# Presentation: 504948

## Comparison of intrinsic susceptibility of public-supply wells to contamination among selected principal aquifer systems. 

**Leon Kauffman**
**National Water Quality Assessment Program (NAWQA)**

## Take Home Message

**Models can be used as the basis for defining susceptibility**
**Travel time is an important factor in susceptibility/vulnerability of wells**
**Intrinsic susceptibility is the starting point for looking at more specific questions**

## Overall Objectives of the TANC Study

**TANC**** ****- ****Transport of Anthropogenic and Natural Contaminants to Supply Wells**** **
**Study contaminants in **_**public-supply wells**_** with regard to:**
_**Occurrence**_** and **_**sources**_** **
**The effects of **_**natural processes**_** and **_**human activities**_
**Vulnerability assessments in **_**different settings**_** and at **_**different spatial scales**_
**Look at vulnerability in **_**unstudied areas**_** and to **_**emerging contaminants**_
_**Management effects**_** on water quality **

## TANC Large Scale Map

## Intrinsic Susceptibility

**Part of ground-water vulnerability definition**
**Describes the environment of water flow through the aquifer**
**How water ****enters**** **
**How water ****moves**** **
**What are the geochemical ****conditions**
**Independent of individual contaminants**

**GWV ********  f ****{        ****,****     ****,****         }**

**intrinsic**
**susceptibility**

- chemical
- input

- chemical mobility
- and persistence

**Notes:**
Chemical and physical

## Intrinsic Susceptibility Components

**Intrinsic Susceptibility Components**

- _Input_
- Location
- Type of recharge
- Soil Properties
- Unsaturated zone

- _Travel Through Aquifer_
- Travel Time (aquifer properties, recharge rate)
- REDOX conditions
- Temperature
- Rock Type

- _Output_
- Pumping Rate
- Open Interval
- Timing of Pumping

## Areas Contributing Recharge (ACR)

- _From regional MODFLOW models_
- 70 – 5000 km2
- Steady state

- Particle
- Tracked
- To well

- Particles tracked from water table to well
- Travel time associated with each pathline

- 100 – 1500
- particles per
- well

- 12-104 wells/study area
- Target all pumping quartiles

- 8 study areas
- 384 ACR simulated
- 112 with water quality from Source Water Quality Assessment

- ACR is defined by all particles terminating at a given well

**Notes:**
Wells from all quartiles of pumping
Use TANC logo to explain contributing area

## Travel Time Is an Important Component of Intrinsic SusceptibilityThere are different implications for different chemicals

**Travel Time Is an Important Component of Intrinsic Susceptibility****There are different implications for different chemicals**

_**Anthropogenic Contaminants**_
- (in general go down in time)

_**Natural Contaminants**_
- (in general go up in time)

- Other possibilities

- Other possibilities

**Notes:**
Age description
Give examples to clarify points

## Travel Time Distribution for One WellTravel times of water entering a single pumping wells can vary greatly 

**Notes:**
Color code points on cdf
Reinforce points from previous graph – link to interpretation

## Travel Time Distribution for One Study AreaTravel time distributions for different wells in a single study vary greatly

**Travel Time Distribution for One Study Area****Travel time distributions for different wells in a single study vary greatly**

**Summary**

**All Wells**

**Notes:**
Importance of well depth

## Travel Time for All Study Areas

- Basin and Range Aquifers
- Relatively thick, low recharge

- Glacial Deposit Aquifers
- Relatively thin, high recharge

## Comparison to NAWQA Data

**Comparison to NAWQA Data**

- Glacial-CT

- Glacial-OH

- Central Valley-CA

- Floridan-Fl

- Basin and Range-UT

- High Plains-NE

- Basin and Range-NV2

- Basin and Range-NV1

**Add effect of**
**well bore **
**leakage?**

**Notes:**
Add that this is the highest quartile
Label the extremes at least.  

## Uncertainty Discussion

**Models are not perfect**
**Heterogeneity**
**Short-circuiting**
**Limited number of wells**
**More confidence in study-unit summaries than individual wells**
**Process of increased understanding**
**Models help understand water quality results**
**Water quality results help improve models**
**Smaller scale studies improve understanding at larger scale**

## Building Block for Further Analysis

- Analysis can be explanatory or predictive
- Management can control inputs and outputs

**Notes:**
Travel time is a composite of several factors .

## Take Home Message

**Models can be used as the basis for defining susceptibility**
**Travel time important factor in susceptibility/vulnerability of wells**
**Intrinsic susceptibility is the starting point for looking at more specific questions**