1. M. Walaszek 1, P. Bois 1, J. Laurent 1, A. Wanko 1 1 Ecole Nationale du Génie de l’Eau et de l’Environnement de Strasbourg (ENGEES) Laboratoire des Sciences de l’Ingénieur, de l’Informatique et de l’Imagerie (Icube), 2 rue Boussingault, 67000 Strasbourg, France Ponding water ultrasonic measurements in urban stormwater constructed wetland for clogging monitoring

2. The Ostwaldergraben mwalasze@engees.eu WETPOL 20152 The EU Water Framework Directive: good status before 2027 Ostwaldergraben: bad status - presence of pollutants (nutrients, organic matter, hydrocarbons, metals)  Necessity to improve the stream quality

3. 2011 – Construction of 3 systems (sedimentation pond + constructed wetland) to compare their treatment efficacity To reduce pollution in stormwater before discharging into the stream The general project: the stream restauration mwalasze@engees.eu WETPOL 20153 Watershed 3 Ostwaldergraben Watershed 2 Watershed 1

4. Objectives of the study mwalasze@engees.eu WETPOL 20154 Stormwater constructed wetland (SCW): a specific functionning Variable input flow  Heterogeneous spatial and temporal water distribution inside the SCW, even if presence of a distribution system  Suspended solids in runoff and reeds litter: infiltration capacity reduce and physical clogging risk What are space and time dynamics of water ponding ? Observations Issues What can we deduce on clogging from water ponding ? Link rain event characteristics and SCW hydraulic response Describe the ponding behaviour after a rain event Study markers to prevent the clogging Objectives

5. The experimental site mwalasze@engees.eu WETPOL 20155 Context and objectives Watershed 3 Ostwaldergraben Manhole Runoff Catchment area Total area (ha) 1.8 Active area (m²) 5,200 TypeResidential Artificial pondArea (m²)18 Hydraulic load (m 3 /m²/h) 10 Constructed wetland Area (m²) 100 Hydraulic conductivity (m/s) 5.10 -5 Hydraulic load (m 3 /m²/h) 0.5 to 1 % of active area (m²) 2%

6. mwalasze@engees.eu WETPOL 20156 Context and objectives Link rain event characteristics and SCW hydraulic response Objective 1 Rain event Instrumenta tion Weather station (800m away) Information s provided Rain event duration Water height Intensity Dry period Return period Duration (h) Cumulated water height (mm) Average intensity (mm/h) Dry period (d) Return period 26/04/201325.10.18.80.063 to 6 months 27/04/201320.129.84.20.053 to 6 months 02/05/20130.844.92.012 weeks to 1 month 03/05/20131.84.22.30.91 to 2 weeks 04/05/20132.92.60.90.57< 1 week 04/05/20130.21.89.80.272 weeks 07/05/20130.425.20.681 to 2 weeks 08/05/20130.71.62.40.11< 1 week 10/05/20135.55.417.40.272 weeks 20/06/20130.710.4160.46 months 03/07/20134.78.861.93.691 month 08/09/201323.81.90.611 to 2 weeks 10/09/20131.65.23.20.042 weeks to 1 month 11/09/20133.511.43.30.081.5 to 3 months 14/09/2013 10.52.24.91.491 to 2 weeks 14/09/2013 20.29.858.80.331 to 2 years 16/09/20130.53.47.61.982 weeks to 1 month 18/09/20130.43.27.72.062 weeks to 1 month 03/11/20131.48.86.40.91.5 to 3 months 08/11/201316.66.40.041 to 1.5 months 19/11/201310.716.41.510.691.5 to 3 months April to november 2013 139 rain events 21 studied Use of the Hierarchical Ascendent Clustering (HAC) analysis  To classify rain events and SCW parameters by similarity

7. mwalasze@engees.eu WETPOL 20157 Context and objectives Describe the ponding behaviour during a rain event Objective 2 Peak ponding height Average ponding height Upward ponding time Downward ponding time Average ponding time Start ponding time End ponding time + upward and downward ponding velocity Ponding Instrumentation Ultrasoni c sensor (x9, Ijinus – M0111) Informations provided Ponding height Calculation of ponding parameters: + Statistical moments 9 X

8. mwalasze@engees.eu WETPOL 20158 Context and objectives Study markers of clogging Objective 3 dh dt Clogging prevent by ponding and piezometric water levels comparison : Ponding Instrumentation Piezometric probes (2 pression probes) Informations provided Piezometric height Infiltration Capacity Unsaturated permeability Kns (using ponding water dynamic): Where : L the thickness of the SCW (0,3 m) ΔH the difference of ponding heights

9. mwalasze@engees.eu WETPOL 20159 Context and objectives Correlate ponding water and Phragmites australis biomass Objective 4 Reed biomass Instrumentation / method Height and diameter measurements per 0.25m² Quadrat Informations provided Phragmites biomass for summer & winter 2013 To compute: And compare with heterogeneous ponding water distribution in the SCW But only 2 sampling campaigns not enough to conclude …

10. Rain event characteristics and SCW response link Cluster 1 e1, e2 Cluster 2 e6, e7, e8, e4, e12, e 3, e5, e11, e21 Cluster 1 e14, e15, e16, e19, e17, e13, e18, e20, e9, e10 mwalasze@engees.eu WETPOL 201510 Context and objectives Cluster 1 e16 Cluster 2 e11, e17, e18, e3, e15, e9, e10, e14, e19, e13, e20, e6, e5, e4, e12, e7, e8 Cluster 3 e21 Cluster 4 e1, e2 SCW parameters classification Rain event classification Group 1 (e1&e2): ponding height & downward velocity  low infiltration velocity Group 2: big events & high ponding height variability Cluster 1Cluster 2Cluster 3Cluster 4 Duration (h) 10.7 22.6 0.21.7 Water height (m) 0.016 0.038 0.0010.005 Intensity (m/h)0.0020.0065 0.059 0.0059 Dry period (days) 10.69 0.060.330.94 Cluster 1Cluster 2Cluster 3 Ponding height (m) 0.09 0.030.08 Rise time (h) 7.9 1.20.9 Descent time (h) 16.2 1.41.2 Rise velocity (m/s) 4.0E-061.2E-05 3.7E-05 Descent velocity (m/s) 4.0E-061.0E-05 4.0E-05 Reduce variance 1.25 1.31 1.27 Average ponding time 11.7 1.10.9 SCW hydraulic response impacted by urban watershed hydrology

11. Spatial ponding water heterogeneity mwalasze@engees.eu WETPOL 201511 Context and objectives Rain eventSensor detection (%) 26/04/2013 44 (4 sensors/9) 27/04/2013 22 02/05/2013 22 03/05/2013 33 04/05/2013 11 04/05/2013 11 07/05/2013 11 09/05/2013 11 10/05/201 3 56 20/06/2013 33 03/07/2013 11 08/09/2013 11 10/09/2013 33 11/09/2013 100 14/09/2013 22 14/09/2013 11 16/09/2013 22 18/09/2013 11 03/11/2013 11 08/11/2013 22 19/11/2013 11 3 to 6 months 3 months 6 months SensorDetected rain event (%) 157 233 319 433 548 614 75 810 95

12. Spatial ponding water heterogeneity mwalasze@engees.eu WETPOL 201512 Context and objectives Average parameters for each ponding sensor from April to November 2013 Quartiles groups (quartiles 2 et 3 together) 4 & 7  High ponding heights 7 & 2  High descent velocity (high infiltration capacity) Heterogeneous ponding understanding  soil sampling location

13. mwalasze@engees.eu WETPOL 2015 Markers of clogging: ponding and piezometric measures 13 Context and objectives dh dt Piezometric heights reduce + Ponding heights stability  Δh peaks increase Time of equilibrium increase  Clogging risk

14. Markers of clogging: unsaturated permeability Kns Kns  infiltration capacity of the SCW No significant Kns variation for this period (Max Kns= 0.080 m/s, min Kns=0.064 m/s) Kns Intrinsic SCW property mwalasze@engees.eu WETPOL 201514 Context and objectives

15. Conclusion and perspectives mwalasze@engees.eu WETPOL 201515 Perspectives Pursuit of the study in the 1rst SCW (watershed 1) Extend the measurement period to 1 whole year Conclusion Impact of the variable incoming flow on SCW hydraulic characteristics  Highlight of ponding, infiltration capacity Monitoring possible with simple instrumentation and 2 water levels Ponding map  Help to choose soil and reed sampling locations

16. Thank you for your attention ! Any questions ?