Changes in Physical Properties of Inland Streamwaters Induced by Earth and Atmospheric Tides

Abstract

Earth and atmospheric tides create oscillations in water parameters of inland rivers, mainly due to the similar behavior of groundwaters. Tidal oscillations of inland rivers were termed orthotides and were detected in fluctuations of water level and specific conductivity of some rivers. However, few things are understood about orthotides because of their recent discovery. Here, we show that orthotidal signals exist in streamwater temperature too. Wavelet and T_TIDE analyses are used to study streamwater temperature and specific conductivity. We found solar and lunar semidiurnal orthotides (S2 and M2) in Alapaha River (USA) water temperature and Wybong River (Australia) water specific conductivity with amplitudes of up to 0.6 °C and 11.3 µS/cm. We demonstrate that the tidal semidiurnal cycles have statistical significance and are caused by similar cycles in groundwater. Oscillations found in water temperature time series for some new moon time intervals have shapes that correlate with the gravitational tides. Diurnal and fortnightly tidal cycles were found and overlapped with other natural cycles with similar periodicities. The inclusion of more water parameters to the list of orthotidally sensitive parameters indicates the wider than expected environmental impact of the small periodic natural changes.