The Drin River Basin is home to 1.6 million people in the Western Balkans. Their lives depend on this system, which provides the resources they need for electricity generation, irrigation, fishing and recreational activities. Increasing floods and droughts in the Mediterranean region, and especially in the Western Balkans, will pose ever greater risks to the economy, flora, fauna and human health.

One of the clearest examples of climate change that I could have noticed in the past few years is the extensive flooding that struck areas in Western Serbia, Eastern Bosnia and parts of Croatia. Even though some of the damage can be contributed to human factors such as human polution that lead to the drainage systems being clogged, the sheer amount of rainfall in the time between 3-16 May 2014 is evidence enough to support the claim that this is truly a climate change related problem

Picture 1: Precipitation in Europe 13-16 May 2014 [mm/4day], ECMWF analysis.The torrential rains and catastrophic floods that raged through parts of Bosnia and Herzegovina, Serbia, and Croatia were unprecedented in the historical record of the region, going back 120 years. The flooding event began on May 13 when an area of low pressure developed as warm, moist air from over the Mediterranean Sea clashed with colder air from the north. The low became cut-off from the jet stream, which would ordinarily usher the system across the region instead, it remained parked over southeast Europe, dumping rain for several days. In just a few days, some areas received an amount of rain equivalent to one third of their annual total.The flooding was so bad in part because the region had already seen unusually strong rains since mid-April, so soils were saturated and unable to soak up some of the tremendous excess. Instead, water went crashing down slopes and into numerous streams and rivers of the Danube watershed, many of which breached their banks and set record flood levels.These rains caused large-scale flooding, with loss of life and extensive damage. A question that often arises is whether this event was related to climate change. In a first look at the event based on preliminary data we find no evidence that the warming trend has contributed significantly to the severity of the precipitation leading to the floods in this area.The precipitation event of 13-16 May 2014 on the Sava and Danube rivers was very rare, with a return time higher than 60 years. However, as it only covered a few per cent of the area of Europe an event with a return time like this is expected every year or two somewhere on the continent just due to the natural variability of the weather. There is no clear trend of 4-day precipitation events prior to this year in the observations and climate models only show a very small increase up to now. Results from hydrological models suggest that the probability of a flood on these rivers can decrease, rather than increase, due to climate change.Sources:1. https://www.knmi.nl/kennis-en-datacentrum/achtergrond/climate-aspects-of-the-floods-in-bosnia-and-serbia-may-20142. https://www.giz.de/en/worldwide/29000.html