Kostanjevica na Krki has been known for its ever-increasing floods in the last decade, which has attracted the attention of experts, researchers and journalists. After the construction of the Krško hydro power plant, Kostanjevica na Krki started to suffer from even worse flooding than in previous years. This was the reason for the launch of hydrological research and more detailed measurements of precipitation and watercourses. Within the framework of various projects, they wanted to protect the environment and people from flooding and to mitigate the consequences by building flood dikes, more precise gauges and channels for faster water drainage. During the construction of the new hydroelectric power plant Brežice, new questions about the flooding of the lower part of the Krka River in the vicinity of Kostanjevica were re-opened. In addition to frequent methods such as measuring the amount of precipitation and monitoring the conditions of riverside rivers, a dendromorphological method can also be used for such research. In Slovenia, this method began to be practiced with the aim of studying avalanches and debris flows (Novak, 2017), while abroad it is also more frequently used for researching past floods of endangered areas (Stoffel and Wilford, 2012).
In my graduation thesis I used the dendromorphological method. It is based on tree rings, which we drill through a hand drill from a tree. By studying different parameters of the rings, we can also reconstruct the past climatic conditions and, in the case of floods from damage to trees, we also learn about the height of water during floods (Fritts 1976).
All of the drilled samples were taken from the willow genus (Salix), which are most commonly found in the investigated area. My research has shown that, due to their hydrophilicity, these trees are more suitable for recognizing drought periods that will stronger affect willows than smaller floods. Among the more pronounced drought periods were years 1999, 2001, 2003 and 2011. I used data from the ARSO to compare the flows before and after the construction of the HE Krško and before and after the construction of flood protection infrastructures on the Krka River near Kostanjevica na Krki. It turned out that since the construction of the HE Krško, there has been too little time to see the long-term impacts on the height of the Krka River.