Application of Gumbel’s Distribution Method for Flood Frequency Analysis of Lower Ganga Basin (Farakka Barrage Station), West Bengal, India

The analysis of flood frequency will depend on the historical peak discharge data for at least 10 years. This study has taken into account peak annual maximum discharge data for 72 years (1949 to 2020). The discharge data was collected from the Farakka Barrage Gauging station (24°48'15.10" N and 87°55'52.70" E) situated in the upper part of lower Ganga basin. The flood frequency analysis of the lower Ganga basin’s upper portions has been carried out using Gumbel’s frequency distribution method. Gumbel’s method (XT) is a prediction analysing statistical approach. The discharge data was tabulated in descending order and rank has been assigned based on the discharge volume. The return period was calculated based on Weibull’s formula (P) for this analysis. The flood frequency data was plotted on a graph where X-axis shows the return period and the Yaxis is the discharge value. The R2 value of this graph is 0.9998 which describe Gumbel’s distribution method is best for the flood frequency analysis. The flood frequency analysis is an essential step to assess the flood hazard.

Impact assessment of structural barriers and flow regulation on the Ganga River morphology and ecology

<p>The Ganga-Brahmaputra river system in the Himalayan Foreland supports diverse aquatic fauna. Decades of flow regulation through dams and barrages have affected their habitat suitability. To evaluate the impacts of large barrages on the morphology and habitat ecology we studied two different reaches (middle and lower) of the Ganga River. These reaches are the habitat of the endangered Ganga River dolphin (<em>Platanista gangetica</em>). In a reach in the middle Ganga between Bijnor and Narora barrage, a reported rise in dolphin population has been documented. In contrast, near the Farakka barrage in the lower reach of the Ganga River, a significant decline in the dolphin population has been observed.</p><p>We use Corona and time-series Landsat satellite images along with flow discharge data to assess the morphological and ecological impact of the barrages. In middle Ganga, the dolphin habitat is isolated between the Bijnor and Narora barrage where the minimum flow is available throughout the year for the dolphins to thrive.  On the other hand, in the lower Ganga, contrasting impacts are observed in the proximity (upstream/downstream) of the Farakka barrage. In the downstream, reduction in water (by one-third in the pre-monsoon discharge) and sediment discharge has decoupled the channel belt to its floodplain resulting in a loss of lateral connectivity. The presence of minimum flow between the Bijnor and Narora barrage has aided the dolphin population rise while the loss of lateral connectivity and excess siltation at the Farakka barrage has made the river reach unsuitable for habitation.   </p>

Commercial approach and river-related conflicts in South Asia

Chapter 5 uses the experience of South Asia to illustrate how the Commercial approach leads to conflicts among co-riparian countries. It notes that river basins were fragmented in South Asia by borders that were drawn based on political considerations and not physical geography. While greater cooperation among South Asian countries was necessary to protect the river basins, adoption of the Commercial approach led to more conflicts than cooperation. India, which lies at the center of the region, has borders with most South Asian countries, including Bangladesh, Bhutan, Nepal, and Pakistan and finds itself in conflict with all of them. The chapter focuses on the most serious and numerous conflicts, which are with Bangladesh, and center on such major water diversionary barrages as the Farakka Barrage and the Gajoldoba Barrage. It notes that India’s proposed River Linking Project is only likely to aggravate these conflicts. The chapter also reviews India’s conflicts with Nepal and Bhutan regarding sharing the costs and benefits of the dams that it has constructed under joint ventures as well as conflicts with Pakistan over sharing the Indus River. Finally, the chapter notes the burgeoning conflicts with China regarding the Brahmaputra River.

Fluid Epistemologies

By using the term “fluid”, this article critically interrogates western ontologies of “solid” (land) and “liquid” (flowing waters), which were transplanted in colonial South Asia and transmitted in post-Independence river/water policies and actions with severe socio-ecological implications. Drawing lessons from recent environmental history and political ecology of water (“hydrosocial”) literature that shed light on liminal scapes beyond the mainstream land/water binary in hydrological studies, this study conceptualizes “fluidscapes” by drawing on field research in the river islands (chars) of Lower Bengal. By capturing snippets of livelihoods in the chars of the Malda and Murshidabad districts, West Bengal, situated upstream and downstream of the Farakka Barrage respectively, this article advances why and how it is imperative to rethink sediment beyond its physical-geomorphological existence and to see it as social sites of interactions. It unravels avenues through which chars can be perceived as not only emblems of uncertainty but also as zones of possibility bestowed with rich ecosystem services and the collective resilience of choruas.