|
|
|
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 |
Billabong Creek Location: Centred on Holbrook, New South Wales. Area: 3 000 km2. Rainfall: 600 mm in the west to 900 mm in the east. Land use Mainly cereal cropping in the west and pasture grazing in the east. Reference: Baker et al. (2001) Salinity Only 150 ha or 1% of the upper Billabong Creek catchment is mapped as expressing dryland salinity. However, there are worrying rises in stream salinity in the lower part of the catchment. Modelling shows water levels reaching the ground surface in specific locations within the next 50 years. Most bores in the catchment have a rising trend, with some levelling off in recent years due to below average rainfall. Groundwater system The main aquifer is an intermediate-scale confined sand and gravel aquifer (Lachlan Formation) containing fresh water. This is overlain by an unconfined clay aquiclude (Cowra Formation) containing saline groundwater. This aquifer configuration is similar to others in the main river valleys (e.g., Loddon Plains). Groundwater flow in the Lachlan Formation is relatively rapid from east to west, consistent with gradients in surface topography. Water movement in the Cowra Formation is predominantly vertical and, where the Formation is thin, may recharge the Lachlan Formation. Management Modelling indicates that a reduction in direct recharge of 50% will delay groundwater rise by up to 50 years, while a 90% reduction will stop water levels reaching the surface. Farm-scale modelling indicates that a 60 to 90% recharge reduction would be possible through planting of lucerne, depending on whether it is part of a rotation or continuously grown. The appropriate management and persistence of lucerne will be crucial, because the soil properties and climatic conditions in some of the eastern upper parts of the catchment are not optimal. Groundwater pumping is a feasible option in this catchment because the alluvial aquifer has a relatively high hydraulic conductivity. Simulating a water extraction program of 500 ML per year resulted in a drop of water level by up to 1 metre, and a delay in water level rise of an additional 20 and 50 years. |
Simmons Creek near Walbundrie Click for large conceptual model 
Salt scalding near Simmons Creek |
 |
| design & production by Talkin' Technical Communications | last updated: April 2002 |