Water releases from dams improve ecological health and societal benefits in downstream estuaries

Abstract

This review study investigated the response of low-inflow estuaries (LIEs) to dam releases as this type of estuary is particularly sensitive to freshwater inflow modification. LIEs occur in arid and semi-arid regions and are subject to periods of little to no freshwater inflow. Case studies were used to identify ecological health and societal benefits associated with flow releases. Successful releases have been made to keep the estuary mouth open, ensure mixing, facilitate a salinity gradient and provide recruitment pulses to the marine environment for fish and invertebrates. Baseflow inputs ensured ecosystem connectivity and maintained estuary water quality gradients. Flow pulse releases in certain seasons stimulated spawning migrations of fish between freshwater and estuarine habitats. Holistic and adaptive restoration approaches were successful in terms of providing ecosystem services and societal benefits such as improved fisheries and livelihoods. Ongoing engagement, inclusion of communities, support from river users, and cooperation between multiple agencies were also important. However, this management solution for LIEs is threatened by increasing abstraction of water, competing water uses, over allocation, and frequent droughts. Moving forward, freshwater releases from dams should be considered an important restoration action that can improve ecological health, estuary function, ecosystem services, and societal benefits. This should take place within a socio-ecological system framework using an adaptive management and monitoring approach. Other key considerations for planning and implementation of future dam releases to LIEs were recommended.