Hydroclimate and catchment processes impacting runoff in the northern Murray−Darling Basin

The hydrology theme enhanced hydrological knowledge and advanced modelling capacity to inform water resources management and planning in the Murray–Darling Basin.

Science and research

MD-WERP theme	Hydrology
MD-WERP research question	How to better disentangle and model the impacts of climate and development drivers on the hydrology of the Basin?
Project title	Drivers of northern Basin hydrology
Research lead	CSIRO
Authors	Jorge Peña-Arancibia, Francis Chiew, Yingying Yu, and Guobin Fu
Author contact details	Jorge L. Peña-Arancibia
Date of publication	June 2023
Report full title	Hydroclimate and catchment processes impacting runoff in the northern Murray−Darling Basin
Keywords	northern Basin; Murray–Darling Basin
Summary of output	The report examines the influence of climate and catchment processes on runoff within the Murray–Darling Basin, with particular attention on the northern Basin and on factors that can alter hydroclimate characteristics and dominant hydrological processes, commonly referred to as 'hydrologic non-stationarity'. It provides an updated assessment of the Basin’s hydrological dynamics, complementing previous analyses conducted by the MDBA, CSIRO and Basin State agencies.
Key findings / recommendations	Rainfall has declined over most of the Basin, particularly in the northern and southern Basin uplands, where most of the Basin's runoff is generated. Evaporative demand has statistically significantly increased across the Basin, largely because of the increase in temperature. This increase can amplify the decrease in rainfall and lead to decreased runoff. Runoff has mostly decreased across the Basin, with statistically significant declines in the southern Basin uplands and slopes, and the northern Basin uplands. The decline is primarily observed during the cool season. Actual evapotranspiration has declined over most of the Basin, except for densely forested areas in the southern Basin uplands. These declines occur throughout the year, indicating a shift towards ecosystem water limitation in some areas. The southern Basin exhibits significant "greening" trends (increase in Leaf Area Index (LAI)), while the northern Basin does not show significant changes in vegetation LAI. Groundwater level has generally declined in bore observations in some northern Basin valleys, primarily attributed to reduced groundwater recharge from reduced rainfall and groundwater extraction for irrigation, potentially leading to disconnection of the vadose zone from streams. GRACE Groundwater Storage anomalies indicate a prolonged dry period during the Millennium drought, followed by wetter conditions during the La Niña years. However, the northern Basin has experienced a consistent drying trend since 2012/13. Irrigation water use changed little during the Millennium drought and the 2017–2019 dry period. The irrigated surface area reduced during the drought but with more water applied to the smaller irrigated area. Farm dams across the Basin have shown growth, particularly during the 1990s and the Millennium Drought. However, growth rates have slowed since 2010. Farm dams can contribute to reductions in runoff, especially during low flow periods, and may compound the effects of reduced rainfall and water scarcity in the Basin.
Target audience	Researchers, hydrological modellers, groundwater modellers, Australian Government, state governments, local governments, conservation advocacy groups, landholders and primary producers, water and environmental consultants

Report
Publication title	Published	File type	File size
Hydroclimate and catchment processes impacting runoff in the northern Murray−Darling Basin	11 Jun 2024	PDF	11.86 MB

Published date: 19 May 2025