Infrastructure Engineering - Research Publications

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    Recharge mechanisms in an Arid Zone River: Effects of channelisation
    Costelloe, JF ; Western, AW ; Irvine, EC (Conference Organising Committee, 2006)
    Arid zone, ephemeral rivers typically experience very high transmission losses. Most international studies have identified infiltration into stream sediments and subsequent percolation to the unconfined alluvial aquifer as the major cause of transmission losses. There is relatively little data regarding mechanisms and stores controlling transmission loss processes in Australian arid zone streams, particularly in regards recharge to the unconfined aquifer. This study reports on a field study of recharge mechanisms occurring in the Neales River of the Lake Eyre Basin (northern South Australia). Piezometric monitoring, numerical and analytical modelling were used to identify and quantify recharge to the unconfined aquifer during streamflow events in 2004-2005. Significant recharge only occurred in channelised reaches and rates of recharge did not show a clear relationship with stage but tended to be higher for flow events occurring after longer periods of no flow. Reaches lacking a single, well-defined channel are common in the anastomosing rivers of the Lake Eyre Basin. Piezometers monitoring the alluvial sediments at two locations lacking well-defined channels did not measure any development of a saturated zone in the alluvial aquifer following flow events. The data suggests that most percolation and recharge occurs through the bank, rather than the floodplain and this needs to be taken into account when estimating transmission losses for these river systems.
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    Riparian tree water use by eucalyptus coolabah in the Lake Eyre Basin
    Payne, EGI ; Costelloe, JF ; Woodrow, IE ; Irvine, EC ; Western, AW ; Herczeg, AL (Conference Organising Committee, 2006)
    The Lake Eyre Basin (LEB) is characterised by enormous stream flow variability, low rainfall, saline groundwater and at times saline surface water; conditions that demand flexible tree water use strategies in the riparian zone. In the lower reaches of the Diamantina River, the water sources and extraction patterns of Eucalyptus coolabah were examined using isotope data from xylem, soil water, groundwater and surface water. Additionally, soil chloride and matric potential data were used to infer zones of water availability for root uptake. It was found that despite their elevated salinity, groundwater and soil water formed a large proportion of the transpiration flux, with little contribution from standing pools of surface water. At two sites located on the dry floodplain, the data indicated E. coolabah relied substantially on groundwater with a salinity exceeding 30,000 mgL-1Cl. However, some dilution with fresher soil water was evident at most sites, highlighting the importance of flooding in replenishing soil water. Water extraction primarily occurred in the unsaturated zone where a compromise between salinity and source reliability was required. However, E. coolabah was found to have higher salinity tolerances than previously reported for Eucalyptus species.
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    Salt and water flux in an arid zone intermittent river: The role of the floodplain environment
    Irvine, EC ; Costelloe, JF ; Western, AW ; Hayes, S (Conference Organising Committee, 2006)
    Exchange between the surface water and local groundwater systems in intermittent rivers is not well understood, however the ecological functioning of these riverine environments can be dependent on the degree of interaction between the two domains. Spatial and temporal changes in the isotopic (δ18O/δ2H) and major ion composition of the floodplain aquifers in the lower reaches of the intermittent Diamantina River, South Australia, along with hydrologic data and sedimentary analysis, are used to identify localized groundwater recharge following flow events. The approximately synchronous response of groundwater levels to surface water events over two years (encompassing the recession of one major flood involving substantial floodplain inundation and two smaller events) particularly in near channel locations, indicates connectivity between surface water and local groundwater systems. The increase in δ18O/δ2H values and decrease in the salinity of groundwater <100m from the river subsequent to major flooding indicates event recharge of the shallow alluvial aquifers. Over time, groundwater compositions return to more saline and isotopically depleted values, considered here to be base conditions. Groundwater salinity and isotopic compositions of the mid and outer floodplains varied little over the course of the study period despite flood inundation and change in groundwater head. Sedimentary analysis of the predominantly silt and clay floodplain surface indicates the potential of these soils to develop seals and thus limit infiltration of flood waters. Thus event recharge was limited to near bank areas or zones of preferential infiltration over the course of the study period. CFC dating and isotopic data give some indication that sustained recharge to the floodplain groundwater system occurs during successive large flood events or wet years.