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