Unexpected results
The river water levels were monitored between 1971 and 2010 and compared the observations with simulations from climate models – with unexpected results. When evaluating the data from the river monitoring stations with regards to possible changes in river flows, a team of researchers, amongst them Fang Zhao from the East China University and the Potsdam Institute for Climate Impact Research (PIK), found that in some cases more floods occurred, but in others there were longer periods of low water. What the findings had in common, however, is that they cannot be explained without human-induced climate change – these results were recently published in the renowned scientific journal Science. In contrast to the scientist’s expectations, water management, for example through dams, or the consequences of land use, for example through deforestation, had no measurable global impact in the changes of rivers and streams.
The study
In search of an explanation for their observations, the researchers used several global hydrological models. They fed these with the climate data from the period studied (1971 to 2010). The team then proved the human influence by comparing the measured data with two different results from climate models: One was calculated with man-made greenhouse gases and one without. Only in the first case did the simulation match with the real observed river measurement data suggesting that the observed changes are highly unlikely without climate change.
In a second step, the team also included human interventions such as the construction of dams or land use changes such as deforestation in the model calculations. This, however, did not change the results, which support the findings and show that human-induced climate change and not adjustments in water and land management are the cause of global changes in rivers.
The press release can be found here
The full article can be found here