Ecohydrology of a groundwaterdependent

Transcription

1 Workshop Model Application for Wetlands Hydrology and Hydraulics 1-3 April 2004, Bialystok, Poland Ecohydrology of a groundwaterdependent Alder carr J. Severyns, J. Fourneau, O. Batelaan, F. De Smedt Department of Hydrology & Hydraulic Engineering Vrije Universiteit Brussel (VUB), Belgium Department of Ecosystem management Universiteit Antwerpen (UA), Belgium

2 Ecohydrology

3 nature reserve Vijverbroek Gravel pits Streams km The etherlands orth Sea Flanders Model area Flemish provinces Walloon provinces

4 Groundwater modelling Vegetation mapping Ecohydrological research Groundwater quality analysis Soil sampling

5 DEM Topography [mtaw] Landuse Soil peat sandy loam landgebruik water akker weiland ruigte bomenrij groeve dijk populier moeras wilgenstruweel bebouwing elzenbroek

6 Groundwater modelling MODFLOW (Harbaugh & McDonald, 2000) & WetSpass (Batelaan & De Smedt, 2001) MODPATH (Pollock, 1994) SW Topography E Quaternary layer Model: 25 m x 25 m cells 3 layers Formation of Kasterlee Formation of Diest Formation of Bolderberg Fracture Jagersborg Unit Jagersborg Unit Formation of Voort Formation of Eigenbilzen Brunssum I Formation of Boom

7 WetSpass model ET P R = P ET - S S R

8 ... overview simulations Scenario Model type Steady st. Transient st. Situation 2002 Situation average gw.level/depth - discharge (location + flux) - flow time - average gw.level/depth summer - average gw.level/depth winter - average gw.level/depth - discharge (location + flux) - average gw.level/depth summer - average gw.level/depth winter Hypothetical Situation average gw.level/depth - discharge (location + flux)

9 Model area o flow boundary Campine Plateau Plain of Bocholt Alluvial plain Constant head boundary Meuse River Geological passages Piezometers Gravel pits Model area

10 Yearly average groundwater recharge: Situation Recharge [mm/year] <

11 Yearly average groundwater depth: Situation Groundwater depth [m] < >

12 Situation 2002: (winter - summer) Difference gw.level: (winter - summer) [m] < 0,

13 Situation( ) Difference gw.level: Situation( ) [m] >

14 Yearly average groundwater level: Situation(2002 Hypoth.1995) Difference gw.level: Sit.( Hypoth.1995) [m] >

15 Yearly average discharge flux: Situation Discharge flux [mm/d] < 5 no discharge

16 Yearly average discharge flux: Situation( ) Difference discharge flux: Situation( ) [mm/d] no difference <

17 Yearly average discharge flux: Situation(2002 Hypoth.1995) Difference discharge flux: Sit.( Hypoth.1995) [mm/d] no difference <

18 Recharge areas & flow times: Situation Flow time [years] > 200 Classification zones

19 Determination of controlling variables for vegetation using CCA (Canonical Correspondence Analysis) Variables considered: Groundwater quality (2002) Groundwater level: mean summer gw.level (MSGL) Soil nutrients: extraction/destruction Findings: the controlling variables are: MSGL ph: impact rainwater + soil processes [phosphate]: external supply + soil processes

20 CCA-output peat: axes 1 and 2 CCA-output veen: as 1 en 2 H4+ bodem soil Axis 2 CAREXACT STACHPAL CALYSSEP PHRAGAUS POPULCA PHALAARU GLYCEMAX METHAQU CALLI-SP EQUISFLU BERULERE ph water SYMPHOFF TUSSIFAR LYCOPEUR LYTHRSAL IIRIS_PSE MYOSOPAL SOLADUL RIBESIG POLYAMP TYPHALAT ph RAUREP ALISMPLA LOTUSULI RUBUSFRU PEUCEPAL CALTHPAL ALUSGLU LEMAMI CAREXPSE CALAMCA SCUTEGAL DRYOPDIL GLECHHED VALEROFF CARDMAMA CAREXREM CAREXELO GLYCEFLU SPARGERE THELYPAL URTICDIO GALIUAPA GALEOTET FILIPULM JUCUEFF SAMBUIG POA TRI STACHSYL GLG STELLAQU SCIRPSYL GLG MSGL Axis 1

21 [Phosphate] in groundwater [Phosphate] in mg/l

22 Vegetation (phreatophytes) predictions Based on results of groundwater model Delineation gw.depth-ranges pro species Optimal range Broad range Predictions based on these ranges Simulation of Situation 2002: control Simulation of Situation 1995

23 Occurence Caltha palustris 2002 Prediction Caltha palustris 2002 Prediction Caltha palustris 1995 Soil map Soil map Soil map Predictions: not exact, however, indicative to trace the effects of restoration measures (here: filling up of gravel pits)

24 Conclusions The methodology is useful: to obtain insight in groundwater systems: gw.levels & depths recharge & discharge area to obtain ecohydrological insight in wetlands: influence of hydrological stresses (e.g. drainage depth) prediction of vegetation/ nature potential