Hydrogeochemistry, Isotopic Composition and Water Age in the Hydrologic System of a Large Catchment within a Plain Humid Environment (Argentine Pampas): Quequén Grande River, Argentina
“…Groundwater discharges often make up a substantial share of surface flows (e.g., Bolduc et al, ; Calvi et al, ; Cao et al, ; Cook et al, ; England et al, ; Foks et al, ; Fritz et al, ; Genereux et al, ; Georgek et al, ; Hooper et al, ; Le Maitre & Colvin, ; Ma et al, ; Martinez et al, ; Pinder & Jones, ; Sklash & Farvolden, ; Smerdon et al, ; Smith et al, ; Tague et al, , ; Tague & Grant, , ; Turner et al, ; Walvoord & Striegl, ; Wang, Li, & Jiang, ; Zimmer et al, ). Groundwater discharges sustain streamflow even when rain is not falling and snow is not melting, influencing riverine solute loads, moderating stream temperatures, and creating perennial aquatic habitat (e.g., Bertrand et al, ; Boulton & Hancock, ; Briggs et al, ; Hayashi & Rosenberry, ; Irvine et al, ; Jefferson et al, ; Kløve et al, ; Kurylyk et al, ; McGuire et al, ; O'Driscoll & DeWalle, ; Petts et al, ; Poff & Zimmerman, ; Rose et al, ; Sear et al, ; Wood et al, , ).…”
Section: Groundwater Discharges To Riversmentioning
Groundwater 18O/16O, 2H/1H, 13C/12C, 3H, and 14C data can help quantify molecular movements and chemical reactions governing groundwater recharge, quality, storage, flow, and discharge. Here, commonly applied approaches to isotopic data analysis are reviewed, involving groundwater recharge seasonality, recharge elevations, groundwater ages, paleoclimate conditions, and groundwater discharge. Reviewed works confirm and quantify long held tenets: (i) that recharge derives disproportionately from wet season and winter precipitation; (ii) that modern groundwaters comprise little global groundwater; (iii) that “fossil” (>12,000‐year‐old) groundwaters dominate global aquifer storage; (iv) that fossil groundwaters capture late‐Pleistocene climate conditions; (v) that surface‐borne contaminants are more common in younger groundwaters; and (vi) that groundwater discharges generate substantial streamflow. Groundwater isotope data are disproportionately common to midlatitudes and sedimentary basins equipped for irrigated agriculture, but less plentiful across high latitudes, hyperarid deserts, and equatorial rainforests. Some of these underexplored aquifer systems may be suitable targets for future field testing.
“…Groundwater discharges often make up a substantial share of surface flows (e.g., Bolduc et al, ; Calvi et al, ; Cao et al, ; Cook et al, ; England et al, ; Foks et al, ; Fritz et al, ; Genereux et al, ; Georgek et al, ; Hooper et al, ; Le Maitre & Colvin, ; Ma et al, ; Martinez et al, ; Pinder & Jones, ; Sklash & Farvolden, ; Smerdon et al, ; Smith et al, ; Tague et al, , ; Tague & Grant, , ; Turner et al, ; Walvoord & Striegl, ; Wang, Li, & Jiang, ; Zimmer et al, ). Groundwater discharges sustain streamflow even when rain is not falling and snow is not melting, influencing riverine solute loads, moderating stream temperatures, and creating perennial aquatic habitat (e.g., Bertrand et al, ; Boulton & Hancock, ; Briggs et al, ; Hayashi & Rosenberry, ; Irvine et al, ; Jefferson et al, ; Kløve et al, ; Kurylyk et al, ; McGuire et al, ; O'Driscoll & DeWalle, ; Petts et al, ; Poff & Zimmerman, ; Rose et al, ; Sear et al, ; Wood et al, , ).…”
Section: Groundwater Discharges To Riversmentioning
Groundwater 18O/16O, 2H/1H, 13C/12C, 3H, and 14C data can help quantify molecular movements and chemical reactions governing groundwater recharge, quality, storage, flow, and discharge. Here, commonly applied approaches to isotopic data analysis are reviewed, involving groundwater recharge seasonality, recharge elevations, groundwater ages, paleoclimate conditions, and groundwater discharge. Reviewed works confirm and quantify long held tenets: (i) that recharge derives disproportionately from wet season and winter precipitation; (ii) that modern groundwaters comprise little global groundwater; (iii) that “fossil” (>12,000‐year‐old) groundwaters dominate global aquifer storage; (iv) that fossil groundwaters capture late‐Pleistocene climate conditions; (v) that surface‐borne contaminants are more common in younger groundwaters; and (vi) that groundwater discharges generate substantial streamflow. Groundwater isotope data are disproportionately common to midlatitudes and sedimentary basins equipped for irrigated agriculture, but less plentiful across high latitudes, hyperarid deserts, and equatorial rainforests. Some of these underexplored aquifer systems may be suitable targets for future field testing.
“…Therefore, studies in the plain region with moderate terrain may help us to figure out how the catchment scale influences MRT. However, previous studies in plain referred to MRT focus on using MRT as a tool to investigate catchment hydrology rather than studying the relationship between MRT and catchment scale 20 , 21 . For example, Cao et al 22 estimated the MRT of groundwater in the Yang-Dai River plain to identify pollution status and groundwater cyclical pattern.…”
The oxygen and hydrogen isotopic compositions (δ18O and δ2H) were measured on river water and precipitation collected from four sub-catchments within the upper Tuojiang River catchment. δ18O values of river water and precipitation exhibit significant seasonal variations. These seasonal variations are used for estimating the mean residence time (MRT) for four sub-catchments by an exponential model, ranging from 346 to 493 days. The correlation between catchment MRT and mean slope of the catchment (r2 = 0.29) is weak, while the correlations between catchment MRT, catchment area (r2 = 0.79) and topographic index (r2 = 0.98) are strong. These results indicate that topography and catchment area, both control the catchment MRT and the topographic index may be a reliable parameter for estimating the catchment MRT. Moreover, the relationship between land use types and MRT was investigated. The results show that paddy fields (r2 = 0.95) compared to the other land use types may have a greater impact on the MRT of the irrigation-dominated catchment. This study provides a preliminary exploration of the factors affecting MRT in the plain region and a basis for simulating MRT in the future.
“…Figure 6.Graph of δ 18 O SMOW versus δD VSMOW values of modern waters from the study area. The global meteoric water line and three local meteoric water lines from Rohrmann et al (2014), Dettinger et al (2015), and Martínez et al (2017) are very similar. Dotted lines are evaporation lines (m = 3.76) fit to the local water data.…”
Section: Resultsmentioning
confidence: 73%
“…First, evidence from detrital zircons, as well as strontium isotopes from shell material and water (presented more fully later), point to filling of the basin by flooding of Andean river water derived from a source that is a long distance from the basin. River water is typically in or close to isotopic 14 C equilibrium with the atmosphere, although local depletion in 14 C can arise due to groundwater inputs, especially during the dry season (e.g., Ishikawa et al, 2013; Martínez et al, 2017). The influence of ground water on river 14 C should be greatly reduced during flooding.…”
The Salinas del Bebedero occupies an isolated basin in the foreland of central Argentina at 33°S and was flooded repeatedly over past 25 ka. Isotopic evidence demonstrates that this flooding was due to overflow of the nearby Río Desaguadero with waters derived from the distant (≥300 km) central Andes between 28–34°S. Stratigraphic and shoreline evidence shows that floods occurred most frequently between 14.4 and 15.7 ka, followed by lesser events between 14.3 to 11.4 ka, and during the late Holocene from 2.6 to ca. 0.2 ka. Hydraulic modeling (2D HEC-RAS) shows that these floods could have originated from repeated subglacial drainage or sudden outbursts with a volume of >100 × 106 m3 and a peak discharge of >1,000 m3 s-1 each. The absence of flood deposits from 11 to 3 ka points to exceptionally dry and virtually ice-free conditions in the Andes between 28–34°S. The floods were probably caused by major rainfall or dammed-lake outbursts clustered largely during wet pluvial periods in the otherwise moisture-limited central Andes and Atacama Desert, such as when the Intertropical Convergence Zone was shifted southward. These include Central Andean pluvial events (CAPE) I (17–14.5 ka) and II (12.5–9 ka), and the Neoglacial/Formative archeological period 2500 ka to near-present.
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