Near surface water balance in the Northern Murray-Darling Basin

Area of Science:

• Hydrology
• Environmental Science
• Agricultural Science

Background:

• Deep drainage is a critical component of the hydrological cycle.
• Deep drainage has been historically linked to salinity outbreaks in dryland and irrigated areas.
• Previously, deep drainage was underestimated in the Northern Murray-Darling Basin's alluvial plains.

Purpose of the Study:

• To assess the current understanding of water balance in the Northern Murray-Darling Basin.
• To highlight the significance of deep drainage under irrigated agriculture.
• To identify the need for comprehensive measurements of water balance components.

Main Methods:

• Utilizing water balance calculations and simulation studies.
• Considering catchment-scale factors like land use, groundwater connection, and prior streams.
• Analyzing potential sources of uncertainty in measurements and calculations.

Main Results:

• Recent studies indicate substantial deep drainage occurs under irrigated agriculture in the region.
• Estimates of deep drainage are subject to significant uncertainties due to measurement and spatial variability.
• Catchment-scale factors are crucial for accurate assessment.

Conclusions:

• There is a critical need for a concerted effort to measure all water balance components in the Northern Murray-Darling Basin.
• Understanding deep drainage is essential for managing salinity and its impact on shallow groundwater quality and levels.
• Further research is required to reduce uncertainties and improve the accuracy of water balance models in this region.