Poster Presentation Australasian Groundwater Conference 2017

Can land management intervention ameliorate the affect of geological impediments to groundwater flow in an upland NSW catchment? (#99)

Tony Bernardi 1 , Leah Moore 2 , Mark Littleboy 3 , Allan Nicholson 4
  1. NSW Department of Primary Industries, Orange, NSW, Australia
  2. University of Canberra, Canberra, ACT, Australia
  3. NSW Office of Environment & Heritage, Armidale, NSW, Australia
  4. NSW Department of Primary Industries, Wellington, NSW, Australia

This research program aims to develop an improved understanding of natural processes of a sub-catchment undergoing landscape transformation and how the hydrology is impacted by changes in climate.

The Baldry Key Site is a 1.9 km2 study site, located within the Little River sub-catchment of the Macquarie River. The catchment slopes to the north and is bisected by an ephemeral stream running north into Little River. The western side of the stream was planted to a eucalyptus plantation in 2001. Monitoring of components of the hydrological cycle including climate and groundwater began in mid-2003.

Equipotential lines of the fractured rock groundwater system in 12 bores indicate complex flow pattern. Initially the groundwater flows in a northerly direction in the upper part of the site. Flow direction begins to veer to the NNW approximately 250m up slope of the salt scald and flows to the NW in the middle of the scald.  Water levels were similar across the slope in the upper and mid sections of the study site.

Analysis of monthly groundwater data from 2003 on the 12 boreholes using the auto-regressive model HARTT showed that the non-climatic trend was for the fractured groundwater system to fall between 136 mm/annum to 240 mm/annum. The highest and lowest rates occurred in the plantation with rates being higher on the upper slopes of study site.

The salt scald was caused by groundwater being interrupted in its flow north towards Little River by a sub-surface geological formation acting like a dam wall. The groundwater flow slowed and rose closer to the surface in the scald area as it found an alternative route down the slope.  The planting of trees had little to no influence on the rate of groundwater movement, with its movement more strongly influenced by the underlying geological variability.

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