Announcements

World Water Day is celebrated at the Centre for Limnology of the Estonian University of Life Sciences on 22 March, 2024.

For 30 years, under the leadership of the UN-Water, this date has been dedicated to fresh water as one of the most important resources on Earth. Against the background of the growing population and the accompanying higher consumption of fresh water, more and more efforts must be made to preserve lakes, rivers and wetlands in good condition, and the supply of clean drinking water.

The theme of this year's Water Day is "Water for peace". When water is scarce or contaminated, when people do not have access to clean water, tensions can arise between communities and countries. According to the World Health Organization WHO, an estimated 27% of humanity, or 2.2 billion people, do not have adequate access to clean drinking water. According to UNESCO, in 2020, 44% of the world's wastewater was returned to the environment untreated. Water-related disasters have topped the list of natural disasters over the past 50 years, accounting for 70 percent of all natural disaster-related deaths (World Bank, 2022).

The focus of Estonian lake scientists is, of course, on our freshwater bodies. At the seminar on March 22, several topics that are important for Estonia will be discussed, also in the global context. In other words, what can be our contribution to the preservation of world water peace.

60% of the world's fresh water bodies are transboundary, but among 153 countries whose territory includes at least one transboundary basin or aquifer, only 24 countries, including Estonia, have cross-border cooperation agreements for the management of these waters. Transboundary water cooperation, based on Water Convention is directed to lead to equatable and peaceful use of water resources with aim to achieve concrete economic and environmental benefits. Transboundary water cooperation facilitates dialogue and has great potential to increase geopolitical stability, peace and security. The obligations of riparian parties to the Water Convention, particularly the duty to cooperate and the obligations to hold consultations and exchange information are essentially aimed at preventing conflicts and wars over transboundary waters. Those important policy directions and potential benefits are important in today’s World where many countries from Africa, Latin America and Asia are actively joining with Water Convention during last years. Since February 24, 2022 when Russia attacked Ukraine, Estonia's cooperation with Russia on the border water bodies is at the minimum necessary level of data exchange, all cooperation projects have been suspended.

Under the most pessimistic IPCC climate scenario (RCP8.5), the global sea level rises by 1.6m by the end of this century (10.4m by 2300). Over the next 30-70 years, water temperature may increase by up to 4.5 °C in Estonian lakes on average, the content of dissolved oxygen in the bottom of water bodies may decrease by 20-30%, and strong thermal stratification may occur also in the currently none stratified shallow lakes during the summer period. Even by the optimistic scenario (RCP2.6), ocean levels rise by 0.9m by the end of this century (2.5m by 2300). A massive climate retrate is a realistic prospect for the world, with entire nations losing their identity.

Sufficient availability of fresh water ensures a stable life for people. However, freshwater resources directly depend on precipitation. Based on some examples from South and Central America, we can see that unfortunately, scientists' predictions are starting to come true. In 2023, Brazil was hit by an unprecedented heatwave accompanied by an extreme drought. Many rivers dried up, transportation routes disappeared, and large areas suddenly became isolated from the rest of the world. This led to food and water shortages, the spread of diseases, and many other problems. The repercussions of this environmental disaster will inevitably reach us in Europe as well.

Many different micro- and macro-organisms live in water, whether they are good or bad from a human point of view often depends on their origin and number. As the climate warms, it is expected that more heat-tolerant pathogenic species will spread to more North. Therefore, it is becoming more and more important to ensure the very good quality of water used for drinking as well as for agriculture and swimming.

Eutrophication of water bodies can be alleviated by reducing phosphorus amounts in water ecosystems, and avoiding further phosphorus loads from catchment by effective phosphorus recycling without losses into the water bodies. Lake sediments can be used as fertilizers or soil improvers, or even as binding agents in fertilizer granules and composts. Phosphorus in fish waste compost can easily be recycled in agriculture, since up to 60% of it is immediately available for plants, while in generally very phosphorus-rich sewage sludge compost only 6% of it is bioavailable.

In the freshwater science, one of the most modern and promising directions is the development and application of eDNA methods to study the biota of water bodies and to assess their condition. eDNA methodology can successfully assess the abundance of fish species in water bodies. Additionally, the eDNA methodology is suitable for analyzing the composition of fish communities. More fish species

were identified with this methodology than with traditional net and trawl methods. The method promises to be useful both for the fulfilment of nature conservation goals and for the planning and implementation of measures aimed at rehabilitating water bodies.

Every drop of clean water is important, every organization and every single person can contribute to this. Among the topics of the seminar is only a small part of what the hydrobiologists of the Estonian University of Life Sciences are doing. It is certain that the good condition of water bodies in Estonia and the whole world is our biggest goal.