<p>The outcrop extent of the McBride Basalt Province, selected from the Queensland Detailed Surface Geology vector polygon mapping, March 2017. <p>© State of Queensland (Department of Natural Resources and Mines) 2017 Creative Commons Attribution

The Upper Burdekin Chloride Mass Balance Recharge web service depicts the recharge rates have been estimated at borehole locations in the Nulla and McBride basalt provinces. Using rainfall rates, rainfall chemistry and groundwater chemistry, the recharge rates have been estimated through the Chloride Mass Balance approach.

The Upper Burdekin Basalt extents web service delivers province extents, detailed geology, spring locations and inferred regional groundwater contours for the formations of the Nulla and McBride Basalts. This work has been carried out as part of Geoscience Australia's Exploring for the Future program.

This data release presents regional scale groundwater contours developed for the Upper Burdekin Groundwater Project in North Queensland, conducted as part of Exploring for the Future (EFTF), an Australian Government funded geoscience data and information acquisition program. The four-year (2016-20) program focused on better understanding the potential mineral, energy and groundwater resources in northern Australia. The Upper Burdekin Groundwater Project is a collaborative study between Geoscience Australia and the Queensland Government. It focuses on basalt groundwater resources in two geographically separate areas: the Nulla Basalt Province (NBP) in the south and the McBride Basalt Province (MBP) in the north. This data release includes separate, regional-scale groundwater contour datasets for the Nulla and McBride basalt provinces developed by Geoscience Australia in: Cook, S. B. & Ransley, T. R., 2020. Exploring for the Future—Groundwater level interpretations for the McBride and Nulla basalt provinces: Upper Burdekin region, North Queensland. Geoscience Australia, Canberra, https://pid.geoscience.gov.au/dataset/ga/135439. As detailed in that document, the groundwater contours were drawn by hand based on: - Groundwater levels from monitoring bores measured mostly on 17 February 2019 following extensive rainfall. - Surface topography. - Surface water features (rivers and springs). - Remote sensing data. The inferred groundwater contours were used in various Upper Burdekin Groundwater Project components to frame hydrogeological discussions. It is important to note that they were drawn following a wet period; groundwater contours are temporally variable and those presented in this data release therefore only represent part of the regional groundwater flow system.

This grid dataset is an estimation of the relative surface potential for recharge within the McBride Basalt Province. This process combined numerous factors together as to highlight the areas likely to have higher potential for recharge to occur. Soil permeability and surface geology are the primary inputs. Vegetation and slope were excluded from consideration, as these were considered to add too much complexity. Furthermore, this model does not include rainfall intensity – although this is known to vary spatially through average rainfall grids, this model is a depiction of the ground ability for recharge to occur should a significant rainfall event occur in each location. The relative surface potential recharge presented is estimated through a combination of soil and geological factors, weighting regions that are considered likely to have greater potential for recharge (e.g. younger basalts, vent-proximal facies, and highly permeable soils). Near-surface permeability of soil layers has been considered as a quantified input to the ability for water to infiltrate soil strata. It was hypothesised that locations proximal to volcanic vents would be preferential recharge sites, due to deeply penetrative columnar jointing. This suggestion is based on observations in South Iceland, where fully-penetrating columnar joint sets are more prevalent in proximal facies compared to distal facies in South Iceland (Bergh & Sigvaldson 1991). To incorporate this concept, preferential recharge sites are assumed to be within the polygons of vent-proximal facies as derived from detailed geological mapping datasets. Remaining geology has been categorised to provide higher potential recharge through younger lava flows. As such, a ranking between geological units has been used to provide the variation in potential recharge estimates. <b>References</b> Bergh, S. G., & Sigvaldason, G. E. (1991). Pleistocene mass-flow deposits of basaltic hyaloclastite on a shallow submarine shelf, South Iceland. Bulletin of Volcanology, 53(8), 597-611. doi:10.1007/bf00493688

This report provides an initial summary of the hydrogeochemistry of the McBride Basalt Province (MBP) and Nulla Basalt Province (NBP) of the Upper Burdekin Region of North Queensland, completed as part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. Groundwater hydrogeochemistry studies can improve system understanding by reflecting host formation compositions and groundwater processes. These studies also provide regional baseline groundwater datasets that can inform environmental monitoring, resource use and decision making. During 2017 and 2018 Geoscience Australia collected 38 groundwater samples and 80 surface water samples (including quality control samples) to evaluate groundwater system processes including potential flow paths, recharge and groundwater-surface water-interactions. These surveys were conducted across three months of fieldwork, sampling water for a comprehensive suite of hydrogeochemical parameters. The present report includes surface water and groundwater data and information on: 1) sampling sites; 2) field physicochemical parameters (EC, pH, Eh, DO and T); 3) field measurements of total alkalinity (HCO3-); 4) laboratory results of major anion and cation results; 5) laboratory results for isotopes of water (δ18O and δD), DIC (δ13C), and dissolved strontium (87Sr/86Sr); and 6) hydrogeochemical maps representing the spatial distribution of these parameters. Pending analyses include: CFCs, SF6 and radiogenic isotopes δ14C and δ36Cl. Analysis that were largely below detection limit include: trace element concentrations, dissolved sulfide (S2-), ferrous iron (Fe2+), and dissolved sulfate (affecting sampling of δ34S and δ18O). This study demonstrates that hydrogeochemistry surveys, with full suites of chemical parameters including isotopes, can reveal fundamental groundwater system processes such as groundwater flow paths, groundwater recharge and groundwater-surface water interactions. The chemical ‘fingerprints’ identified here indicate groundwater flow paths are largely restricted to within the MBP and NBP aquifers, which have little interaction with adjacent and underlying non-basaltic rocks. The results also indicate groundwater is largely recharged from rainfall in higher elevations of the basalt provinces, with variable rainfall inputs to groundwater from lower elevation and rivers along flow paths. Groundwater-surface water interactions show several chemical signatures linking groundwater to springs, tributary rivers and the Burdekin River. Results from the Upper Burdekin Hydrogeochemistry Survey for the MBP and NBP have been plotted and mapped with initial interpretations presented below. Further detailed interpretation of this hydrogeochemistry data will be the focus of future publications. This data release is part in a series of staged outputs from the EFTF program. Relevant data, information and images are available through the Geoscience Australia website.

This dataset includes point estimates of groundwater recharge in mm/year. Recharge rates have been estimated at monitoring bore locations in the basaltic aquifers of the Nulla and McBride basalt provinces. Recharge estimates have been calculated using the “chloride mass balance” method. The chloride mass balance process assumes that the chloride ion is a conservative tracer in precipitation, evapotranspiration, recharge and runoff; and that all the chloride is from rainfall, instead of for example halite saturation or dissolution processes. So the volumetric water balance and the flux of chloride balance must both be true. Assuming that runoff and evapotranspiration are negligible (so approximated by zero), the equation is simplified: Water balance P=ET+R+Q Water balance multiplied by chloride concentrations (chloridefluxbalance) P∙Cl_ppt=ET∙Cl_ET+R∙Cl_gw+Q∙Cl_riv | ΔCl_reac≈0 Assumptions to simplify equation P∙Cl_ppt=R∙Cl_gw | Q≈0 & ET≈0 Rearranging for recharge rate (unknown) R=P∙(Cl_ppt)/(Cl_gw ) | Q≈0 & ET≈0 Where P = precipitation rate; ET = evapotranspiration rate; R = recharge rate; Q = runoff to streams; Clppt = concentration of Cl in precipitation; ClET = concentration of chloride in evapotranspiration; Clgw = concentration of Cl in groundwater; Clriv = concentration of chloride in river runoff; ΔClreac = change in chloride concentrations from reactions.

Groundwater-dependent ecosystems (GDEs) rely on access to groundwater on a permanent or intermittent basis for some or all of their water requirements (Queensland Government, 2018). Remotely sensed data from Digital Earth Australia (DEA) (Geoscience Australia, 2018) were used to map potential aquatic and other GDEs and enhance understanding of surface water – groundwater interactions in the Upper Burdekin region. Two Landsat TM satellite products (Water Observations from Space (WOfS; Mueller et al. 2016) summary statistic and Tasselled Cap Index (TCI) wetness summary)) were used to investigate the persistence of surface water and soil moisture in the landscape to identify perennial streams, springs and other parts of the landscape that may rely on groundwater discharge. The WOfS summary statistic represents, for each pixel, the percentage of time that water is detected at the surface relative to the total number of clear observations. Due to the 25-m by 25-m pixel size of Landsat data, only features at least 25 m wide are detected and only features covering multiple pixels are consistently detected. The WOfS summary statistic was produced over the McBride and Nulla Basalt provinces for the entire period of available data (1987 to 2018). Pixels were polygonised and classified in order to visually enhance key data in the imagery, such as the identification of standing water for at least 80% of the time. The TCI is a method of reducing six surface reflectance bands of satellite data to three bands (Brightness, Greenness, Wetness) using a Principal Components Analysis (PCA) and Procrustes' Rotation (Roberts et al., 2018). The published coefficients of Crist (1985) are applied to DEA's Landsat data to generate a TCI composite. The resulting Tasselled Cap bands are a linear combination of the original surface reflectance bands that correlate with the Brightness (bare earth), Greenness and Wetness of the landscape. The TCI wetness summary (or Tasselled Cap Wetness (TCW) percentage exceedance composite), derived from the Wetness band, represents the behaviour of water in the landscape, as defined by the presence of water, moist soil or wet vegetation at each pixel through time. The summary shows the percentage of observed scenes where the Wetness layer of the Tasselled Cap transform is above the threshold, i.e. where each pixel has been observed as ‘wet’ according to the TCI. Areas that retain surface water or wetness in the landscape during the dry season are potential areas of groundwater discharge and associated GDEs. The TCW threshold is set at -600 to calculate the percentage exceedance. This threshold is based on scientific judgment and is currently in the research/testing phase. It is based on Australian conditions and conservative in nature. The dry season, when surface runoff to streams and rainfall are minimal, is particularly useful for identifying and mapping groundwater-fed streams, springs and other ecosystems that rely on access to groundwater during periods of limited rainfall. The Upper Burdekin region was especially dry between May and October 2013, with low rainfall totals in the months preceding this dry season and overall below-average rainfall conditions (i.e. decline in rainfall residual mass). The TCW exceedance composite was classified into percentage intervals to distinguish areas that were wet for different proportions of time during the 2013 dry season. Field validation of the remote sensing data products would be required to confirm the preliminary identification of parts of the landscape where groundwater discharges to the surface and potentially supports GDEs. This release includes the classified WOfS summary statistic and classified TCW percentage exceedance composite (May-October 2013) data products for the McBride and Nulla basalt provinces in the Upper Burdekin region, North Queensland. <b>References: </b> Crist EP (1985) A TM Tasseled Cap equivalent transformation for reflectance factor data. Remote Sensing of Environment 17(3), 301–306. Doi: 10.1016/0034-4257(85)90102-6. Geoscience Australia (2018) Digital Earth Australia. Geoscience Australia, http://www.ga.gov.au/dea. Mueller, N., Lewis, A., Roberts, D., Ring, S., Melrose, R., Sixsmith, J., Lymburner, L., McIntyre, A., Tan, P., Curnow, S. and Ip, A. (2016) Water observations from space: Mapping surface water from 25 years of Landsat imagery across Australia. Remote Sensing of Environment 174, 341-352, ISSN 0034-4257. Queensland Government (2018) Groundwater dependent ecosystems, WetlandInfo 2014. Queensland Government, Brisbane, https://wetlandinfo.des.qld.gov.au/wetlands/ecology/aquatic-ecosystems-natural/groundwater-dependent/. Roberts D, Dunn B and Mueller N (2018) Open Data Cube Products Using High-Dimensional Statistics of Time Series. International Geoscience and Remote Sensing Symposium. Valencia, Spain: IEEE Geoscience and Remote Sensing Society.

This report presents key results of groundwater barometric response function development and interpretation from the Upper Burdekin Groundwater Project in North Queensland, conducted as part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. The Upper Burdekin Groundwater Project is a collaborative study between Geoscience Australia and the Queensland Government. It focuses on basalt groundwater resources in two geographically separate areas: the Nulla Basalt Province (NBP) in the south and the McBride Basalt Province (MBP) in the north. The NBP and MBP basalt aquifers are heterogeneous, fractured, vesicular systems. This report assesses how water levels in monitoring bores in the NBP and MBP respond to barometric pressure changes to evaluate the degree of formation confinement. The main process used to evaluate water level response to barometric pressure in this study is based on barometric efficiency (BE). The BE of a formation is calculated by dividing the change in monitoring bore water level by the causative barometric pressure change. Both parameters are expressed in the same units, so BE will typically be some fraction between zero and one. BE is not necessarily constant over time; the way BE changes following a theoretical step change in barometric pressure can be described using a barometric response function (BRF). BRFs were calculated in the time domain and plotted as BE against time lag for interpretation. The BRF shape was used to assess the degree of formation confinement. Although there is some uncertainty due to monitoring bore construction issues (including long effective screens) and potentially air or gas trapped in the saturated zone, all BRFs in the current project are interpreted to indicate unconfined conditions. This finding is supported by the identification of recharge at many monitoring bores through hydrograph analysis in other EFTF project components. We conclude that formations are likely to be unconfined at many project monitoring bores assessed in this study.

The Upper Burdekin Chloride Mass Balance Recharge web service depicts the recharge rates have been estimated at borehole locations in the Nulla and McBride basalt provinces. Using rainfall rates, rainfall chemistry and groundwater chemistry, the recharge rates have been estimated through the Chloride Mass Balance approach.