Climate change is drying lakes

Researchers with new insights about the future of our waters

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By means of model calculations, scientists have succeeded in separating the consequences of direct human intervention on the influence of climate in water bodies. It is clear that even in the summer months, smaller rivers and streams and ponds in the Berlin-Brandenburg region are drying up. However, the subterranean catchment areas are also changing.

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Dried riverbeds or ponds are no longer a rarity in the summer months due to climatic changes in Berlin-Brandenburg. Scientists at the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) in Berlin have been researching the underlying processes for a long time. For example, they were able to use model simulations to calculate how much water can be lost underground if the groundwater levels of groundwater sink.

In the department of Professor Gunnar Nützmann such hydrological models are developed and applied. Support comes from external cooperation partners. First studies on the Fredersdorf mill stream showed that human interference and climatic influences are superimposed. But with the help of models, the scientists succeed in depicting and quantifying the processes separately.

The last example of this successful collaboration goes beyond describing conditions that have already occurred by simulating management scenarios for former Rieselfeld areas in the north of Berlin using coupled surface groundwater models. This results in the scientific basis for local and regional water management. display

Importance of evaporation is growing

Nützmann adds: "In view of the climatic changes that have already occurred and their predictions for the next decades, the water household size evaporation is also becoming increasingly important." Torsten Strube carried out calculations for the Müggelsee in the IGB's Ecohydrology department.

They showed that the average levels of evaporation for 2006 are 22 percent higher for June and 47 percent higher for July than for the comparable months of 2000-2005. These numbers are confirmed by long-term measured time series of the evaporation of the Stechlinsee. From these it can be seen that sea evaporation in so-called dry years can be about twice the evaporation of wet years.

Understand interactions between ground and surface waters

With the change in runoff dynamics and altitude, subterranean catchment areas and thus the basics of previous balancing changes. Last but not least, climate change also influences the water's internal processes. These include, for example, the vertical temperature distribution and dynamics, which, among other things, can have a controlling effect on the plankton distribution and biomass production of a lake.

Nützmann emphasizes: "If we understand the interactions between ground and surface waters, we can elucidate the formation of runoff and its changes due to climate change." This applies in the quantitative as well as the qualitative sense. "The bottom line is the understanding of aquatic ecological processes, which are not only controlled internally, but also influenced substantially externally, " says Nützmann.

(idw - Forschungsverbund Berlin, 13.06.2007 - DLO)