Model-aided quantification of dissolved carbon and nitrogen release after  windthrow disturbance in an Austrian karst system

Hartmann, Andreas; Köbler, Johannes; Králík, Martin; Dirnböck, Thomas; Humer, Franko; Weiler, Markus

doi:10.5194/bg-13-159-2016

Cited by 50 publications

(42 citation statements)

References 78 publications

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“…VarKarst includes the karstic heterogeneity and the complex behaviour of karst processes using distribution functions that represent the variability of soil, epikarst and groundwater and was applied successfully at different karst regions over Europe (Hartmann et al, 2013a(Hartmann et al, , 2014b(Hartmann et al, , 2016. We use a simple linear relationship that takes into account effective porosities and base level of the groundwater wells (see Eq.…”

Section: Methodsmentioning

confidence: 99%

“…We present different calibration distributions to show the use of auxiliary data for parameter identifiability. Parameter ranges were chosen following previous experience with the VarKarst model (Hartmann et al, 2013a(Hartmann et al, , b, 2014b(Hartmann et al, , 2016. Besides the quantitative measure of efficiency, a split sample test (Klemeš, 1986) was carried out.…”

Section: Model Calibration and Evaluationmentioning

confidence: 99%

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Process-based modelling to evaluate simulated groundwater levels and frequencies in a Chalk catchment in south-western England

Brenner

Coxon

Howden

et al. 2018

Nat. Hazards Earth Syst. Sci.

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Abstract. Chalk aquifers are an important source of drinking water in the UK. Due to their properties, they are particularly vulnerable to groundwater-related hazards like floods and droughts. Understanding and predicting groundwater levels is therefore important for effective and safe water management. Chalk is known for its high porosity and, due to its dissolvability, exposed to karstification and strong subsurface heterogeneity. To cope with the karstic heterogeneity and limited data availability, specialised modelling approaches are required that balance model complexity and data availability. In this study, we present a novel approach to evaluate simulated groundwater level frequencies derived from a semi-distributed karst model that represents subsurface heterogeneity by distribution functions. Simulated groundwater storages are transferred into groundwater levels using evidence from different observations wells. Using a percentile approach we can assess the number of days exceeding or falling below selected groundwater level percentiles. Firstly, we evaluate the performance of the model when simulating groundwater level time series using a spilt sample test and parameter identifiability analysis. Secondly, we apply a split sample test to the simulated groundwater level percentiles to explore the performance in predicting groundwater level exceedances. We show that the model provides robust simulations of discharge and groundwater levels at three observation wells at a test site in a chalk-dominated catchment in south-western England. The second split sample test also indicates that the percentile approach is able to reliably predict groundwater level exceedances across all considered timescales up to their 75th percentile. However, when looking at the 90th percentile, it only provides acceptable predictions for long time periods and it fails when the 95th percentile of groundwater exceedance levels is considered. By modifying the historic forcings of our model according to expected future climate changes, we create simple climate scenarios and we show that the projected climate changes may lead to generally lower groundwater levels and a reduction of exceedances of high groundwater level percentiles.

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Section: Methodsmentioning

confidence: 99%

Section: Model Calibration and Evaluationmentioning

confidence: 99%

Process-based modelling to evaluate simulated groundwater levels and frequencies in a Chalk catchment in south-western England

Brenner

Coxon

Howden

et al. 2018

Nat. Hazards Earth Syst. Sci.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Due to the complexity of karst processes, karst models usually require more than six model parameters to reflect the most important hydrological processes. Some studies tried to compensate for this apparent lack of information by using auxiliary data such as gravimetric information (Mazzilli et al, 2012), artificial tracer experiments (Hartmann et al, 2012;Oehlmann et al, 2015), or hydrochemical information (Charlier et al, 2012;Hartmann et al, 2013bHartmann et al, , 2016. However, to our knowledge the problem of disinformative observations, either discharge observations or auxiliary information, has not been addressed explicitly in karst modelling studies.…”

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confidence: 99%

On the value of water quality data and informative flow states in karst modelling

Hartmann

Barberá

Andreo

2017

Hydrol. Earth Syst. Sci.

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Abstract. If properly applied, karst hydrological models are a valuable tool for karst water resource management. If they are able to reproduce the relevant flow and storage processes of a karst system, they can be used for prediction of water resource availability when climate or land use are expected to change. A common challenge to apply karst simulation models is the limited availability of observations to identify their model parameters. In this study, we quantify the value of information when water quality data (NO − 3 and SO 2− 4 ) is used in addition to discharge observations to estimate the parameters of a process-based karst simulation model at a test site in southern Spain. We use a three-step procedure to (1) confine an initial sample of 500 000 model parameter sets by discharge and water quality observations, (2) identify alterations of model parameter distributions through the confinement, and (3) quantify the strength of the confinement for the model parameters. We repeat this procedure for flow states, for which the system discharge is controlled by the unsaturated zone, the saturated zone, and the entire time period including times when the spring is influenced by a nearby river. Our results indicate that NO − 3 provides the most information to identify the model parameters controlling soil and epikarst dynamics during the unsaturated flow state. During the saturated flow state, SO 2− 4 and discharge observations provide the best information to identify the model parameters related to groundwater processes. We found reduced parameter identifiability when the entire time period is used as the river influence disturbs parameter estimation. We finally show that most reliable simulations are obtained when a combination of discharge and water quality date is used for the combined unsaturated and saturated flow states.

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“…In contrast to environmental agency monitoring programs, scientific programs often focus on headwater catchments free of point-sources and with relatively homogeneous landscape types (Fealy et al, 2010;McGonigle et al, 2014), where in-stream processes are often considered to be minimal (Salmon-Monviola et al, 2013). A comparison of export regimes in contrasting catchments representing different landscape types can be performed to investigate the effect of, for example, contrasting dominant land use, dominant flow paths or climate (Outram et al, 2014;Dupas et al, 2017;Minaudo et al, 2017), sometimes aided by the use of models (e.g., Dupas et al, 2016a;Hartmann et al, 2016). In headwater catchments, several studies have highlighted the important role of landscape heterogeneity within hillslopes (Herndon et al, 2015;Musolff et al, 2017), notably the crucial role of reactive zones such as riparian wetlands (Dick et al, 2015;Pinay et al, 2015;Tiwari et al, 2017) in controlling solute export regimes.…”

Section: Introductionmentioning

confidence: 99%

Carbon and nutrient export regimes from headwater catchments to downstream reaches

et al. 2017

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Abstract. Excessive amounts of nutrients and dissolved organic matter in freshwater bodies affect aquatic ecosystems. In this study, the spatial and temporal variability in nitrate (NO − 3 ), dissolved organic carbon (DOC) and soluble reactive phosphorus (SRP) was analyzed in the Selke (Germany) river continuum from three headwaters draining 1-3 km 2 catchments to two downstream reaches representing spatially integrated signals from 184-456 km 2 catchments. Three headwater catchments were selected as archetypes of the main landscape units (land use × lithology) present in the Selke catchment. Export regimes in headwater catchments were interpreted in terms of NO − 3 , DOC and SRP land-to-stream transfer processes. Headwater signals were subtracted from downstream signals, with the differences interpreted in terms of in-stream processes and contributions from point sources. The seasonal dynamics for NO − 3 were opposite those of DOC and SRP in all three headwater catchments, and spatial differences also showed NO − 3 contrasting with DOC and SRP. These dynamics were interpreted as the result of the interplay of hydrological and biogeochemical processes, for which riparian zones were hypothesized to play a determining role. In the two downstream reaches, NO − 3 was transported almost conservatively, whereas DOC was consumed and produced in the upper and lower river sections, respectively. The natural export regime of SRP in the three headwater catchments mimicked a point-source signal (high SRP during summer low flow), which may lead to overestimation of domestic contributions in the downstream reaches. Monitoring the river continuum from headwaters to downstream reaches proved effective to jointly investigate land-to-stream and instream transport, and transformation processes.

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Model-aided quantification of dissolved carbon and nitrogen release after windthrow disturbance in an Austrian karst system

Cited by 50 publications

References 78 publications

Process-based modelling to evaluate simulated groundwater levels and frequencies in a Chalk catchment in south-western England

Process-based modelling to evaluate simulated groundwater levels and frequencies in a Chalk catchment in south-western England

On the value of water quality data and informative flow states in karst modelling

Carbon and nutrient export regimes from headwater catchments to downstream reaches

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