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Case Studies 1. Kyeamba Creek 2. Liverpool Plains 3. Billabong Creek 4. Wanilla 5. Axe Creek 6. South Loddon Plains 7. Kamarooka 8. Lake Warden 9. Brymaroo Printing help |
South Loddon Plains Location: Central Victoria, 40 km northwest of Bendigo, bounded to the north by the Waranga Irrigation Channel. Area: 600 km2. Rainfall: 425 mm. Land use 60% grazing, 25% cereal cropping, 15% irrigated agriculture. Reference: Hekmeijer and Dawes (2001a) Salinity This aquifer is responsible for salinity in the Riverine Plain areas of the Loddon River valley and is similar to aquifers in other riverine environments. Groundwater processes in these aquifers are predicted to generate large broad-scale areas of land salinity in Victoria (MDBC Salinity Audit, 1999). Groundwater system Lateral pressure transmission is possible over long distances through the regional confined alluvial (sand and gravel) aquifer (Calivil Formation). The aquifer configuration, with the Calivil Formation overlain by a clay-rich layer containing shoestring sands (Shepparton Formation), is similar to Billabong Creek, but is much larger and more transmissive. Floods predominantly recharge the Calivil Formation, leading to a step-shaped groundwater hydrograph with rises registered in extremely wet years. The absence of any decline in the hydrographs indicates a lack of drainage through the aquifer down-gradient, where there is increased recharge from irrigated and dryland areas overlying the Shepparton Formation aquifer system. Wherever the shoestring sands in the Shepparton Formation can provide a release valve for the confined heads in the Calivil, groundwater can discharge, particularly in topographic low areas. Several sites were "activated" by flooding in 1973 to 1975, e.g., Bears Lagoon and Pompapiel Creek. Management The most obvious way to control water levels here is to pump the deep aquifer and remove the groundwater from the system. Extensive irrigation from the Calivil Formation already occurs. Modelling showed that recharge from the Shepparton Formation induced by local drawdown could be as much as double the average yearly recharge rate; drawdown could be reduced by more than 10 m. The modelling results also showed that this option may not stop rising water levels in the southern part of the study area, nor reduce high heads near the northern irrigation area. Attempting to remove the blockage at the northern end of the system by reducing recharge from both the irrigation and dryland areas will not have the desired effect due to the typically poor drainage of the Shepparton Formation. Reducing recharge rates in the Calivil Formation cannot be attained because natural sheet flooding events are outside management control. |
Groundwater discharge area in the lower Loddon Plains Click for large conceptual model 
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