Inconsistent hydrological trends do not necessarily imply spatially heterogeneous drivers

Trend analyses are widely used to check for climate change effects on hydrological systems. However, often inconsistent patterns have been found, that is, non-significant as well significant but opposing trends in the same data set. These inconsistencies ascribed local, mostly anthropogenic like wetland draining or land use change. In this study local were subtracted from time series of lake water level and groundwater head covering a 28 years period Northeast Germany. But did hardly affect observed trends. contrast, apparent behavior could be different degrees low-pass filtering recharge signal. Due successively increasing attenuation high frequency oscillations during passage through vadose zone minor long-term input signal became increasingly more visible, resulting monotonic year period. There is strong evidence phenomenon frequency-dependent damping which has found wide range natural processes, including