Multi-Model Assessment of Streamflow Simulations under Climate and Anthropogenic Changes Exemplified in Two Indian River Basins

This study aims to evaluate the climate- and human-induced impacts on two contrasting river basins in India, specifically, the Ganges and the Godavari. Monthly discharge simulations from global hydrological models (GHMs), run with and without human influence using CMIP5 projections under the framework of the Inter-Sectoral Impact Model Intercomparison Project, are utilized to address the scientific questions related to the quantification of the future impacts of climate change and the historical impacts of human activities on these river basins. The five state-of-the-art GHMs were considered and subsequently used to evaluate the human and climate change impacts on river discharges (seasonal mean discharge and extreme flows) during the pre-monsoon, monsoon, and post-monsoon seasons under the RCP2.6 and RCP8.5 emission scenarios. Results showed that human impacts during the baseline period on long-term seasonal discharge in the Ganges and Godavari River basins for the pre-monsoon season are around 40% and 23%, respectively, and these impacts are stronger than the future climate change impact in the pre-monsoon season for the Ganges basin, whereas, for the Godavari basin, the same pattern is observed with some exceptions. The human impact in the course of the historical period on the pre-monsoon flows of both the Ganges and the Godavari are more significant than on the monsoon and post-monsoon flows. In the near future (2010–39) time slice, the impact of climate change on the streamflow of the Ganges is highest for the post-monsoon season (13.4%) under RCP 8.5 as compared to other seasons. For Godavari, in the near-future period, this impact is highest for the pre-monsoon season (18.2%) under RCP 2.6. Climate-induced changes in both of the basins during both the monsoon and post-monsoon seasons is observed to have a higher impact on future flows than direct human impact-induced changes to flow during the current period. High flows (31.4% and 19.9%) and low flows (51.2% and 36.8%) gain greater influence due to anthropogenic actions in the time of the pre-monsoon season compared to other times of year for the Ganges and Godavari basins, respectively. High flows for the Ganges during the near future time slice are most affected in the monsoon season (15.8%) under RCP 8.5 and, in the case of the Godavari, in the pre-monsoon season (18.4%) under the RCP 2.6 scenario. Low flows of the Ganges during the near-future period are most affected during the monsoon season (22.3%) and for the Godavari, low flows are affected most for the post-monsoon season (22.1%) under RCP 2.6. Uncertainty in the streamflow estimates is more pronounced for the Godavari basin compared to the Ganges basin. The findings of this study enhance our understanding of the natural and human-influenced flow regimes in these river basins, which helps the formation of future strategies, especially for inter-state and transboundary river management.

Urbanising Delta: What Lessons Dhaka Offers to Face Challenges

Cities built on deltaic regions are always prone to environmental risks like aggravated flooding, wetland reduction, compromised water quality, continuing water scarcity, and tainted air and these have been remarkable as the challenges while urbanizing deltas. On top of that, rapid urbanization adds more to the deterioration of ecosystem functions. Drawing insights from Bangladesh's capital Dhaka lying in the Ganges, Brahmaputra, and Meghna basin, this study basically appraises the common concerns of deltaic megapolises through a systematic literature review. The current literature has been brought up by analysing the status, factors, and impacts of the challenges and management by authorities. In addition, it is further updated with some urban experts' views, secondary records on groundwater levels, and remote sensing imageries. This paper also concludes with recommended guidelines from the reviews for more practical deltaic urbanization, especially when there is no turning back for urban transferability to a new region of the delta. Particularly, success demands (1) specifying current situation in quantifiable terms (e.g., numeric values, percentages, scores, indices), (2) practical but adaptive multi-objective plans/policies with a set of assessable targets, and (3) timely robust evaluation for tracking data for specific, measurable, and meaningful outcomes.

Contrasting surface velocities between lake- and land-terminating glaciers in the Himalayan region

Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are expected to occur in coming decades. About 10 % of the Himalayan glacier population terminates into proglacial lakes, and such lake-terminating glaciers are known to exhibit higher-than-average total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a composite (2017–2019) glacier surface velocity dataset, derived from Sentinel 2 imagery, covering central and eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers (N = 70; umedian: 18.83 m yr−1; IQR – interquartile range – uncertainty estimate: 18.55–19.06 m yr−1) are on average more than double those of land-terminating glaciers (N = 249; umedian: 8.24 m yr−1; IQR uncertainty estimate: 8.17–8.35 m yr−1) and show substantially more heterogeneity than land-terminating glaciers around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which causes about half of the lake-terminating glacier population to accelerate towards the glacier termini. Numerical ice-flow model experiments show that changes in the force balance at the glacier termini are likely to play a key role in accelerating the glacier flow at the front, with variations in basal friction only being of modest importance. The expansion of current glacial lakes and the formation of new meltwater bodies will influence the dynamics of an increasing number of Himalayan glaciers in the future, and these factors should be carefully considered in regional projections.

Archaic Route of Budhi Ganga Formerly Known As River Ganga

The present route of Budhi Ganga starts from Ishaqwala and reaches Hastinapur via Saifpur Firozpur.Based on preliminary survey, the Budhi Ganga starts from Ishaqwala. On the old road, we still get to see many ancient temples such as Siddha Peeth Shiva temple in Saifpur Firozpur, Pandeshwar temple in Hastinapur, Karna Ghat temple and Draupadi Ghat temple, maybe even as far as Garhmukteshwar many more temples find in the way. The ancient route of the Ganges in Saifpur Firozpur was spread over a considerable area, the evidence of which is present even today. In this research paper, many small evidences including these facts have been presented, which may not have been done in the past. Keywords : Dewal , Ishaqwala , Budhi Ganga, Hastinapur

Optimum Sowing Date and Salt Tolerant Variety Boost Rice (Oryza sativa L.) Yield and Water Productivity during BoroSeason in the Ganges Delta

Rice-fallow and rice-rice are major cropping systems in the salt affected region of the Ganges Delta covering West Bengal, India and Bangladesh. The dry season rice (Boro) is grown mostly by irrigation from ground water in this water scarce region. Boro encounters soil and water salinity, air temperature fluctuations and intense evaporative demand. We studied six sowing dates (1 October, 15 October, 1 November, 15 November, 1 December and 15 December) and three varieties (WGL 20471, Bidhan 2 and IET 4786) of rice to find an interacting effect on yield and water productivity. Soil and water salinity varied during the growing period with lower soil salinity during the month of November (2.20–2.53 dS m−1) and higher soil salinity towards the end of the growing season (4.30–5.23 dS m−1). The mean field water salinity was higher (1.78 dS m−1) during the Boro 2017–18 compared to that (1.65 dS m−1) during 2016–17, as about 49 mm rainfall was received in the month of March 2017. Sowing dates significantly affected the yield of Boro rice. Earliest sowing on 1 October is not feasible as it significantly reduced the grain and straw yields. Sowing of nursery up to 1 of November was found to be the best possible option, and it should not be delayed up to 15 December. The rice variety IET 4786 was found to be susceptible to salinity with the lowest grain yield 2.65–2.98 t ha−1, compared to Bidhan 2 (3.41–5.95 t ha−1) and WGL 20471 (3.40–5.81 t ha−1). Both irrigation and economic water productivity of Boro were affected by sowing dates and variety. Rice variety IET 4786 required less irrigation water (1320 mm) than the other two varieties (1350 mm). Higher (>0.5 kg m−3) irrigation water productivity of Boro can be achieved by selecting salt tolerant varieties (WGL 20471 and Bidhan 2) and optimum sowing window of 1–15 November.

Estuarine-deltaic controls on coastal carbon burial in the western Ganges-Brahmaputra delta over the last 5,000 years

The Ganges–Brahmaputra fluvial system drains the Himalayas and is one of the largest sources of terrestrial biosphere carbon to the ocean. It represents a major continental reservoir of CO2 associated with c. 1–2 billion tons of sediment transported each year. Shallow coastal environments receive substantial inputs of terrestrial carbon (900 Tg C yr−1), with allochthonous carbon capture on connected floodplains. Vegetated coastal ecosystems play a dominant role in the sequestration of carbon and operate as highly efficient carbon sinks. Mangrove sediments are subject to intense carbon-fixing processes that have a potentially high impact on the global carbon budget. The Sundarbans is the largest tidal mangrove forest in the world (10,200 km2 in area) and is located on the marine-terrestrial boundary of the Ganges-Brahmaputra delta and the Bay of Bengal, in West Bengal (India) and Bangladesh. Estimates of sedimentation on the tidal delta plain of the Ganges-Brahmaputra delta reveal mean rates of ∼1.1 cm yr−1 with accretion understood to approximately equal the regional rate of sea-level rise of ∼1.0 cm yr−1. In this study, the properties of sediments from the western Ganges-Brahmaputra delta are used to investigate controls on coastal carbon burial over the past 5,000 years. Our main findings are: (1) Beta regression of aluminium and silica ratio data is a robust method of estimating total organic carbon in sediment from the Indian Sundarbans; (2) the estimated rate of sediment deposition over last 5,000 years is between 1.0 and 2.5 mm yr−1, with uncertainty surrounding the reworked origins of sediment; and (3) temporal variation of total organic carbon accumulation through the last 5,000 years is generated by varying sedimentary depositional processes. The delivery and burial of total organic carbon is predicated on the continual supply of sediment to the Sundarbans, which future management strategies may need to consider given changing rates of deposition.

Leveraging the World Heritage Convention for conservation in the Hindu Kush Himalaya

The Himalaya proper is commonly defined as the rugged arc between the Tibetan Plateau and the Ganges Plain stretching from the Indus River in the northwest to the great bend of the Brahmaputra River (Yarlung Tsangpo) in the east. The natural and cultural wealth of the HKH region is as overwhelming as its scenic beauty. The same holds true for the region’s enormous ecosystem services underpinning the livelihoods, food security and energy provision of a substantial part of the world’s human population in the region itself and downstream along the numerous major rivers originating in it. It is clear that such an exceptional region is of significant relevance to an intergovernmental agreement with the objective to identify and conserve the world’s most precious cultural and natural heritage, the World Heritage Convention. This assessment is strictly technical in nature; it aims at shedding light on the regional potential of the Convention from a nature conservation perspective based on a literature review and expert consultation.