Potential of unsaturated soil zone models for assessment of managed aquifer recharge

Transcription

1 Sponsored by Junior Research Group Global Change 4+1 Potential of unsaturated soil zone models for assessment of managed aquifer recharge ISMAR9 symposium Mexico City, June 2016

2 Unsaturated Soil Zone & MAR defines the quantity and quality of natural and managed groundwater recharge soil passage fosters filtering of organic matter, trace organic compounds, nitrogen and bacteria soil aquifer treatment (SAT) Fig. 2: SAT system for pre-treated wastewater (Miotlinski et al., 2010) Associated MAR types: 1. Spreading methods 2. In-channel modifications 3. Runoff and rainwater harvesting 4. Well, shaft and borehole recharge 2

3 Why modeling? faster, less expensive than field experiments risk assessment, prognosis scenario analysis (best case/worst case, long-term) process understanding Modeling can accompany practical investigations: 1. developing management strategies that optimize defined objectives 2. understanding hypothetical hydrogeological questions 3. assessment of predictive scenarios 3

4 Literature Study Based on study of Ringleb et al. (2015) 18 publications (10 with transport modeling, 9 with groundwater modeling) MARTHE and HYDRUS most commonly used Number of modeling studies Groundwater model Vadose zone model Fig. 3: Historical development of use of groundwater and vadose zone models Fig. 4: Model application by MAR type 4

5 Literature Study Objectives: assessment of geochemical processes, impact of MAR on groundwater, planning of MAR scheme Planning and optimizing of extension of Shafdan MAR site Fig. 5: Use of models through MAR site planning in Shafdan (Kloppmann et al., 2012) 5

6 Experimental Study HYDRUS 2D/3D was used to plan field-scale experiments conducting managed infiltration under different boundary conditions Fig. 6: Concept and top view of test site in Pirna 6

7 Dimensioning the infiltration unit Influence of outside precipitation on measurements for different basin widths/lenghts 2 m depth 1 m depth E E E E E E E E 04 Precipitation [mm] E E 04 Precipitation [mm] 5.0E E E E E 04 Side Center Side with Precip. Center with Prec. Precipitation E 04 Side Center Side with Prec. Center with Prec. Precipitation Fig. 7: Pressure head distribution at a depth of 2 m and 1 m below surface for a basin of 1 m width and 2 m length 7

8 Dimensioning the infiltration unit Influence of basin depth on calculated pressure head values Center Side m 1 m 1.5 m 2 m m 1 m 1.5 m 2 m Fig. 8: Pressure head distribution in the center and at the side underneath an infiltration unit showcasing water movement in different depths below surface. 8

9 Design of observation network Number and location of measurement tools Center vs. side Influence of boundaries Location at center Fig. 8: Comparison of possible placement options for measurement devices in 1.5 m depth comparing the effect of centered devices vs. devices at the side (a), the effect of boundaries of the infiltration basin (b) and the influence of location in the center of the basin (c). 9

10 Experimental Scenario planning Comparing steady-state and intermittent transient infiltration scenarios Scenario Infiltration [l] Groundwater recharge [l] % of infiltrated water to reach groundwater Standard rain scenario for Pirna l/h for 1 day, then increase of 0.1 l each h for next 3 days 1 l/h for 1 day, 3 l/h for 1 day, 10 l/h for 1 day, l/h for 1 day 1 l/h for 7 days l/h for 1 day, 1 day break, (x7) l/h for 1 day, 3 day break, (x7) l/h for 14 days l/h for 21 days l/h for 7 days l/h for 1 day, 1 day break, (x7) l/h for 1 day, 3 day break, (x7) l/h for 14 days l/h for 21 days l/h for 7 days l/h for 1 day, 1 day break, (x7) l/h for 1 day, 3 day break, (x7) l/h for 14 days l/h for 21 days

11 Discussion - SWOT Opportunities Strength preliminary modeling: define scope of data collection careful design of test site to manage spatial and temporal requirements observation unit: adequate number and location experimental set-up: infiltration scenarios, built-in materials, duration design and optimization of test sites long term qualitative assessment (adequate model!) differentiation between natural and managed recharge, comparison of MAR methods higher calculation times due to finer discretization predictive models- subsequent data collection and calibration to adjust and verify model results high requirements regarding parameters van Genuchten parameters for coarse materials ponded infiltration not available in all model types Weakness Threats 11

12 Contact Technical University Dresden Institute of Waste Management and Circular Economy Pratzschwitzer Str Pirna GERMANY Phone: References Hölting, B. (1996): Hydrogeologie: Einführung in die allgemeine und angewandte Hydrogeologie. Enke Verlag, Stuttgart. Miotlinksi, K.; Barry, K.; Dillon, P. (2010): Alice Springs SAT Project Hydrological and Water Quality Monitoring Report CSIRO Water for a Healthy Country National Research Flagship. Ringleb,J.;Stefan,C.(2015): Review on model applications to evaluate managed aquifer recharge. Rendiconti Online della Società Geologica Italiana.Supplemento n.1 al Vol. 39/2016 Kloppmann, W., Aharoni, A., H. Chikurel, P. Dillon, I. Gaus, J. Guttman, T. Kaitzer, et al.(2012): Use of Groundwater Models for Prediction and Optimisation of the Behaviour of MAR Sites. In Water Reclamation Technologies for Safe Managed Aquifer Recharge, edited by C. Kazner, T. Wintgens, and P. Dillon. London: IWA Publishing.. 13

13 Geochemical processes during infiltration of tertiary treated waste water at Wulpen 1D simulation of column experiments 2D modelling of breakthrough scenarios (cross section) Embedded in regional model (3D) Modelling with MARTHE, behaviour of contaminants for risk assessment