Groundwater Vulnerability

Is There a Groundwater Quality Is There a Groundwater Quality Problem?Problem?

• U.S. Geological Survey, IN Dept of U.S. Geological Survey, IN Dept of Environmental Management, USEPA, and Environmental Management, USEPA, and IN Dept of Natural Resources assembled IN Dept of Natural Resources assembled groundwater quality databasegroundwater quality database

• 18 pesticides and 5 “breakdown products” 18 pesticides and 5 “breakdown products” detected in 9% of samplesdetected in 9% of samples

Is There a Groundwater Quality Is There a Groundwater Quality Problem?Problem?

• Pesticides detected most oftenPesticides detected most often

– alachlor, atrazine, atrazine metabolitesalachlor, atrazine, atrazine metabolites

– di-ethylatrazine, di-isopropylatrazinedi-ethylatrazine, di-isopropylatrazine

– dicamba, 2,4-D, metolachlordicamba, 2,4-D, metolachlor

• Nitrate above 2 ppm in 50% of sampled Nitrate above 2 ppm in 50% of sampled wellswells

State Groundwater Management State Groundwater Management Plan - PresentPlan - Present

• Applies to pesticidesApplies to pesticides

• Education/OutreachEducation/Outreach

• Best management practicesBest management practices

• Sampling wellsSampling wells

State Groundwater Management State Groundwater Management Plan - Future?Plan - Future?

• Necessary regulatory management Necessary regulatory management approachesapproaches

• Restrictions on pesticide product use Restrictions on pesticide product use where neededwhere needed

DRASTICDRASTIC

DDepth to water tableepth to water table

RRecharge (aquifer)echarge (aquifer)

AAquifer mediaquifer media

SSoil mediaoil media

TTopography (slope)opography (slope)

IImpact of vadose zonempact of vadose zone

CConductivity (hydraulic)onductivity (hydraulic)

DRASTICDRASTIC

• Expert/numerical ranking modelExpert/numerical ranking model

• DRASTIC IndexDRASTIC Index

DDrrDDww + R + RrrRRww + A + ArrAAw w + S+ SrrSSw w + T+ TrrTTww + I + IrrIIw w + C+ CrrCCww

where r = Rating w = Weightwhere r = Rating w = Weight

DRASTIC Ratings for Depth DRASTIC Ratings for Depth to Waterto Water

Water TableDepth (ft)

DRASTICRating

0-5 10

5-15 9

15-30 7

30-50 5

> 100 1

DRASTIC Factor DRASTIC Factor WeightsWeights

Depth to Water Table 5

Recharge 4

Aquifer Media 3

Soil Media 2

Topography 1

Impact of Vadose Zone 5

Conductivity (Hydraulic) 3

DRASTICDRASTIC

DDrrDDww + R + RrrRRww + A + ArrAAw w + S+ SrrSSw w + T+ TrrTTww + I + IrrIIw w + C+ CrrCCww

8 * 5 + 2 * 4 + 8 * 3 + 6 * 2 + 7 * 1 + 1 * 5 + 7 * 38 * 5 + 2 * 4 + 8 * 3 + 6 * 2 + 7 * 1 + 1 * 5 + 7 * 3 = 117= 117

Data SourcesData Sources

• NRCS State Soils Geographic NRCS State Soils Geographic Database (STATSGO)Database (STATSGO)• Scale 1:250,000Scale 1:250,000• Info attribute tablesInfo attribute tables

• USGS DEM and geologyUSGS DEM and geology

• IGS hydrogeologic unit mapsIGS hydrogeologic unit maps

• IDNR and IGS water depthsIDNR and IGS water depths

DRASTIC Rating DRASTIC Rating TableTable

Vulnerability Rating Range

Low 1-100

Moderate 101-140

High 141-200

Very High > 200

Groundwater Groundwater Vulnerability IssuesVulnerability Issues

• Based only on hydrogeologic factorsBased only on hydrogeologic factors

• Does not consider land uses, Does not consider land uses, management, pesticide propertiesmanagement, pesticide properties

• High or very high vulnerability rating does High or very high vulnerability rating does not mean pesticides will be present in not mean pesticides will be present in groundwatergroundwater

• Low rating does not mean pesticides will Low rating does not mean pesticides will not be presentnot be present

0

10

20

30

40

50

Area (%)

Low

Moderate

High

Very

High

Vulnerability Category Areas

0

10

20

30

40

50

Wells with

Detects (%)

Low

Moderate

High

Very

High

Observed Pesticide Detections

BenefBenefitsits

• Provides reasonable estimates of Provides reasonable estimates of groundwater vulnerabilitygroundwater vulnerability

• Protects groundwaterProtects groundwater

• Targets sites for educationTargets sites for education

• Provides foundation for state groundwater Provides foundation for state groundwater management planmanagement plan

• Offers cost savings while improving Offers cost savings while improving groundwater protectiongroundwater protection