Investigating Ugandan crater lake water quality and hydrology using novel monitoring data sets.

NERC: Laura Hunt: NE/L002604/1

Tropical lakes provide important water resources and ecosystem services to their communities, but their response to climate and environmental change is poorly understood. In western Uganda more than 80 crater lakes provide critical resources to rural communities. These include household water use, and resource for crops and livestock, in addition to provision of opportunities for artisanal fisheries and ecotourism. Previous work (e.g. Mills, 2009; Saulnier-Talbot et al., 2014) has shown that these crater lakes and their catchments are under increasing pressure from human impacts, such as deforestation, and climate change. By understanding the response of the crater lakes to past environmental changes across various timescales, it is possible to predict future changes in their water balance and water quality, thus helping inform sustainable management of surface water supplies (Mills et al., 2017).
Long-term monitoring data from tropical lakes is sparse, and where they do exist, they tend to be discontinuous and cover relatively short time periods (<20 years), however the Kibale Fish Project (led by Prof. Lauren Chapman from McGill University in Canada) has routinely monitored Lake Nkuruba since 1991, making this small Ugandan lake one of the best-monitored lakes in Africa. The proposed research project will collate, organise, and digitise lake pH, conductivity and rainfall data collected by this project, creating the longest record of water quality measurements from eastern Africa. Compared to many other lakes in the region, the catchment of Lake Nkuruba has experienced a low level of human disturbance and so offers a rare opportunity to understand the impact of climate change on a lake system and its function, and upon water quantity and quality, without the significant added impact of people.
In addition to long-term monitoring, palaeolimnology, the study of lake sediments, can be used to extract information about past environmental and climatic changes, but over a much longer time frame. Many components of a lake system (including biological and geochemical components) are recorded in the lake sediments, which act as a history book for the lake and its catchment, and can be analyzed to infer environmental change and its drivers. The sediments can be dated using radiometric techniques, so that timing of changes can be understood and correlated with other known environmental changes. Studies of the environmental indicators preserved in lake sediments from Lake Nkuruba (Saulnier-Talbot et al., 2014, 2018) and a number of the other Ugandan crater lakes (e.g. Mills et al., 2014; Mills et al., 2018; Ryves et al., 2011), have shown there have been significant fluctuations of the crater lake water balance over time.
The improved understanding of Lake Nkuruba's hydrological system that we will get from this research will improve understanding of these Ugandan lake systems in general, which will help interpretation of the records obtained from lake sediments about past lake conditions as well as helping to understand the potential impact of climatic change on the water quality of these socially, economically, and environmentally important lakes in the future.