Disturbance of water‐air temperature synchronisation by dam reservoirs

Abstract

Abstract A thermal regime of aquatic ecosystems determines the possibility of survival and development of aquatic biota. Thermal stratification of river water impounded by dam reservoirs can cause a permanent disturbance in the naturally existing water‐air temperature relationship downstream of reservoirs. This article aims at determining the role of dam reservoirs in the disturbance of naturally shaped synchronous behaviour of water‐air temperatures. The object of the analysis is the Carpathian river Dunajec downstream of a reservoir complex built in 1994–1997. Results of spectral analysis indicate that the annual scale is the main scale of water temperature (WT) variation, and this scale corresponds to the main frequency of phase synchronisation. However, following the reservoirs construction, the definite synchronous behaviour of interacting air and WTs was apparently distorted, because the response time of WT to changing atmospheric conditions has considerably increased in comparison with the predam period.