Temporal trends of groundwater levels in the Lower Balonne 2000-2014

Temporal trends of groundwater levels in the Lower Balonne 2000-2014

Groundwater levels at the outskirts of the Balonne floodplain and the newer irrigation areas away from St George have remained relatively stable over the last decade, reflecting no association with temporal changes of rain and river flow within the same period. In contrast, there are several bores, located along the major streams, which indicate an induced streambed recharge during the 2010-2013 high flow period; this evidence, along with groundwater level contours and soil mapping, suggest that streambed recharge is probably more substantial in areas where the stream incises lighter textured soils, e.g., Sodosols.
The groundwater levels under the 'original' St George Irrigation Area (SGIA) and another irrigated area (Kia Ora farm and surroundings), where groundwater has not been intensively monitored, are rising continuously, as deep drainage is accumulating at the water table. The deep drainage is roughly estimated to be in the order of 45-120 mm/yr, which coincide with the overall range for irrigated cotton in Australia.
It is highly recommended to recommence the frequent monitoring scheme in the SGIA, which ceased in the late-2000s. It is also recommended to initiate monitoring at other irrigated areas which are not monitored at the moment. This will allow better risk management in the future.

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