Lake Balaton hydrology and climate change

Károly Kutics,Gabriella Kravinszkaja

doi:10.19040/ecocycles.v6i1.165

Abstract

Situated in the western part of Hungary, Lake Balaton is the second largest shallow lake in the European Union after Lake Peipus and the largest one laying entirely within the borders of the EU. Despite of its large surface area of some 600 km2, its average depth is only 352 cm. Lake Balaton is an exorheic lake on multiannual basis, but dry spells in the last 2 decades resulted in a 64-month period without outflow. Studies by the authors and others proved that human impacts of global and local nature resulted in the significant decrease of the natural water balance (NWB) in the last 3-4 decades. Climate change is already manifested in the reduction of the discharge of most of the tributaries including the largest one, Zala river. The statistically significant decrease in the last 3 decades of the discharge of Zala river and Kiskomaromi-canal corresponds to a deficit of 67 lake mm/year. The impact of further human interventions including reconstruction of Balaton Minor, a vast wetland and mining resulted in a further deficit of 119 to 154 lake mm/year. The average of the annual NWB of the last 30 years is only 63% of the long-term average. In addition to the decrease in the average discharges and NWB, variability of these values increased considerably. Some of these phenomena can be attributed to climate change. Future impacts of climate change are evaluated and it is concluded that the Lake Balaton watershed may turn into an endorheic basin in the second half of the 21st century. Lake Balaton, human impact, climate change, water balance, future trends

Highlights

Lake Balaton is the largest lake in Central-Europe with a 605 km2 surface area
The mill dams along the Sió river resulted in higher water levels both in Lake Balaton and the marshlands making the agricultural utilization of land and transportation of agricultural goods very difficult
The fitted linear regression line shows definite increasing trends with statistical significance of p < 0.03. These results indicate that climate change may already have a serious impact on the natural water balance of

Summary

Introduction

Lake Balaton is the largest lake in Central-Europe with a 605 km surface area It is one of the most important lakes in Europe in terms of ecological, economic and cultural significance. Up to the beginning of the 19th century, the lake and its surrounding marshlands were rather a burden than a blessing for the people inhabiting the area since occasional flooding of the lake damaged crops and made transportation around the lake difficult, if not impossible. Perhaps the only benefit of the lake in the 16th and 17th centuries was that its extremely high water level and the flooded marshlands hindered the advance of Turkish occupation and provided refuge for the Hungarian population. The mill dams along the Sió river resulted in higher water levels both in Lake Balaton and the marshlands making the agricultural utilization of land and transportation of agricultural goods very difficult. The situation was recognized as a problem in the middle of the 18th century, and the onset of a series of the numerous human interventions in the Lake Balaton environment can be dated to this period

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