163 | P a g e Design and methodology: To determine the most effective bioremediation strategy, statistical analysis was conducted on sampling data collected over >10 years in and around the water treatment plant. This allowed for further understanding of the hydrogeochemical site characteristics, to help inform the experimental phase. As a result, seven triplicate microcosms using the native groundwater ecosystem were established. The microcosms were used to test how inorganic electron donors at different concentrations affect the natural attenuation of nitrogen. Simultaneously, the effects of the different treatments on the microbial ecosystem were explored to determine any detrimental effects nitrogen plumes and the accompanying
remediation efforts may have on the groundwater ecosystems.
Original data and results: Multivariate statistical analysis of sampling data showed that iron concentrations were significantly correlated with total N and NH4+ but not NO3- (P-values of 2.54*10-14, 1.65*10-4 and 0.283 respectively) and sulphur was significantly correlated with NH4+ but not total N and NO3- (P-values of 6.54*10-7, 0.18, 0.05627 respectively). These correlations are consistent with an important role for redox in the behaviour of N contamination in the groundwater.
Conclusions: The findings of the statistical analysis of the sampling data show correlations between iron and sulphur concentrations and total nitrogen, NH4+ and NO3- concentrations. By combining these data with microcosm experimental results, we hope to delineate how different concentrations of these ions affect the natural attenuation of nitrogen-contaminated groundwater. This in turn can be used to design bioremediation strategies based upon biostimulation of the native ecosystem.
164 | P a g e positive. However, attitudes towards perennial rivers were more positive, particularly in comparison attitudes towards IRES when they were not flowing and in regard to their aesthetic value and recreational amenity. There were no significant differences in attitudes towards perennial rivers and IRES in one teaching unit in Australia, and responses were more often more positive at the end of teaching units in the UK.
Conclusion: Our study indicates education can change attitudes. The overall positive response to statements may reflect underlying environmental awareness and pre- existing interest of participants enrolled in environmental and biology degrees, but not necessarily specific knowledge of IRES. General environmental education across the wider community could improve attitudes towards IRES, particularly when they are not flowing or in regions where they are uncommon or inconspicuous, and could support positive protection measures and innovative, inclusive management of surface and groundwaters alike.
Identification and systematic prioritisation of surface water refuges to sustain freshwater biodiversity in eastern Australian intermittent stream networks
Mark J. Kennard 1 , Songyan Yu 1 , Nick R. Bond 2 , Stuart E. Bunn 1 1. Griffith University, Nathan, QLD, Australia
2. LaTrobe University, Albury, VIC, Australia
Objectives: The hydrological variability of intermittent streams means that the spatial distribution of aquatic refuges within river networks and the temporal
dynamics of hydrological connectivity between them are critical for the persistence of aquatic biodiversity. We demonstrate a new approach to identify surface
waterbodies as potential refuges for freshwater biodiversity in river networks and efficiently prioritise them for on-ground conservation management.
Design and Methodology: We developed models of surface water extent and of daily streamflow to represent spatio-temporal variation in surface water extent and hydrological connectivity within river networks of eastern Australia over a 107-year period. We also assembled spatially explicit freshwater fish species distribution data as targets for refugia prioritisation and elicited estimates of their relative mobility potential within river networks. We then applied a systematic prioritisation algorithm to identify areas that provide all resident fish species with access to a minimum number of aquatic refuges while maximizing the length of stream potentially accessible for recolonisation after dry periods.
Original data and results: Simulated long-term variations in streamflow intermittency and surface water extent were highly dynamic through space and time over the past century. A subset of highly irreplaceable aquatic refuges for freshwater fish were identified that were widely distributed throughout the river networks, encompassing main stems to headwater streams. A set of on-ground conservation management actions to maintain the refugial-values of these areas is recommended to minimize disturbance from livestock and feral animals, pollution, water extraction, local aquifer drawdown, and other threats.
Conclusion: Our study presents a novel and practical approach to identify priority aquatic refuges for targeted conservation management to enhance the resistance and resilience of freshwater biodiversity in intermittent stream ecosystems.
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Use of multiple methods for studying recharge/discharge processes in regulated and unregulated reaches of the Dumaresq River
Dawit Berhane 1 , A. McKay 2 , T. Mullins 2 , S. Wells 2 , N. Corbett 1 1. Department of Environment and Science, Brisbane, QLD, Australia
2. Department of Natural Resources, Mines and Energy, Brisbane, QLD, Australia Rivers of arid and semi-arid regions of Australia are among the most variable in terms of discharge of any rivers worldwide and are characterised by extended periods of no flow regimes. During extended dry spells, aquatic habitat are able to survive in billabongs.
Since the onset of the current drought, there has been several environmental flow releases from the Glenlyon Dam, located on Pikes Creek, a tributary of the Dumaresq River. The environmental flows mitigated dry conditions to maintain aquatic
ecosystem health and services, by filling and connecting waterholes.
In this paper, hydrogeological processes (recharge/discharge) of the Dumaresq River are studied, at different spatial and time scales, using multiple methods. The study area extends from Glenlyon Dam to Keetah Bridge, representing unregulated and regulated reaches. The methods used are:
• Conjunctive analysis of surface water gauging stations and groundwater monitoring networks in QLD and NSW
• Heat as a groundwater tracer
• EC routing, and
• Normalised Difference Water Index (NDWI).
Understanding of hydro(geo)logical processes at a reach scale will lead to better informed surface and groundwater management in the upper parts of the Border Rivers basin.
The canary or the coalmine? Isotopic evidence of drying climate versus groundwater outflow as the cause for recent losses from Thirlmere Lakes, NSW
Mark A. Peterson 1 , Dioni Cendón 1 , Catherine Hughes 1 , Jagoda Crawford 1 , Stuart Hankin 1 , Martin Krogh 2 , Kirsten L. Cowley 2 , Tim Cohen 3 , Martin S.
Andersen 45 , Christian Anibas 45 , Will Glamore 6 , Shenyang Chen 6 , Wendy Timms 7 , Tim McMillan 48
1. ANSTO, Lucas Heights, NSW, Australia
2. Office of Environment and Heritage, Sydney, NSW, Australia
3. GeoQuest Research Centre, School of Environmental Sciences, University of Wollongong, NSW, Australia
4. Connected Waters Initiative, UNSW Sydney, NSW, Australia
5. School of Civil and Environmental Engineering, UNSW Sydney, NSW, Australia
6. Water Research Laboratory, School of Civil and Environmental Engineering, UNSW Sydney, NSW, Australia
7. School of Engineering, Deakin University, Waurn Ponds, VIC, Australia
8. School of Minerals and Resources Engineering, UNSW Sydney, NSW, Australia
The Thirlmere Lakes Research Program (TLRP) is a collaboration investigating water loss mechanisms in recent drying of five adjacent lakes, located 75 km south-west of
166 | P a g e Sydney. Some stakeholders and previous studies have perceived a correlation with local longwall coal mining history and suspect deep fracture outflow. Others suggest the lakes are simply responding to a drier climate, serving as the canary in the broader climate-change ‘coal mine’.
ANSTO has applied recurrent isotopic and chemical monitoring of the lakes and adjacent groundwater over two years to unravel some of the mystery of their recent water losses. Each lake behaved uniquely, but they shared some common trends.
Steady enrichment of stable water isotopes, 2H and 18O, indicates the dominance of evaporation, with minimal losses to groundwater or through transpiration. Lake Cl/Br ratios were very low and clustered in three groups, two trending away from initial ratios indicative of groundwater input. 3H and 14C show recent rainfall and/or runoff as the main contributors to lake waters, with apparent ages in the adjacent shallow groundwater up to several decades. High levels of 222Rn from shallow bores suggest a close association between the peats enclosing the lakes and 238 U from ancient
erosion, or proximity of an underlying shale lens. The only deep piezometer (72-84 m) near the lakes showed negligible contributions from the lakes or recent surface water.
The trends in isotopic and chemical parameters infer that evaporation is sufficient to explain recent water losses from most of these perched lakes. Trends in some lakes hint that these had previous inputs from groundwater. While the historical variability of groundwater input to the lakes remains unknown, there is no current evidence of major losses to groundwater. Thirlmere Lakes will exist only intermittently under dry climate conditions.
Streamflow generation mechanisms for an intermittent- ephemeral catchment in South Australia: a modelling approach
Karina Y. Gutierrez-Jurado 1 , Margaret Shanafield 1 , Daniel Partington 1 1. Flinders University, Bedford Park, SA, Australia
In Australia, Intermittent Rivers and Ephemeral Streams (IRES) are the common features that dominate the landscape. Contributing with roughly 70% of the stream network, IRES are key for ecosystems health, are important for farming and
agriculture and represent a main source of groundwater recharge. However, the understanding of streamflow generation mechanisms for IRES remains a challenge.
This study examines an intermittent-ephemeral catchment in South Australia where little is scientifically known about the processes leading to streamflow generation and the contributing mechanisms, although there are many well-developed hypotheses among the local vineyard owners. Previous research in the catchment has shown complex spatiotemporal interactions between the creek and the shallow aquifer, outlining changes in losing and gaining conditions along the creek during the
intermittent flow season. We used a fully integrated surface-subsurface hydrological model coupled with the hydraulic mixing-cell method to investigate the processes leading to the onset of flow for the intermittent season and to determine the spatiotemporal variability of the streamflow generation mechanisms. For this, we analyzed the development of flow generating areas and the dominant contributing flow generation mechanisms at different locations along the catchment at the onset of flow, and during the transition from ephemeral to intermittent flow. The expected results from this study will allow us to better understand streamflow generation at the threshold of flow and at the transition from ephemeral to intermittent flow for an intermittent-ephemeral creek in South Australia. This will be useful to aid IRES management decisions such as those pertaining to ecosystems health monitoring,
167 | P a g e the vulnerability of the catchment to the effects of droughts, and potential impacts of declines to the shallow groundwater system.
Geological controls on the spatial variability of ephemeral flow regimes
Sarah Bourke 1 , Josephine Searle 2 , Jasmin Rothery 1 , Amy Perrin 1 , Brad Degens 2 , Nik Callow 1
1. University of Western Australia, Crawley, WA, Australia
2. Department of Water and Environmental Regulation, Perth, WA, Australia
As global population increases and climates shift, intermittent rivers and ephemeral streams (IRES) are receiving increased attention from researchers and water
resource managers. These types of systems are commonly associated with arid regions of the world but are also present in temperate Mediterranean-type
climates. While the distinction between IRES and perennial systems can be useful, not all streams or rivers neatly into one of these categories. Here we present two examples of streams in different climates that have both ephemeral and perennial flow regimes along their length. Longitudinal stream surveys, groundwater
monitoring and geophysical mapping identified that in both cases the underlying geology is the key control on the surface water flow regime. The first site is the Donnelly River in south-west Western Australia (WA). The Donnelly River flows across the deeply weathered granite of the Yilgarn Craton and onto the
unconsolidated alluvial sediments of the Scott Coastal Plain (SCP). Decreasing rainfall has resulted in a change from perennial to ephemeral flow over the Yilgarn Craton, but our data demonstrate that groundwater discharge across the geological transition to the SCP still maintains perennial flow along the lower reaches of the river. The second site, Spring Creek, is located on the Dampier Peninsula in the Kimberley region of northern WA. The headwaters coincide with perennial groundwater springs, below which we identified a sequence of perennial and
ephemeral reaches on the order of 10 km in length. Geophysical surveys identified a previously un-mapped confining layer that results in the “pinching out” of the upper Broome Sandstone aquifer. This geological transition causes groundwater discharge that maintains stream flow along the perennial reaches of the stream. These two examples from varying climates highlight the importance of geological controls on stream flow generation in intermittent and ephemeral stream systems. This type of process-based understanding of stream flow generation is critical to ensure
appropriate monitoring and management of IRES under threat from changing climate or increased water use.
Directly measured soil evaporative losses in the semiarid Pilbara
Grzegorz Skrzypek 1 , Thomas Tugwell-Wootton 1 2 , Shawan Dogramaci 2 , Jim Mccallum 1 , Pauline Grierson 1
1. The University of Western Australia, Crawley, WA, Australia 2. Rio Tinto Iron Ore, Perth, WA, Australia
Soil evaporative loss is an important but usually only coarsely estimated component of the catchment water budget of dryland streams. Most estimates reflect a potential maximal evaporative (reference) loss as they are based on the energy budget
(Penman-Monteith) or weather parameters (Hargreaves-Samani) but rarely account for the actual soil moisture content. While these estimates are credible in wet
climates with evenly distributed precipitation throughout the year, they are less
168 | P a g e accurate in more arid regions where rainfall can be strongly seasonal and potential pan evaporation can exceed precipitation ten-fold.
In this study, we used an RTG weighing lysimeter (Umwelt-Geräte-Technik,
Germany) to quantify soil evaporative loss in situ and to assess how evaporative loss varied between wet and dry cycles. Our experimental site was in the semiarid and subtropical Hamersley Basin of the Pilbara region of northwest Australia. Measured mean daily evaporative losses during dry cycles were 0.33 mm day-1 (2016, over 86 days) and 0.25 mm day-1 (2017, over 73 days). These rates were three (0.95 mm day-1 in 2016) to five (1.21 mm day-1 in 2017) times lower than estimated potential reference evaporative losses using common theoretical calculations. During the wet cycle (2018 over 81 days), the measured evaporative loss rates were significantly higher (3.64 mm day-1 81 days) and similar to the potential reference evaporative loss (3.61 mm day-1); however, rates varied greatly from 0 to 13.04 mm day-1 and increased significantly in the days following rainfall events occurring during hot summers. The difference between the calculated theoretical potential reference evaporation and the actual measured evaporation at the scale of our study
catchment (4,000 km2) lead to the daily overestimation of ~ 5 GL during dry cycles.
A new proposed correction factor applied to the Hargreaves-Samani method
significantly improved the accuracy of soil evaporative estimations based on weather parameters.
Water velocity and groundwater upwelling control benthic algal biomass in an intermittent tropical river: implications for water resource development
Ryan M. Burrows 1 , Leah Beesley 2 , Michael M. Douglas 2 , Brad J. Pusey 2 , Mark J.
Kennard 1
1. Australian Rivers Institute, Griffith University, Brisbane, QLD, Australia
2. School of Biological Sciences, University of Western Australia, Perth, WA, Australia Benthic algae are a major source of carbon supporting aquatic food webs in tropical northern Australia, but little is known about the factors that regulate algal production particularly over small scales. We surveyed benthic algal biomass in mainstem
habitats in an unregulated sand-bed tropical river during a base-flow period.
Physicochemical parameters (e.g. water velocity, substrate, water quality) were measured at each sampling point and groundwater upwelling (as indicated by radon) and nutrients were measured at a sub-set of points. We used predictive models to reveal the factors controlling algal biomass in mainstem habitats. We found that water velocity was an important driver - algal biomass was lower at higher water velocities. Sub-surface flow was also influential - algal biomass increased in locations where upwelling occurred, as evident by a positive relationship between algal
biomass and elevated radon and ammonium concentrations. Micro-algal constituents (diatoms, green algae, cyanobacteria) displayed the same pattern as total algal biomass. In this sand-bed river, it is likely that high flow velocity destabilises the sandy substrate preventing the establishment of algal biofilms. However, where flow velocity is low enough for algal establishment, groundwater upwelling promotes algal growth by delivering limiting resources (e.g. nutrients) and/or creating stable
physicochemical conditions that promote algal production. The importance of surface and sub-surface flow conditions to benthic algae biomass means that any
modification to the Fitzroy River catchment that alters dry-season longitudinal flows (via river regulation) and/or groundwater levels (via groundwater extraction) may directly influence river algal production.
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