Assessing the water quality of Himalayan glacier-fed rivers

More than 1.4 billion people depend on water from the rivers of the Himalaya (Immerzeel et al., 2010) and there are more than 6000 rivers flowing from the Himalayan Mountains to the hills and plains in Nepal (CBS, 1995). Most of these rivers are glacier fed and provide sustained flow during the dry season to meet the water requirements for those living downstream (Ghimire et al., 2013). While much research has focussed on the impact of climatic changes on the timing and magnitude of water supplies to downstream areas (e.g. Lutz et al., 2014), much less attention has been devoted to the impact of anthropogenic pollution on the water quality of these mountain streams and rivers.

Studies have shown that pollution of lowland rivers in Nepal increases with distance from the mountains and with proximity to urban centres, due to increasing population, agricultural activity and inputs of effluent from industry and untreated sewage (e.g. Mishra et al., 2017). Much less is known about the water quality of remote mountain areas, yet in these parts surface water may be used directly for irrigation, sanitation, and in some cases, consumption. Historic datasets collected during the early 1990s in the Khumbu, Annapurna and Langtang catchments (Reynolds et al., 1995; 1998) show that the bedrock geology was the primary driver of the spatial variability in water chemistry in these regions. However, although stream water nitrate concentrations were generally small, large values were recorded in some areas and there was a positive correlation with altitude suggesting either a larger atmospheric deposition at higher altitude and/or that uptake of nitrate by both terrestrial and aquatic systems decreased with altitude. Subsequent surveys of water bodies in the Khumbu region in 2008, 2009 and 2010 showed that both nitrate and phosphate concentrations have increased since 1992 and over the period 2008-2010 (Ghimire et al., 2013).

Additionally, over the last 25 years, these mountain areas have faced increasing anthropogenic pressures from population growth, increase in tourism, land use change, atmospheric pollution and climate change. Such pressures are likely to have had an impact on water chemistry and quality via an associated increase in sewage waste, fertiliser use, atmospheric deposition of sulphur, nitrogen and heavy metals and in non-biodegradable solid waste such as plastic containers and batteries. In addition to increasing nutrient and metal concentration, these pressures may also lead to the presence of microplastics and other emerging pollutants (EPs), such as pharmaceuticals, which have not yet been monitored in remote mountainous streams but have the potential to enter the environment and cause adverse ecological and human health effects.

The major aim of this project will be to evaluate contemporary water quality in major mountain regions of Nepal, and establish how this compares with the chemistry of surface waters that were originally surveyed in the early 1990s. This 30 year temporal analysis will be the first of its kind in this region, and has the potential to bring the issue of water quality, and how it will change with continued pressure on resources, to the forefront of the policy agenda.

In this project, you will work with scientists at the University of Leeds to quantify the impact of different anthropogenic pressures on water chemistry and aquatic ecosystems in one or more of the Khumbu, Annapurna and Langtang regions of Nepal. This will be achieved through fieldwork in Nepal and subsequent laboratory analysis on return to Leeds. In particular, according to their particular research interests, the successful student could:
1. Determine how surface water nutrient concentrations have changed over time with variations in discharge and routing;
2. Investigate whether microplastics and other emerging contaminants are present in aquatic ecosystems of the source areas that feed major rivers of the region;
3. Evaluate which anthropogenic pressures are having the most significant impact on water quality and how this will evolve with future changes in supply.