Evaluation of the impact of brine discharge position on salinity in the Persian/Arabian Gulf’s slow flushing zone

The Persian/Arabian Gulf is the sink of hypersaline effluent (brine) for plants with about half of
the world’s seawater desalination capacity. Many of these plants discharge brine into the Gulf’s
southwestern region where the salt in brine accumulates because seawater there is not replaced
often by the Gulf’s residual circulation (i.e., the region is poorly flushed). This circulation flushes
the whole Gulf and inhibits salt accumulation at the basin scale. But flushing is not effective in
the southwestern region, which has been described as the “Gulf’s slow flushing zone.” Here, the
impact of brine discharge position on salinity in this zone is evaluated by comparing two scenarios
of brine discharge into the Gulf’s residual circulation dynamics. In the first scenario, brine from the
24 largest seawater desalination plants in the Gulf is introduced into the residual circulation; and in
the second scenario, the brine discharge position of one of these 24 plants is positioned away from
the slow flushing zone. In the two scenarios, brine discharge caused salt buildup in the slow flushing
zone. However, annual area-average salinity there is about 1.10–1.55 PSU smaller in scenario two
compared to scenario one, indicating the influence of discharge position on salt buildup because
of brine discharge. This study, accordingly, suggests a methodology for selecting brine discharge
position in the Gulf’s slow flushing zone.