Impact of karst areas on runoff generation, lateral flow and interbasin groundwater flow at the storm-event timescale

Abstract. Karst development influences the hydrological response of catchments. However, such an impact is poorly documented and even less quantified, especially over short scales of space and time. The aim of this article is thus to define karst influence on the different hydrological processes driving runoff generation, including interbasin groundwater flow (IGF) for elementary catchments at the storm-event timescale. IGFs are estimated at the scale of the river reach, by comparing inlet and outlet flows as well as the effective rainfall from the topographic elementary catchment. Three types of storm-event descriptors (characterizing water balance, hydrograph shape and lateral exchanges) were calculated for the 20 most important storm events of 108 stations in three French regions (Cévennes Mountains, Jura Mountains and Normandy), representative of different karst settings. These descriptors were compared and analysed according to catchment geology (karst, non-karst or mixed) and seasonality in order to explore the specific impact of karst areas on water balance, hydrograph shape, lateral exchanges and hydrogeological basin area. A statistical approach showed that, despite the variations with study areas, karst promotes (i) higher water infiltration from rivers during storm events, (ii) increased characteristic flood times and peak-flow attenuation, and (iii) lateral outflow. These influences are interpreted as mainly due to IGF loss that can be significant at the storm-event scale, representing around 50 % of discharge and 20 % of rainfall in the intermediate catchment. The spatial variability of such effects is also linked to contrasting lithology and karst occurrence. Our work thus provides a generic framework for assessing karst impact on the hydrological response of catchments to storm events; moreover, it can analyse flood-event characteristics in various hydro-climatic settings and can help with testing the influence of other physiographic parameters on runoff generation.

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Impact of karst areas on runoff generation, lateral flow and interbasin groundwater flow at the storm-event timescale

10.5194/hess-2020-229 ◽

2020 ◽

Author(s):

Martin Le Mesnil ◽

Roger Moussa ◽

Jean-Baptiste Charlier ◽

Yvan Caballero

Keyword(s):

Water Balance ◽

Groundwater Flow ◽

Water Infiltration ◽

Storm Event ◽

Hydrological Response ◽

Storm Events ◽

Runoff Generation ◽

Event Scale ◽

Event Time ◽

Karst Areas

Abstract. Karst development influences the hydrological response of catchments. However, such impact is poorly documented and even less quantified, especially over short space and time scales. The aim of this article is thus to define karst influence on the different hydrological processes driving runoff generation, including interbasin groundwater flow (IGF) for elementary catchments at the storm-event time scale. Three types of storm-event descriptors (characterising water balance, hydrograph shape and lateral exchanges) were calculated for the 20 most important storm events of 108 stations in three French regions (Cévennes Mountains, Jura Mountains and Normandy), representative of different karst settings. These descriptors were compared and analysed according to catchment geology (karst, non-karst, or mixed) in order to explore the specific impact of karst areas on water balance, hydrograph shape and lateral exchanges. A statistical approach showed that, despite the variations with study areas, karst promotes: i) Higher water infiltration from rivers during storm events; ii) Increased characteristic flood times and peak-flow attenuation; and iii) Lateral outflow. These influences are interpreted as mainly due to IGF loss that can be significant at the storm-event scale, representing around 50 % of discharge and 20 % of rainfall in the intermediate catchment. The spatial variability of such effects is also linked to contrasting lithology and karstification degree. Our work thus provides a generic framework for assessing karst impact on the hydrological response of catchments to storm events; moreover, it can analyse flood-event characteristics in various hydro-climatic settings, and can help testing the influence of other physiographic parameters on runoff generation.

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Interactive comment on “Impact of karst areas on runoff generation, lateral flow and interbasin groundwater flow at the storm-event timescale” by Martin Le Mesnil et al.

10.5194/hess-2020-229-rc2 ◽

2020 ◽

Author(s):

Anonymous

Keyword(s):

Groundwater Flow ◽

Lateral Flow ◽

Storm Event ◽

Runoff Generation ◽

Karst Areas

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Review of Le Mesnil et al., Impact of karst areas on runoff generation, lateral flow and interbasin groundwater flow at the storm-event timescale.

10.5194/hess-2020-229-rc1 ◽

2020 ◽

Author(s):

Anonymous

Keyword(s):

Groundwater Flow ◽

Lateral Flow ◽

Storm Event ◽

Runoff Generation ◽

Karst Areas

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Fine Sediment Modeling During Storm-Based Events in the River Bandon, Ireland

Water ◽

10.3390/w11071523 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1523 ◽

Cited By ~ 1

Author(s):

Juan T. García ◽

Joseph R. Harrington

Keyword(s):

Suspended Sediment ◽

Suspended Sediment Concentration ◽

Sediment Concentration ◽

Fine Sediment ◽

Storm Event ◽

Storm Events ◽

Event Scale ◽

Model Based ◽

Sediment Volume ◽

Bed Erosion

The River Bandon located in County Cork (Ireland) has been time-continuously monitored by turbidity probes, as well as automatic and manual suspended sediment sampling. The current work evaluates three different models used to estimate the fine sediment concentration during storm-based events over a period of one year. The modeled suspended sediment concentration is compared with that measured at an event scale. Uncertainty indices are calculated and compared with those presented in the bibliography. An empirically-based model was used as a reference, as this model has been previously applied to evaluate sediment behavior over the same time period in the River Bandon. Three other models have been applied to the gathered data. First is an empirically-based storm events model, based on an exponential function for calculation of the sediment output from the bed. A statistically-based approach first developed for sewers was also evaluated. The third model evaluated was a shear stress erosion-based model based on one parameter. The importance of considering the fine sediment volume stored in the bed and its consolidation to predict the suspended sediment concentration during storm events is clearly evident. Taking into account dry weather periods and the bed erosion in previous events, knowledge on the eroded volume for each storm event is necessary to adjust the parameters for each model.

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Driving factors of non-linearity rainfall-runoff relationships at different time scales in small Mediterranean-climate catchments

10.5194/egusphere-egu2020-3127 ◽

2020 ◽

Author(s):

Josep Fortesa ◽

Jérôme Latron ◽

Julián García-Comendador ◽

Miquel Tomàs-Burguera ◽

Jaume Company ◽

...

Keyword(s):

Mediterranean Climate ◽

Annual Rainfall ◽

Land Uses ◽

Hydrological Response ◽

Rainfall Runoff ◽

Runoff Generation ◽

Event Scale ◽

Annual Variability ◽

Temporal And Spatial ◽

Annual Scale

The complexity of Mediterranean fluvial systems is caused by the multiple temporal and spatial heterogeneity in the relationships between the natural and human-induced abiotic and biotic variables. Accordingly, Mediterranean rivers are characterized by a large heterogeneity in hydrological regimes promoting significant temporal and spatial differences in the hydrological response.This research investigates the non-linearity in the rainfall-runoff relationship at multiple temporal scales to achieve a better understanding of the hydrological response in representative small Mediterranean-climate catchments (i.e., < 10 km2). Rainfall-runoff was evaluated at annual and event scales. At annual scale, data from 43 catchments were collected to assess the influence of lithology on runoff response. At event scale, 203 events from 12 catchments were classified according to (a) seasonal occurrence (autumn, winter, spring or summer), (b) pervious or impervious lithology and (c) main land use (agricultural, agroforestry, forest or shrub). Besides, the inter- and intra-annual variability of the rainfall-runoff and the temporal downscaling (i.e., annual to event scale) was studied in Es Fangar Creek catchment (3.35 km2; Mallorca, Spain) during five hydrological years (2012-2017).The assessment of rainfall-runoff relationships at annual scale in small Mediterranean-climate catchments showed a strong linearity in the hydrological response due to the importance of the annual rainfall amount. However, lithology effects on runoff generation explained an increase of the scattering in these relationships because pervious and impervious materials triggered larger and lower runoff contribution respectively. Although the significant correlation between rainfall and runoff, Es Fangar Creek dataset illustrated a huge intra-annual variability of the rainfall-runoff relationship as seasonal rainfall and evapotranspiration dynamics controlled the runoff response. These dynamics were observed in the average seasonal runoff coefficients, decreasing from winter to summer. These differences should be considered as a starting point of the non-linearity generation in the rainfall-runoff relationships at event scale.At event scale, lineal and non-lineal performances were observed in the rainfall-runoff relationships in small Mediterranean-climate catchments suggesting that different factors conditioned the runoff response. Total rainfall was the most significant driver factor although the interaction between seasonality and the spatial diversity of lithology and land uses at catchment scale also played an important role on runoff generation. Thus, the highest correlations at seasonal scale were observed in those events occurred in winter and spring when the highest water reserves favoured the runoff response. Lithology caused higher dispersion in rainfall-runoff relationships at event scale in the set of small Mediterranean-climate catchments because pervious materials required higher antecedent wetness conditions. Agricultural land uses promoted the highest runoff generation.&#160;These findings will improve the comprehension of hydrological processes as the temporal downscaling of rainfall-runoff linked to the driven factors with the linearity and non-linearity knowledge is needed for accuracy and precision into hydrological modelling at event scale.This work was supported by the research project CGL2017-88200-R &#8220;Functional hydrological and sediment connectivity at Mediterranean catchments: global change scenarios &#8211;MEDhyCON2&#8221; funded by the Spanish Ministry of Science, Innovation and Universities, the Spanish Agency of Research (AEI) and the European Regional Development Funds (ERDF).&#160;

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Multiple Temporal Scales Assessment in the Hydrological Response of Small Mediterranean Catchments

10.20944/preprints201911.0185.v1 ◽

2019 ◽

Author(s):

Josep Fortesa ◽

Julian García-Comendador ◽

Aleix Calsamiglia ◽

Miquel Tomàs-Burguera ◽

Jérôme Latron ◽

...

Keyword(s):

Agricultural Land ◽

Biotic Factors ◽

Hydrological Response ◽

Rainfall Runoff ◽

Runoff Generation ◽

Temporal Scales ◽

Event Scale ◽

Hydrological Variability ◽

Abiotic And Biotic Factors ◽

Annual Scale

Mediterranean catchments are characterized by significant spatial and temporal hydrological variability caused by the interaction of natural as well human-induced abiotic and biotic factors. This study investigates the (non-)linearity rainfall-runoff relationship at multiple temporal scales in representative small Mediterranean catchments (i.e., < 10 km2) to achieve a better understanding of the hydrological response. Rainfall-runoff relationship was evaluated in 44 catchments at annual and event –203 events in 12 of these 44 catchments– scales. A linear rainfall-runoff relation was observed at annual scale with higher scatter in pervious than impervious catchments. Larger scattering was observed at event scale, although pervious lithology and agricultural land use promoted significant rainfall-runoff linear relations in winter and spring. These relationships were particularly analysed during five hydrological years in Es Fangar catchment (3.35 km2; Mallorca, Spain) as a temporal downscaling to assess intra-annual variability in which antecedent wetness conditions played a significant role in runoff generation.

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Understanding of Storm Runoff Generation in a Weathered, Fractured Granitoid Headwater Catchment in Northern China

Water ◽

10.3390/w11010123 ◽

2019 ◽

Vol 11 (1) ◽

pp. 123 ◽

Cited By ~ 3

Author(s):

Sihan Zhao ◽

Hongchang Hu ◽

Ciaran Harman ◽

Fuqiang Tian ◽

Qiang Tie ◽

...

Keyword(s):

Potential Evapotranspiration ◽

Stream Water ◽

Fractured Rock ◽

Northern China ◽

Storm Event ◽

Hydrograph Separation ◽

Storm Events ◽

Stable Water Isotopes ◽

Runoff Generation ◽

Streamflow Generation

Few of the classical field studies of streamflow generation in headwater watersheds have been conducted in catchments with thin soils and deeply weathered crystalline silicate bedrock. As such, the role of the (potentially very large) storage capacity of weathered, fractured rock in baseflow and storm event discharge remains poorly characterized. Here we present a study of streamflow generation in an upland semi-humid watershed (Xitaizi Experimental Watershed, XEW, 4.22 km2) dominated by baseflow feeding one of the main water supply reservoirs for the city of Beijing, China. This catchment is relatively dry (625 mm/yr precipitation, 480 mm/yr Evapotranspiration), but has strongly seasonal precipitation that varies in phase with strongly seasonal potential evapotranspiration. The catchment was instrumented with four weather stations and precipitation collectors, 11 deep wells drilled into the bedrock along three hillslopes, and additional soil moisture sensors and water samplers along one hillslope. In six storm events over two years, samples of rainfall, soil water (10–80 cm depth), groundwater, and stream water were collected with high frequency and analyzed for stable water isotopes (δ18O and δ2H). Tracer-based hydrograph separation showed that event water (precipitation) makes up the majority of the hydrograph peak above baseflow, and pre-event water contributions (on average) simply represent the steady release of groundwater. The quantity of event water corresponded to a very small effective contributing area (<0.2% of the catchment) that nevertheless showed a clear dependence on catchment wetness as measured by the streamflow. The streamflow itself was isotopically identical to the deep groundwater in wells. This suggests that the fractured, weathered, bedrock system dominates the production of streamflow in this catchment.

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Multiple Temporal Scales Assessment in the Hydrological Response of Small Mediterranean-Climate Catchments

Water ◽

10.3390/w12010299 ◽

2020 ◽

Vol 12 (1) ◽

pp. 299 ◽

Cited By ~ 4

Author(s):

Josep Fortesa ◽

Jérôme Latron ◽

Julián García-Comendador ◽

Miquel Tomàs-Burguera ◽

Jaume Company ◽

...

Keyword(s):

Land Use ◽

Mediterranean Climate ◽

Agricultural Land ◽

Hydrological Response ◽

Rainfall Runoff ◽

Runoff Generation ◽

Temporal Scales ◽

Event Scale ◽

Hydrological Variability ◽

Abiotic And Biotic Factors

Mediterranean-climate catchments are characterized by significant spatial and temporal hydrological variability caused by the interaction of natural as well human-induced abiotic and biotic factors. This study investigates the non-linearity of rainfall-runoff relationship at multiple temporal scales in representative small Mediterranean-climate catchments (i.e., <10 km2) to achieve a better understanding of their hydrological response. The rainfall-runoff relationship was evaluated in 43 catchments at annual and event—203 events in 12 of these 43 catchments—scales. A linear rainfall-runoff relationship was observed at an annual scale, with a higher scatter in pervious (R2: 0.47) than impervious catchments (R2: 0.82). Larger scattering was observed at the event scale, although pervious lithology and agricultural land use promoted significant rainfall-runoff linear relations in winter and spring. These relationships were particularly analysed during five hydrological years in the Es Fangar catchment (3.35 km2; Mallorca, Spain) as a temporal downscaling to assess the intra-annual variability, elucidating whether antecedent wetness conditions played a significant role in runoff generation. The assessment of rainfall-runoff relationships under contrasted lithology, land use and seasonality is a useful approach to improve the hydrological modelling of global change scenarios in small catchments where the linearity and non-linearity of the hydrological response—at multiple temporal scales—can inherently co-exist in Mediterranean-climate catchments.

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Challenges for Application of the Derived Distribution Approach to Flood Frequency

10.5194/egusphere-egu21-15044 ◽

2021 ◽

Author(s):

Ross Woods ◽

Yanchen Zheng ◽

Roberto Quaglia ◽

Giulia Giani ◽

Dawei Han ◽

...

Keyword(s):

Data Analysis ◽

Water Balance ◽

Flood Frequency ◽

Alternative Methods ◽

Rainfall Runoff ◽

Runoff Generation ◽

Distribution Method ◽

Event Scale ◽

Continuous Simulation ◽

Generation Mechanisms

Flood estimation in ungauged basins is important for flood design, and for improving our understanding of the sensitivity of flood magnitude to changes in climate and land cover. Flood estimates by current methods (e.g. statistical regression, unit hydrograph) have high uncertainty, even in places with dense observing networks (e.g. +/- 50-100% in the UK). Reductions in this uncertainty are being sought by using alternative methods, such as continuous simulation using hydrological models (spatially-distributed or lumped), and event-scale derived distribution approaches. The very significant challenges for reliable application of continuous simulation models in ungauged catchments are well described in the literature.The event-scale derived distribution approach also has challenges, which we explore below. The derived distribution approach at the event scale typically combines the following elements: a stochastic rainfall model, an event-scale rainfall-runoff model (including &#8220;losses&#8221; and a &#8220;baseflow&#8221; component), and a runoff routing model. In principle, every element of this approach may be considered as a (seasonally varying) random variable. The flood peak distribution is obtained by integrating over joint distributions of the model elements.First challenge: what is the physical basis for estimating the event runoff coefficient? In the 1970s, this was addressed using infiltration theory, but other runoff generation mechanisms are often more important. How do we connect our knowledge of seasonal water balance and runoff generation processes to the probability distribution of event runoff coefficients, and its seasonal variation? We suggest (i) begin with locations which are dominated by a small number of runoff generation mechanisms (ii) make use of existing theory on links between climate, catchment characteristics and seasonal water balance (iii) adapt relevant simple concepts of runoff generation which link seasonal water balance to runoff generation.Second challenge: how do we parsimoniously quantify the impacts of within-storm temporal rainfall patterns on the flood hydrograph? Existing approaches use stochastic rainfall models to explicitly generate (hourly) time series of rainfall; since catchments damp out high frequency forcing, we suggest that these rainfall series often contain excessive temporal detail and obscure the most informative interactions between rainfall and catchment response. We propose that we use stochastic models that can generate hydrologically relevant attributes of rainfall events (e.g. intensity/depth/duration, spatial and temporal moments), and then apply rainfall-runoff transformations which operate on rainfall moments, and do not require excess detail in temporal (or spatial) patterns of rainfall.Third challenge: What is an event? This is no problem for theoretical models, but it is hard as a data analysis question, and we need data analysis to implement and evaluate the derived distribution method. The event identification methods of engineering hydrology are subjective, require manual intervention and are poorly suited for large sample hydrology! We suggest the answer lies in the catchment&#8217;s response time.The underlying conceptual framework to link seasonal climate and hydrology to floods is already available (Sivapalan et al, 2005). What these challenges require is that we integrate and apply more of our existing hydrological concepts and knowledge to implement the process-based theory of flood frequency.&#160;

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