evolution and significant socio- economic consequences. This paper aimed at highlighting the evolution of the study area over the last 120 years, analysing the land-uses changes in relation to the land subsidence, and using these findings to discuss the main management issues of this fragile low lying area in the decades to come. The analysis of the land use evolution from 1892 to 2015 and the information derived from the metrics measurement suggest a simplification of the land use with a decrease of the saltmarsh extent and an enlargement of the agricultural cover. The analysis of land subsidence, mainly due to gas-bearing groundwater withdrawal, confirms a strong impact on the delta territory, and in particular on its geomorphological asset. In the early 1900s the elevation of the delta plain ranged between −1.0 and +1.6 m above msl, while in 2007 it reduced between −2.8 to +0.3 m above msl. The land reclamation projects have largely increased the farmland usable for crop production but the concurrent loss of land elevation has resulted in a territory extremely difficult to be managed. Because of its elevation, the delta is particularly vulnerable to weather and marine events. As a consequence, the present management of the area is mainly aimed at maintaining the agricultural productivity. Unfortunately, if the human impacts will continue with the actual trend, the stability of the natural ecosystems, such as the wetlands, which represent important socioeconomic realities, will be further undermined. Surely, the conservation of these natural environments should be a priority in the future land use management.

Impacts of tidal link drain, along the coastal areas of districts Badin and Sujawal in Indus deltaic region, Sindh Pakistan

Impacts of tidal link drain, along the coastal areas of districts Badin and Sujawal in Indus deltaic region, Sindh Pakistan

Analysis of Rainfall Trends and its Spatial Patterns During the Last Century over the Gangetic West Bengal, Eastern India

Long-term spatial and temporal trends of rainfall at monthly, seasonal, and annual scales have been studied for 12 meteorological stations of the Gangetic West Bengal located in Eastern India during 1901–2002 using 102 years of rainfall data. The non-parametric Mann-Kendall test and Sen’s slope estimator were used to detect trends and their slope. The changes are calculated in percentage over the time period. The results highlight a marked increase in post-monsoon (33.87%), the overall increase in annual (2.61%), a considerable decrease in winter (14.83%) as well as pre-monsoon (4.03%), and an inconsequential increase in monsoonal (1.21%) rainfall. In the annual and monsoonal series, the trend is positive in the southern half but negative in the northern counterpart. A considerable decrease in rainfall during June and August at most stations signifies that monsoon is losing in the early monsoonal months with an occurrence of mid-season dry spells. The increase in rainfall during September (13.80%) and October (34.38%) reveals that the monsoon is shifting toward these late monsoon and post-monsoon months, respectively. Both the decrease of rainfall in June (early monsoonal month), as well as an increase in rainfall in September (late monsoonal month) and October (start of post-monsoonal month), suggest that the monsoon is being delayed on its onset and withdrawal. In the Rarh region, monsoon rainfall is reducing whereas post-monsoon rainfall is increasing. In the Deltaic region, both monsoon and post-monsoon rainfalls are increasing. Such altering patterns of rainfall call for reviewing the agricultural practices and water use in this region.