Depth of Solute Generation Is a Dominant Control on Concentration‐Discharge Relations

Water Resources Research, Journal Year: 2020, Volume and Issue: 56(8)

Published: Aug. 1, 2020

Abstract Solutes in rivers often come from multiple sources, notably precipitation (above) and generation the subsurface (below). The question of which source is more influential shaping dynamics solute concentration cannot be easily addressed due to general lack input data. An analysis concentrations their dependence on discharge across 585 catchments nine countries leads us hypothesize that both timing vertical distribution are important drivers export at catchment scale. We test this hypothesis running synthetic experiments with a tracer‐aided distributed hydrological model. results reveal depth most control concentration‐discharge (C‐Q) relation for number solutes. Such shows C‐Q patterns vary dilution (Ca 2+ , Mg K + Na Cl − ) weakly enriching (dissolved organic carbon). imposes signature temporal dynamics, evident nutrients, adds uncertainty exponent relation.

Language: Английский

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Nitrate removal and young stream water fractions at the catchment scale

Hydrological Processes, Journal Year: 2020, Volume and Issue: 34(12), P. 2725 - 2738

Published: April 15, 2020

Abstract Despite extensive research on nitrate export and removal, nutrient contamination remains a major threat to water bodies worldwide. At the local scale, removal is governed by biogeochemical conditions that vary in space time, making integration entire landscapes critical. Water transit times have often been used describe solute transport, but relation between age at catchment scale still poorly understood. We test hypothesis peaks when fraction of young discharge its minimum, because occurs mostly under dry where deeper, older groundwater dominates streamflow. tested this exploring detailed quality record from Kervidy–Naizin (FR) comparing dynamics those conservative (chloride). find estimates are consistent with previous site they show good (inverse) correlation streamflow younger than 2.5 months. However, cannot be predict winter–spring period, no observed regardless age. While leads us reject our during winter it also suggests distributions their can possibly reveal distinct sources stream different hydrologic regimes relevant reactions.

Language: Английский

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Vertical Connectivity Regulates Water Transit Time and Chemical Weathering at the Hillslope Scale

Water Resources Research, Journal Year: 2021, Volume and Issue: 57(8)

Published: July 13, 2021

Abstract How does hillslope structure (e.g., shape and permeability variation) regulate its hydro‐geochemical functioning (flow paths, solute export, chemical weathering)? Numerical reactive transport experiments particle tracking were used to answer this question. Results underscore the first‐order control of variations (with depth) on vertical connectivity (VC), defined as fraction water flowing into streams from below soil zone. Where decreases sharply VC is low, >95% flows through top 6 m subsurface, barely interacting with rock at depth. High also elongates mean transit times (MTTs) weathering rates. however less an influence under arid climates where long drive equilibrium. The results lead three working hypotheses that can be further tested. H1 : depth MTTs stream more strongly than shapes; shapes instead younger . H2 arising high depths enhances by promoting deeper penetration water‐rock interactions; weakens larger hillslopes longer H3 regulates contrasts between shallow deep waters (C ratio ) export patterns encapsulated in power law slope b concentration‐discharge (CQ) relationships Higher leads similar versus chemistry ∼1) chemostatic CQ Although supporting data already exist, these tested carefully designed, co‐located modeling measurements soil, rock, waters. Broadly, importance subsurface indicate it essential regulating earth surface hydrogeochemical response changing climate human activities.

Language: Английский

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A comparison of catchment travel times and storage deduced from deuterium and tritium tracers using StorAge Selection functions

Hydrology and earth system sciences, Journal Year: 2021, Volume and Issue: 25(1), P. 401 - 428

Published: Jan. 27, 2021

Abstract. Catchment travel time distributions (TTDs) are an efficient concept for summarizing the time-varying 3D transport of water and solutes towards outlet in a single function age estimating catchment storage by leveraging information contained tracer data (e.g., deuterium 2H tritium 3H). It is argued that preferential use stable isotopes O H as tracers, compared to tritium, has truncated our vision streamflow TTDs, meaning long tails distribution associated with old tend be neglected. However, reasons truncation TTD still obscured methodological limitations. In this study, we went beyond these limitations evaluated differences between TTDs calculated using only (2H) or (3H). We also mobile (derived from TTDs) each tracer. For this, additionally constrained model successfully simulated high-frequency stream measurements 24 over same period (2015–2017). used forested headwater Weierbach (42 ha) Luxembourg. Time-varying were estimated consistently both tracers within framework based on StorAge Selection (SAS) functions. found similar 2H- 3H-derived estimates, despite statistically significant certain measures storage. The mean was at 2.90±0.54 years, 2H, 3.12±0.59 3H (mean ± 1 SD – standard deviation). Both suggested less than 10 % older 5 years. small previous studies other catchments, contrary prior expectations, more pronounced young water. could explained calculation uncertainties limited sampling frequency tritium. conclude do not seem systematically underestimate times Using radioactive reduced uncertainties. Tritium had ability reveal short streamflow. together better exploited specific about longer inherently contains due its decay. two thus different contents overall. slightly informative analysis, lower number samples. future, it would useful similarly test consistency estimates potential those catchments characteristics, considerable fraction since emphasize role decay discriminating younger

Language: Английский

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From Soils to Streams: Connecting Terrestrial Carbon Transformation, Chemical Weathering, and Solute Export Across Hydrological Regimes

Water Resources Research, Journal Year: 2022, Volume and Issue: 58(7)

Published: June 13, 2022

Abstract Soil biota generates carbon that exports vertically to the atmosphere (CO 2 ) and transports laterally streams rivers (dissolved organic inorganic carbon, DOC DIC). These processes, together with chemical weathering, vary flow paths across hydrological regimes; yet an integrated understanding of these interactive processes is still lacking. Here we ask: How what extent do subsurface transformation, solute export differ structure regimes? We address this question using a hillslope reactive transport model calibrated soil CO water chemistry data from Fitch, temperate forest at ecotone boundary Eastern mid‐continent grasslands in Kansas, USA. Model results show droughts (discharge 0.08 mm/day) promoted deeper paths, longer transit time, carbonate precipitation, mineralization (OC) into (IC) (∼98% OC). Of IC produced, ∼86% was emitted upward as gas ∼14% exported DIC stream. Storms (8.0 led dissolution but reduced OC (∼88% OC) production (∼12% lateral fluxes (∼53% produced IC). Differences shallow‐versus‐deep permeability contrasts smaller difference (<10%) than discharge‐induced differences were most pronounced under wet conditions. High (low vertical connectivity) enhanced fluxes. generally delineate hillslopes active producers transporters dry conditions, transporter

Language: Английский

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