Physical Conditions of Saline Water Intrusion into a Coastal Lagoon, Lake Shinji, Japan.

Abstract

In a coastal lagoon, Lake Shinji, saline water intrusion frequently occurs from the lower Ohashi River. Continuous observation of current velocity, salinity and water level in the Ohashi River revealed that intermittent intrusions takes place when diurnal periods of astronomical tide coincide with the rising stage of meteorological tides during a low discharge from the influent Hii River.The dynamics of tidal currents and saline transport in the Ohashi River were examined by numerical simulation with a simplified onedimensional model using water level and salinity data from both river-channel ends. The calculated results reproduced well the observed time series of current velocity and salinity, though some disparity appeared under the two-layered structure. Related phenomena following the intrusion were described with respect to the formation of the stratified structure in Lake Shinji.

Analysis of the dynamic characteristics of seawater intrusion using partial wavelet coherence: a case study at Nakaura Watergate, Japan

“…Brackish water from Lake Shinji flows into Lake Nakaumi through Ohashi River forming the surface layer. Bottom layer with high salinity in Lake Nakaumi is occasionally driven by the wind-induced internal waves and tides towards the lake coast and upstream into Ohashi River and Lake Shinji (Ishitobi et al 1999(Ishitobi et al , 1989. The effect of wind stress on internal oscillation is greater than that of astronomical tides.…”

“…The westward water transport, mainly driven by MISSV, occurred often with the time scale over a few days to a week, contributing to the exchange of water between the two lakes (Nakata et al 2000). The salinity in Ohashi River, between Lakes Shinji and Nakaumi, vary acutely as a result of water moving back and forth with tides, freshwater input and other physical factors (Uye et al 2000;Ishitobi et al 1989Ishitobi et al , 1999.…”

Phosphorus release and sedimentation in three contiguous shallow brackish lakes, as estimated from changes in phosphorus stock and loading from catchment

“…Inflow from the Hii River from the west end of Lake Shinji accounts for 75% of total runoff to the lake. Saline water intrusion from Lake Nakaumi via the Ohashi River is influenced by weather and tidal fluctuations (Ishitobi et al 1993(Ishitobi et al , 1999. Therefore, the salinity of Lake Shinji varies every year; its average salinity was 3.7 practical salinity unit (PSU) from January 1993 to December 2002.…”

Bodies of Water Along the Coast of a Tideless Sea in Areas with Young Pleistocene Accumulation from Scandinavian Glaciers (Baltic Sea)

“…Seawater intrusions are some of the most common events taking place during extreme weather conditions. The effects of seawater intrusions have been observed in coastal lakes (Saeijs, Stortelder, 1982;Tiruneh, Motz, 2003), lagoons (Ishitobi et al, 1999;Tanaka et al, 2005), wetlands (Glover, 1959;Flynn, McKee, 1995) and mouth sections of rivers (Foster, 1980;Giambastiani et al, 2007). Seawater intrusions cause an increase in water salinity (van der Thuin, 1990) and abruptly increased water levels (Haslett, 2008).…”

“…Davidson et al (1991) characterized estuaries in Great Britain. Ishitobi et al (1999) described physical effects resulting from seawater intrusions into the coastal lake Shinja. Godo et al (2001) described the effects of wind on the mixing of water from two coastal lakes in Japan.…”