The response of salt intrusion to changes in river discharge, tidal range, and winds, based on wavelet analysis in the Modaomen estuary, China

Abstract

Salt intrusion is a serious environmental problem and is affected by many external forcings, and Modaomen Estuary in China's Pearl River Delta is no exception. Based on the cross-wavelet and wavelet coherence analysis, this study investigated the responses of salt intrusion to different forcings, including tidal range, river discharge, alongshore and cross-shore winds, in different timescales. In the intraseasonal timescale, the response times for the salt intrusion to the tidal range, river discharge, alongshore and cross-shore winds are 1.8–6.2, 1.2–9.2, 3.6–10.5, and 3.0–10.4 days, respectively. When averaging the magnitude of response in each winter over 2004–2016, it is found that the most important forcing in influencing the interannual variability of salt intrusion is the tidal range, followed by cross-shore wind, alongshore wind, and river discharge. The winds have great impacts on the salt intrusion, in which a strong downwelling-favorable alongshore wind enhances the salt intrusion and in general, a down-estuary cross-shore wind imposes a similar effect, although its effect varies considerably. This study is of implications for the regional water resource management in the Modaomen Estuary.