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Methodology for preparing hazard maps and vulnerability assessment of karst aquifers Kaan Tunçok Antalya, 2015 Module 2: Water Budget, Pressures and Impacts, Significant Water Management Issues, Monitoring, Characterization Report

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Page 1: Methodology for preparing hazard maps and vulnerability assessment of karst aquifers Methodology for preparing hazard maps and vulnerability assessment

Methodology for preparing hazard maps and vulnerability assessment of karst

aquifers

Kaan Tunçok

Antalya, 2015

Module 2: Water Budget, Pressures and Impacts, Significant Water Management Issues,

Monitoring, Characterization Report

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Groundwater from karst aquifers

Carbonate rock outcrops in Europe

most important drinking water resource in Europe: • 35 % of the land-surface• significant portion of the drinking water

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Karst Areas

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Conceptual Model of a Karst Aquifer

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Conceptual Model of a Karst Aquifer

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Characteristics of karst systems

highly heterogeneous and anisotropic. Interpolation and extrapolation of field data is more problematic

dual porosity due to fractures and solutional voids (conduits) and frequently by a triple porosity due to the additional presence of intergranular pores (matrix).

Groundwater storage takes place in pores and fractures, while conduits act as drains. contaminants can be transported very fast or stored for a very long time

temporal variations of the groundwater table often reach several tens of metres.

groundwater table is discontinuous and difficult to determine.

large and hydraulically connected over long distances.

karst springs often overlap and the flow paths proved by tracer tests often cross each other.

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Karst Systems

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• Models: predictions of groundwater levels

•Calibration: process of matching model

prediction to observed conditions

• Typically only done for groundwater levels

• In Karst it is critical that models are also calibrated to

• spring flows (regional)

• observable conduit velocities (tracer tests, observed responses to storms or collapse, etc)

Karst Systems

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Flow Through A Porous Media Aquifer Recharge DischargeIsotropic & Homogeneous

Karst Systems

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Flow Through A Karst Aquifer Recharge DischargeHeterogeneous - Anisotropic

Karst Systems

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No-Cave Model Cave Model

Quarry Area

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MAX

Pollution

1. When should the pollution start

Time

2. To which level?

3. For how long?

1. how long does it take until the contamination reaches the target

2. at what concentration level will the target be contaminated

3. for how long will the contamination last

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C

Time

B

A

A

B

Case a

Case b

target

AoBo

1. When should the pollution start

2. To which level?

3. For how long?

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COST Action 620

COST: Cooperation in Science and Technology

an approach to “vulnerability and risk mapping for the protection of carbonate (karst) aquifers”

sustainable water use based on long-term protection of water resources.

3 Working Groups (WG): WG1 developed an approach to the mapping of intrinsic vulnerability of

karst groundwater, based on sound scientific principles WG2 established a system to characterise the vulnerability of groundwater to

specific contaminants or groups of contaminants. WG3 worked on hazard and risk mapping.

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WG1

intrinsic vulnerability is a function of the geological, hydrogeological and hydrological properties of a system

by definition independent of the properties of specific contaminants.

Main intrinsic factors, which decide on the vulnerability of groundwater to contamination, are overlying layers, flow concentration, precipitation regime and properties of the aquifer

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WG2

specific vulnerability takes into account both the properties of the system and those of the contaminants, such as; nitrates, bacteria, chlorinated solvents and heavy metals.

Important processes for specific contaminant attenuation include; cation exchange, biodegradation, precipitation, filtration and decay.

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WG3

Hazards are activities and land-use practices that pose a threat to groundwater, such as agriculture, tourism, traffic and industry.

Risk maps consider the activities that present the “risk” that threatens groundwater.

They are obtained by synthesising the information presented on both hazard and vulnerability maps.

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Groundwater Vulnerability

Intrinsic vulnerability of groundwater to contaminants takes into account geological, hydrological and hydrogeological characteristics of an area, independent of the nature of the contaminants and contamination scenario.

Specific vulnerability takes into account the properties of a particular contaminant or group of contaminants in addition to the intrinsic vulnerability of the area.

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Resource Vulnerability For resource protection the GW surface in the aquifer is the target Pathway:

vertical passage through the layers above GW surface (unconfined) surface of the aquifer (confined)

Source Vulnerability For source protection water in a well or spring is the target Pathway: mostly horizontal flow within the aquifer

Groundwater Vulnerability

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Groundwater vulnerability

related to source–pathway–receptor model of contamination

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Groundwater vulnerability

Combination of Vulnerability, Hazard, and Consequence contribute to overall Risk.

Vulnerability evaluates pathway

Hazard evaluates source,

Consequence evaluates cost of losing resource at the receptor

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Specific vulnerability assessments include intrinsic properties as well as transport properties of specific contaminant(s).

Intrinsic vulnerability accounts only for hydrogeological characteristics, independent of properties of specific contaminants.

Each contaminant or group of contaminants behaves differently in different layers.

Groundwater vulnerability

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Intrinsic Vulnerability

3 aspects to be considered: advective transport time from the origin to the target; physical attenuation, e.g. by dispersion, dilution and porosity effects; relative quantity of contaminants which can reach the target (a portion of the

contaminants may never reach the target but leave the catchment via surface runoff).

WG 1 developed a conceptual framework for vulnerability assessment and mapping with special consideration of karst aquifers, the “European Approach”

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Specific Vulnerability

COST Action 620 also proposes an approach to Specific Vulnerability Mapping, which combines two types of information:

physical and chemical behaviour of contaminants (or groups of contaminants). different for each contaminant, but common for all field applications.

Information about physical and chemical properties of layers. different for each layer due to different layer combinations and particular

properties (tectonics, karstification etc.) for each monitoring point of the assessed area

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Vulnerability Assessments

D R A S U O

DRASTIC (Aller et al. 1987) INVAl-Hanbali and Kondoh (2008), Draoui (2008), Liggett et al. (2006)

GOD (Foster 1987) INV Gogu et al. (2003), Neukum and Hötzl (2007)

EPIK (Doerfliger et al. 1999) INVVías et al. (2005), Neukum and Hötzl (2007)

Aquifer Vulnerability Index (AVI) (Van Stempvoort et al. 1993) INVWei (1998), Alberta Land Resource Atlas of Alberta (2009)

Logistic Regression (Helsel and Hirsch 1992) SPVLaMotte and Greene (2007), Antonakos and Lambrakis (2007)

Numerical Models (e.g., MODFLOW [US Geological Survey]) INV or SPVFrind et al. (2006), Butscher and Huggenberger (2008)

a INV = intrinsic vulnerability; SPV = specif ic vulnerability.

Process Methods

b D = depth to w ater; R = recharge/inf iltration; A = aquifer characteristics (material, conductivity, etc.); S = saturated zone characteristics (e.g., f low patterns, layering, hydraulic gradient); U = unsaturated zone characteristics (material, hydraulic conductivity, soil moisture); O = other characteristics (e.g., explicit level of confinement, karst features, permeable pathw ays).

Light blue: parameters included in a given method. White boxes: parameters are not included. Purple boxes: possible inclusion of parameters, based on actual study.

Parametersb

Name and reference Typea Examples

Statistical Methods

Index Methods

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Hazard Mapping

7-step work plan starts from a definition and inventory of hazards leads to eventual production of hazard maps

hazard maps must be simple if they are to serve as efficient tools in planning and decision-making processes

hazard is defined as a potential source of contamination resulting from human activities taking place mainly at the land surface.

hazard inventory starts from a differentiation between three main types of land use: infrastructure, agricultural and industrial activities. to cover all various hazards that are considered relevant to groundwater to allow, mapping, evaluation and assessment of hazards in economically feasible

and practical manner

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Risk Analysis

“risk” is used for the likelihood of a specific adverse consequence. Following origin-pathway-target model risk depends on three elements:

(1) hazards and their probability that a hazardous event occurs, (2) vulnerability of geological sequence and (3) consequences for groundwater.

Risk assessment split in two parts: Step 1, “risk estimation”, analyse potential intensity of relevant impact reaching

groundwater. deals with point (1) and (2). Step 2, “risk evaluation”, focuses on adverse consequences. depend on the

groundwater sensibility, like flow condition, and on the ecological and economical value of the damages.

To separate different parts of risk assessment and to quantify their importance “risk intensity index (RII)”, “risk sensitivity index (RSI)” and “total risk index (TRI)”

were introduced.

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Verification and Validation

Independent of map-making process

can range from; physically testing mapped area using techniques as tracer tests, through to numerical models to ratify conceptual understanding represented by the map

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GW Vulnerability Mapping (Intrinsic)

DRASTIC Method, best suited to regional assessments (1:50 000 and 1:100 000 scales) and has been applied in a large number of countries worldwide. Underestimates vulnerability of fractured aquifers Weighting system is not scientifically based

GLA Method and its modification, PI-Method, used by the German states German State Geological Surveys (GLA) and the Federal Institute of Geosciences and Natural Resources (BGR) established a method for assessing

the protective function of the layers above the groundwater surface. does not address saturated zone within an aquifer. Does not take into account special properties of karst puts considerable emphasis on travel time as a measure of effectiveness of overlying layers to protect underlying groundwater Due to integration of infiltration via I factor, PI method suitable for all geological conditions.

EPIK-Method used by Swiss authorities developed at University of Neuchatel in the early 1990’s to address risks posed to groundwater quality in the mountainous Alpine Karst of Switzerland typically applied at a scale of 1:10,000 Formula is not always applicable Not defined for all hydrogeologic settings Transformation of vulnerability classes into source protection zones is disputable

COP-Method, “European Approach” in Karst areas Similar to PI-Method with the exception of Precip Parameters easy to acquire

Choice of most appropriate method data availability, spatial data distribution, scale of mapping, purpose of the map and hydrogeological setting.

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DRASTIC Overview

DRASTIC – guided by EPA Developed by EPA & National Water Well Assoc.

Purpose Over large areas, identify regions where groundwater is more or less

susceptible to impact from pollution.

Overview Simplified GW vulnerability model Qualitative Produces a relative-risk scale Applicable over large areas Used as a screening tool Results guide land development & resource protection For small, specific sites, more detailed assessment needed

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DRASTIC Method Assumptions

Assumptions:1. Contamination is introduced at the ground surface

2. Contamination is flushed into the groundwater by precipitation

3. Contamination has the mobility of water

4. Area being evaluated is 0.4km2 or larger

If these assumptions are not met, then DRASTIC is not appropriate

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DRASTIC Factors

Seven hydrogeologic factors used, form the acronym DRASTIC

D – Depth to Water

R – Net Recharge

A – Aquifer Media

S – Soil Media

T – Topography

I – Impact of Vadose Zone Media

C – Hydraulic Conductivity of Aquifer

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Weights & Ratings

Significance of each factor in contaminant transport varies Relative weight is assigned to each factor

Scale of 1 to 5 1 is least important factor 5 is most important factor

Each factor also has a Rating (1-10) applied according to a category or range of values.

Feature DrasticAgricultural

DrasticDepth to Water 5 5Net Recharge 4 4Aquifer Media 3 3Soil Media 2 5Topography 1 3Impact of Vadose Zone Media 5 4Hydraulic Conductivity of Aquifer 3 2

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DRASTIC – The Equation

Once ratings and weights have been applied, they are multiplied and added

DRASTIC equation:

DrDw + RrRw + ArAw + SrSw + TrTw + IrIw + CrCw = Pollution Potential

r = ratingw = weight

Results are symbolized on a map overlaying study area

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Each physical parameter is mapped spatially in GIS

Each map is rated according to its effect on vulnerability

subsequent parameter maps are combined to a final map

DRASTIC scores are grouped into vulnerability categories ranging from high to low.

Number of categories can vary.

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GLA-Method and PI- Method

GLA-Method (Hoelting (1995)) based on a point count system like DRASTIC model.

Goldscheider (2002) developed GLA-method into PI-method (European COST 620)

Unlike DRASTIC, GLA-method only takes unsaturated zone into consideration.

Attenuation processes in the saturated zone are not included in the vulnerability concept.

Degree of vulnerability specified according to protective effectiveness of soil cover and unsaturated zone.

Parameters considered for assessment of overall protective effectiveness are: Parameter 1: S- effective field capacity of the soil (rating for SeFC in mm down to 1m depth) Parameter 2: W- percolation rate Parameter 3: R- rock type Parameter 4: T- thickness of soil and rock cover above the aquifer Parameter 5: Q- bonus points for perched aquifer systems Parameter 6: HP- bonus points for hydraulic pressure conditions (artesian conditions)

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Protective effectiveness (PT) PT = P1 + P2 + Q + HP

Where P1 - protective effectiveness of soil cover:

P1 = S*W

P2 - protective effectiveness of unsaturated zone (sediments or hard rocks): P2 = W* (R1*T1 + R2*T2 + ........ + Rn*Tn).

GLA-Method

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Based on the German mapping approach, highest value assigned for factor W, is 1.75 for a groundwater recharge of less than 100mm/a.

A modified scale for the factor W was introduced which reflects low amounts of groundwater recharge in many areas.

Groundwater Recharge (mm/a)

Factor W

>400 0.75

>300 – 400 1.00

>200 – 300 1.25

>100 – 200 1.50

>50 – 100 1.75

>25 – 50 2.00

≤ 25      2.25

GLA-Method

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PI-method

modification of GLA method, integrates protective cover (P) and infiltration factor (I).

Protective cover and infiltration factor are separately mapped as individual maps and then combined to GW vulnerability map.

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PI map

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EPIK Method

Development of the Epikarst, Effectiveness of the Protective cover Conditions of Infiltration and Development of the Karst network.

For each parameter a standard weighting coefficient is used.

Classification for each parameter and area is obtained by systematic mapping for these parameters.

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EPIK Method

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EPIK Method

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Standard values for the EPIK parameters

Standard weighing coefficients for EPIK parameters

overall protection index F

EPIK Method

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Non-existent

High vulnerability

Medium Vul.

Low Vul.

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European Approach

Four factors are considered: Overlying layers (O), Concentration of flow (C), Precipitation regime (P) and Karstic network development (K).

- O, C and K: internal characteristics of the system- P: external stress applied to the system.

- Resource vulnerability mapping (top of saturated zone)

O, C and P taken into consideration

- Source vulnerability mapping (karst water supply such as a borehole or a spring)

K (in addition)

COP – Index = (C score) * (O score) * (P score)

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European Approach

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Overlying layers (O factor)

consist of up to four types of layers: topsoil, subsoil, non karst rock and unsaturated karst rock. topsoil (layer 1)

biologically active zone of weathering of the earth crust. composed of minerals, organic substance, water, air and living matter. Effective field capacity (eFC) to assess protective function

subsoil (layer 2) granular, non-lithified material below the topsoil, for example Quaternary deposits

made of gravel, sand, silt and/or clay or alluvium. grain size distribution to evaluate protective function

non karst rock (layer 3) ithified, non karstified rocks, for example sandstone, schist, shale, basalt

unsaturated karst rock (layer 4) unsaturated (vadose) zone of the water bearing, karstified unit.

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O factor takes into account protective function of unsaturated zone and properties of the layers soil (OS – soil subfactor) and unsaturated zone ( OL- lithology subfactor).

Both are separately calculated and then added to obtain O factor: O = OS + OL

European Approach

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C Factor

In some karst areas, surface runoff is concentrated and channeled into swallow holes

Represents degree of concentration of flow water towards karstic conduits that are directly connected with the saturated zone and thus indicate how the protection capacity is reduced.

2 scenarios. Scenario 1: C is calculated based on

parameters distance to the swallow hole (dh), distance to the sinking stream (ds) and combined effects of slope and vegetation (SV): C = dh * ds * sv

Scenario 2 occurs in areas where aquifer is not recharged through a swallow hole. C factor is calculated based surface features (sf) and slope (s) and combined effects of slope and vegetation (sv): C = sf * sv

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P factor

Represents total quantity, frequency, duration of precipitation as well as intensity of extreme events, which are considered to be chief influencing factors for the quantity and rate of infiltration.

Obtained by summation of subfactors: quantity of precipitation (PQ) and intensity of precipitation (PI): P = PQ + PI

The calculation of the subfactor PI is based on the assumption that a higher rainfall intensity results in an increased recharge and thus a reduced protection of the groundwater resource.

The “mean annual intensity” or PI is calculated Mean annual intensity = mean annual precipitation (mm)

Mean number of rainy days

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COP Method

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Intrinsic vulnerability treats all substances as having similar transport behaviour as that of water,

specific assessment additionally deals with differences between particular contaminant behaviour and their specific interaction host rock.

European approach for specific vulnerability. Based on

principles of physical and chemical properties of layers and related processes properties of contaminants and related processes

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European approach for specific vulnerability

Specific weighting factor

(S factor) an additional factor for

correcting the intrinsic vulnerability values,

layer conditions (potential process in respect to subsurface conditions)

contaminant attenuation capacities (potential process of the particular contaminant)

contaminant factor concerns the physical and chemical contaminant properties.

Each contaminant has its own contaminant factor

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Specific source and resource vulnerability maps

aim is to use criteria from intrinsic vulnerability assessment of an area, and to determine a positive specific attenuation index for each point in a catchment.

Specific weighting factor maps show spatial distribution of specific attenuation for individual contaminant.

S factor has to be linked to intrinsic overlying layers factor (O factor), in order to obtain groundwater resource specific vulnerability maps. both the O factor and karst network factor (K factor), for compiling source specific vulnerability maps

S factor modifies and upgrades the values of both intrinsic factors.

Specific vulnerability assessment must be based on a set of intrinsic information.

Specific vulnerability maps can be transformed into risk maps by the inclusion of hazards, probability of contaminant spills value of groundwater resources.

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Saturated karst layer may be very important for intrinsic vulnerability (high advection, high dilution),

it plays only a minor role for specific processes, due to their very low contribution in saturated conduit flow.

Specific maps for source protection are unlikely to differ significantly from those for resource protection.

Each specific contaminant requires an individual attenuation assessment, using a standard 10-step procedure.

3 main factors: contaminant factor (steps 1 and 2), layer factor (steps 3 to 9) and resulting specific weighting factor (step 10)

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Specific vulnerability method

10-step plan for implementation of Specific vulnerability method

Step 1 Choice of contaminant and related processes Step 2 Evaluation of contaminant process indices Step 3 Evaluation of layer process indices Step 4 Fitting of layer and contaminant process indices Step 5 Process weighting Step 6 Summation of processes Step 7 Consideration of layer thickness Step 8 Consideration of hydraulic properties Step 9 Summation of layers Step 10Specific attenuation classes

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Procedure for specific attenuation evaluation

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Rating and Weighting are focused on the most important processes and parameters use a qualitative judgement.

Hydraulic property evaluation is also based on greatly simplified considerations, with a discrete differentiation between diffuse and preferential flow.

Some of the input parameters are not stable in time.

Use of validation tools is clearly envisaged. Computer modelling Artificial and natural tracing for simulating behaviour of specific contaminants.

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Statistical methods

Calculation of probability of a particular contaminant exceeding a certain concentration.

start with analysis and mapping of water quality from known sites (e.g., samples from wells or soil).

integrate into linear regression models in which contaminant concentration is related to a series of factors such as geology, well depth, and/or land use.

produce spatially distributed probabilities of exceedance, rather than a categorized high, medium, and low ranking.

may be used instead of indexing methods when there is specific interest for a particular contaminant over a large area and sufficient data exists on water quality in relation to the contaminant in question.

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Process-based methods

physically based and do not provide an output of simple relative values (e.g., SAAT, SWAT, MODFLOW).

Surface to Aquifer Advection Time (SAAT) estimates average time required for a particle of water to travel from a point at ground to the aquifer

Soil and Water Assessment Tool (SWAT): USDA

MODFLOW: USGS 3D finite-difference groundwater model

use deterministic approaches to estimate time of travel, contaminant concentrations, and duration of contamination to quantify areas of high and low vulnerability

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Groundwater assessment requirements

Vulnerability classification

Groundwater assessment requirements

Low

Groundwater contamination assessment report: Requires a desk study to identify hazards and risk to groundwater or the environment, and the need for any further action.

Low-moderate

Site investigation with monitoring:Requires limited site investigation, groundwater monitoring, testing, and delineation of flow system in addition todesk study.

Moderately high

Detailed site investigation and monitoring:Requires more detailed site investigation including ongoing monitoring and protection design factors (e.g., natural attenuation, physical barriers) in addition to requirements above.

High

Demonstrated remedial action plan: Requires a remedial action plan that analyzes effectiveness of remediation in achieving designated water quality criteria, and financial capacity of the responsible party to enact the plan.

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GENESIS project

funded under the thematic area Environment (including Climate Change) of the Seventh Framework Programme of the European Community for research, technological development and demonstration activities (2007-2013).

Total Cost: 9.170.600 €

Duration: 60 months (start 1. April 2009)

Consortium: 25 partners from 17 countries

Project Coordinator: Prof. Bjørn Kløve, Norwegian Institute for Agricultural and Environmental Research (Bioforsk), NORWAY

www.thegenesisproject.eu

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time frame of year 2015 for achieving a good status of groundwater bodies is unrealistic mostly due to the considerably long time scales of contaminant transport in groundwater systems.

Consequently, the vulnerability assessment methods have to address temporal and transient aspects of contaminant spreading and to represent them in a quantitative manner in vulnerability indices

In order to support groundwater managers and decision makers in application of this physically-based approach to vulnerability assessment a decision tree is proposed.

GENESIS project

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WFD and GWD aim at preservation and improvement of groundwater status.

Groundwater bodies are classified as being or not being at risk of failing to meet these objectives.

Those at risk are subject to more precise risk assessments outlined in CIS No. 26 concept of vulnerability is considered in the context of the source-pathway-receptor. within this conceptual framework vulnerability is related to the pathway part of the risk

assessment scheme.

Assessment of vulnerability cannot be abstracted from characteristics of the pressures on the groundwater body (CIS No. 3) and

from characteristics of the receptors of impacts (CIS No. 18). Identification of the source(s) and receptor(s) is thus an indispensable component of the problem statement.

GENESIS project

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groundwater vulnerability problems and their relevance to GENESIScase studies.

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Specific Vulnerability

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Work plan for hazard maps

Step 1: Definition and Inventory of Hazards

Step 2: Hazard Data Requirements

Step 3: Rating and Weighting of Hazards

Step 4: Graphical Interpretation

Step 5: Mapping Techniques

Step 6: Data Evaluation

Step 7: Production of Hazards Maps

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Step 1: Hazard types and hazard classification

emission of air pollution; discharge of waste water and non aqueous organic liquids; storage and disposal of solid waste; excavations in connection with mining, foundation and construction

work; distribution of fertilizers and pesticides.

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Classification of hazards for GW protection

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Step 2: Hazard Data Requirements

Each type of hazard requires information on the following: process or nature of activity (production, storage, etc.); type of harmful substances; amount of substances which can be released; age and status of installations and plants.

Collection of information on various hazards to be based on combined use of: extraction from topographic maps; evaluation of aerial photos; collection of data from archives and agencies; field surveying; direct inquiries with companies, etc.

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Step 3: Rating and Weighting of Hazards

Necessary in the hazard assessment computation to arrive at a classification of the hazards: establish a weighting system to allow comparison between different type

of hazards within a relative assessment scheme, and is suitable to formulate possible groundwater protection zones or measures;

establish a ranking procedure for hazards of same type, which fits above mentioned criteria;

develop an assessment scheme to determine likelihood that a release of contaminant may take place in connection with a hazard;

define a mathematical algorithm to calculate potential degree of harmfulness for each hazard by considering weighting and ranking coefficients as well as probability term to represent likelihood of a contamination event.

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Weighting Procedure

The main criteria for weighting different hazards concern toxicity of relevant substances associated with each type of hazards as well as their properties regarding solubility and mobility.

They determine the weighting coefficient or the “harmfulness of a hazard to groundwater (H)”.

Three parallel approaches were considered by WG3 to estimate harmfulness of each hazard type.

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Approach 1, judge importance of each type of hazards by assigning figures between 0 and 10 according to their relevance in the respective test areas

Approach 2, preliminary weighting factors were calculated with a formula, which is used in connection with Italian vulnerability assessment scheme SINTACS.

based on EU Directive on toxic sources of contamination. “contamination index” is calculated for each hazard by adding up potential “environmental

impacts caused by specific human activities”, which are considered most important parameters to assess degree of harmfulness for groundwater.

different environmental impacts are grouped according to EU classification of waste hazards and water demand generated by human activities.

environmental impact associated with each of these causes of environmental impact is assigned a score ranging from 0 to 3 according to general experience on environmental impact.

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Approach 3, six experts were asked to assign weights to all the hazards appearing on the inventory list. They were asked to do so independently from the previous approaches and only according to their experience and the general toxicity. It was requested that values should be distributed with a range from 0 (not harmful) to 100, indicating extreme harmfulness.

Finally, using the results obtained from each of the three approaches, a weighted average was calculated for every hazard type

If it is necessary to extend the list of hazards provided by Cost 620, it is possible to follow the second approach

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Ranking Procedure

For a comparison between hazards of the same type, once again all the different factors influencing the degree of harmfulness have to be considered.

ranking procedure should neither lead to a drastic minimization nor excess overvaluing within a same category of hazards

to maintain a fair balance with the average weighting values, it is recommended that these weighting values should be changed only slightly by multiplying them with a ranking factor between 0.8 and 1.2 in order to indicate low or high amounts respectively of toxic substances compared with the general average

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Likelihood of groundwater contamination

This coefficient provides an assessment of the probability for a contamination event to occur.

If no information on the above mentioned factors is available, then Rf=1.

Zero, there is no risk of groundwater contamination, One, there are no reasons known to reduce the likelihood of an impact

to the groundwater

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Calculation of the Hazard Index (HI)

HI = H Qn Rf

HI hazard index, H weighting value of each hazard, Qn ranking factor (0.8 to 1.2) and Rf reduction factor.

possible range of the hazard index HI from 0 to 120 scores. a subdivision of no more than five or six classes is recommended.

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mapping procedure

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Risk Assessment

Risk: possible contamination as a result from a hazardous event

Risk of contamination depends on: hazard posed by a potential polluting activity (equivalent to origin) intrinsic vulnerability of groundwater to contamination (equivalent to pathway) potential consequences of a contamination event (target is GW)

Risk assessment: evaluation process for estimating potential impact of a chemical, biological or physical agent on groundwater

Assessment has to take the following into account: likelihood of an impact intensity of a potential impact with which it affects GW (impact intensity) sensitivity of GW wrt impact (groundwater sensitivity)

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Risk intensity assessment What can go wrong? Hazard identification and associated outcomes How likely is it to go wrong? Estimation of probability of these outcomes How far can hazardous impact reach the target? Estimation of possible impact reduction

Risk sensitivity assessment What would happen to the target if it does go wrong? Evaluation of the sensitivity of

target against the impact (consequence analysis) Is the risk acceptable and can it be reduced? Evaluation of damage wrt environmental

and economic value

Risk management What decisions arise from risk assessment? What control measures are needed to minimize risk?

Sustainable risk management

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Risk Map

Risk map: A method of summarising result total risk assessment with regard to spatial distribution of risk.

Risk intensity map: result of risk intensity assessment. combination of hazard map and vulnerability map.

Risk sensitivity map: result of risk sensitivity assessment. depicts sensitivity of GW against a certain impact under consideration of economical and ecological

value of the resource.

Risk map represents all aspects of assessment procedure.

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Risk assessment

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Risk intensity assessment

high vulnerability and low risk index, if no significant pollutant loading

high risk index value and low vulnerability, if pollutant loading is exceptional or if possibility of bypassing in less vulnerable areas.

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Risk intensity maps

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Key Map Validation Tools

Hydraulics and spring hydrographs BFW: base flow water, RIW: rapid infiltration water, RDIW: rapid delayed infiltration water CIW: concentrated infiltration water SIW: slow infiltration water

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Natural Tracers can be grouped into: Ions and organic molecules in solution Dissolved gases like radon and CO2 Environmental isotopes Particles, including turbidity and bacteria/microorganisms

Do not provide information form precisely known injection points like artificial tracers, can provide information on an aquifer wide basis

Artificial Tracers:

Three basic aspects have to be considered: Travel time of a contaminant from the origin to the target; Relative quantity of the contaminant that can reach the target; Attenuation processes decreasing the contaminant concentration.

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Analytical and numerical modelling: data are needed in order to proceed Geometrical and geological data for spatial discretisation of model domain Parameters for characterising discretised zones for each simulated

process Stress-factors influencing groundwater quantity (infiltration, pumping and

re-injection rates) and groundwater quality (input/output of contaminant fluxes)

Historical data (distributed both spatially and through time) relating to groundwater quantity (measured piezometric levels, water pressures, spring discharges, hydrographs, tracer tests) and groundwater quality (measured concentrations, chemographs, tracer tests).