Connecting flow and ecology in Nepal: Current state of knowledge for the Koshi Basin

[摘要] Key findingsNepal's plentiful water resources, like other countries across the globe, require careful management to ensure equitable use across the many competing facets of water consumers. These include agricultural production, hydropower generation and human consumption. As Nepal progresses on a water reform journey, it is an opportune time to investigate the current understanding of the links between river flow and the freshwater ecosystems supported by these water resources. This report had dual purposes: to establish a baseline understanding of the current knowledge, in relation to ecological water requirements of aquatic ecosystems under natural flow variability conditions within the Koshi Basin of Nepal; and to stimulate research to address knowledge gaps and investigate species which might be good indicators of the ecological impacts of flow change in the future (indicator species). The overarching aim was to provide information to assist with Nepal’s water reform journey with an emphasis on protecting freshwater ecosystems.Through a process of expert elicitation, workshops and literature reviews, a number of conceptual models were created to highlight the known links between river flow and specific ecological components such as birds, fish, buffalo, crocodiles/gharials, invertebrates, flora and the freshwater Ganges River Dolphin. Additional information was collated to provide context around the current understanding of threats to aquatic ecosystems in relation to flow change; water regimes and environmental water requirements; and the importance of biodiversity to support livelihoods in the Basin. It appears that overall, there is a paucity of published studies which investigate the water requirements of the selected ecological components in the Koshi Basin and Nepal in general. This is understandable given the agreement at the workshops, that much of the knowledge related to flora and fauna was generally locked away in the minds of experts or in unobtainable grey literature.For the first time in Nepal and the Koshi Basin, both qualitative and quantitative flow‐ecology relationships were collated, where quantitative data express specific thresholds to flow change, which once exceeded cause a change (generally a decline) in native species populations. Qualitative data refers to knowledge which comes from observation but which hasn’t been scientifically tested to determine a specific threshold to flow change.Wild Water BuffaloIn the international literature, there is a lack of published studies that relate flow regimes to the Wild Water Buffalo, specifically in Nepal and the Koshi Basin. While Water Buffalo are a species on the brink of extinction in Nepal, there is little known in relation to its key habitat and water requirements. It is known from observation that Water Buffalo require mixed riverine forest in order to have shade and to exfoliate after wallowing. Key quantitative relationships identified for the Water Buffalo include:- a requirement for alluvial tall grassland composed of 80% Saccharum spp for grazing- a requirement to wallow 6‐8 hours a day to cool themselves.However, there are many more knowledge gaps. Little is known about how big wallows need to be, what depth of water is required in the wallows and what temperature and water quality are required, to name a few.FishThe hydrological variables that might impact fish and in particular fishery viability have been studied in more detail. A first time review undertaken within, identifies 141 reported fish species of which 134 are indigenous and seven are exotic. Factors such as high longitudinal river connectivity, oxygenated, unpolluted freshwater and minimal macrophyte area, enhance fish and fishery viability. Key quantitative relationships identified for fishes include:- Snow Trout (Schizothorax spp) require the ability to migrate upstream to spawn in March to June at water temperatures between 14–21oC. They also require clea...

[发布日期] 2016-06-22 [发布机构] CSIRO

[学科分类] 地球科学(综合)