Search

Anthropogenic environmental changes are having complex effects on all aspects of the hydrological cycle. In estuarine areas, these factors are coalescing to increase saline contamination. Between 2006 and 2007, coastal Bangladesh experienced a sudden and dramatic increase in water salinity, with the saline front shifting inland by roughly 20km. We use this exceptional event to explore the impact of salinity on economic activity and agricultural production. Our results indicate that locations that experienced a sudden increase in water salinity incurred a 33% reduction in economic activity, as measured by nightlight intensity. This coincides with a decline in the cultivation of high-yielding rice varieties, which are not salt tolerant, as well as the removal of land from production. There is no robust evidence that changes in population drove these losses in economic activity. While sea level rise may be only one factor in this shift of the salinity front, our findings suggest that the future impacts of sea level rise have the potential to be quite large and may not be limited to coastline locations. [ABSTRACT FROM AUTHOR]

Climate change-induced sea-level rise, salinity intrusion, sudden water surge, natural calamities, etc. affect the fish biodiversity, food security, and coastal livelihoods that highlight the necessities of developing climate-resilient strategies e.g. adaptive aquaculture techniques. Cage culture of salinity-tolerant fish may be an adaptation strategy to compensate for the losses of freshwater fish production by climate change in coastal areas. Therefore, a 120-day long field experiment was conducted to evaluate the cage culture potentiality of Mystus gulio in the coastal region of Bangladesh. Three treatments at the stocking density of 90 (T1), 135 (T2), and 180 (T3)/m2 were stocked in nine cages (1.115 m2). Significantly (p<0.05) higher growth performance and feed utilization were recorded in T1 followed by T2 and T3. In return, considering overall growth, survival, production, coast-benefit analysis, T2 was found more profitable followed by T3 and T1. This result revealed that the culture of M. gulio in floating net cages might be a potential climate-adaptive aquaculture technique in the coastal region. However, further research works are necessary for optimizing stocking density, nutrition, social acceptance, etc. before conclude it as a viable climate-resilient adaptive aquaculture practice. [ABSTRACT FROM AUTHOR]

• Community Livelihood Adaptation (CLA) can have significant impacts on polder management. • The shift from rice to shrimp, as unanticipated livelihood pathway for salinization, has changed the polder functionality. • Tidal River Management has risen as livelihood adaptation to waterlogging led by social (un)acceptance of polder management. • Delta planners should listen to CLA, and accommodate uncertainties resulting from CLA for robust and adaptive investment. To deal with large uncertainties about future climate and socio-economic developments, planners in deltas are adopting an integrative and adaptive planning approach referred to as Adaptive Delta Management (ADM). Bangladesh has used the ADM approach for the development of its adaptive plan; Bangladesh Delta Plan 2100 (BDP 2100). The success of policy strategies in an adaptive delta plan critically depends on a specific adaptation of livelihoods of local communities (Community Livelihood Adaptation; CLA), especially in an agriculture-oriented society like Bangladesh. For example, while triple rice cropping might be evaluated as a robust strategy in all futures considered, its success eventually depends on whether farmers' will actually make that choice, which is deeply uncertain. In this paper, we use literature review, insights from interviews and field observations to examine how the uncertainty in CLA impacts (adaptive) delta management. We study two historical cases of livelihood adaptation of farmer communities confronted with salinization and waterlogging in the polders of southwest Bangladesh since the 1960s. We conclude that historically the uncertainty about CLA in polders has been ignored in the development of policy plans, leading to the failure of anticipated policy outcomes. We recommend planners in Bangladesh and other deltas worldwide to take account of CLA as uncertainty when developing long-term adaptive plans. [ABSTRACT FROM AUTHOR]

While there is little dissent in the scientific community that climate change directly correlates to human-caused greenhouse-gas emissions, action to reduce those emissions has not followed from the United States and many other governments around the world. Meanwhile, climate changes are already underway, and will continue to some degree even if emissions are drastically curtailed, thanks to emissions already in the atmosphere. Some countries and states are making their own plans to adapt to expected impacts including higher sea levels, more intense rainfall, droughts, heat waves, and loss of water supplies—and to reduce their local emissions. In this Global Forum, three experts highlight efforts by national and local governments in planning for 2100 and beyond. From the Netherlands, Arthur Mynett (2011); from Bangladesh, Saleemul Huq; and from California, Martha Krebs (2011). Over the months of January and February, this forum will continue at www.thebulletin.org. [ABSTRACT FROM AUTHOR]

Pervasive salinity in soil and water is affecting agricultural yield and the health of millions of delta dwellers in Asia. This is also being exacerbated by climate change through increases in sea level and tropical storm surges. One consequence of this has been a widespread introduction of salt water shrimp farming. Here, we show, using field data and modeling, how changes in climate and land use are likely to result in increased salinization of shallow groundwater in SE Asian mega-deltas. We also explore possible adaptation options. We find that possible future increase of episodic inundation events, combined with salt water shrimp farming, will cause rapid salinization of groundwater in the region making it less suitable for drinking water and irrigation. However, modified land use and water management practices can mitigate the impacts on groundwater, as well as the overlying soil, from future salinization. The study therefore provides guidance for adaptation planning to reduce future salinization in Asian deltas. [ABSTRACT FROM AUTHOR]

Salinization in coastal regions of Bangladesh challenges sustainable development of different sectors like agriculture, forestry, fisheries, livestock, and health. Particularly its southwest region largely faces increased salinity risks because of its geographical location and environmental settings. This study analyzes the causes of salinity increase, their cascading impacts on different coastal systems, and their livelihood implications, and assesses potential coping measures through innovative adaptation pathways for the most affected coastal systems. These pathways integrate bottom-up and top-down perceptions in adaptation planning through a driver-pressure-state-impact-response framework, multicriteria analysis, and adaptation turning point approaches. We surveyed 200 households and interviewed 20 key informants. We observed that household-level respondents' perceptions are more closely related to socioeconomic aspects than to the biophysical environmental aspects and focus on issue-based action. However, the key informants focus more on the biophysical changes and the large-scale measures. The developed framework shows that salinity increase is an interconnected process of climatic-social-ecological-economic systems in the coastal environment. It also shows that responses already taken, i.e., polders and shrimp farming, to cope with salinization have later become pressures, i.e., riverbed siltation, waterlogging, and intensive salinization, on the systems. In total, we identified six interconnected causes of salinity increase and 24 potential measures to address them. Also we distinguished three coastal systems, i.e., crop-agriculture, drinking water sources, and the Sundarbans mangrove, most affected by salinity increase. Finally we proposed 16 adaptation pathways for these coastal systems based on the multicriteria analysis and adaptation turning points of the potential measures. [ABSTRACT FROM AUTHOR]

To identify the causes of salinization and arsenic contamination of surface water on an embanked island (i.e., polder) in the tidal delta plain of SW Bangladesh we collected and analyzed water samples in the dry (May) and wet (October) seasons in 2012-2013. Samples were collected from rice paddies (wet season), saltwater ponds used for brine shrimp aquaculture (dry season), freshwater ponds and tidal channels (both wet and dry season), and rainwater collectors. Continuous measurements of salinity from March 2012 to February 2013 show that tidal channel water increases from ~0.15 ppt in the wet season up to ~20 ppt in the dry season. On the polder, surface water exceeds the World Health Organization drinking water guideline of 10 μg As/L in 78% of shrimp ponds and 27% of rice paddies, raising concerns that produced shrimp and rice could have unsafe levels of As. Drinking water sources also often have unsafe As levels, with 83% of tubewell and 43% of freshwater pond samples having >10 μg As/L. Water compositions and field observations are consistent with shrimp pond water being sourced from tidal channels during the dry season, rather than the locally saline groundwater from tubewells. Irrigation water for rice paddies is also obtained from the tidal channels, but during the wet season when surface waters are fresh. Salts become concentrated in irrigation water through evaporation, with average salinity increasing from 0.43 ppt in the tidal channel source to 0.91 ppt in the rice paddies. Our observations suggest that the practice of seasonally alternating rice and shrimp farming in a field has a negligible effect on rice paddy water salinity. Also, shrimp ponds do not significantly affect the salinity of adjacent surface water bodies or subjacent groundwater because impermeable shallow surface deposits of silt and clay mostly isolate surface water bodies from each other and from the shallow groundwater aquifer. Bivariate plots of conservative element concentrations show that all surface water types lie on mixing lines between dry season tidal channel water and rainwater, i.e., all are related by varying degrees of salinization. High As concentrations in dry season tidal channel water and shrimp ponds likely result from groundwater exfiltration and upstream irrigation in the dry season. Arsenic is transferred from tidal channels to rice paddies through irrigation. Including groundwater samples from the same area (Ayers et al. in Geochem Trans 17:1-22, 2016), principal components analysis and correlation analysis reveal that salinization explains most variation in surface water compositions, whereas progressive reduction of buried surface water by dissolved organic carbon is responsible for the nonconservative behavior of S, Fe, and As and changes in Eh and alkalinity of groundwater. [ABSTRACT FROM AUTHOR]

Background: High salinity and arsenic (As) concentrations in groundwater are widespread problems in the tidal deltaplain of southwest Bangladesh. To identify the sources of dissolved salts and As, groundwater samples from the regional shallow Holocene aquifer were collected from tubewells during the dry (May) and wet (October) seasons in 2012-2013. Thirteen drill cores were logged and 27 radiocarbon ages measured on wood fragments to characterize subsurface stratigraphy. Results: Drill cuttings, exposures in pits and regional studies reveal a >5 m thick surface mud cap overlying a ~30 m thick upper unit of interbedded mud and fine sand layers, and a coarser lower unit up to 60 m thick dominated by clean sands, all with significant horizontal variation in bed continuity and thickness. This thick lower unit accreted at rates of ~2 cm/year through the early Holocene, with local subsidence or compaction rates of 1-3 mm/year. Most tubewells are screened at depths of 15-52 m in sediments deposited 8000-9000 YBP. Compositions of groundwater samples from tubewells show high spatial variability, suggesting limited mixing and low and spatially variable recharge rates and flow velocities. Groundwaters are Na-Cl type and predominantly sulfate-reducing, with specific conductivity (SpC) from 3 to 29 mS/cm, high dissolved organic carbon (DOC) 11-57 mg/L and As 2-258 ug/L, and low sulfur (S) 2-33 mg/L. Conclusions: Groundwater compositions can be explained by burial of tidal channel water and subsequent reaction with dissolved organic matter, resulting in anoxia, hydrous ferric oxide (HFO) reduction, As mobilization, and sulfate (SO) reduction and removal in the shallow aquifer. Introduction of labile organic carbon in the wet season as rice paddy fertilizer may also cause HFO reduction and As mobilization. Variable modern recharge occurred in areas where the clay cap pinches out or is breached by tidal channels, which would explain previously measured C groundwater ages being less than depositional ages. Of samples collected from the shallow aquifer, Bangladesh Government guidelines are exceeded in 46 % for As and 100 % for salinity. [ABSTRACT FROM AUTHOR]

The Ganges-Brahmaputra-Meghna delta of Bangladesh is one of the most populous deltas in the world, supporting as many as 140 million people. The delta is threatened by diverse environmental stressors including salinity intrusion, with adverse consequences for livelihood and health. Shrimp farming is recognised as one of the few economic adaptations to the impacts of the rapidly salinizing delta. Although salinity intrusion and shrimp farming are geographically co-located in the delta, there has been no systematic study to examine their geospatial associations with poverty. In this study, we use multiple data sources including Census, Landsat Satellite Imagery and soil salinity survey data to examine the extent of geospatial clustering of poverty within the delta and their associative relationships with salinity intensity and shrimp farming. The analysis was conducted at the union level, which is the lowest local government administrative unit in Bangladesh. The findings show a strong clustering of poverty in the delta, and whilst different intensities of salinization are significantly associated with increasing poverty, neither saline nor freshwater shrimp farming has a significant association with poverty. These findings suggest that whilst shrimp farming may produce economic growth, in its present form it has not been an effective adaptation for the poor and marginalised areas of the delta. The study demonstrates that there are a series of drivers of poverty in the delta, including salinization, water logging, wetland/mudflats, employment, education and access to roads, amongst others that are discernible spatially, indicating that poverty alleviation programmes in the delta require strengthening with area-specific targeted interventions. [ABSTRACT FROM AUTHOR]

This study analyzed water and soil quality and environmental impacts of shrimp farming in the southwestern coastal region of Bangladesh. Shrimp farming in the region is very traditional in nature where two culture systems viz. shrimp-rice and shrimp-only are being practiced, which are characterized by lower production, repeated stocking, irregular feeding, and fertilizing. Water quality in both farming systems was found suitable for optimum growth and survival of shrimp ( Penaeus spp.). The level of 5-day biological oxygen demand (BOD) in both systems even in canal water was within the recommended level provided by the Government of Bangladesh which is less than 5 mg/l. Therefore, effluents of shrimp farms in the study area did not show any nutrient pollution on the surrounding environment. However, saltwater intrusion has caused many problems like loss of agricultural production, reduced availability of fodder for livestock, and fresh water for domestic uses in the coastal region. The findings of this study confirmed that shrimp farming using saline water have long-term effect of soil salinization. As a result, it poses a real threat toward sustainability of coastal shrimp farming as well as coastal development in Bangladesh. [ABSTRACT FROM AUTHOR]

Dissolved major ions and important heavy metals including total arsenic and iron were measured in groundwater from shallow (25–33 m) and deep (191–318 m) tube-wells in southeastern Bangladesh. These analyses are intended to help describe geochemical processes active in the aquifers and the source and release mechanism of arsenic in sediments for the Meghna Floodplain aquifer. The elevated Cl− and higher proportions of Na+ relative to Ca2+, Mg2+, and K+ in groundwater suggest the influence by a source of Na+ and Cl−. Use of chemical fertilizers may cause higher concentrations of NH and PO in shallow well samples. In general, most ions are positively correlated with Cl−, with Na+ showing an especially strong correlation with Cl−, indicating that these ions are derived from the same source of saline waters. The relationship between Cl−/HCO ratios and Cl− also shows mixing of fresh groundwater and seawater. Concentrations of dissolved HCO reflect the degree of water–rock interaction in groundwater systems and integrated microbial degradation of organic matter. Mn and Fe-oxyhydroxides are prominent in the clayey subsurface sediment and well known to be strong adsorbents of heavy metals including arsenic. All five shallow well samples had high arsenic concentration that exceeded WHO recommended limit for drinking water. Very low concentrations of SO and NO and high concentrations of dissolved Fe and PO and NHions support the reducing condition of subsurface aquifer. Arsenic concentrations demonstrate negative co-relation with the concentrations of SO and NO but correlate weakly with Mo, Fe concentrations and positively with those of P, PO and NHions. [ABSTRACT FROM AUTHOR]

Household drinking water security is one of the major issues among coastal communities in Bangladesh. To examine the groundwater quality and social consequences, groundwater samples and household questionnaires were administered across the study area. Instrumental and statistical tools were used to analyze the water quality and social survey data. The average concentrations of electrical conductivity (EC) (7135.67 μS/cm), total dissolved solids (TDS) (3691 mg/L), Na+ (1569.51 mg/L), Ca2+ (289.5 mg/L), Mg2+ (340.51 mg/L), Cl− (2940.78 mg/L), F− (11.85 mg/L), NO 3 − (54.44 mg/L), NO 2 − (162.95 mg/L), PO 4 3− (105.19 mg/L), Fe (4.9 mg/L), Mn (1.22 mg/L), As (16.55 μg/L), B (833.28 μg/L), and Pb (34.22 μg/L) were observed in groundwater, and exceeded the drinking water standards from 30% to 100% depending on the sampling location. Thus, the remarkably high contents of EC, TDS, Cl−, and Na+ represented possible saltwater intrusion along the coastal aquifer. The positive correlations between EC and trace and toxic elements indicated the potential influence of groundwater salinization on the dissolution of more chemical contaminants in the aquifer. These results showed that 100% of samples were unsuitable for drinking purposes. Severe drinking water scarcity is a serious issue, and local people have been affected by water-related diseases owing to the long-term consumption of contaminated water. Salinity problems in drinking water and related health diseases have increased significantly in the past several years. In addition, climate change and its associated hazards, including sea-level rise, cyclonic storm surges, flooding, and resulting inundation problems, have intensified the drinking water scarcity and health problems at the community level. To ensure household water security, environmental exposure, hydrogeology, and anthropogenic interventions must be considered to determine future sustainable water policies. • Groundwater was severely contaminated owing to salinity intrusion. • High concentrations of EC, TDS, and Cl− and low pH increased the co-contamination risk, such as from trace metals. • High concentrations of co-contaminants in groundwater are a great concern for future drinking water security among coastal communities. • Groundwater was completely unsuitable for drinking, which poses a significant public health risk. • Statistical analysis showed a significant correlation between salinity and trace elements contamination, which was found to be consistent with local perceptions. [ABSTRACT FROM AUTHOR]