Groundwater evolution and mean water age inferred from hydrochemical and isotopic tracers in a tropical confined aquifer

2018 ◽  
Vol 32 (14) ◽  
pp. 2158-2175 ◽  
Author(s):  
Pedro Villegas ◽  
Vanesa Paredes ◽  
Teresita Betancur ◽  
Jean D. Taupin ◽  
Luis E. Toro
Keyword(s):  
Confined Aquifer ◽  
Water Age ◽  
Isotopic Tracers ◽  
Groundwater Evolution

scholarly journals Aggregation in environmental systems: catchment mean transit times and young water fractions under hydrologic nonstationarity

2015 ◽  
Vol 12 (3) ◽  
pp. 3105-3167 ◽  
Author(s):  
J. W. Kirchner
Keyword(s):  
Direct Determination ◽  
Weighted Average ◽  
Flow Regimes ◽  
Box Model ◽  
Water Age ◽  
Isotopic Tracers ◽  
Water Fraction ◽  
Transit Times ◽  
Precipitation Seasonality ◽  
Water Fractions

Abstract. Methods for estimating mean transit times from chemical or isotopic tracers (such as Cl−, δ18O, or δ2H) commonly assume that catchments are stationary (i.e. time-invariant) and homogeneous. Real catchments are neither. In a companion paper, I showed that catchment mean transit times estimated from seasonal tracer cycles are highly vulnerable to aggregation error, exhibiting strong bias and large scatter in spatially heterogeneous catchments. I proposed a different measure of transit times, the young water fraction, and showed that it is virtually immune to aggregation error under spatial heterogeneity. Here I extend this analysis by exploring how nonstationarity affects mean transit times and young water fractions estimated from seasonal tracer cycles, using benchmark tests based on a simple two-box model. The model exhibits complex nonstationary behavior, with striking volatility in tracer concentrations, young water fractions, and mean transit times, driven by rapid shifts in the mixing ratios of fluxes from the upper and lower boxes. The transit-time distribution in streamflow becomes increasingly skewed at higher discharges, with marked increases in the young water fraction and decreases in the mean water age, reflecting the increased dominance of the upper box at higher flows. Even this simple two-box model exhibits strong equifinality; hydrograph calibration cannot constrain four of its five parameters. This equifinality problem can be partly resolved by simple parameter transformations. However, transit times are primarily determined by residual storage, which cannot be constrained through hydrograph calibration and must instead be estimated by tracer behavior. Seasonal tracer cycles in the two-box model are very poor predictors of mean transit times, with typical errors of several hundred percent. However, the same tracer cycles predict young water fractions within a few percent, even in model catchments that are both nonstationary and spatially heterogeneous (although they may be biased by roughly 0.1–0.2 at sites where strong precipitation seasonality is correlated with precipitation tracer concentrations). Flow-weighted fits to the seasonal tracer cycles accurately predict the flow-weighted average young water fraction in streamflow, while unweighted fits to the seasonal tracer cycles accurately predict the unweighted average young water fraction. Young water fractions can also be estimated separately for individual flow regimes, again with a precision of a few percent, allowing direct determination of how shifts in hydraulic regime alter the fraction of water reaching the stream by fast flowpaths. One can also estimate the chemical composition of idealized "young water" and "old water" end-members, using relationships between young water fractions and solute concentrations across different flow regimes. These results demonstrate that mean transit times cannot be estimated reliably from seasonal tracer cycles, and that, by contrast, the young water fraction is a robust and useful metric of transit times, even in catchments that exhibit strong nonstationarity and heterogeneity.

Use of chemical and isotopic tracers to assess nitrate contamination and ground-water age, Woodville Karst Plain, USA

2004 ◽  
Vol 289 (1-4) ◽  
pp. 36-61 ◽  
Author(s):  
Brian G. Katz ◽  
Angela R. Chelette ◽  
Thomas R. Pratt
Keyword(s):  
Ground Water ◽  
Nitrate Contamination ◽  
Water Age ◽  
Isotopic Tracers

scholarly journals Aggregation in environmental systems – Part 2: Catchment mean transit times and young water fractions under hydrologic nonstationarity

2016 ◽  
Vol 20 (1) ◽  
pp. 299-328 ◽  
Author(s):  
J. W. Kirchner
Keyword(s):  
Direct Determination ◽  
Weighted Average ◽  
Flow Regimes ◽  
Box Model ◽  
Water Age ◽  
Isotopic Tracers ◽  
Water Fraction ◽  
Transit Times ◽  
Precipitation Seasonality ◽  
Water Fractions

Abstract. Methods for estimating mean transit times from chemical or isotopic tracers (such as Cl−, δ18O, or δ2H) commonly assume that catchments are stationary (i.e., time-invariant) and homogeneous. Real catchments are neither. In a companion paper, I showed that catchment mean transit times estimated from seasonal tracer cycles are highly vulnerable to aggregation error, exhibiting strong bias and large scatter in spatially heterogeneous catchments. I proposed the young water fraction, which is virtually immune to aggregation error under spatial heterogeneity, as a better measure of transit times. Here I extend this analysis by exploring how nonstationarity affects mean transit times and young water fractions estimated from seasonal tracer cycles, using benchmark tests based on a simple two-box model. The model exhibits complex nonstationary behavior, with striking volatility in tracer concentrations, young water fractions, and mean transit times, driven by rapid shifts in the mixing ratios of fluxes from the upper and lower boxes. The transit-time distribution in streamflow becomes increasingly skewed at higher discharges, with marked increases in the young water fraction and decreases in the mean water age, reflecting the increased dominance of the upper box at higher flows. This simple two-box model exhibits strong equifinality, which can be partly resolved by simple parameter transformations. However, transit times are primarily determined by residual storage, which cannot be constrained through hydrograph calibration and must instead be estimated by tracer behavior. Seasonal tracer cycles in the two-box model are very poor predictors of mean transit times, with typical errors of several hundred percent. However, the same tracer cycles predict time-averaged young water fractions (Fyw) within a few percent, even in model catchments that are both nonstationary and spatially heterogeneous (although they may be biased by roughly 0.1–0.2 at sites where strong precipitation seasonality is correlated with precipitation tracer concentrations). Flow-weighted fits to the seasonal tracer cycles accurately predict the flow-weighted average Fyw in streamflow, while unweighted fits to the seasonal tracer cycles accurately predict the unweighted average Fyw. Young water fractions can also be estimated separately for individual flow regimes, again with a precision of a few percent, allowing direct determination of how shifts in a catchment's hydraulic regime alter the fraction of water reaching the stream by fast flowpaths. One can also estimate the chemical composition of idealized "young water" and "old water" end-members, using relationships between young water fractions and solute concentrations across different flow regimes. These results demonstrate that mean transit times cannot be estimated reliably from seasonal tracer cycles and that, by contrast, the young water fraction is a robust and useful metric of transit times, even in catchments that exhibit strong nonstationarity and heterogeneity.

PRELIMINARY STUDY PROPERTI AKUIFER TERHADAP SIMULASI NUMERIK PENURUNAN MUKA AIRTANAH DENGAN METODE BEDA HINGGA AKIBAT PEMASANGAN INCLINED DRAIN HOLE PADA LOW WALL PIT E BMO 2 PT. BC

2017 ◽  
Author(s):  
Pascalia Vinca Alvando ◽  
Achmad Darul ◽  
Dasapta Erwin Irawan
Keyword(s):  
Confined Aquifer ◽  
Parameter Adjustment ◽  
Drain Hole ◽  
Preliminary Study

Airtanah merupakan salah satu faktor penting yang berkontribusi terhadap ketidakstabilan lereng, air akan mengisi pori tanah sehingga tekanan air pori meningkat. Pada tahun 2009 di Pit E, PT. BC khususnya low wall pernah terjadi longsor, tujuan penelitian ini untuk mengetahui besar penurunan muka airtanah (drawdown) serta melakukan simulasi dalam waktu 8 tahun kedepan setelah upaya dewatering pada tahun 2016 dengan menggunakan sistem drain hole yang dipasang secara inclined. Model konseptual daerah penelitian dibangun dengan data pengamatan muka airtanah mula-mula, curah hujan, topografi dan properti hidrogeologi yang ditentukan berdasarkan asumsi teoriritis. Simulasi numerik menggunakan metode beda hingga dilakukan dalam dua skenario yaitu pada tiga IDH aktif dan penambahan tiga IDH di luar model pada akuifer terkekang dengan variasi kedalaman 50 m dan 80 m. Drawdown hasil simulasi kemudian dikalibrasi dengan perhitungan metode Theis. Hasil studi menunjukan nilai drawdown dari perhitungan Theis lebih kecil dari hasil simulasi numerik. Outflow pada pemodelan juga menghasilkan nilai yang lebih besar dari pengamatan di lapangan. Parameter adjustment berupa nilai konduktivitas hidraulik kemudian dilakukan untuk mengetahui pengaruhnya terhadap besar drawdown. Hasilnya menunjukan bahwa nilai konduktivitas hidraulik memiliki pengaruh yang signifikan terhadap perubahan besar drawdown. (Pre-print)Kata kunci: drawdown, confined aquifer, inclined drain hole, dewatering

The Pawnee Aquifer, Denver-Julesburg Basin, Northeastern Colorado

2017 ◽  
Vol 54 (1) ◽  
pp. 15-32
Author(s):  
Theresa Jehn-Dellaport ◽  
Tammi Renninger
Keyword(s):  
Total Dissolved Solids ◽  
Quality Data ◽  
Petrographic Analysis ◽  
Confined Aquifer ◽  
Water Quality Data ◽  
Well Drilling ◽  
Fine Grained ◽  
Water Wells ◽  
Geophysical Logs ◽  
Arkosic Sandstone

A partially defined and largely unexplored confined aquifer in Colorado, Nebraska, and Wyoming is identified regionally through interpretation of geophysical logs, well drilling, coring, petrographic analysis, and GIS interpretation. The aquifer is a fine-grained arkosic sandstone, with thickness ranging up to 1000 ft in some areas. The aquifer represents a significant water resource for ranching and other development in northeastern Colorado and may be a resource for Wyoming, and Nebraska. Nomenclature for this aquifer is suggested. Water wells penetrating the entire aquifer have produced up to 200 gpm. Water quality data is presented including total dissolved solids, boron, and microbial methane.

Reflex Epilepsy with Hot Water: Clinical and EEG Findings, Treatment, and Prognosis in Childhood

2020 ◽  
Vol 51 (05) ◽  
pp. 336-340 ◽  
Author(s):  
Fatma Hanci ◽  
Sevim Türay ◽  
Paşa Balci ◽  
Nimet Kabakuş
Keyword(s):  
Seizure Control ◽  
Hot Water ◽  
Reflex Epilepsy ◽  
Therapeutic Approaches ◽  
Water Age ◽  
Epileptiform Discharges ◽  
Neurology Clinic ◽  
Neuromuscular Development ◽  
The Brain ◽  
International League

AbstractHot water epilepsy (HWE) is a subtype of reflex epilepsy in which seizures are triggered by the head being immersed in hot water. Hot water or bathing epilepsy is the type of reflex epilepsy most frequently encountered in our clinic. We describe our patients with HWE and also discuss the clinical features, therapeutic approaches, and prognosis. Eleven patients (10 boys, 1 girl), aged 12 months to 13 years, admitted to the pediatric neurology clinic between January 2018 and August 2019, and diagnosed with HWE or bathing epilepsy based on International League Against Epilepsy (ILAE)-2017, were followed up prospectively for ∼18 months. Patients' clinical and electroencephalography (EEG) findings and treatment details were noted. All 11 patients' seizures were triggered by hot water. Age at first seizure was between 2 months and 12 years. Seizure types were generalized motor seizures, absence, and atonic. EEG was normal in two patients, but nine patients had epileptiform discharges. Magnetic resonance imaging of the brain was performed and reported as normal (except in one case). Histories of prematurity were present in two patients, unprovoked seizures in one, and low birth weight and depressed birth in the other. Patients with HWE have normal neuromuscular development and neurological examination results, together with prophylaxis or seizure control with a single antiepileptic drug, suggesting that it is a self-limited reflex epilepsy.

scholarly journals Investigating Groundwater Condition and Seawater Intrusion Status in Coastal Aquifer Systems of Eastern India

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1952
Author(s):  
Subrata Halder ◽  
Lingaraj Dhal ◽  
Madan K. Jha
Keyword(s):  
Groundwater Quality ◽  
Seawater Intrusion ◽  
Groundwater Level ◽  
Coastal Aquifer ◽  
Quality Data ◽  
Confined Aquifer ◽  
Groundwater Levels ◽  
Post Monsoon ◽  
Aquifer Systems ◽  
Sustainable Water Supply

Providing sustainable water supply for domestic needs and irrigated agriculture is one of the most significant challenges for the current century. This challenge is more daunting in coastal regions. Groundwater plays a pivotal role in addressing this challenge and hence, it is under growing stress in several parts of the world. To address this challenge, a proper understanding of groundwater characteristics in an area is essential. In this study, spatio-temporal analyses of pre-monsoon and post-monsoon groundwater-levels of two coastal aquifer systems (upper leaky confined and underlying confined) were carried out in Purba Medinipur District, West Bengal, India. Trend analysis of seasonal groundwater-levels of the two aquifers systems was also performed using Mann-Kendall test, Linear Regression test, and Innovative Trend test. Finally, the status of seawater intrusion in the two aquifers was evaluated using available groundwater-quality data of Chloride (Cl−) and Total Dissolve Solids (TDS). Considerable spatial and temporal variability was found in the seasonal groundwater-levels of the two aquifers. Further, decreasing trends were spotted in the pre-monsoon and post-monsoon groundwater-level time series of the leaky confined and confined aquifers, except pre-monsoon groundwater-levels in Contai-I and Deshpran blocks, and the post-monsoon groundwater-level in Ramnagar-I block for the leaky confined aquifer. The leaky confined aquifer in Contai-I, Contai-III, and Deshpran blocks and the confined aquifer in Nandigram-I and Nandigram-II blocks are vulnerable to seawater intrusion. There is an urgent need for the real-time monitoring of groundwater-levels and groundwater quality in both the aquifer systems, which can ensure efficient management of coastal groundwater reserves.

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