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UWI Interim MeetingCommon topic presentation
19.05.17
Groundwater – surface water interactions in urban areas
JONAS SCHAPER1,2, TABEA BROECKER3, MIKAEL GILLEFALK1, FATIMA AL- ATMAN21 Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany
2 Technical University Berlin, Department of Water Quality Control, Strasse des 17. Juni 135, 10623 Berlin, Germany3 Chair of Water Resources Management and Modeling of Hydrosystems,Gustav-Meyer-Allee 25, 13355 Berlin, Germany
Slide 2
GW-SW interactions in urban areas
Key processes in hydrological cycles• water quantity • water quality
Winter et al. 2008 USGS, circ1139
Water quality in urban areas• controls ecosystem health • drinking water resources• recreational activities
Urban water bodies• “urban stream syndrome”• anthropogenic imprint on chemical quality and hydrology
• high loads of nutrients, and trace contaminants (metals, organics etc. )• altered flow/exchange patterns (water tables, abstraction,
morphology etc.)
Slide 3
River Erpe – typical urban stream
Loosing urban stream that receives WWTP effluent• elevated SW water table• potential threat to GW?• fate of trace organic compounds such as ICM?
Slide 4
Potential mechanisms
Physical processes Chemical processes
Biological processes
Lake water quality
Bank filtration
Macrophyte disappearance
Water table lowering- Increased wind exposure- Bottom freezing
- DIC (CO2) availability- Sediment characteristics
CO2
Modified after Voltz, T., University of Applied Sciences Dresden (HTW)
Macrophytes stabilize clear-water conditions by: - Nutrient uptake- Reduced resuspension- Providing shelter for zooplankton- Allelochemical release
Slide 5
SW-GW interactions group approach
Field observationsN5: Effects of bank
filtration on lake ecosystems
N6: Fate of organic micropollutants in hyporheic reactors
Process understanding lab work
T6: Deiodination of iodinated contrast media
N7: Modeling of flow andtransport in hyporheic zones
Group task:Can we optimize GW-SW interactions in urban areas so that ecosystem resilience and services are enhanced?
Modeling & Prediction
Slide 6
• HZ can act as sinks for TrOCs in urban rivers
• redox conditions control source sink function of TrOC in HZs
• residence times are the most important factor controlling redox conditions
Fate of TrOCs in Hyporheic zones
optimal residence time distribution in the HZ?
Slide 7
Deiodination of ICM under anaerobic conditions
anaerobic environment,low redox potential
RKM: IOP Corrinoid: 5 µM DCC
RedoxpotentialE0′ [mV]
TiCi = -480MV = -450DTT = -330Cys = -210
reducing agents:Titan(III)Citrat (TiCi), Methylviologen (MV), Dithiothreitol (DTT) oder Cystein (Cys)
Slide 8
Residence times in the alluvial aquiferAge dating using Radon
> 15 d
> 15 d
> 15 d
> 15 d
Slide 9
Fate of TrOCs during Riparian bank filtrationadsorbable organic bound iodine (AOI)
> 15 d
> 15 d
> 15 d
> 15 d
Slide 10
Our Vision
Field observations• redox conditions are a key driver for TrOC/nutrient attenuation• residence times in turn influence redox conditions
Winter et al. 2008 USGS, circ1139
River and lake engineering• can we “design” exchange flows in order to promote
• attenuation of certain compounds via redox zone heterogeneity• promote certain functional groups (e.g. macrophytes)
Modeling
PCLake• integrated ecosystem model
Modeling Hyporheic exchange• hydraulic transport model
Slide 11
• Parameter study• ripple geometry (ripple height, distance, length)• velocity
Free-surface flow and transport over streambeds with ripples
3 m
1 m
1 m
Velocity (m/s)
Pressure (Pa)
Flow
airwater
Slide 12
Modeling hyporheic exchange
“predicting” residence time distributions in urban rivers during river restauration
• hyporheic exchange/residence time as function of• porosity & median grain size• surface water velocity• stream geometry
𝜕𝜕C𝜕𝜕t
+ 𝛻𝛻(𝐶𝐶𝐶𝐶) + 𝛻𝛻(Dphys + Dturb)𝛻𝛻C = 0
with Dturb = 𝜇𝜇𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡/𝜌𝜌𝑆𝑆𝑆𝑆𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡
governing transport equation
• novel coupling of surface water and hz transport • upscaling!• hyporheic contribution to whole stream processes
Slide 13
Modelling bank filtration scenarios using PCLake
Bank filtration effects ConsequenceMacrophyte growth rate (CO2) Decrease
Temperature variation Increase
Sediment clogging Increase
Lake type parameters Values
GW flow None Inflow Outflow
GW nutrientconcentration
High Low
Fetch length Long Short
Depth “Deep” Shallow
CO2
Modified after Voltz, T., University of Applied Sciences Dresden (HTW)
9°C
Slide 14
• sensitivity analysis for all of the parameters. Possible response variables:
• Chlorophyl a• Macrophyte coverage• Secchi depth
• investigate impact of initial conditions (lake types) for the effect of bank filtration
• overall goal from a management perspective: • Find most suitable lake type for bank filtration, in
the case where there are multiple choices. • An alternative to bank filtration: infiltration ponds.
Modelling bank filtration scenarios using PCLake
Resilience
Slide 15
Conclusions
Winter et al. 2008 USGS, circ1139
• understanding exchange flows in SWGW interfaces is crucial (lakes and rivers)
• lab findings provide process understanding which is required to interpret field observations (ICMs)
• self purification capacity of urban rivers can be enhanced via river engineering
• HZ exchange modeling assists in prediction of residence time distributions:
• enhances river engineering options• offers upscaling approaches
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