Factors controlling saltwater intrusion across multi-time scales in estuaries, Chester River, Chesapeake Bay

Abstract

The relative dominance of controlling factors in saltwater intrusion depends on the time scale in which the variability in characterized. Long-term time series data of salinity and temperature has been collected in the Chester River, Chesapeake Bay, showing considerable variabilities of saltwater intrusion with time scales from days to years. In this study, the Finite-Volume Community Ocean Model (FVCOM) was applied to the data over a decadal time scale from 2002 to 2011 to identify the drivers and their relative importance in controlling the variability of saltwater intrusion with different time scale ranging from events of a few days, through seasonal to interannual variations. FVCOM successfully reproduced the observed variations in saltwater intrusion over the entire simulation period, and thus completed time series data from monthly samples to daily and even at a higher temporal resolution for statistical analysis. The results shows that river discharge is the primary factor controlling the saltwater intrusion variability on interannual time scales, but sea surface level is more dominating on seasonal variations, while wind has more important influence on short-time scales during weather events, mostly through modulation of sea surface level on regional scales rather than local wind strain and Ekman transport. Tide has limited influence due to short tidal excursion and amplitude in the Chester Estuary. The estuarine geometry has a significant influence on the two-layer estuarine circulation and saltwater intrusion in the Chester Estuary. The upper estuary is the shallow narrow channel where two-layer estuarine circulation is limited, the meanders in the mid-estuary also restrict the development of the two-layer circulation due to helical circulation, while the lower estuary has stronger stratification and two-layer circulation as compared to the upper and mid-estuary.