Rapid climate change as a result of global warming has made deforestation a widespread phenomenon and a major environmental problem, fueled by an uptick in fire events, droughts, heat waves, pests, and pathogens.
Forests play a key role in the water cycle. They filter water and bind nutrients and are therefore necessary for good water quality. The fewer nutrients – i.e. nitrogen or phosphorous compounds – contained in the water in reservoirs, the better it is for drinking water treatment. According to UFZ lake researcher and co-author Dr. Karsten Rinke, “This makes it more difficult for algae to develop, making drinking water treatment at the treatment plant more economical and easier.”
Deforestation, on the other hand, leads to the loss of key ecosystem functions and has an impact on water reservoirs by altering flow patterns or intensifying nutrient loading from these reservoirs.
The direct and indirect effects on reservoir ecology are complicated to attribute to external factors. Despite widespread familiarity with climate change’s direct effects on water bodies, the cumulative indirect effects on the watershed due to land use change, particularly deforestation, remain generally unquantified.
In August 2022, scientists studied a unique watershed system in central Germany that had two reservoirs with different trophic states (mesotrophic and eutrophic) that both drained into Germany’s largest drinking water reservoir. Due to the long drought from 2015 to 2018, the watershed of the mesotrophic reservoir lost more forest area than ever before (an increase on an exponential scale since 2015 and a loss of about 17.1% in 2020 alone). They linked the catchment nutrient exports (HYPE) and reservoir ecosystem dynamics (GOTM-WET) models using a process-based modeling method. The coupled model was tested with data from times when forests were being cut down quickly. This led to very accurate predictions for the future.
On a short-term scale (up to 2035), the results show that a large amount of deforestation (80% loss) can change the mesotrophic reservoir into its counterpart’s eutrophic state by increasing the flow of nutrients from the basin. Eutrophication makes potentially toxic algae blooms (HAB) grow, which can be very dangerous. The results show that the effects of deforestation are more important than the direct effects of climate change on water quality and ecological services for aquatic ecosystems further downstream. But on a long-term scale (until 2100), the direct effects of climate change on lakes and reservoirs may become more important because of changes in the way heat moves through the water.
As a final thought, the researchers suggest assessing the effects of climate change on lakes and reservoirs using an updated time-dependent framework. This framework gives priority to the implementation of adaptation strategies in the upstream watershed in the near future and in the reservoir in the long term.
The availability of monitoring data is also an important part of this kind of comparison. Usually, sampling is only done to get a full picture of a complex, interconnected catchment-reservoir system. Instead, the researchers suggest a method of monitoring that checks watersheds and reservoirs often and reports on their differences.
LG Sonic understands the significance of high-frequency monitoring of water bodies. We’ve been working on a technology that provides real-time data on water quality. To determine water quality, we measure parameters such as chlorophyll-a, phycocyanin, pH level, water temperature, turbidity, and dissolved oxygen. Giving you a complete picture of your water body.
We recently developed a Vertical Profiler, which records what happens in the critical benthic zone. This allows us to monitor reservoirs much more precisely. This tool is used to monitor the hypoxic and anoxic zones found in many stratified lakes. All of this historical and current information is easily accessible via MPC-View.