Abstract
Water temperature in estuaries is sensitive to thermal discharges and expansive tidal flats; as such, this parameter is essential in maintaining estuarine ecosystem. Semi-enclosed water bodies with poor water exchange easily accumulate heat. This is especially true for Xiangshan Bay, which contains two power plants and a large area of tidal flats. This bay was used as an example to study water temperature and heat dynamics, considering the thermal discharge and tidal flats. This study developed and validated a three-dimensional hydro-heat flux numerical model using field data on tidal elevation, currents, water temperature, and tidal flat temperature. The Finite Volume Community Ocean Model combines an accurate thermal discharge model with the air-water-tidal flat heat flux model. The findings showed that thermal discharge provides heat to the bay in summer and winter, and increases the water temperature of the entire bay by 0.7°C in summer, while maintaining water temperature at 0.52°C in winter. The atmosphere and open seas had greater impacts on heat in the bay in winter and summer. The atmosphere and tidal flats provided heat to the bay in summer and absorbed heat from the bay during winter; the opposite was true for the open sea. The effect of tidal flats in summer is less than that in winter, and provides 1.31 × 1013 J of heat to the bay in summer, while taking 8.63 × 1013 J of heat from the bay in winter. This study provides a comprehensive understanding of the effects of tidal flats and thermal discharge on water temperature and heat in macro-tidal bays and estuaries; its results are applicable to similar bays around the world.
Highlights
Water temperature in bays and estuaries is a fundamental factor for estuarine ecosystems and marine aquaculture
The thermal discharges from Ninghai power plant affected Tie Port, while warm water from Wushashan power plant mainly affected the central area of the bay; this range of impact was constrained to coastal areas
Ninghai power plant is located at the bay head, where the thermal discharge extends into this port during flood tides and toward the bay mouth during ebb tides
Summary
Water temperature in bays and estuaries is a fundamental factor for estuarine ecosystems and marine aquaculture. This study quantitatively estimates the influence of thermal discharge and tidal flats on heat dynamics and budget in bays and estuaries, using Xiangshan Bay as an example To this end, a three-dimensional (3D) numerical model was developed and validated using field data on tidal elevation, currents, water temperature, and tidal flat temperature. This paper illustrates and discusses the effects of thermal discharge and tidal flats on water temperature and heat flux using model results and sensitivity tests. Previous studies on Xiangshan Bay have mainly focused on the hydrodynamics (Li et al, 2015), water exchange (Peng, 2013), sediment dynamic processes (Gao et al, 1990), sediment composition (Sun et al, 2014), air-sea heat flux (Deng, 2007), and the effect of thermal discharge (Zeng et al, 2011; Fei, 2012; Fei et al, 2013). The effect of tidal flats on water temperature in the bay was significantly low
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