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You don´t always need huge finances for research, as long as you have your head screwed on right! This is demonstrated by a scientific aggregate for measuring water exchange in the bottom of a lake built by Marko Vainu, a TU Doctoral student of Ecology.

Throughout my university studies the main question of my research has been why some lakes contain the exact amount of water that they do; in other words, what does the quantity of water in a lake depend on. It is known that water is a result of precipitation on the surface of a lake as well as on the drainage basin of the lake from where the water reaches the lake in the form of rivers, streams and/or groundwater. On the other hand, lakes lose water through evaporation, emanation and permeation into groundwater. As the interaction mechanisms of lakes and groundwater have remained rather un-investigated, even on a global level, then my doctoral thesis is focused on that field.

Let´s imagine a nice small forest lake into which no visible river or stream flows in or out. It seems that the water in this lake does not change. But the reality is something else – it is very likely that, depending on the size of the lake, many or even many dozens of cubic meters of ‘invisible’ water flow through that lake every hour - water that comes from and returns to groundwater. My doctoral thesis is based on the study of this flow of ‘invisible water’. I am mostly interested in the sources of this ‘invisible water’ and the factors that influence the inflow and outflow volume of water.

At first, this may seem to be just a question of purely theoretical, fundamental scientific interest. But in the Ida-Virumaa and Kurtna lakes region for example, the area of my main research so far, this theoretical topic also has a very practical application. For instance, between the lakes, there is the Vasavere catchment area from which large quantities of groundwater are pumped out as the source of drinking water for the inhabitants of Jõhvi. Four decades ago this caused a decrease of groundwater level of several meters, and also a decrease in the water level of nearby closed-basin lakes that are under natural protection and of high recreational value. After the restoration of Estonian independence, water abstraction decreased and the water level of the lakes recovered but a few years ago, the drilling of wells was reintroduced and once again more groundwater was pumped out from near the lakes. Today, the water level of the lakes close to the wells that have been drilled has decreased again by up to one meter.

It has not been possible to anticipate this unwelcome, and in the case of the protected lakes, a prohibited, decrease in water level. And the reason for this is that the significance of the role of groundwater in the water quantity of these lakes is not understood and neither are the exact patterns of inflow and outflow of groundwater in the bottom of the lakes. Therefore my research results could some day help to better predict what could happen to the water level of lakes when groundwater levels are changed nearby.

Since I am only in the middle of my doctoral studies, unfortunately I don’t have any very fundamental discoveries. With the self-built filtration meter shown in the video clip, I have shown that in the lakes that are situated in the middle of the Kurtna lakes region, groundwater really does enter from one side of a lake and flows out the other side of the lake towards the wells that have been drilled. I have also discovered that the patterns of groundwater exchange in the bottom of the lakes are very diverse. For example, when moving from the side of the lake towards the deeper centre of the lake, the inflow and outflow speed of groundwater doesn’t increase or decrease equally, but is quite variable. The most surprising discovery has been that groundwater can also filter in the lake through a layer of mud a few meters thick.

Thus my research has shown the very common truth in science – the processes taking place in nature are much more complicated than what would be comfortable for people. When studying an object, a phenomenon or a process, more and more questions emerge and there will probably never be the moment where everything about something will be clear. At different moments, we can just make mid-term reviews of the current status of knowledge for the public interest.

Therefore my research continues in Kurtna for now. The measurement data of groundwater exchange after the reintroduction of drilling wells and increasing the quantities of water pumped out have been collected and now I can compare the way in which this activity that has lowered the water level of the lakes, has changed the groundwater exchange patterns of the lakes. Everything is designed to learn even more and one day, reach a conclusion that has a practical use.