NFRWSP: Groundwater Quality Analysis

Briefing

Jennifer Gihring SJRWMD

February 17, 2015

Water Supply Plan

Projected Demand

Estimated Conservation

Potential

Net Demand

Net Demand

Water Available

From Traditional

Sources

Alternative Water Supply

Projects Needed

= -

- =

Water Resource Assessment

Purpose of Water Resource Assessment

Quantify volume of fresh groundwater available for water supply, constrained by potential for unacceptable water resource

impacts.

Informs magnitude of project options needed to meet future demands and

avoid unacceptable impacts.

Water Resource Assessment Components

• Minimum flows and levels - Lakes - Springs - Flowing Systems - Note: Includes adopted MFLs; may include

proposed MFLs • Waterbodies without MFLs • Wetland vegetation • Groundwater quality • Water reservation

Use of Water Resource Assessment Components

Quantitative Estimate of

Groundwater Availability

Indication of Future Water

Resource Constraints

MFLs

Groundwater quality

Wetland vegetation

Waterbodies without MFLs

Water reservation

Groundwater Quality Assessment: Approach

• Statistical analysis of observed data to identify areas where current and future use of the Floridan aquifer system may be affected by groundwater quality

• Analysis compares well data to FDEP safe drinking water standards

• Identifies current areas of concern and potential future areas of concern through trend analysis

• Wells: Identify existing wells in NFRWSP that have groundwater quality data with adequate period of record

• Method: Calculated two metrics; relative to FDEP safe drinking water standards

• Results: Methods paper; tables; graphics

Groundwater Quality Analysis: Method

Groundwater Quality Analysis: Wells

• Reviewed groundwater quality data from 429 water supply/monitoring wells (406 SJR; 23 SR)

• Included monitoring wells and production wells used for AG, CII, LRA, DSS, PG, & PS

• Wells used in the analysis had an adequate period of record, consistent sampling, and clean QA/QC of laboratory results.

Groundwater Quality Analysis: Wells

• Criteria: FDEP safe drinking water standard of 250 mg/L chloride; 500 mg/L TDS

• Two metrics: - Wells that exhibit statistically significant trends

in chloride/TDS concentration (95% SL) - Year when wells would exceed standards for

chloride/TDS • Major ion/anion groundwater geochemistry

quantified on Piper diagrams for wells with significant upward trends

Groundwater Quality Analysis: Method

• Wells that exhibit statistically significant trends in chloride

• Identified via Mann-Kendall regression & Sen’s test (95% SL)

Groundwater Quality Analysis: Metrics

High Medium Low “Freshening”

> 3 mg/L/yr 1-3 mg/L/yr 0-1 mg/L/yr < 0 mg/L/yr

• Year when wells would exceed chloride/TDS standard

- High/medium risk wells - Regression carried trend through 2035; used

to determine year in which chloride concentration would equal or exceed 250 mg/L chloride

- Similar regression on TDS concentrations

Groundwater Quality Analysis: Metrics

Chloride Trends

Groundwater Quality Assessment: Results

133 wells exhibited

significant trend

92 increasing

33 high

35 medium

24 low 41 decreasing

• 6 wells exceeded 250 mg/L in 2015 • 11 additional wells projected to exceed 250 mg/L

by 2035.

Located in Duval, Flagler, Nassau, & St. Johns counties; 65 FAS & 3 SAS

TDS Trends

Groundwater Quality Assessment: Results

• Assessed stations selected from high/medium risk chloride wells

• 20 wells exceeded 500 mg/L in 2015 • 4 additional wells projected to exceed

500 mg/L by 2035.

Groundwater Quality Analysis: Results

Chloride Trend

High

Medium

Low

Groundwater Quality Analysis: Results

High Chloride Trend Wells: Use Type

PS

CII

LRA

Use of Water Resource Assessment Components

Quantitative Estimate of

Groundwater Availability

Indication of Future Water

Resource Constraints

MFLs

Groundwater quality

Wetland vegetation

Waterbodies without MFLs

Water reservation

Groundwater Quality Analysis: Status and Next Steps

• Districts complete edits on draft memo • Distribute to SAC for review (anticipated

by end of Feb.) • Districts make final edits • SAC recommendation

Questions?

Groundwater Quality Analysis