The estuaries team at the Water Research Laboratory has more than a decade of experience in developing physical models of estuarine hydrodynamics and water quality. With climate change, estuaries are facing severe impacts from sea level rise, oceanic warming and changing rainfall and runoff regimes, and our fully-calibrated models are the ideal tool for quantifying the nature of these impacts.

Effects of sea level rise on estuarine tidal dynamics and water quality

As shown in the tidal animation of the Hunter River Estuary below, estuaries typically exhibit complex tidal dynamics due to the combined effects of friction, entrance restrictions and tidal wave resonance. Estimating the impacts of sea level rise within an estuary isn’t as simple as vertically lifting historic water levels, which has often been the case in previous studies.

To estimate the real impact of sea level rise, researchers at WRL have been running a large number of hydrodynamic estuarine models under different sea level rise scenarios. This research will reveal some of the complex and non-linear changes in estuarine water levels in response to sea level rise, information that is critical for climate change impact and adaptation planning.

Using drones and satellites to track climate change footprints in estuaries

In New South Wales, climate change has already caused an increase in mean sea level of over 10 cm, changes in the seasonality of rainfall, increases in the average land temperature of around 0.8°C  and in the average sea surface temperature of 1.5°C.

These changes in the climate and ocean system have already started to impact estuaries around Australia. By using satellite and drone remote sensing we can quantify exactly how much estuarine environments have already changed over the last couple of decades, using LandSat. The LandSat satellite mission is the longest continuous earth observation satellite mission and provides a continuous archive of satellite images since 1985.

Researchers at WRL are using this historic image record to reconstruct changes in the water quality, geomorphology and vegetation of estuaries around Australia and other parts in the world. The animation below shows the surface water dynamics of the Nadgee Lake ICOLL on the NSW South Coast from 1993 to 1995 as seen by the LandSat satellite, and after processing it using the Normalised Difference Water Index. This water index highlights areas of water in blue (below 0 in the cross section) and dry areas such as beaches and dunes in red (above 0 in the cross section).

Assessing the impacts of climate change on estuarine water quality and ecology

In collaboration with marine ecologists, our team is currently working on a first quantitative assessment of climate change impacts in selected NSW estuaries accounting for multiple climate change stressors at the same time.

We are working with a range of models to simulate the impacts of changing rainfall and runoff regimes, atmospheric and oceanic temperatures and sea level rise. After simulating the likely changes in the physical estuarine environment (e.g. increases in water temperature and salinity), we are using the Eco-Thresholds Database to estimate the impact of these changes on key species that live in the estuary.

This research will provide a first-of-its-kind holistic assessment of when and where estuarine ecosystems in NSW will likely suffer noticeable impacts from climate change. The figure below illustrates some of the impacts of sea level rise on intertidal vegetation communities that are being studied as part of this research. For a detailed explanation of the figure see Module-4 of the Risk Assessment Guide.

Illustration by Anna Blacka, UNSW Sydney, Water Research Laboratory