# Springsheds of the 

# Santa Fe River Basin Sam B. Upchurch, Ph.D., P.G. Jian Chen, P.G. Crystal R. Cain SDII Global Corporation Tampa, Florida May 9, 2008

## Springshed
• Area contributing water to the discharge of a spring. • Includes

– Groundwater basin and
– Surface water basin

# Sample Map – Ichetucknee Springs
• Based on high resolution data • 1 -foot contour interval • Note that basin appears to pass under the Northern Highlands Upchurch and Champion (2005)

## Project Expanded to Two Phases

• Phase I

– Literature review
– Springshed delineation using existing upper Floridan potentiometric surface data from 2000
– Capture zones modeled using USGS and SRWMD groundwater flow models
– Reported on in June 2007
– Comments by Alachua County and FDEP

## Project Expanded to Two Phases
• Phase II

– Alachua County developed • High -resolution monitoring network • “Newberry Plain” of the Western Valley
– Sites located and surveyed
– Water levels measured in September 2007

# Project Expanded to Two Phases

– Phase II Continued • Geostatistical analysis to evaluate adequacy of monitoring network • Delineation of springsheds using high resolution monitoring network and 1 foot contours • Revision of report

## Area Overview

## Spring Clusters

## Physiographic Provinces

## Aquifer Confinement

## 2000 Potentiometric Surface

## Why Index Period of 2000? • The District’s groundwater flow model was calibrated to conditions in 2000 (Schneider and others, 2008), • 2000 was a dry year, so the potentiometric surface should have maximum relief and enhance ability to identify springsheds, and • Potentiometric data were relatively abundant .

## Springshed Delineation from Potentiometric Surface Data

• Well density is low in many critical areas • Available data contoured at 1 -foot interval • Contour map reconciled with known geology and USGS 2000 potentiometric surface

# Results B = Betty Spring cluster (north) A = Ichetucknee cluster H = Santa Fe Rise G = Hornsby-Columbia Spring cluster F = Poe-July Springs cluster E = Ginnie Springs cluster D = Sunbeam and Wilson Spring clusters C = Betty Spring cluster (south)

# Phase I Delineation Evaluation • Individual springsheds could not be identified because of

– Low monitoring well density
– High hydraulic conductivities and/or conduit flow results in relatively flat potentiometric surfaces near springs 

### • Springsheds could be identified for spring clusters

# Phase II, High - Resolution Springshed Delineation

• Mix of domestic wells, monitoring wells and piezometers • Includes

– Alachua County network,
– SRWMD WARN data,
– Danone/Coca-Cola wells

# Regional Potentiometric Surface • Distal wells provide boundary conditions • Reproduces 

### potentials in Newberry 

### Plain well

# Local Potentiometric Surface

• Focus on Newberry 

### Plain area • Note coneof 

### depression near 

### Gainesville

# Geostatistical Analysis
• Used to evaluate monitoring network in terms of

– Spacing of sampling points
– Need for additional sampling points
– Level of uncertainty associated with contour maps (I.e., potentiometric surface maps)
– Identification of anomalous data points

# Geostatistical Analysis

• Two steps

– Structural analysis • “Rules” of contouring • Detection of local variability • Uncertainty related to distance between sampling points
– Kriging • Map showing property distribution • Map showing uncertainty distribution • Map that identifies “outliers”

# Variogram
• Reflects model developed to characterize variability between sample pairs as a function of sample point spacing Nugget = 15 ft. 2 Range =350,000 ft. Sill =800 ft. 2 Nugget Range Sill

# Nugget Effect

• Caused by local variability

– Short term
– Transient
– Caused, in part, by sampling over a month period Gilchrist County Well

# Kriged Potentiometric Surface

# Kriged Standard Deviation

• Shows the distribution of uncertainty • Units of feet based on KSD (kriged standard deviations)

# Residuals
• Observed water level
– kriged water level • Helps identify outliers

# Network Evaluation
• Network is good within the Newberry Plain and vicinity • There is no need for additional wells 

### in the Newberry Plain area • There is an uncertainty (the nugget) 

### when contouring between wells of up to ± 10 feet because of local variability

# High - Resolution Springshed Delineation

# Springshed Evaluation
• High - resolution monitoring allows for resolution of springsheds with much more confidence than with the typical 

### regional potentiometric surface map • Confidence in springsheds of major spring clusters ranges from moderate to high • There is still a problem with where 

### the water in the southern part of the Newberry Plain discharges

# Modeling Capture Zones
• Identify spring contribution areas through groundwater flow modeling • USGS Megamodel by Sepúlveda (200 2) • Suwannee River WMD Model by Schneider and others (2008) 

### • 5, 10, 100 year capture zones attempted • Utilized inverse particle tracking to 

### model capture zones

# Why Use Two Models?

• Models rarely agree • Conservative to include results of all models • Models differ in features and construction Rainbow Springs 10-year travel times

# USGS Megamodel

• Regional model • 3 - D model • 5,000 x 5,000 ft. cells • Layers
– 1, Surficial Aquifer, is a constant head boundary
– 2, Intermediate Aquifer System
– 3, upper Floridan Aquifer • Does not account for most springs • Cannot deal with conduit flow

# USGS Megamodel

# Megamodel Conclusions
• Could not accurately reproduce capture zones of springs not explicitly in model

– Steady state run produced spatially and temporally unrealistic results
– Absence of many springs and of siphons that capture river water in model a limitation
– Constant head in Layer 1 apparently prevents accurate representation of dispersed recharge

# District Model • Regional model 

### • 3 - D model • 5,000 x 5,000 ft. cells 

### • Active Layers
– 1, Surficial Aquifer
– 2, Intermediate Aquifer System
– 3, upper Floridan Aquifer
– 4, middle confining unit
– 5, lower Floridan aquifer

# District Model (cont.)
• Accounts for

– All 1 st and 2 nd magnitude springs,
– Many 3 rd magnitude springs, and
– All major siphons and swallets 

### • Cannot deal with conduit flow

# District Model Rose Creek Sink Siphon Creek Worthington, Santa Fe Hornsby, Treehouse, Columbia Ginnie to Poe

# District Model Conclusions
• Appears reasonable with respect to many springsheds in steady-state mode 

### • This is important because the District uses steady-state modeling to evaluate permit applications • Model cannot accurately model capture zones based on travel time 

### because it cannot account for conduit flow

# District Model Conclusions
• Model provides insight into flow systems

– When aquifer approximates flow through homogeneous aquifer, travel times can be approximated
– When flow is dominated by conduit transport, the model may approximate springshed in steady-state mode but not short-term capture zones

# Evaluations of Springsheds

• Springsheds from potentiometric surface and model are consistent within limitations • Addition of swallets and siphons is critical to capture zone modeling • Rum Island – Gilchrist Blue springshed remains large for magnitude of spring discharge • Flow to springs is limited from Bell Ridge/Waccasassa Flats area and Northern Highlands

# Evaluations of Springsheds
• Many springs are dominated by swallets that capture water from Northern Highlands 

### • Springs are dominated by conduit flow • Worthington and Santa Fe Springs are not consistent with Floridan aquifer potentials

# Recommendations • It is not appropriate to set up protection zones based on model - based travel times

– Models do not deal with conduit flow – karst flow is too complex
– Dye tracing proves that basins are larger than model predictions and that travel times in conduits are shorter • Spring protection zones should consist of all areas within the springshed and streams that discharge to swallets

# Recommendations
• Siphon-spring systems have been identified by Butt et al. (2007), do they need special protection strategies? • The entire Newberry Plain should be considered a springshed and subject to primary protection measures • Areas north of the river in Columbia County are as important as those areas of Alachua and Gilchrist counties in the Newberry Plain

# Recommendations
• Sub - regional model

– Needed because of growth in Lake City and Gainesville/Alachua areas
– Allow refinement of karst system
– Transient model
– Integrated surfacewater/groundwater model

# Recommendations
• Model being developed privately for Western Valley may better refine knowledge 

## • Dye tracing
– Robinson Sinks


### – Western Valley
– Poe Springs

# Thank You, Any



# Questions?