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Largest freshwater Mediterranean lake may dry out in this century due to climate change and abstraction

February 10, 2017
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The town of Beyşehir on the banks of Lake Beyşehir, Turkey. Image: Wikipedia Commons

Freshwater systems in the Mediterranean region are on the front line of climate change impacts in Europe. Future climate projections for the region indicate increasing air temperatures and decreasing precipitation rates through the 21st century.

Whilst fluctuations in water level and flow are a natural feature of freshwaters in the region, climate change is predicted to cause dramatic reductions in river flows and lake levels, causing severe water scarcity issues for the humans and non-humans that rely on them.

A new study suggests that if water abstraction rates from the region’s largest lake – Lake Beyşehir in Turkey – are not reduced, the lake will dry out in this century, potentially as early as the 2040s. The research, led by Tuba Bucak as part of the EU MARS and REFRESH projects, simulated the impact of future climate and land use changes on water levels in the lake.

Their models predict that increased temperatures and reduced rainfall coupled with ongoing water abstraction for agricultural irrigation place Lake Beyşehir at severe risk of drying out. If water abstraction rates are not reduced, the lake ecosystem and its rich biodiversity is likely to be significantly impacted (or even lost), and the human communities who rely on the lake for water and sustenance will lose the services and benefits the ecosystem provides.

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A NASA satellite image of Lake Beyşehir. Image: Wikipedia Commons

All climate change scenarios (which used Representative Concentration Pathways) predicted a significant decreases in total water runoff into the lake (as a result of decreased rainfall), but the timescale of the decrease varied between the models. In comparison, simulated changes in land use had a minor impact on total runoff.

The decrease in water runoff common to each climate change scenario was projected to be more pronounced after the 2070s due to reduced precipitation and enhanced potential evapo-transpiration in the catchment. However, in one climate scenario modeled by the researchers, the lake was predicted to dry out completely by the 2040s.

The researchers write that despite the variance in their modelling results, that “a 9–60% reduction in outflow withdrawal was needed to prevent the lake from drying out by the end of this century.” In a water-scarce region, it would seem a challenging task for environmental managers and politicians to guide such a drastic change in water use.

However, there are precedents for similar large lakes to dry out. One Turkish lake, Lake Akşehir, has completely dried up in recent years, resulting in the extinction of the Central Anatolian Bleak.  Two other endemic fish species, the Eber Gudgeon and a local dace (Leuciscus anatolicus) are now critically endangered.

For Tuba Bucak, lead author of the study, water management in the region needs to undergo a significant shift if Lake Beyşehir is to be protected. She says,

“Mediterranean lakes may face a risk of drying out and losing their ecosystem service values in future if essential mitigating measures will not be taken into account. We need to implement adapting measures (eg. reducing water needs by promoting drought resistant crops and efficient irrigation technologies) for maintaining water sources in Mediterranean and ensure sustainable water usage in order to meet the future water demands.”
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