scholarly journals A multi-tracer approach to constraining artesian groundwater discharge into an alluvial aquifer

Author(s):  
Charlotte P. Iverach ◽  
Dioni I. Cendón ◽  
Karina T. Meredith ◽  
Klaus M. Wilcken ◽  
Stuart I. Hankin ◽  
...  

Abstract. Understanding pathways of recharge to alluvial aquifers is important for maintaining sustainable access to groundwater resources. Water balance modelling is often used to proportion recharge components and guide sustainable groundwater allocations. However, it is not common practice to use hydrochemical evidence to inform and constrain these models. Here we compare geochemical versus water balance model estimates of artesian discharge into an alluvial aquifer, and demonstrate why multi-tracer geochemical analyses should be used as a critical component of water budget assessments. We selected a site in Australia where the Great Artesian Basin (GAB), the largest artesian basin in the world, discharges into the Lower Namoi Alluvium (LNA), an extensively modelled aquifer, to convey the utility of our approach. Water stable isotopes (ẟ18O and ẟ2H) and the concentrations of Na+ and HCO3− suggest a continuum of mixing in the alluvial aquifer between the GAB (artesian component) and surface recharge, whilst isotopic tracers (3H, 14C and 36Cl) indicate that the alluvial groundwater is a mixture of groundwaters with residence times of

2017 ◽  
Vol 21 (11) ◽  
pp. 5953-5969 ◽  
Author(s):  
Charlotte P. Iverach ◽  
Dioni I. Cendón ◽  
Karina T. Meredith ◽  
Klaus M. Wilcken ◽  
Stuart I. Hankin ◽  
...  

Abstract. Understanding pathways of recharge to alluvial aquifers is important for maintaining sustainable access to groundwater resources. Water balance modelling is often used to proportion recharge components and guide sustainable groundwater allocations. However, it is not common practice to use hydrochemical evidence to inform and constrain these models. Here we compare geochemical versus water balance model estimates of artesian discharge into an alluvial aquifer, and demonstrate why multi-tracer geochemical analyses should be used as a critical component of water budget assessments. We selected a site in Australia where the Great Artesian Basin (GAB), the largest artesian basin in the world, discharges into the Lower Namoi Alluvium (LNA), an extensively modelled aquifer, to convey the utility of our approach. Water stable isotopes (δ18O and δ2H) and the concentrations of Na+ and HCO3− suggest a continuum of mixing in the alluvial aquifer between the GAB (artesian component) and surface recharge, whilst isotopic tracers (3H, 14C, and 36Cl) indicate that the alluvial groundwater is a mixture of groundwaters with residence times of < 70 years and groundwater that is potentially hundreds of thousands of years old, which is consistent with that of the GAB. In addition, Cl− concentrations provide a means to calculate a percentage estimate of the artesian contribution to the alluvial groundwater. In some locations, an artesian contribution of up to 70 % is evident from the geochemical analyses, a finding that contrasts with previous regional-scale water balance modelling estimates that attributed 22 % of all inflow for the corresponding zone within the LNA to GAB discharge. Our results show that hydrochemical investigations need to be undertaken as part of developing the conceptual framework of a catchment water balance model, as they can improve our understanding of recharge pathways and better constrain artesian discharge to an alluvial aquifer.


Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 178
Author(s):  
Muhammad Aslam ◽  
Ali Salem ◽  
Vijay P. Singh ◽  
Muhammad Arshad

Evaluation of the spatial and temporal distribution of water balance components is required for efficient and sustainable management of groundwater resources, especially in semi-arid and data-poor areas. The Khadir canal sub-division, Chaj Doab, Pakistan, is a semi-arid area which has shallow aquifers which are being pumped by a plethora of wells with no effective monitoring. This study employed a monthly water balance model (water and energy transfer among soil, plants, and atmosphere)—WetSpass-M—to determine the groundwater balance components on annual, seasonal, and monthly time scales for a period of the last 20 years (2000–2019) in the Khadir canal sub-division. The spatial distribution of water balance components depends on soil texture, land use, groundwater level, slope, and meteorological conditions. Inputs for the model included data on topography, slope, soil, groundwater depth, slope, land use, and meteorological data (e.g., precipitation, air temperature, potential evapotranspiration, and wind speed) which were prepared using ArcGIS. The long-term average annual rainfall (455.7 mm) is distributed as 231 mm (51%) evapotranspiration, 109.1 mm (24%) surface runoff, and 115.6 mm (25%) groundwater recharge. About 51% of groundwater recharge occurs in summer, 18% in autumn, 14% in winter, and 17% in spring. Results showed that the WetSpass-M model properly simulated the water balance components of the Khadir canal sub-division. The WetSpass-M model’s findings can be used to develop a regional groundwater model for simulation of different aquifer management scenarios in the Khadir area, Pakistan.


2013 ◽  
Vol 499 ◽  
pp. 110-123 ◽  
Author(s):  
Tesfamichael Gebreyohannes ◽  
Florimond De Smedt ◽  
Kristine Walraevens ◽  
Solomon Gebresilassie ◽  
Abdelwasie Hussien ◽  
...  

2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Baina Afkril

<p>Area studi terletak di bagian tenggara Dataran Tinggi Blackwood, Australia Barat mencakup 71 km<sup>2</sup>. Akifer Yarragadee di daerah studi utamanya tersusun oleh batu pasir yang mengandung lapisan-lapisan batu lempung dan liat. Akifer ini merupakan akifer tak-tertekan karena muncul dipermukaan sepanjang alur Sungai Blackwood pada daerah hilir di Nannup dan merupakan sumber airtanah yang keluar ke sungai. Sungai Blackwood mengalir melintasi Dataran Tinggi Blackwood. Selama musim kering, aliran permukaan ke dalam Sungai Blackwood dapat diabaikan, namun aliran dasar dari airtanah menjadi sumber utama bagi aliran sungai. Neraca air pada daerah studi dilakukan dengan menggunakan analisa jaring-aliran dan kesetimbangan air guna mengevaluasi masukan airtanah dari akifer Yarragadee ke dalam Sungai Blackwood. Mayoritas sel-sel jaring-aliran adalah sel-sel keluaran dan kebanyakan aliran airtanah masuk ke dalam Sungai Blackwood di daerah studi. Curah hujan rata-rata tahunan area studi sekitar 6.7 x 10<sup>7</sup> m<sup>3</sup> a<sup>-1</sup>. Sekitar 9 % dari total curah hujan rata-rata tahunan ini masuk ke dalam tanah sebagai sumber bagi air tanah dan 91 % hilang melalui proses evapotranspirasi. Volume total airtanah yang masuk ke dalam Sungai Blackwood antara stasiun Darradup dan Layman Flat yang dihitung menggunakan analisis jarring-aliran dan kesetimbangan air sekitar 8.1 GL a<sup>-1</sup>.  </p>


2012 ◽  
Vol 16 (8) ◽  
pp. 2485-2497 ◽  
Author(s):  
B. Leterme ◽  
D. Mallants ◽  
D. Jacques

Abstract. The sensitivity of groundwater recharge to different climate conditions was simulated using the approach of climatic analogue stations, i.e. stations presently experiencing climatic conditions corresponding to a possible future climate state. The study was conducted in the context of a safety assessment of a future near-surface disposal facility for low and intermediate level short-lived radioactive waste in Belgium; this includes estimation of groundwater recharge for the next millennia. Groundwater recharge was simulated using the Richards based soil water balance model HYDRUS-1D and meteorological time series from analogue stations. This study used four analogue stations for a warmer subtropical climate with changes of average annual precipitation and potential evapotranspiration from −42% to +5% and from +8% to +82%, respectively, compared to the present-day climate. Resulting water balance calculations yielded a change in groundwater recharge ranging from a decrease of 72% to an increase of 3% for the four different analogue stations. The Gijon analogue station (Northern Spain), considered as the most representative for the near future climate state in the study area, shows an increase of 3% of groundwater recharge for a 5% increase of annual precipitation. Calculations for a colder (tundra) climate showed a change in groundwater recharge ranging from a decrease of 97% to an increase of 32% for four different analogue stations, with an annual precipitation change from −69% to −14% compared to the present-day climate.


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