© Thomas Harter, University of California, Davis, 2009

Thomas Harter, Ph.D.University of California, Davis

ThHarter@ucdavis.edu

http://groundwater.ucdavis.edu

© Thomas Harter, University of California, Davis, 2009

Vulnerability Concept

adopted from: Fetter, 1988

Provide a basic planning tool thataccounts for and summarizes: T potent. contaminating activities T physical barrier effectiveness T travel time to well

© Thomas Harter, University of California, Davis, 2009

Overview

! What is vulnerability?<Vulnerability OF what?<Vulnerability TO what?

! Why do it?

! How?

! Which method works best?

! What area should be looked at?

! What if there aren’t enough data?

! Limitations & Role in GroundwaterManagement

© Thomas Harter, University of California, Davis, 2009

Groundwater Vulnerability:Definitions

L (Specific) Vulnerability (includes assessmentof existing sources)

L Susceptibility (intrinsic vulnerability, naturalvulnerability)

! “Possibility of percolation ofcontaminants into water tableaquifers”

! “Degree of endangerment of anaquifer”

! “Sensitivity of groundwater qualityto anthropogenic activities”

! “Likelihood for contaminants toreach a specified location in thegroundwater system”

© Thomas Harter, University of California, Davis, 2009

Why Assess GroundwaterVulnerability?

National Research Council, 1993

! Facilitate policy analysis and developmentat the local & regional level

! Provide program management

! Inform land use decisions

! Provide general education and awarenessof a region’s hydrogeological resources

© Thomas Harter, University of California, Davis, 2009

First Question to Clarify:Vulnerability OF WHAT?

! Water table?

! Specific aquifer?

! Specific well?

© Thomas Harter, University of California, Davis, 2009

What Factors Determine Vulnerability?Intrinsic Vulnerability

! Precipitation

! Runoff vs. Infiltration (slope, surfaceroughness, landuse)

! Soil type / unsaturated zone properties:permeability, infiltration capacity, claycontent

! Depth to groundwater

! Travel time from recharge at water tableto well site

! Aquifer characteristics (hydraulicconductivity, material)

© Thomas Harter, University of California, Davis, 2009

Appropriate Scale of Investigation

! Regional: mapping vulnerability

! Local: computing vulnerability of specificlocation

well

Warning! Vulnerability is always simplified into a(aerial view) map, but groundwater flow is 3-D!

DWSAP: T vertical movement: physical barrier effectiveness T horizontal movement: travel time to well via Zone A/B5/B10

© Thomas Harter, University of California, Davis, 2009

Intrinsic Vulnerability in DWSAPMethod

Intrinsic Vulnerability

! Precipitation

! Runoff vs. Infiltration (slope, surfaceroughness, landuse)

! Soil type / unsaturated zone properties:permeability, infiltration capacity, claycontent

! Depth to groundwater

! Travel time from recharge at water tableto well site

! Aquifer characteristics (hydraulicconductivity, material)

Physical BarrierEffectiveness(PBE)

Protection Zone

© Thomas Harter, University of California, Davis, 2009

from:Vrba and Zaporocec (eds.), 1994,Guidebook on Mapping GroundwaterVulnerability, International Associationof Hydrogeologist, Volume 16