The freshwater ecosystems provide energy, water and food to people and serve as critical habitats for many aquatic animals including keystone species such as Gangetic River Dolphin, Mahseer, Otter, macroinvertebrates (mayflies, stoneflies, caddisflies), and others. Rivers also have great cultural and spiritual significance, and people perform many important rituals along the rivers. Despite their importance, many rivers in Nepal are severely degraded or at risk, which has undermined their ability to provide critical ecosystem services and related benefits.
In recent decades, rivers in Nepal have increasingly been dammed or regulated for hydroelectricity, irrigation, and drinking water supply. This has altered their physical characteristics such as flow regime, mineral habitat, water temperature, and sediment transport. Human interventions have also impacted the upstream and downstream linkages of the river systems. Most importantly, migratory species are under threat as such species migrate seasonally from lowland rivers to highland rivers for spawning. Rivers are also habitats of many instream biota such as periphyton, diatoms, macroinvertebrates (insects, gastropods, crabs, amphipods) which are essential for nutrient cycling in the ecosystem and some of the organisms are important food sources for many local people.
The Environment Protection Act 2019 and Environment Protection Rules 2020 clearly state that all hydropower projects are required to conduct an Initial Environmental Examination (IEE) and an Environmental Impact Assessment (EIA) prior to project commencement in order to avoid, minimize and mitigate the project’s negative impacts. Collecting reliable data through scientific studies is crucial for setting the baseline and making evidence-based decisions. A robust scientific methodology is required to detect the changes that river ecosystems have undergone as a result of hydropower development. In this context, this handbook serves as a step-by-step guide for assessing water flows, physical habitat, water quality and the riparian and instream biotic community of river ecosystems. Site information sheet, field data sheets for each taxonomic group, data presentation sheets, and pictorial illustrations have been designed for systematic collection, processing and presentation of the data. The handbook covers the assessment of aquatic biota such as micro-biota (phytoplankton and zooplankton), periphyton, macrophytes, benthic macroinvertebrates, fish, and riparian vegetation. Introduction, field and laboratory methods, and data analysis and presentation are provided for each component. Further, it includes detailed descriptions of biodiversity hotspots, biological corridors and connectivity, important bird and plant area, protected/conservation area, and ecosystem services. Eventually, this handbook explains the process of assessing and managing environmental impacts.
The number of sites, their distribution, and their frequency over the seasons and years are crucial aspects of ecosystem assessment in environmental studies including Environmental Impact Assessment (EIA) and Initial Environment Examination (IEE). It is recommended that the assessment cover at least six sites spatially distributed in the mainstem and its tributaries in each influence zone – above the dam (in control sites and impounded zone), below the dam (diversion reach), and downstream of the powerhouse. Each site should be adequately representative of the location so that the sample consists of a broad range of organisms residing in the location.
The handbook aims to provide a complete set of information and tools for freshwater biodiversity assessment in order to guide and help practitioners involved in IEE, related processes of hydropower projects and other environment-related studies.