Constraining groundwater flow, residence times, inter-aquifer mixing, and aquifer properties using environmental isotopes in the southeast Murray Basin, Australia

Cartwright, Ian, Weaver, Tamie R., Cendón, Dioni I., Fifield, L. Keith, Tweed, Sarah, Petrides, Ben, and Swane, Ian (2012) Constraining groundwater flow, residence times, inter-aquifer mixing, and aquifer properties using environmental isotopes in the southeast Murray Basin, Australia. Applied Geochemistry, 27 (9). pp. 1698-1709.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website: http://dx.doi.org/10.1016/j.apgeochem.20...
47


Abstract

Environmental isotopes (particularly δ¹⁸O, δ²H, and δ¹³C values, ⁸⁷Sr/⁸⁶Sr ratios, and α¹⁴C) constrain geo-chemical processes, recharge distribution and rates, and inter-aquifer mixing in the Riverine Province of the southern Murray Basin. Due to methanogenesis and the variable δ¹³C values of matrix calcite, δ¹³C values are highly variable and it is difficult to correct ¹⁴C ages using δ¹³C values alone. In catchments where δ¹³C values, ⁸⁷Sr/⁸⁶Sr ratios, and major ion geochemistry yield similar α¹⁴C corrections, similar to 15% of the C is derived from the aquifer matrix in the silicate-dominated aquifers, and this value may be used to correct ages in other catchments. Most groundwater has α¹⁴C above background (similar to 2 pMC) implying that residence times are <30 ka. Catchments containing saline groundwater generally record older ¹⁴C ages compared to catchments that contain lower salinity groundwater, which is consistent with evapo-transpiration being the major hydrogeochemical process. However, some low salinity groundwater in the west of the Riverine Province has residence times of >30 ka probably resulting from episodic recharge during infrequent high rainfall episodes. Mixing between shallower and deeper groundwater results in ¹⁴C ages being poorly correlated with distance from the basin margins in many catchments; however, groundwater flow in palaeovalleys where the deeper Calivil-Renmark Formation is coarser grained and has high hydraulic conductivities is considerably more simple with little inter-aquifer mixing. Despite the range of ages, δ¹⁸O and δ²H values of groundwater in the Riverine Province do not preserve a record of changing climate; this is probably due to the absence of extreme climatic variations, such as glaciations, and the fact that the area is not significantly impacted by monsoonal systems.

Item ID: 23552
Item Type: Article (Research - C1)
ISSN: 1872-9134
Funders: Australian Research Council (ARC), National Centre for Grounwater Research and Training, Monash University
Date Deposited: 03 Oct 2012 05:31
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040299 Geochemistry not elsewhere classified @ 100%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961103 Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and @ 100%
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page