Abstract
Excessive salinity can harm ecosystems and compromise the various
anthropogenic activities that take place in river deltas. The issue of
salinization is expected to exacerbate due to natural and/or
anthropogenic climate change. Water regulations are required to secure a
sufficient water supply in conditions of limited water volume
availability. Research is ongoing in seek of the optimum flow
distribution establishing longer-lasting and fresher conditions in
deltas. In this study a three–dimensional (3D) numerical model was used
to unravel the influence of hydrographs shape on the deltas salinity.
Our results show that it is possible to improve the freshwater
conditions in deltas without seeking for additional water resources but
by modifying the water distribution. The peak flow magnitude and timing
and the tails of a hydrograph were found to be important parameters
affecting stratification, freshwater residence and renewal times.
Hydrographs having lighter tails and smaller range were the most
successful in keeping the delta and its river inlet fresher for longer
periods. Salinity distributions showed a slower response to decreasing
rather than increasing river discharges. An increase in the flow rate
can achieve a desired salinity standard in much shorter time.
Hydrographs with heavier tails can push the salt intrusion limit further
away and are more efficient in mixing the water column. However, they
present low freshwater residence and high water renewal times. These
results have implications for coastal scientists and stakeholders
dealing with the management of freshwater resources in river deltas
across the world.