Relationships Between Discharge And Water Quality In Florida Springs

Transcription

1 Relationships Between Discharge And Water Quality In Florida Springs Erich Marzolf, Ph.D. Ann B. Shortelle, Ph.D. Suwannee River Water Management District

2 Data & Methods Data from SRWMD monitoring efforts, with a few examples from SJRWMD and from SWFWMD (Heyl 2012 Technical Memo) Focus on water quality at spring vents, springshed processes rather than processing with spring runs Significance testing based upon paired linear regression WQ Vs. Time WQ residuals Vs. Flow WQ Vs. Flow WQ residuals Vs. Time

3 SRWMD Springs and FDEP s Nitrate Criterion Drinking Water Standard (10.0 mg N-NOx/L) Numeric Nitrate Criterion (0.35 mg N-NOx/L) Source: SRWMD data, all springs listed have at least one nitrate value, however only those with 5 or more samples since 2000 show a bar.

4 Nitrate Correlation with Flow Nitrate Results Nitrate Trend Over Time Positive None Negative Positive Ruth / Little Sulfur, Convict, Madison Blue, Silver, Weeki Wachee Suwannee Blue, Santa Fe, Troy, Telford, Columbia, Falmouth, Palm, Sanlando, Miami Hornsby, Poe, Little River, Rock, Wekiwa None Manatee, Fanning, Gilchrist Blue, Ginnie, Hart, Rock Bluff, Chassahowitzka, Homosassa, Pump House & Trotter, Silver, Gum Springs, Rainbow Otter, Rum Island, Wacissa, Alaphaha Rise (weak), Apopka, Starbuck Treehouse Negative Blue Hole (weak)

5 FGS Bulletin No. 69; REGIONAL AND STATEWIDE TRENDS IN FLORIDA'S SPRING AND WELL GROUNDWATER QUALITY ( )

6 Nitrate Vs. K Ginnie Springs

7 Ginnie Springshed & Conduits

8 Ginnie Cave Map

9 Nitrate Vs. K Multiple Springs

10 Nitrate Vs. K

11 Nitrate Correlation with Flow Nitrate Results Nitrate Trend Over Time Positive None Negative Positive Ruth / Little Sulfur, Convict, Madison Blue, Silver, Weeki Wachee Suwannee Blue, Santa Fe, Troy, Telford, Columbia, Falmouth, Palm, Sanlando, Miami Hornsby, Poe, Little River, Rock, Wekiwa None Manatee, Fanning, Gilchrist Blue, Ginnie, Hart, Rock Bluff, Chassahowitzka, Homosassa, Pump House & Trotter, Silver, Gum Springs, Rainbow Otter, Rum Island, Wacissa, Alaphaha Rise (weak), Apopka, Starbuck Treehouse Negative Blue Hole (weak)

12 Exurgence Vs. Resurgence Unconfined Springshed

13 Suwannee s First Magnitude Springs ALAPAHA RIVER RISE COLUMBIA SPRING FALMOUTH SPRING JULY SPRING LIME RUN SPRING MANATEE SPRING SANTA FE RIVER RISE SIPHON CREEK RISE TREEHOUSE SPRING WACISSA SPRINGS BLUE HOLE SPRING DEVILS EAR SPRING HOLTON CREEK RISE LAFAYETTE BLUE SPRING MADISON BLUE NUTALL RISE SANTA FE SPRING STEINHATCHEE RIVER RISE TROY SPRING

14 Suwannee s First Magnitude Springs ALAPAHA RIVER RISE COLUMBIA SPRING FALMOUTH SPRING JULY SPRING LIME RUN SPRING MANATEE SPRING SANTA FE RIVER RISE SIPHON CREEK RISE TREEHOUSE SPRING WACISSA SPRINGS BLUE HOLE SPRING DEVILS EAR SPRING HOLTON CREEK RISE LAFAYETTE BLUE SPRING MADISON BLUE NUTALL RISE SANTA FE SPRING STEINHATCHEE RIVER RISE TROY SPRING Exurgence Resurgence Karst Window Spring/Sink

15 Sources of Change in Groundwater Nitrate Nitrate Trends could be driven by: Changes in N loading within springshed (w/ time lags) Changes in GW N loss mechanisms (DO, DOC relationships) Changes in flow when nitrate and flow are correlated Nitrate Flow Relationship Trends in flow from multiple GW sources with different [nitrate] (shallow & deeper GW sources, where shallow is relatively more nitrate enriched due to proximity to surface N sources) Changes in relative flow from GW (exurgence) vs. SW (resurgence) Variation in springshed area with hydrologic fluctuations

16 Nitrate Correlation with DO Nitrate & Dissolved Oxygen Nitrate Trend Over Time Positive None Negative Positive Telford, Gilchrist Blue Suwannee Blue Little River Potential for DO limited denitrification to contribute to declining NOx, however majority of DO between 1 2 mg/l DO We will learning a great deal in near future as a few springs are instrumented with real-time WQ monitoring equipment. Thank you DEP. None Negative Convict, Ruth / Little Sulfur, Madison Blue, Manatee, Fanning, Ginnie, Hart, Rock Bluff, No indication that there are springs where denitrification is limited by DO and denitrification has increased to prevent a positive trend Troy, Otter (limited data), Rum Island, Blue Hole, Wacissa, Santa Fe, Columbia, Poe, Treehouse, Hornsby

17 Delineated Springsheds Small fraction of identified springs have been delineated Creates challenges for costeffective hydrologic or water quality restoration efforts Continuous WQ Monitoring Soon Ginnie Blue Hole (Ichetucknee) Convict Royal Fanning Manatee

18 Continuous Data Analyses Example of rainfall grid for Silver Springshed Examine monthly water flux in each grid with continuous river flow Opportunity to examine new continuous WQ data, with landuse based load estimates Empirically identify locations more closely linked to spring vents, independent of any assumptions related to karst features, transmissivity, rock uniformity, etc.

19 Aid In Groundwater Protection Aid in identifying which sink features are most important Water Quality Protection Hydrologic Restoration Land Acquisition and/or Management Target acquisitions Evaluate offers

20 Concluding Ramblings Need to better understand source(s) of water & nutrients Delineate springsheds (and watersheds) Identify karst features (sinks, caves, conduits) Measure flow reversals Consider water quality relationships with hydrology Need to understand aquifer denitrification rates, limiting conditions Look for opportunities to recharge aquifers with clean water

21 Questions while you watch the Dead River Disappear?