A University of Sydney engineering student is helping to explore whether nature-based solutions can help strengthen Sydney’s long-term water resilience by improving hydrological performance of the Warragamba catchment in New South Wales, Australia.
A recent honours thesis by University of Sydney civil engineering student Robert Mueller explored whether nature-based solutions could help strengthen Sydney’s long-term water resilience by improving the hydrological performance of the Warragamba catchment.
The project investigated the concept of “landscape rehydration”. This is an approach to land and water management that aims to restore the natural ability of landscapes to retain, infiltrate and slowly release water. Landscape rehydration seeks to improve catchment function to increase water yields, better attenuate flows and improve water quality.
The research focused on the Wollondilly River catchment, one of the major tributaries flowing into Lake Burragorang behind Warragamba Dam. This catchment contains extensive agricultural land that has experienced significant historical degradation through vegetation clearing, grazing pressure, erosion and channel incision. These processes have altered how rainfall moves through the landscape, increasing runoff and erosion while reducing groundwater recharge and long-term moisture retention.
Robert’s thesis examined whether restoring more natural hydrological processes could increase inflows to Warragamba Dam during drought periods. The landscape rehydration methods considered included leaky weirs, contour banks, riparian revegetation and improved grazing and vegetation management practices designed to maintain permanent ground cover.
Many of these ideas are inspired by Australia’s historical “chain-of-ponds” systems. These are wetland-like landscapes that once naturally slowed water movement through catchments across southeastern Australia. These systems historically stored water within floodplains and shallow aquifers, sustaining stream baseflows and vegetation during dry periods. European settlement, land clearing and channel erosion disrupted many of these systems, changing catchment hydrology.
To investigate the potential impacts of restoring these functions, Robert developed a series of rainfall-runoff models using the eWater Source platform and the GR4J hydrological model. The modelling framework incorporated rainfall, evapotranspiration, land-use and streamflow data collected across several decades. Different model configurations were then calibrated to represent “wet,” “dry,” and “rehydrated” landscape conditions.
Figure 2 Simulated cumulative catchment yield for the Wollondilly during the 1993-1994 dry spell, comparing scenarios with and without landscape rehydration (Mueller 2025).
The modelling results suggested that catchment-scale landscape rehydration could produce substantial increases in water yield during drought conditions. Simulated drought-period inflows increased by approximately 20–30%, equivalent to more than 20 gigalitres of additional inflow annually. While this would not eliminate Sydney’s future water security challenges, it represents a potentially significant contribution toward improving drought resilience within the city’s existing water supply system.
The research also demonstrates the growing importance of advanced hydrological modelling tools in evaluating nature-based interventions. Using eWater Source, GIS analysis and long-term climate and streamflow datasets, the project moved beyond conceptual discussion and quantitatively tested how restored landscape processes may influence large-scale water supply outcomes.
Need more information?
To read Robert Mueller’ full thesis papers: Research Papers – eWater
To learn more about the University of Sydney’s Civil Engineering School: School of Civil Engineering – The University of Sydney
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