Modeling Karstic Controls on Watershed- Scale Groundwater Flow in the Floridan Aquifer of North Florida

Transcription

1 Mdeling Karstic Cntrls n Watershed- Scale Grundwater Flw in the Flridan Aquifer f Nrth Flrida Tdd Kincaid, Ph.D. Brent Meyer, M.S. GeHydrs, LLC Jhn Radtke, P.G. Cca-Cla Nrth America Rdney DeHan, Ph.D. Flrida Gelgical Survey f 34

2 Guiding Philsphy Texas Water Develpment Bard - February 2011 Design the simplest pssible mdel that hnrs as many f the bservable cnditins as pssible with the fewest hydrgelgically defensible assumptins as pssible. 2 f 34

3 Texas Water Develpment Bard - February 2011 Springs Imprtant Hydrgelgic Cmplexities large magnitude discrete discharges Cnduits Very significant preferential flw paths GW / SW Mixing Impacts water budget Swallets Large magnitude discrete recharge 3 f 34

4 Hydrgelgic Cmplexities: WKP Cnfinement 1 st Mag. Springs Wakulla Spring Creek grup St. Marks Wacissa grup 2 nd Mag. Springs Many Nt addressed yet Swallets 12 primary At least 5 secndary Caves Mapped (~47 miles) Tracer-defined Inferred f 34

5 Texas Water Develpment Bard - February 2011 Hydrgelgic Cmplexities: SFRB Cnfinement Rck Permeability Springs (>200) Swallets (10/13) Caves GW/SW mixing Land use - recharge 5 f 34 Karst features create the dminant cntrls n flw

6 Springs: Discrete Large Discharges Mre than 200 springs in the SRWMD 1 st Mag (>= 100 cfs): 18 2 nd Mag ( cfs): 81 3 rd Mag (1-10 cfs): 60 4 th Mag (.1-1 cfs): in the Santa Fe River Basin 1 st Mag: 9 2 nd Mag: 36 Hrnsby Spring 3 rd Mag: 23 4 th Mag: 8 Nt all springs are the same Autgenic lcal recharge Allgenic swallet recharge Texas Water Develpment Bard - February 2011 Devil s Ear / Devil s Eye Springs 6 f cfs Must address springs & spring types discretely /40 cfs

7 Texas Water Develpment Bard - February 2011 Swallets: Discrete Rapid Recharge Swallets: disappearing streams that fully cnnect the land surface t the FAS. 11 knwn & dcumented features O len Sink, Clay Hle Grup (3), Rse Creek, Mill Creek (2), Hammck, Pareners Branch, Waters Lake, Devil s Millhpper Swallet-Seeps: basins cntaining perched water abve FAS that deliver high recharge. 13 features Burnett s Lake, Lee Creek Sink, Turkey Creek Sink, Blues Creek Sink, Alligatr Lake, Lake Luna, Lake Ogden, Lake Wilsn, Hancck Lake, Orange Pnd, String f Pnds, Lake Jeffrey, Hgtwn Prairie 7 f 34 Swallets are significant cmpnents f the water budget

8 Texas Water Develpment Bard - February 2011 Caves: Preferential Flw Paths Numerus explred & mapped caves Old Bellamy, Hrnsby, Devil s Ear, Mill Creek, Rse Sink, Ginnie, etc. Depths trend ft Diameters: ~3 30 ft Mre traced caves Rse Creek, Clay Hle, Mill Creek, San Felasc, Ichetucknee, Ginnie ~ m/day Prbably many mre that have nt been dcumented Large flw & velcity range Spring caves Sinkhle caves 8 f 34 Caves have significant cntrl n flw patterns Devil s Ear Cave System

9 Texas Water Develpment Bard - February 2011 Grundwater / Surface Water Mixing 9 Mixing ccurs ver very rapid time scales - days rather than years Can accunt fr % f flw Degree f mixing is reflected by clr f the discharge Need t cnstrain mixing in rder t establish an accurate water budget Mixing impacts the water budget f 34

10 Texas Water Develpment Bard - February 2011 Hydrstratigraphy: Aquifer Cnfinement Dminant Circulatin Zne Springs & River Swallets Cnfined Regin 10 f 34 Flw is 3D due t variable cnfinement

11 Cmparable Mdeling Objectives Texas Water Develpment Bard - February 2011 WKP Define all springsheds that may interact under varying cnditins t cntrl water and cntribute water flw t Wakulla Spring. Develp a mdel that will deliver reliable predictins f travel-times. Develp a mdel that incrprates karst features and cnduit flw patterns. Develp a mdel that calibrates t high and lw water cnditins. Slicit and incrprate sufficient feedback frm the relevant stakehlders such that the mdel will be used by water resurce managers as a decisin supprt tl. SFRB Define all springsheds that may interact under varying cnditins and cntribute water t Ginnie Springs & CCNA s well. Develp a mdel that will deliver reliable predictins f travel-times. Develp a mdel that incrprates karst features and cnduit flw patterns. Develp a mdel that calibrates t high and lw water cnditins in the western Santa Fe River Basin. Develp a mdel that can be trusted by gvernment resurce managers. Share the mdel and mdel results with gvernment resurce managers and the public. 11 f 34

12 Basic Cnceptualizatin Optins Texas Water Develpment Bard - February 2011 Mst cmmnly assumed Mst cmmnly true 12 f 34 Start with an accurate cnceptualizatin

13 Numerical Apprach & Sftware Texas Water Develpment Bard - February 2011 Hybrid Mdel (Dual Permeability) Cntinuum mdel fr matrix prus media > Darcy flw Discrete mdel fr cnduits Pipe flw Flw can exchange between the tw media Finite-element frmulatin Maximum flexibility fr gemetric design Cmputatinal efficiency mre mdel runs = higher cnfidence FEFLOW TM Cmmercially available (DHI-WASY) Cmmnly used by natinal labratries & research institutins. Discrete element features allw fr hybrid mdel design f 34

14 14 f 34 Our Apprach t Mdeling Karst Watershed-scale mdels Need t be sufficiently large t allw the critical springsheds t be internally defined. Design t establish cntinuity at bundaries between adjacent basins. Flrida s Karst Belt wuld be subdivided int 4 r 5 basin mdels t delineate all majr springsheds. Detailed data analysis Delineate vertical extent f aquifers / znes via well cmpletin, head, & pumping analyses Expand calibratin datasets via hydrgraph analysis & crrelatin Dual-permeability Explicitly define cnduits Use realistic matrix permeabilities in gelgically defensible znes Multiple lines f calibratin Heads Spring & river flws Tracer/ hydrgraph defined velcities Multiple calibratin perids High water Lw water Pssibly transient Texas Water Develpment Bard - February 2011

15 Texas Water Develpment Bard - February 2011 FE - Dual Permeability Mesh Design 15 f 34 Mesh refined arund all key hydrlgic features springs, rivers, cntacts, wells, etc Cnduits are 1D linear features Assigned alng limbs f triangular elements Nt pre-defined in mesh develpment Can be mved fr calibratin

16 919 Wells in FL & GA Surrunding Mdel Dmain Develping a Calibratin Dataset Mar Water Level Data by Quarter Dec 09 Texas Water Develpment Bard - February 2011 Dramatically increases data density fr calibratin Analyze data and bin int grups representative f high & lw water perids Use well-well regressin analyses n all wells t expand datasets with data frm wells that crrelate (nt perfrmed yet fr this mdel) Use gruped data t develp high-water and lw-water ptentimetric surface maps Use pt surface maps t define initial cnduit layut Use high-water and lw-water datasets fr mdel calibratin 16 f 34

17 Grundwater Mdeling Prcess Texas Water Develpment Bard - February 2011 Design mdel t match knwn physical cnditins gelgy, caves, well & spring lcatins, swallet inputs Recharge ranges (bunded by rainfall data & land use) Define physics f grundwater flw Prus media in rck / Pipe flw in caves Run mdel and cmpare results against data Grundwater levels, Springs, Grundwater velcities (tracing) Adjust mdel parameters (within reasnable limits) Rck permeability, Cave lcatins & dimensins Recharge (bunded by data and znes defined by land use) Rerun mdel with new settings Repeat prcess until simulatin matches data Run mdel with lw water recharge (nly adjust recharge) Cmpare results against data Adjust mdel parameters and rerun as necessary Repeat whle prcess until mdel simulates bth high water and lw water cnditins with same parameter settings 17 f 34

18 What we knw 18 f 34 Mdeling Cnduits Cnduits cnvey water rapidly t springs Grundwater surface arund cnduits is depressed Grundwater surface in sand wuld be smth Grundwater surface has trughs & ridges in the SFRB The rcks are fairly similar acrss the regin Assumptins Cmplexity in grundwater surface is due t cnduits Cnduits fllw trughs in the grundwater surface Step-1: Assign cnduits t knwn lcatins Mapped caves / Tracer defined pathways Step-2: Assign cnduits alng trughs Between knwn cnnected pints Up-gradient frm springs Dwn-gradient frm swallets T unexplained clsed depressins Step 3: Mdify cnduits t match data Simplest pssible pattern (lw water cnditins) Dimensins set t carry necessary water t springs (high water cnditins) Suthern Regin Nrthern Regin Texas Water Develpment Bard - February 2011

19 Texas Water Develpment Bard - February 2011 Mdel Results: Grundwater Levels Green = calibrated (Red = high / Blue = lw) High water: 143/145 wells calibrated Lw water: 176/188 wells calibrated 1998/1999; 2004/ /2002; / m (~3 ft) +/ m (~3ft) 19 f 34 Bth scenaris are very well calibrated

20 Texas Water Develpment Bard - February 2011 Mdel Results: Grundwater Velcities High Water Lw Water Cnduits mdel: ~ 100 t ~3000 m/day Cnduits bserved: ~ same Matrix mdel: ~ 10-3 t 10-1 m/day Matrix bserved: ~ 10-6 T 10-3 m/day Cnduits mdel: ~ 100 t ~1000 m/day Cnduits bserved: ~ same Matrix mdel: ~ 10-3 t 10-1 m/day Matrix bserved: ~ 10-6 T 10-3 m/day 20 f 34 Bth scenaris are very well calibrated

21 Flw is t clsest cnduits Clsest twns nt always f mst cncern Newberry Ginnie Spring - ~12 miles - ~1000 days - cnduit flw Alachua Hrnsby Spring - ~7 Miles - ~500 days - cnduit flw High Springs River - ~2 miles - ~10,000 days - n cnduit Texas Water Develpment Bard - February 2011 Applicatins: Aquifer Vulnerability Municipalities: Santa Fe River Basin, Flrida 21 f 34

22 Cntrlled by cnduits Simulated velcity range m/day m/day Texas Water Develpment Bard - February 2011 Applicatins: Surce Water Prtectin Springs Vulnerability: Santa Fe River Basin, Flrida 22 f 34

23 Defined frm frward particle track analysis Bundaries change between high water & lw water cnditins Spring Grup High (km 2 ) Applicatins: Springshed Delineatins Lw (km 2 ) Ginnie / Blue Blue Hle Grup Hrnsby Ichetucknee Pe / Lilly River Rise Sunbeam Twin Rum Island July f 34 Mdel has defined springsheds based n flw Texas Water Develpment Bard - February 2011

24 Defined frm frward particle track analysis Bundaries change between high water & lw water cnditins Spring Grup High (km 2 ) Applicatins: Springshed Delineatins Lw (km 2 ) Ginnie / Blue Blue Hle Grup Hrnsby Ichetucknee Pe / Lilly River Rise Sunbeam Twin Rum Island July f 34 Mdel has defined springsheds based n flw Texas Water Develpment Bard - February 2011

25 Mdel Results: Wakulla Springshed Wakulla & Spring Creek springsheds cannt be truly segregated because bth springs are cnnected t the same cnduit netwrk. When Spring Creek stps flwing, water frm nearly all f the cmbined springshed flws t Wakulla. When Spring Creek is flwing, it prbably takes water frm the western part f the cmbined springshed. 25 f 34

26 Applicatins: Pumping Impacts Texas Water Develpment Bard - February 2011 Pumping diminishes spring flws within the impacted springsheds. Particle tracking shws that pumping impacts the size and shape f the springsheds. Mdel simulates impacts t flws & springsheds. Example: Lake City Average rate: 4.5 MGD N pumping springsheds Ichetucknee: km 2 Blue Hle: km 2 Pumping springsheds Ichetucknee: km 2 Blue Hle: km 2 Reductins Ichetucknee: -1% / 0% Blue Hle: -19% / -30% 26 f 34 Mdel simulates pumping impacts under varying cnditins

27 Applicatins: Pumping Impacts Texas Water Develpment Bard - February 2011 Pumping diminishes spring flws within the impacted springsheds. Particle tracking shws that pumping impacts the size and shape f the springsheds. Mdel simulates impacts t flws & springsheds. Example: Lake City Average rate: 4.5 MGD N pumping springsheds Ichetucknee: km 2 Blue Hle: km 2 Pumping springsheds Ichetucknee: km 2 Blue Hle: km 2 Reductins Ichetucknee: -1% / 0% Blue Hle: -19% / -30% 27 f 34 Mdel simulates pumping impacts under varying cnditins

28 Texas Water Develpment Bard - February 2011 Mdel Calibratin: Grundwater Levels R 2 =0.99 R 2 = Plts shw hw well the mdel simulates knwn grundwater levels. Perfect match wuld be the black line. All pints within the red dashed lines are calibrated. Culd nt achieve this gd f a match if it were nt fr including the cnduits. Even the pints that fall utside the red lines are clse t target levels. Additinal small adjustments t the cnduit lcatins culd prbably get all pints within range. Thse adjustments will nt significantly impact the mdel predictins. 28 f 34 Bth scenaris are very well calibrated

29 High Water Simulatin Data fr 17 springs Mdel within bserved range at 13 Mdel very clse at 3 Over estimated Santa Fe River Rise Des nt impact grundwater flw because the cnduit is mstly surface water Mdel Calibratin: Spring Flws Texas Water Develpment Bard - February f 34

30 Lw Water Simulatin Fewer data pints Data fr 8 springs Mdel within bserved range at 5 Mdel very clse at 2 Over estimated Mill Pnd Still within reasnable range given average cnditins simulatin Mdel Calibratin: Spring Flws Texas Water Develpment Bard - February f 34

31 Mdel Calibratin: River Gains Texas Water Develpment Bard - February 2011 Aggregate river gains als used as calibratin targets Accunts fr springs and diffuse flw t rivers Mdel matches bserved ranges High Water Lw Water River Stretch Mdel Meas. Mdel Meas. High Springs Ft. White Ft. White - Hildredth f 34 Matches bth discrete discharges & aggregate gains

32 Velcity Calibratin Texas Water Develpment Bard - February 2011 Flurescent Tracer Testing Ptential range in cnduit grundwater velcities estimated frm Tracer Tests (Karst Env. Services) Mill Creek & Lee Sinks Hrnsby Spring m/day Cnstraint n Mill Creek flw paths Rse Creek & Clay Hle Sinks Blue Hle & Missin Springs m/day Cnstraint n ther pathways except Old Bellamy flw path Hydrgraph Analysis: O len State Park High Springs m/day Used t cnstrain Old Bellamy O len Hydrgraph Analysis Stream Pulses High Springs 32 f 34 Cnduit velcities cnstrained by indirect measurements

33 Texas Water Develpment Bard - February 2011 Different apprach can be significant USGS Suwannee River Basin Mdel Flw field pen t the nrth 33 f 34

34 Summary & Cnclusins Texas Water Develpment Bard - February 2011 Mdel successfully simulates realistic flw cnditins t springs in the WSFRB. Mdel can be used t evaluate bth water quantity and quality issues and cncerns relative t springs prtectin. Better mdels can be cnstructed in Flrida s Karst Belt if adequate time is taken t thughtfully address imprtant karst data (spring flws, caves, swallets, tracer testing) Mdels that dn t address these features can be dangerusly wrng and misleading. If the mdels we ve been using were wrking well, we might nt be here tday. Cca-Cla s Santa Fe River Mdel is nw publically available. Cca-Cla is hpeful that it will be used in a cnstructive manner t supprt water resurce prtectin in the WSFRB f 34

35 Why Cca-Cla Built This Mdel? Vested interest in sustained clean freshwater discharge t the Western Santa Fe River Threats t water quality r quantity threaten their business Diminished water quality & quantity diminish their business and their brand Crprate cmmitment t water sustainability Our gal is t safely return t cmmunities and nature an amunt f water equivalent t what we use in all f ur beverages and their prductin. - The Cca-Cla Cmpany - Our prject began in 2005 Build the best pssible mdel Make it hnr the springs, caves, and swallets Make it public when yur dne Texas Water Develpment Bard - February f 34

36 f 34 Questins?

37 Texas Water Develpment Bard - February 2011 Hw wuld FEFLOW apprach differ frm existing mdel? Dual-permeability (discrete cnduits) strnger matrix/cnduit permeability cntrast reduce effective prsity Likely imprve travel-time and springshed predictins Include Trinity Better cntrl n flux int the Edwards frm nrth Ability t extend cnduits t recharge areas if needed Gal t imprve water budget 3D Cnfining Unit, Edwards, Trinity, pssibly sub-units Permeability displacements due t faulting Recharge int the cnfined part f Edwards Delineate prbable cnduit elevatins (effected thickness) Redefine cnduits t include alignment with tracer-defined pathways & velcities 37 f 34