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16 pages, 6484 KiB

Open AccessFeature PaperArticle

The Stable Isotope Characteristics of Precipitation in the Middle East Highlighting the Link between the Köppen Climate Classifications and the δ¹⁸O and δ²H Values of Precipitation

by Mojtaba Heydarizad, Luis Gimeno, Rogert Sorí, Foad Minaei and Javad Eskandari Mayvan

Water 2021, 13(17), 2397; https://doi.org/10.3390/w13172397 - 31 Aug 2021

Cited by 8 | Viewed by 2522

Abstract

The Middle East is faced with a water shortage crisis due to its semiarid and arid climate. In this paper, precipitation as an important part of the water cycle was evaluated in 43 stations across the Middle East using the stable isotope technique [...] Read more.

The Middle East is faced with a water shortage crisis due to its semiarid and arid climate. In this paper, precipitation as an important part of the water cycle was evaluated in 43 stations across the Middle East using the stable isotope technique to study the parameters which influence the stable isotope content of precipitation. First, the stepwise regression model was applied to determine the main geographical and climatological factors affecting the stable isotopes in precipitation. Secondly, the stepwise model was also used to simulate the stable isotope values in precipitation. Furthermore, due to the notable climatic variations across the Middle East, the precipitation sampling stations were classified into six groups based on the Köppen climate zones. Significant variations in the stable isotope values of precipitation were observed in the stations of each climate zone. Finally, the Middle East meteoric water line was developed for the dry and wet periods based on the average stable isotopes in the studied stations. The developed lines showed a lower slope compared to the GMWL due to the higher air temperature and relative humidity in the Middle East compared to the average global conditions. To conclude, the stable isotope contents in precipitation showed significant temporal and spatial variations due to the notable climatic variations across the Middle East. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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24 pages, 4661 KiB

Open AccessArticle

Hydrogeochemistry Studies in the Oil Sands Region to Investigate the Role of Terrain Connectivity in Nitrogen Critical Loads

by John J. Gibson, Sandra Jean Birks, Michael C. Moncur, Amy Vallarino, Caren Kusel and Mikaela Cherry

Water 2021, 13(16), 2204; https://doi.org/10.3390/w13162204 - 13 Aug 2021

Cited by 4 | Viewed by 2149

Abstract

Hydrology and geochemistry studies were conducted in the Athabasca Oil Sands region to better understand the water and nitrogen cycles at two selected sites in order to assess the potential for nitrogen transport between adjacent terrain units. A bog—poor fen—upland system was instrumented [...] Read more.

Hydrology and geochemistry studies were conducted in the Athabasca Oil Sands region to better understand the water and nitrogen cycles at two selected sites in order to assess the potential for nitrogen transport between adjacent terrain units. A bog—poor fen—upland system was instrumented near Mariana Lakes (ML) (55.899° N, 112.090° W) and a rich fen—upland system was instrumented at JPH (57.122° N, 111.444° W), 100 km south and 45 km north of Fort McMurray, Alberta respectively. LiDAR surveys were initially conducted to delineate the watershed boundaries and topography and to select a range of specific locations for the installation of water table wells and groundwater piezometers. Field work, which included a range of physical measurements as well as water sampling for geochemical and isotopic characterization, was carried out mainly during the thaw seasons of 2011 to 2015. From analysis of the runoff response and nitrogen species abundances we estimate that nitrogen exchange between the wetlands and adjacent terrain units ranged between 2.2 and −3.1 kg/ha/year for rich fens, 0.6 to −1.1 kg/ha/year for poor fens, and between 0.6 and −2.5 kg/ha/year for bogs, predominantly via surface pathways and in the form of dissolved nitrate. A significant storage of dissolved ammonium (and also dissolved organic nitrogen) was found within the pore water of the bog-fen complex at Mariana Lakes, which we attribute to decomposition, although it is likely immobile under current hydrologic conditions, as suggested by tritium distributions. In comparison with the experimental loads of between 5 and 25 kg/ha/year, the potential nitrogen exchange with adjacent terrain units is expected to have only a minor or negligible influence, and is therefore of secondary importance for defining critical loads across the regional landscape. Climate change and development impacts may lead to significant mobilization of nitrogen storages, although more research is required to quantify the potential effects on local ecosystems. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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14 pages, 5915 KiB

Open AccessArticle

Application of Water Stable Isotopes for Hydrological Characterization of the Red River (Asia)

by Nho Lan Nguyen, Thu Nga Do and Anh Duc Trinh

Water 2021, 13(15), 2051; https://doi.org/10.3390/w13152051 - 28 Jul 2021

Cited by 6 | Viewed by 2396

Abstract

Fraction of young water (Fyw) and mean transit time (MTT,

\bar{τ}

) calculated from water isotope profiles are valuable information for catchment hydrological assessment, especially in anthropogenically impacted region where natural conditions may not be decisive to catchment hydrology. The [...] Read more.

Fraction of young water (Fyw) and mean transit time (MTT,

\bar{τ}

) calculated from water isotope profiles are valuable information for catchment hydrological assessment, especially in anthropogenically impacted region where natural conditions may not be decisive to catchment hydrology. The calculation of Fyw and MTT were performed on three subsets of δ¹⁸O_H₂O data collected at the Hanoi meteo-hydrological station, Red River, in three periods; 2002–2005, 2015, and 2018–2019. The mean (min and max) values of δ¹⁸O_H₂O in rainwater over the three periods are, respectively, −5.3‰ (−11.0 and −1.2‰), −5.4‰ (−10.7 and −1.4‰), and −4.5‰ (−13.9 and 1.7‰). The corresponding values in river water are −8.4‰ (−9.8 and −6.9‰), −8.5‰ (−9.1 and −7.7‰), and −8.4‰ (−9.5 and −7.2‰), respectively. The mean of Fyw calculated from the δ¹⁸O_H₂O data for different periods is 22 ± 9%, 10 ± 5%, and 8 ± 3%. Mean transit time is 4.69 ± 15.57, 1.65 ± 1.53, and 2.06 ± 1.87 years. The calculated Fyw (MTT) is negatively (positively) proportional to change in reservoir volume over the three periods, which is logical, since reservoirs tend to keep more water in the catchment and slower down water flow. The strong variation of Fyw and

\bar{τ}

, two essential variables characterizing the catchment hydrology, represents an anthropogenic impact in the Red River system. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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24 pages, 4936 KiB

Open AccessArticle

Karst Recharge Areas Identified by Combined Application of Isotopes and Hydrogeological Budget

by Silvia Iacurto, Gerardo Grelle, Francesco Maria De Filippi and Giuseppe Sappa

Water 2021, 13(14), 1965; https://doi.org/10.3390/w13141965 - 17 Jul 2021

Cited by 11 | Viewed by 2306

Abstract

The identification of recharge areas in karst aquifers allows us to perform sustainable management of these groundwater resources. Stable isotopes (δ¹⁸O and δ²H) have been largely used to provide information about recharge elevation in many mountainous regions. In this [...] Read more.

The identification of recharge areas in karst aquifers allows us to perform sustainable management of these groundwater resources. Stable isotopes (δ¹⁸O and δ²H) have been largely used to provide information about recharge elevation in many mountainous regions. In this paper, an improved version of a recent “isotope-driven model”, for the identification of recharge areas, was applied to Capodacqua di Spigno Spring (south of the Latium region). The model upgrade consists of a preliminary check procedure to estimate the degree of influence of the rainfall’s isotopic variability on the spring water. This additional procedure gives us an indication of the reliability of the model and its applicability conditions. Moreover, the dataset of the spring was updated to analyze the degree of reliability of the isotope-driven model. The purpose of this study was to combine the previously mentioned isotope-driven model with hydrogeological tools. A quantitative study of the basin, based on the estimation of the average monthly infiltration volume, was performed by using the inverse hydrogeological water budget. In this way, the qualitative model for the recharge areas’ estimation was validated by a quantitative hydrogeological tool. Both models show that, for karst mountain basins, the recharge areas decrease as the average recharge elevations increase, including areas at high altitudes. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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14 pages, 5106 KiB

Open AccessArticle

Sub-Hourly Variability of Stable Isotopes in Precipitation in the Marginal Zone of East Asian Monsoon

by Tingting Han, Mingjun Zhang, Shengjie Wang, Deye Qu and Qinqin Du

Water 2020, 12(8), 2145; https://doi.org/10.3390/w12082145 - 29 Jul 2020

Cited by 12 | Viewed by 2221

Abstract

Isotope data at mid-latitude locations are commonly available on annual, monthly, and daily timescales; however, they are rarely available for the variations occurring on the sub-hourly scale within individual precipitation events. To fill this gap, sub-hourly (every 10 min) sequential samples were collected [...] Read more.

Isotope data at mid-latitude locations are commonly available on annual, monthly, and daily timescales; however, they are rarely available for the variations occurring on the sub-hourly scale within individual precipitation events. To fill this gap, sub-hourly (every 10 min) sequential samples were collected for nine precipitation events, and the δ¹⁸O values of the individual events were analyzed from June to October 2019 in Lanzhou, Northwest China. The Sequential Meteoric Water Line (SMWL) correlation between δ²H and δ¹⁸O is δ²H = 7.33 δ¹⁸O + 9.78 (R² = 0.97, N = 170). All events had a similar decreasing variability pattern in the initial period (before the vertical gray dotted line), while during the later period (after the vertical gray dotted line), negative δ¹⁸O values dominated, exhibiting a different pattern. Variations in the δ¹⁸O values were about 1–5‰ during most intra-events. We found that δ¹⁸O values mainly exhibit three patterns in the intra-event, namely a “V”-shaped pattern, an “L”-shaped pattern, and a decreasing pattern. Positive δ¹⁸O values are controlled by re-evaporation in the beginning period. Relative humidity has no effect on the δ¹⁸O values of precipitation events, mainly because dry and warm conditions are conducive to the evaporation of rainwater in the study region. The changes in the isotopic characteristics of precipitation are closely linked to the regional climate. The continuous analysis of precipitation samples revealed that the rapid change of δ¹⁸O values is related to different moisture sources and transport paths. A new air mass with enriched heavy isotope intrusion can change the isotopic composition in the intra-event. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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14 pages, 3349 KiB

Open AccessArticle

Acquisition of Post-Depositional Effects on Stable Isotopes (δ¹⁸O and δD) of Snow and Firn at Dome A, East Antarctica

by Tianming Ma, Li Li, Guitao Shi and Yuansheng Li

Water 2020, 12(6), 1707; https://doi.org/10.3390/w12061707 - 15 Jun 2020

Cited by 2 | Viewed by 2822

Abstract

Water stable isotopes (δ¹⁸O and δD) in Antarctic snow pits and ice cores are extensively applied in paleoclimate reconstruction. However, their interpretation varies over some climate change processes that can alter isotope signals after deposition, especially at sites with a low [...] Read more.

Water stable isotopes (δ¹⁸O and δD) in Antarctic snow pits and ice cores are extensively applied in paleoclimate reconstruction. However, their interpretation varies over some climate change processes that can alter isotope signals after deposition, especially at sites with a low snow accumulation rate (<30 mm w.e. year⁻¹). To investigate post-depositional effects during the archival processes of snow isotopes, we first analyzed δ¹⁸O and δD variations in summer precipitation, surface snow and snow pit samples collected at Dome A. Then, the effects of individual post-depositional processes were evaluated from the results of field experiments, spectral analysis and modeling simulations. It was found that the sublimation–condensation cycle and isotopic diffusion were likely the dominant processes that modified the δ¹⁸O at and under the snow–air interface, respectively. The sublimation–condensation cycle can cause no significant isotopic modification of δ¹⁸O from field experiments with ~3 cm snow. The diffusion process can significantly erase the original seasonal variation of δ¹⁸O driven by atmospheric temperature, leading to an apparent cycle of ~20 cm average wavelength present in the δ¹⁸O profile. Through the comparison with the artificial isotopic profile, the noise input from the diffusion process was the dominant component in the δ¹⁸O signal. Although some other processes (such as drifting, ventilation and metamorphism) were not fully considered, the quantitative understanding for the sublimation–condensation and diffusion processes will contribute to the paleoclimate construction using the ice core water isotope records at Dome A. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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18 pages, 2143 KiB

Open AccessArticle

Rainstorm Magnitude Likely Regulates Event Water Fraction and Its Transit Time in Mesoscale Mountainous Catchments: Implication for Modelling Parameterization

by Jun-Yi Lee, Yu-Ting Shih, Chiao-Ying Lan, Tsung-Yu Lee, Tsung-Ren Peng, Cheing-Tung Lee and Jr-Chuan Huang

Water 2020, 12(4), 1169; https://doi.org/10.3390/w12041169 - 19 Apr 2020

Cited by 1 | Viewed by 2403

Abstract

Event water transit time estimation has rarely been done for violent rainstorms (e.g., typhoons) in steep and fractured mountainous catchments where the range of transit time, potential controlling factors, and the validity of time-invariant parametrization are unclear. Characterized by steep landscape and torrential [...] Read more.

Event water transit time estimation has rarely been done for violent rainstorms (e.g., typhoons) in steep and fractured mountainous catchments where the range of transit time, potential controlling factors, and the validity of time-invariant parametrization are unclear. Characterized by steep landscape and torrential typhoon rainfall, Taiwan provides great opportunities for inquiring into the above questions. In this study, the hydrometrics and δ¹⁸O in rainwater and streamwater were sampled with a ~3-h interval for six typhoon events in two mesoscale catchments. The TRANSEP (transfer function hydrograph separation) model and global sensitivity analysis were applied for estimating mean transit time (MTT_ew) and fraction (F_ew) of event water and identifying the chronosequent parameter sensitivity. Results showed that the MTT_ew and F_ew varied from 2.0 to 11.0 h and from 0.2 to 0.8, respectively. Our MTT_ew in the mesoscale catchments is comparable with that in microscale catchments, showing a fast rainfall-runoff transfer in our steep catchments. The average rainfall intensity is a predominant indicator, which negatively affects the MTT_ew and positively affects the F_ew, likely activating preferential flow-paths and quickly transferring event water to the stream. Sensitivity analysis among inter- and intra-events demonstrates that parameter sensitivity is event-dependent and time-variant. A quick and massive subsurface flow without distinct mixing with groundwater would be triggered during large rainstorms, suggesting that time-variant parameterization should be particularly considered when estimating the MTT_ew in steep and fractured catchments at rainstorm scale. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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Review

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19 pages, 4262 KiB

Open AccessReview

Ecohydrological Separation Hypothesis: Review and Prospect

by Yaping Liu, Yongchen Fang, Hongchang Hu, Fuqiang Tian, Zhiqiang Dong and Mohd Yawar Ali Khan

Water 2020, 12(8), 2077; https://doi.org/10.3390/w12082077 - 22 Jul 2020

Cited by 7 | Viewed by 3387

Abstract

The ecohydrological-separation (ES) hypothesis is that the water used for plant transpiration and the water used for streams and groundwater recharge comes from distinct subsurface compartmentalized pools. The ES hypothesis was first proposed in a study conducted in the Mediterranean climate region, based [...] Read more.

The ecohydrological-separation (ES) hypothesis is that the water used for plant transpiration and the water used for streams and groundwater recharge comes from distinct subsurface compartmentalized pools. The ES hypothesis was first proposed in a study conducted in the Mediterranean climate region, based on the stable isotope method in 2010. To date, the ES hypothesis has proven to be widespread around the world. The ES hypothesis is a new understanding of the soil water movement process, which is different from the assumption that only one soil reservoir in the traditional hydrology. It is helpful to clear the water sources of plants and establish a new model of the ecohydrological process. However, the theoretical basis and mechanism of the ES hypothesis are still unclear. Therefore, we analyzed the characteristics of ES phenomenon in different climatic regions, summarized the research methods used for the ES hypothesis, concluded the definitions of tightly bound water and mobile water, discussed the mechanism of isotopic differences of different reservoirs and their impacts on ES evaluation and pointed out the existing problems of the ES hypothesis. Future research should focus on the following three aspects: (a) detailed analysis of ES phenomenon characteristics of different plant species in different climatic regions; (b) further understanding of the ES phenomenon mechanism; (c) improvement of the experimental methods. Full article

(This article belongs to the Special Issue Isotope Hydrology)

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