Geophysical Characterization and Monitoring of Groundwater/Surface-Water Interaction in the Hyporheic Corridor at the Hanford 300 Area L. Slater 1, F. Day-Lewis 2, R. Versteeg 3, A. Ward 4, J. Lane 2, D. Ntarlagiannis 1 and A. Binley 5 Columbia River at Hanford 1: Rutgers-Newark; 2: USGS, Office of Groundwater, Branch of Geophysics; 3: Idaho National Laboratory; 4: Pacific Northwest National Laboratory; 5: Lancaster University 1
Acknowledgements U.S. Department of Energy, Subsurface Biogeochemical Research Program Christopher Strickland (PNNL), Jason Greenwood (PNNL), Jay Nolan (Rutgers-Newark), Carol Johnson (USGS), Eric Wood, USGS), Chris Curran (USGS) Charlie Harvey and Hana Karam (MIT) Tim Johnson (INL) John Zachara and Brad Fritz (PNNL) 2
MOTIVATION 3
Hanford 300 Contamination legacy: included 241 metric tons of copper, 117 metric tons of florine, 2060 metric tons of nitrate and between 33 and 59 metric tons of uranium. East from the Hanford 300 Area Spatial and temporal variability in exchange between uranium contaminated groundwater and river water? 4
Primary Study Objectives: Better characterize the hydrogeological framework (regulating exchange) along hyporheic corridor Resistivity/IP imaging 08ER64561 Quantify spatiotemporal variability in (focused) groundwater-surface water exchange and forcing mechanisms Fiber optic distributed temperature sensing (FO- DTS) 5
Hanford Geology Intensively studied inland away from the river corridor Hanford-Ringold contact: important interface controlling flow/transport Pebble to boulder size gravels and interbedded sands [Higher K ~ 100 m/ day, Williams et al., 2007] Improvements in hydrogeological framework required along corridor of surface-water/groundwater exchange Highly heterogeneous, granule to cobble size gravels interbedded with fine sand and silt. [Lower K 0.2 m/day, Williams et al., 2007] Source: Fritz et al., 2007, PNNL-16805 6
Estimations of contributing area from borehole projections Estimated uranium contributing area based on projections from inland boreholes and point probe tests (Fritz et al., 2007) 7
Complexity of surface water-groundwater exchange Non-stationary river stage variations driven by seasonal effects and daily dam operations on Columbia River Paleochannels locally eroded beneath Hanford- Ringold contact March (2009) July (2009) Identified uranium seeps (Fritz et al., 2007) 8
GEOPHYSICAL METHODS 9
Electrical geophysics: induced polarization versus resistivity IP IS LARGELY SENSITIVE TO LITHOLOGY σ Simple schematic for polarization of electrical double layer of interconnected pore surface around a single mineral grain RESISTIVITY IS SENSITIVE TO BOTH FLUID CHEMISTRY & LITHOLOGY
IP Petrophysical relations Increasing evidence for a general empirical relationship between IP and S por 106 samples spanning 8 independent datasets Viable relationship for interpretation of field data? IP equivalent of Archie s Law? (interconnected surfaces instead of interconnected pores) The imaginary conductivity versus S por relation for 106 samples 11 from eight independent datasets (Weller et al., In Press)
Continuous electrical imaging P 9 P 8 P 7 P 6 P 5 P 4 P 3 P 2 P 1 C 2 C 1 E l e c t r o d e N u m b e r 11 10 9 8 7 6 5 4 3 2 1 R E S I S T I V I T Y M E T E R, G P S D a t a L e v e l n = 1 n = 2 n = 3 n = 4 n = 5 n = 6 n = 7 n = 8 D a t a L e v e l n = 1 n = 2 n = 3 n = 4 n = 5 n = 6 n = 7 n = 8 ρ a Depth ρ distribution Distance Numerical methods + Inverse modeling [with appropriate constraints on water layer thickness and conductivity 12
Waterborne IP Apparent resistivity and apparent chargeability at pseudodepth 8.5 m 30 km of line, +60,000 measurements IP is linearly dependent on surface area per unit pore volume (Spor) -> litholgic discriminator Weller et al., In Press 13
Use of temperature data in hydrology Measure transient behavior to understand diurnal or seasonal variations Identifying gaining and losing reaches of streams Profiles are compressed in areas of gw discharge Use contrast in temperature between surface water and groundwater to: Inference of discharge/recharge rates Inference of aquifer properties (K) from Constantz and Stonestrom (2003)
Fiber-optic DTS Utilizes heat as a tracer to capture spatiotemporal variability in surface water/ groundwater exchange along river corridors Backscatter of laser light (function of temperature) recorded from time t 1 to t 2 is from a section of cable x 1 to x 2, allowing spatial localization of measurements by a time-of-flight calculation ~4.5 km of cable; 1 m spatial resolution, 5 min temporal resolution, ~0.1 ºC temperature resolution 15
Water depths Survey geometry 08ER64561 Summary of geophysical acquisition 30 km of waterborne IP line 4.5 km of DTS line Water depths varied from 1-14 m (in channel) Focus on near shore where water depth of a few meters only (also waterborne seismic and GPR, not reported here) IP DTS Contributing area? 16
RESULTS 17
Electrical images of the river corridor Hanford-Ringold contact defined along river corridor Ringold contacts with riverbed locally-incised paleochannels? Line 20 (20 m from shore) Inverted image at 7 m 18
DTS Monitoring of Hyporheic Exchange: Winter (March 24-31, 2009) HIGH STAGE 19
DTS Monitoring of Hyporheic Exchange: Winter (March 24-31, 2009) LOW STAGE Warm anomalies associated with focused groundwater discharge 20
DTS Monitoring of Hyporheic Exchange: Summer (August 1-6, 2009) HIGH STAGE 21
DTS Monitoring of Hyporheic Exchange: Summer (August 1-6, 2009) LOW STAGE Cold anomalies associated with focused groundwater discharge 22
Correlation of DTS and hydrogeologic framework Focused hyporeheic exchange: temperature anomalies and a correlation between stage and temperature occur where Hanford unit thickest; exchange is muted/absent where Hanford is thin locally-incised paleochannels? Line 20 (20 m from shore) Inverted image at 7 m 23
Focused exchange and contributing area along the hyporheic corridor Temperature anomalies coincide with known uranium seeps -> but are many additional temperature anomalies/seeps Estimated variation in thickness of uranium contributing area from IP 24
Statistical analysis of relation between Hanford thickness and stage-temp correlation coefficient Linear: r = -0.59 Spearman rank = -0.68 Hardness = 0.73 25
SELECTED WORK IN PROGRESS 26
Time-frequency analysis of DTS datasets Lengthy time series for timefrequency analysis E.g. Investigate contributions of periodicity in stage variation and groundwater levels on discharge 27
Resistivity monitoring (started Aug 09) Location of 755 m resistivity monitoring array (155 electrodes @ 5 m spacing) Specific conductance is strong indicator of relative mixing of groundwater and river water (groundwater ~ 400 µs/cm; river water ~ 130 µs/cm) Fritz et al., 2007, PNNL-16805 28
Integrated temperature and head/ gradient monitoring at 3 sites 1 2 3 Site 1: 3 temperature probes, piezometer, transducer in still well and MIT probe
Inferring streambed vertical fluxes from 1D temperature data T Boundary conditions Temperature time series in water column Time 08ER64561 A 1-D heat convection/conduction transport model is calibrated to thermistor time series at different depths in the streambed to identify vertical discharge, q. Compare measured and modeled thermistor data Temperature time series 15cm below streambed T 75cm temperature series as lower boundary condition Time q =? T Time Temperature time series 40cm below streambed T Time
Fitting 1D convection/ conduction model Site 1 Ongoing work to incorporate head time series data time varying head and flow reversals 25 20 q = 0.3 cm/hr A(1) 15cm depth Simulated Observed 15 10 5 Aug-26-09 00:00 Sep-09-09 00:00 Sep-23-09 00:00 Oct-07-09 00:00 Oct-21-09 00:00 31
Concluding Remarks Improve conceptual model for hydrogeologic framework at Hanford 300 Area in critical zone of exchange Spatiotemporal variability in flux rates -> implications for modeling for transport at the site Guide sampling efforts for microbiological and biogeochemical studies relating to uranium dynamics and impact on river water quality 32
Thank You. 33