Pine Ridge: A Catchment in Good Hands
On an overcast day in April, CSIRO technician Peter Richardson bids hello to a curious companion' a green tree frog, living most contentedly down an observation well, beside a road called Cattle Lane.
Richardson unplugs the frog, dubbed Froggo, and passes it to me. It hops sticky-footed up my arm, then settles on my camera while the groundwater table is measured and sampled for electrical conductivity (salinity).
Due to an unseasonal dry spell, the water table is 2.2 metres below the surface, almost a metre lower than the previous reading taken in December. It usually hovers between 1.5 and 2 m, the critical depth at which salty groundwater can be drawn upward by capillary rise.
The salinity reading, echoed at 10 other wells across the sub-catchment, is 19.9 decisiemens per metre (dS/m). That's a little saltier than when last measured, and far saltier than any farmer would wish. Anything over 2 dS/m, or 4% as salty as seawater, spells trouble for conventional agriculture.
Cattle Lane intersects the 35 000 ha Yarramanbah/Pump Station Creek sub-catchment, located just north of the Liverpool Range, at the southern end of the 1.2 million-hectare Liverpool Plains catchment in northern New South Wales (see map).
In the 1830s, the Liverpool hills and ranges were heavily timbered and perennial grasses swathed its fertile, alluvial plains. A drive through the region today reveals cattle, sheep and erosion where the trees had been, and crops -- sorghum, sunflowers, cotton, wheat and barley -- on the plains. Less than 15% of the original vegetation remains.
Clearing has transformed the Liverpool Plains into one of Australia's highest-yielding cropping and livestock regions, with an annual production value of more than $150 million. It has also upset the region's water balance in a potentially dangerous way.
In the early 1990s, some 195 000 ha (16%) of the Liverpool Plains were estimated to be at risk from salinisation, with groundwater tables less than 5 m from the surface. Farming on the black clay plains is under threat and the salinity of surface water exported from the catchment is rising, raising fears of further problems downstream.
Community concerns about rising saline water tables led to the formation in 1992 of the Liverpool Plains Land Management Committee, an umbrella organisation which coordinates research, development and extension in natural resource management. Soon after the committee formed, the Liverpool Plains became one of five focus catchments in the National Dryland Salinity Program.
As the program entered its first year, seven progressive farming families from the Yarramanbah/Pump Station Creek and adjoining Warrah Creek catchments formed the Pine Ridge Landcare Group, one of 46 such groups affiliated with the Liverpool Plains committee. The families, initially concerned about increased flooding and waterlogging in the area, have since worked collectively to protect the productivity of their land.
Pine Ridge landholders have contributed to a number of research projects under the National Dryland Salinity Program, sharing information with scientists and allowing experimental sites and observation wells -- such as the one occupied by Froggo -- to be established on their properties. A major outcome relating to these studies, due for completion in 1999, will be land-use recommendations for groundwater management across the Liverpool Plains.
In the meantime, Pine Ridge Landcare Group is investing heavily in change, encountering in the process many challenges confronting similar groups across Australia. These include understanding and monitoring local groundwater systems, weighing risks, setting goals, seeking technical and financial assistance, and trying out land-use strategies that `use water where it falls'.
According to water level data gathered in the past 25 years, groundwater levels in the deep aquifer at Pine Ridge have been rising at a rate of 4 cm a year, and salt levels are rising in the nearby Mooki River. …