# Presentation: 061621

##  Sea Level Rise and Groundwater Sourced Community Water Supplies in Florida  CCSP Workshop: Climate Science in Support of Decision MakingNovember 14, 2005 Randall Freed, ICF Consulting John Furlow, Susan Herrod Julius,US EPA Global Change Research Program

## Background

- Sea Level Rise is among the most certain impacts of climate change
- Salt water intrusion is directly tied to sea level
- Community Water Supplies (CWS) are among the highest-value uses of water
- Site-specific hydrogeological assessment and monitoring is resource-intensive
- Decision support is needed to set priorities for assessing and protecting CWS

## Objectives

- Develop screening tools to characterize
- Vulnerability of groundwater-supplied CWS to saltwater intrusion
- Reliance on current aquifer
- Develop a priority-setting framework based on vulnerability and aquifer reliance
- Demonstrate the framework with coastal CWS in FL

## Relevance to CWS in Florida

-  Very high reliance on GW (~93% of population)
-  Strong water resource management programs
-  Excellent availability of data
- Lat and long of CWS
- DRASTIC scoring of aquifers
- Concern about salt water intrusion

**Source: Fernald, E.A., and E.D. Purdum, 1998. *****Water Resources Atlas of Florida*****. Institute of Science and Public Affairs, FSU**

## Assessing Vulnerability

- DRASTIC developed by EPA & Nat'l Water Well Assoc in 1987
- Widely applied to evaluate vulnerability to contamination
- Basic assumption: contamination is introduced at the ground surface and leaches into ground water via infiltration
- Modified to account for saltwater intrusion caused by sea level rise, which intrudes laterally (or in some cases upward) into aquifers

## Modifying DRASTIC 

- Original system -- vulnerability to surface pollution =  D + R + A + S + T + I + C, where:
- D - Depth to Water
- R - Net Recharge
- A - Aquifer Media
- S - Soil Media
- T- Topography
- I - Impact of Vadose Zone
- C - Conductivity

- Modified system: SLR Vulnerability =
- 	D + R + A +T + I + C + M + P, where
- D (Depth to Water) ranges from 1 (0-5 ft.) to 10 (100+ ft.)
**R (Net Recharge) ranges from 10 (0-2 in./yr) to 2 (10+ in./yr)**
- A (Aquifer Media) ranges from 2 (massive shale) to 10 (karst limestone)
- T (Topography) ranges from 1 (18% slope) to 10 (0-2% slope)
**I (Impact of Vadose Zone) ranges from 10 (confining layer) to 1 (karst limestone)**
- C (Conductivity) ranges from 1 (1-100 gpd/sq.ft.) to 10 (2000+ gpd/sq.ft.)
**M (Miles to Coastline) ranges from 1 (more than 4.35 miles) to 10 (less than 0.31 miles) **
**P (Potentiometric Surface, i.e., water-table elevation) ranges from 1 (greater than 3 feet) to 10 (less than 0.5 feet)**

## Evaluating Aquifer Reliance

- Reliance = 2 * log(Pop served) + AWS
- Population served
- Min = 25 (for a mobile home park)
- Max = 475,000 (for Tampa)
- Availability of alternative water supplies (AWS)
- Biscayne Aquifer (designated by SDWA as sole-source aquifer) = 10
- Water resource caution areas (designated by regional water management districts) = 5
- All others = 1

## Vulnerability and Reliance 

## Mapping Vulnerability and Reliance

## Pensacola

## Miami – Palm Beach

## Findings

- Key Findings
- High vulnerability/ high reliance CWS concentrated in Pensacola and Miami-Palm Beach areas
- Vulnerability index results appear to be consistent with known occurrences of salinity due to salt water intrusion
- Index could be simplified (to drop some DRASTIC factors) and still provide valid results – M and P are most important
- Limitations
- Applicability to confined aquifer systems
- Utility when data availability is limited

## Next Steps

- Identify decision makers best positioned to use this index
- Apply index to other states in Gulf Coast Region and Mid-Atlantic Region
- Develop risk management guidance based on the priority setting framework; identify decision points and actions (site-specific monitoring and risk assessment, long-term planning for alternate supplies, hydraulic controls)

## Contact Information

- Randy Freed
- ICF Consulting
- 9300 Lee Highway
- Fairfax, VA 22031
- Email: RFreed@ICFConsulting.com
- Phone: 703-934-3495

**Contact Information**