Presentation to Sutton Landcare by Dr Albert van Dijk, 10 August 2010
Dr Albert van Dijk from CSIRO’s Division of Land and Water Divsion gave a presentation to
the Sutton Landcare group on 10 August 2010. The subject was water availability in the
Murray-Darling Basin.
The main focus was on farm dams and river flows in the Murrumbidgee and Yass regions.
Sustainability of water sources was not addressed because that is a socio-political matter
outside the scope of the studies under discussion. Some points arising from a recent study by
visiting CSIRO researcher Linda Kuil were:
Hydrology aspects
. there are 1.5 million man-made water bodies in Australia. 745,000 of these are in the
Murray Darling Basin, and 611,000 of the national total are in NSW.
. the Yass River catchment has 8059 dams, roughly six dams per km2, equating to 16 Gl of
water (which represents about 17% of streamflow in the catchment).
. average rainfall in the Yass River catchment in the period 1915-2005 was around 600mm
per year
. in the period 1995-2006, there has been a small but noticeable reduction in streamflow in
the Yass River.
Social aspects
. large dams are more efficient than small ones (eg. less evaporation per stored volume) but
small dams are needed for specific reasons such as rotational grazing.
. studies show a 10% increase in dam numbers over the last decade in the Yass River
catchment.
Discussion
. many sub-divisions have one dam per lot, but some new sub-divisions have just one
communal dam and reticulated supply from there.
. bore water extraction is regulated, but some aquifers are at risk (eg. near Bungendore).
. reduced flows in the Yass River might be caused by the prolonged drought, the increased
number of upstream farm dams, or because more tree planting and riperian improvements
have enabled more water to be retained in the paddocks. Dr van Dijk commented that there
was no definitive scientific evidence to support any of these, although any or all might be
correct. Further observation is needed.
. it will be interesting to see what (if any) attention is paid to the Yass River catchment by
the Government’s pending review of water availability in the Murray-Darling Basin.
Sutton Landcare meets bi-monthly, usually featuring a guest speaker, with supper
afterwards. New members are always welcome.
Contacts: President David Vincent 62303584, Secretary Gay McNeill 62303569.