Floods as agents of vitality: Reaffirming human-nature synergies

The policy response for flood governance should be based on the premise that floods in monsoon-dominated landscapes such as the Ganga-Brahmaputra-Meghna (GBM) basin are inevitable.

What Governance Lesson Does Mekong Bear for Ganges–Brahmaputra–Meghna (GBM) Basin?

This article talks of the various governance lessons that the Mekong basin bears for the Ganges–Brahmaputra–Meghna (GBM) basin. It highlights the existing hydropolitical and ecological problems associated with the GBM basin, the reasons for which are attributed to the reductionist colonial engineering paradigm also delineated in this article as ‘arithmetic hydrology’. The transboundary interactions in the GBM to resolve the problems have largely relied on an issue-based, piecemeal, fragmented approach that has further complicated the problems. It is in this context, the article brings in how a cooperative mechanism in the institutional form of the Mekong River Commission (MRC) has been attempting to promote a participative and integrated approach to river basin governance. The article, therefore, talks of some of the replicable practices and learnings that may help in takeaways for the GBM riparians and stakeholders from the Mekong system. JEL Codes: F02, N50, Q01, Q22, Q24, Q25, Q28

Conceptualizing environmental governance on the GBM basin

River water sharing is an issue that is dealt by the South Asian neighboring countries for the last four decades. Water management of Ganges–Brahmaputra Meghna (GBM) basin is a controversial issue, which is not yet developed as a regional cooperative mechanism. The GBM river basin countries also represent the projection of relative power differences among its upper stream and lower stream countries. Considering the geopolitical context and hydro-politics of the region, the study examines potential scopes for effective regional governance to GBM’s ecological integrity and to share common river water among China, Bhutan, Nepal, India and Bangladesh. The study uses Rittberger et al. (2006) explanatory model (that explains three conditions—Problem, Cognitive and Hegemonic conditions) in the development of multilateral organizations in GBM region. The study deals with the question—what conditions facilitate GBM based water governance among five main riparian countries (upstream and downstream) in resolving the water scarcity challenges in the region. The paper argues that realization of shortage of water and environmental degradation as an interdependent problem, influence of an inclusive epistemic community (cognitive condition) and a hegemonic leadership (power is willing to accept the relative gain of others states for the absolute gain of itself)—are required to foster water resource governance of the GBM for sustainable development of the region.

Model study of the impacts of future climate change on the hydrology of Ganges–Brahmaputra–Meghna basin

The intensity, duration, and geographic extent of floods in Bangladesh mostly depend on the combined influences of three river systems, the Ganges, Brahmaputra and Meghna (GBM). In addition, climate change is likely to have significant effects on the hydrology and water resources of the GBM basin and may ultimately lead to more serious floods in Bangladesh. However, the assessment of climate change impacts on the basin-scale hydrology by using well-calibrated hydrologic modeling has seldom been conducted in the GBM basin due to the lack of observed data for calibration and validation. In this study, a macroscale hydrologic model H08 has been applied over the basin at a relatively fine grid resolution (10 km) by integrating the fine-resolution DEM (digital elevation model) data for accurate river networks delineation. The model has been calibrated via the analysis of model parameter sensitivity and validated based on long-term observed daily streamflow data. The impacts of climate change (considering a high-emissions path) on runoff, evapotranspiration, and soil moisture are assessed by using five CMIP5 (Coupled Model Intercomparison Project Phase 5) GCMs (global circulation models) through three time-slice experiments; the present-day (1979–2003), the near-future (2015–2039), and the far-future (2075–2099) periods. Results show that, by the end of 21st century, (a) the entire GBM basin is projected to be warmed by ~4.3 °C; (b) the changes of mean precipitation (runoff) are projected to be +16.3% (+16.2%), +19.8% (+33.1%), and +29.6% (+39.7%) in the Brahmaputra, Ganges, and Meghna, respectively; and (c) evapotranspiration is projected to increase for the entire GBM (Brahmaputra: +16.4%, Ganges: +13.6%, Meghna: +12.9%) due to increased net radiation as well as warmer temperature. Future changes of hydrologic variables are larger in the dry season (November–April) than in the wet season (May–October). Amongst the three basins, the Meghna shows the highest increase in runoff, indicating higher possibility of flood occurrence. The uncertainty due to the specification of key model parameters in model predictions is found to be low for estimated runoff, evapotranspiration and net radiation. However, the uncertainty in estimated soil moisture is rather large with the coefficient of variation ranging from 14.4 to 31% among the three basins.

Model study of the impacts of future climate change on the hydrology of Ganges–Brahmaputra–Meghna (GBM) basin

The intensity, duration, and geographic extent of floods in Bangladesh mostly depend on the combined influences of three river systems, Ganges, Brahmaputra and Meghna (GBM). In addition, climate change is likely to have significant effects on the hydrology and water resources of the GBM basins and might ultimately lead to more serious floods in Bangladesh. However, the assessment of climate change impacts on basin-scale hydrology by using well-constrained hydrologic modelling has rarely been conducted for GBM basins due to the lack of data for model calibration and validation. In this study, a macro-scale hydrologic model H08 has been applied regionally over the basin at a relatively fine grid resolution (10 km) by integrating the fine-resolution (~0.5 km) DEM data for accurate river networks delineation. The model has been calibrated via analyzing model parameter sensitivity and validated based on a long-term observed daily streamflow data. The impact of climate change on not only the runoff, but also the basin-scale hydrology including evapotranspiration, soil moisture and net radiation have been assessed in this study through three time-slice experiments; present-day (1979–2003), near-future (2015–2039) and far-future (2075–2099) periods. Results shows that, by the end of 21st century (a) the entire GBM basin is projected to be warmed by ~3°C (b) the changes of mean precipitation are projected to be +14.0, +10.4, and +15.2%, and the changes of mean runoff to be +14, +15, and +18% in the Brahmaputra, Ganges and Meghna basin respectively (c) evapotranspiration is predicted to increase significantly for the entire GBM basins (Brahmaputra: +14.4%, Ganges: +9.4%, Meghna: +8.8%) due to increased net radiation (Brahmaputra: +6%, Ganges: +5.9%, Meghna: +3.3%) as well as warmer air temperature. Changes of hydrologic variables will be larger in dry season (November–April) than that in wet season (May–October). Amongst three basins, Meghna shows the largest hydrological response which indicates higher possibility of flood occurrence in this basin. The uncertainty due to the specification of key model parameters in predicting hydrologic quantities, has also been analysed explicitly in this study and found that the uncertainty in estimation of runoff, evapotranspiration and net radiation is relatively less. However, the uncertainty in estimation of soil moisture is quite large (coefficient of variation ranges from 11 to 33% for three basins). It is significant in land use management, agriculture in particular and highlights the necessity of physical observation of soil moisture.