Groundwater Surface Water Interactions and the Water Framework Directive

Transcription

1 Groundwater Surface Water Interactions and the Water Framework Directive ATV Foundation on Soil and Groundwater annual conference on soil and groundwater contamination, March 8-9, 2011 Dr. Mark Whiteman Modelling Specialist (Hydrogeology) Environment Agency of England and Wales

2 Outline WFD requirements Groundwater status tests Conceptual models/typologies Risk assessment UK implementation of WFD Case studies Lessons learned

3 Implementation of WFD Refinement into 2 nd cycle Updated conceptual models start River Basin Planning Cycle Risk screening National datasets Local knowledge characterisation River Basin Plans classification Groundwater status tests Using groundwater models to assess impacts Wetland water supply mechanisms Programmes of Measures Wetland (GWDTE) Investigations case studies

4 WFD (Article 4) objectives for groundwater: 1. Prevent or limit the input of pollutants; 2. Prevent the deterioration of status of groundwater bodies; 3. Achieve good groundwater status (both chemical and quantitative); 4. Implement measures to reverse any significant and sustained upward trend; 5. Meet the requirements of protected areas.

5 Classification tests groundwater status Groundwater Chemical Status Groundwater Quantitative Status G P TEST 1: Saline or other intrusions G P G P TEST 2: Surface Water G P G P G P G P TEST 3: Groundwater Dependent Terrestrial Ecosystems TEST 4: Drinking Water Protected Areas TEST 5: General Quality Assessment TEST 6: Water Balance G P G P GOOD POOR GOOD POOR The results of each test are combined for overall classification of POOR or GOOD STATUS for both quantity and chemical. The worst result is reported for the groundwater body.

6 Tiered risk assessment (CIS Guidance 26)

7 Conceptual models (CIS Guidance 26) (a) Large (Landscape) scale Local, intermediate and regional scale flow systems in a moraine landscape (from Dahl et al., 2007, Journal of Hydrology 344, 1 16)

8 Conceptual models (b) Intermediate scale (1-5 km) from Dahl et al., 2007, Journal of Hydrology 344, 1 16

9 Conceptual models (c) Local scale ( m) from Dahl et al., 2007, Journal of Hydrology 344, 1 16

10 Conceptual models for wetlands: wetland water supply mechanisms (WETMECs) Hydrogeologists are familiar with the development of conceptual hydrogeological models for wetland sites. WETMECs can be seen as add-ons to these, which extend conceptual models to take better account of the properties of the wetland itself. They are, however, generic, rather than site specific Ref: Whiteman et al In: Quevauviller, P. et al. (Eds.), Groundwater Quality Assessment and Monitoring. Wiley,

11 Wetland water supply mechanisms (WETMECS) Reference: Wheeler, Shaw & Tanner, 2009

12 What is the Wetland Framework? Inter-relationships between water source, water quantity, water quality and vegetation type in sites supporting herbaceous wetland vegetation in lowland England and Wales have been used to create a typology of the main eco-hydrological units. 20 Wetland Water Supply Mechanisms (WETMECs) have been identified and described, along with the Ecological Types that are associated with them. In combination,the WETMECs and Ecological Types define ecohydrological habitats.

13 How can we use the Wetland Framework? Conceptualising the functioning of wetlands enables a source pathway receptor type of impact assessment The 20 WETMECs have been described with the generic environmental conditions that support them. This creates a starting point for risk screening and further site specific impact assessment. A spin-off product are the Ecohydrological guidelines, that describe the generic environmental conditions associated with a specific vegetation community The reports are downloadable from:

14 Generic conceptual models Winter water table Springs & Seepages (a) seepage face in permeable bedrock without superficial deposits Wet Woodland ET Rain Winter Aquifer Intermittent Seepage (WETMEC 11) Permanent seepage slope (WETMEC 10) (slope may be uniformly wet or gets wetter downwards) Stream Wet Dune Slacks Valley bottom/basin mires WETMEC 13b: Seepage Percolation Quag ( e.g. Cors Goch) basin is fed by groundwater outflow around margins of depression low permeability wetland deposits may constrain groundwater outflow into the basin proper surface is quite buoyant - in some sites a raft over fairly fluid muds; there may be preferential water flow through, and beneath, the raft Water Table WETMEC 13b Raft of vegetation Fluid Mud Outflow stream Peat Marl

15 Ecosystems within a WFD river basin (from CIS Guidance 12)

16 Groundwater-dependent terrestrial ecosystems (GWDTEs) GWDTEs are directly dependent for their form and function on water from a groundwater body Groundwater provides critical quantities, flow, level or quality needed to sustain the ecosystem (the reason the GWDTE was highlighted as significant), for at least part of the year

17 Photo by Dr Bryan Wheeler Photo: Natural England Photo: Natural England Photo: Iain Diack, Natural England

18 A. Ground Water discharges from saturated soil or rock at one spot (spring) or discrete zone (seepage) Spring GWDTE GWDTE Seepage River or lake Photo by Dr Bryan Wheeler non or seasonally saturated soil or rock layers saturated soil or deeper rock layers Photo: Natural England Groundwater Dependent Terrestrial Ecosystem Photo: Natural England Photo: Iain Diack, Natural England

19 B. Ground Water discharges from saturated soil or rock and collects on an impermeable layer GWDTE River or lake non or seasonally saturated soil or rock layers saturated soil or deeper rock layers impermeable layers

20 Photo by Dr Bryan Wheeler Photo: Natural England C. Ground Water discharges from saturated sand dune sea River or lake non or seasonally saturated soil or rock layers saturated soil or deeper rock layers Photo: Photo: Iain Natural Diack, England Natural England

21 D. Ground Water discharges from saturated soil or rock and feeds ephemeral lakes or rivers Photo by Dr Bryan Wheeler Photo: Natural England River or lake Photo: Natural England Photo: Iain Diack, Natural England

22 Different types of groundwater-dependent terrestrial ecosystems A. Ground Water discharges from saturated soil or rock at one spot (spring) or discrete zone (seepage) B. Ground Water discharges from saturated soil or rock and collects on an impermeable layer GWDTE Spring GWDTE GWDTE Seepage River or lake River or lake non or seasonally saturated soil or rock layers saturated soil or deeper rock layers Groundwater Dependent Terrestrial Ecosystem non or seasonally saturated soil or rock layers saturated soil or deeper rock layers impermeable layers C. Ground Water discharges from saturated sand D. Ground Water discharges from saturated soil or rock and feeds ephemeral lakes or rivers dune sea River or lake River or lake non or seasonally saturated soil or rock layers saturated soil or deeper rock layers

23 GWDTEs and significant damage Terrestrial ecosystems that directly depend upon bodies of groundwater are a component of the groundwater body classification. Significant damage to these ecosystems caused by the status (quantity or quality) of the groundwater body can result in a status failure of the groundwater body significant damage is based upon: the magnitude of the damage and the societal significance of the terrestrial ecosystem.

24 UK implementation of WFD Refinement into 2 nd cycle Updated conceptual models start 1 st cycle River Basin Planning Risk screening National datasets Local knowledge Using groundwater models to assess impacts Wetland water supply mechanisms River Basin Plans Programmes of Measures classification Wetland (GWDTE) case studies

25 A tiered approach to GWDTE assessment Tier 1 Pre-assessment (qualitative risk screening for GW bodies i.e. initial characterisation)

26 A tiered approach to GWDTE assessment Tier 1 Pre-assessment (qualitative risk screening for GW bodies i.e. initial characterisation) Tier 2 Appraisal (semi-quantitative assessment i.e. further characterisation and initial classification)

27 A tiered approach to GWDTE assessment Tier 1 Pre-assessment (qualitative risk screening for GW bodies i.e. initial characterisation) Tier 2 Appraisal (semi-quantitative assessment i.e. further characterisation and initial classification) Tier 3 Characterisation and evaluation

28 Tier 1: risk screening List of 1,386 sites Stage 1 Initial risk assessment (national GIS data) Stage 2 Expert local knowledge (workshops & GIS)

29 EU Designations EU_DES EU Non EU No data Aim: assess every GWDTE for risk of significant ecological damage caused by groundwater pressures Wet Heath Wet Dune Slacks

30 Quantitative pressure Water abstraction Source Degree of dependence of ecology on groundwater Chemical pressure Phosphate in groundwater Sensitivity to nutrients Pathway Hydraulic connection Drift thickness Drift permeability Receptor

31 Risk scoring Influence on each site Possible Notes Scores Quantitative Pressure 3, 2, 1 or 0 3 indicates a high abstraction pressure. 0 indicates no pressure. + Groundwater Connectivity 3, 2, 1 or 0 3 indicates the highest connectivity. 0 indicates no connection with the aquifer. + Groundwater Dependency 3, 2, 1 or 0 3 indicate the highest groundwater dependency. 0 indicates no data. Interim Final Risk Score 0-9 Potential modification of interim final risk score by nonabstraction quantitative pressure Final Risk Score , +1, -1 or -2

32 Case Study: Wybunbury Moss Peat Glaciofluvial sands and gravels River Terrace sands and gravels Alluvium Devensian Till

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34 Wybunbury: risk scores (GIS) Quantitative Pressure Risk Score GW abstraction pressure GW connection Whole body pumping/near-wetland pumping Good connection between aquifer and wetland GW dependency Plant community rating (low) 1 Total Zero risk

35 Wybunbury: risk scores (GIS) Chemical Pressure Risk Score GW pollution pressure PO4 score 2 GW connection Good connection between aquifer and 3 wetland GW dependency Plant community rating (low) 1 Total Medium risk 6

36 Overview of approach List of 1,386 sites Stage 1 Initial risk assessment (national GIS data) Stage 2 Expert local knowledge (workshops & GIS)

37 Wybunbury: risk scores (local workshops) Quantitative Pressure Risk Score GW abstraction pressure Whole body pumping/near-wetland pumping 0 0 GW connection GW dependency Good connection between aquifer and wetland Plant community rating (low) Oligotrophic plant communities present Total 6.0 0

38 Wybunbury: risk scores (local workshops) Chemical Pressure Risk Score GW pollution pressure GW connection PO4 score High nitrates in borehole next to site Good connection between aquifer and wetland GW dependency Plant community rating (low) Oligotrophic plant communities present Total High risk

39 Results of screening wetlands for risk

40 Tier 2: Appraisal (semi-quantitative assessment) Translating potential risk into actual damage Classified each groundwater body in England and Wales at either good or poor status according to whether GWDTEs are significantly damaged. Evidence of actual ecological damage Wet Woodland Reedbed Wet Heath

41 Procedure for test of significant damage of terrestrial ecosystems directly dependent on the groundwater body Criteria for assessing groundwater chemical status for this test (threshold values TV s), Data aggregation, Location of exceedance, Confidence in the assessment (from CIS Guidance 18)

42 Classification process Is a chemical threshold exceeded? What are the required environmental supporting conditions? Are the required conditions in place? If not, is groundwater the cause? Is the wetland significantly damaged? Do we have the evidence?.

43 Wybunbury Moss Risk Screening & Classification North m aod Sand and Gravel Nitrates Groundwater flow to W yb unbury Moss Gro undw ater Tab le in Sand an d Gravel Poor status, high confidence NO3 (N) 20mg/l E.A. Borehole C Spring-fed lagg Threshold 10mg/l Oligotrophic fen communities M18, M2 Wybunbury Moss Lagg E.A. Borehole B All anthropogenic Exceedance >10mg/l Wybunbury village Piezometric Level in Wilkesley Halite Formation Boulder Clay South Peat Raft 40 Wych Mudstone Formation Water Groundwater Flow to Wybunbury Moss from Wilkesley Halite Formation? Fault (from BGS Geological Map 123) Wilkesley Halite Formation 30 Collapse feature due to solution of Halite Possible deep zone of solution and brecciation associated with Faults 500 m

44 Classification results wetland test

45 Tier 3: risk assessment (characterisation and evaluation) Detailed investigations of a few sites, to: increase confidence in the risk screening and classification, and to work out which investigation methods are cost-effective

46 Further investigations Reason for high risk? Site unfavourable Not groundwater Site favourable Site unfavourable groundwater Ecological surveillance needed Ecological and/or hydrological investigation needed

47 Further investigations Reason for high risk? Site unfavourable Not groundwater Medium / low / no risk (no missing data) Site favourable Site unfavourable Risk of significant damage groundwater to site Unknown (missing High risk data) No monitoring Consult conservation body / EA technical specialist Revise risk accordingly Data supplied? Yes Ecological surveillance needed Reason? (refer to GW classification initial screening) Site unfavourable probably not ground Site favourable water pressure? Ecological surveillance needed Conceptualisation Define approach to ecological surveillance Site unfavourable perceived groundwater pressure? Ecological and / or hydrological investigation needed Conceptualisation Define approach to ecological and / or hydrological investigation No Ecological and/or hydrological investigation needed Implement / continue surveillance Implement / continue investigation / monitoring Data Analysis Yes Data Analysis Negative change in site condition? Causal link between GW pressure and ecological change? No No significant damage Yes Yes Continue surveillance? No Significant damage Report to RBP team Report to RBP team Develop / implement / monitor programme of measures

48 Case Study: Wybunbury Moss North m aod 60 Monitoring Point C Monitoring Point B E.A. BoreholeB Wybunbury village South 50 Sand and Gravel flow Groun dwater Moss to W ybunbury undwater Gravel Table Gro and in Sand E.A. BoreholeC Spring-fedlagg Wybunbury Moss Lagg Piezometric Level in Wilkesley Halite Formation Boulder Clay Peat Raft 40 Wych Mudstone Formation Water Groundwater Flow to Wybunbury Moss from Wilkesley Halite Formation? Fault (from BGS Geological Map 123) Wilkesley Halite Formation 30 Collapse feature due to solution of Halite Possible deep zone of solution and brecciation associated with Faults 500 m

49 KEY Peat Glaciofluvial sands and gravels River Terrace sands and gravels Alluvium Devensian Till

50 Wybunbury Investigation Maize field 1980 s dairy discharge

51 Nested piezometers

52 Wybunbury Moss Groundwater heads in shallow piezometers Figure 4.1 Shallow Groundwater Levels at Wybunbury Moss PTA1 = shallow PTA2 = intermediate PTA3 = deep

53 Geophysical survey WNW ESE

54 Targeted ecological survey

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56 Chemical sampling Maize field 1980 s dairy discharge NO3 < 10 mg/l NO3 > 10 mg/l

57 Nitrate Concentrations at Wybunbury Moss in Shallow Piezometers Nitrate mg/l PTA1 PTA2 PTA3 SGA2 SGA3 SGB2 SGB3 SGC2 SGC3 Shallow Intermediate Deep Intermediate Deep Intermediate Deep Intermediate Deep Jun- 09 Jul-09 Aug- 09 Sep- 09 Oct- 09 Nov- 09 Dec- 09 Jan- 10 SGA PTA Date

58 Marsh Lagg Floating Peat Bog Horizontal Flow Area of up welling Upwards flow Red fine sand Red fine sand and clay Wych mudstone Formation Wilkesley Halite formation Lake Peat Bolder clay Sandy topsoil Figure 7.1 Conceptual Cross Section Peat and gravel,(boundary of Peat and sand)

59 Initial conceptual model North m aod 60 E.A. Borehole B Wybunbury village South 50 Sand and Gravel Groundwater flow to Wybunbury Moss Groundwater Table in Sand and Gravel E.A. Borehole C Spring-fed lagg Wybunbury Moss Lagg Piezometric Level in Wilkesley Halite Formation Boulder Clay Peat Raft 40 Wych Mudstone Formation Water Groundwater Flow to Wybunbury Moss from Wilkesley Halite Formation? Fault (from BGS Geological Map 123) Wilkesley Halite Formation 30 Collapse feature due to solution of Halite Possible deep zone of solution and brecciation associated with Faults 500 m

60 Revised conceptual model Figure 5.1 Wybunbury Moss Revised Conceptual Diagram maod BHB 60 LAG PEAT RAFT S & G Piezometric head in Halite BHC Sand & gravel PTA3 PTB3 PTC Boulder Clay 50 PEAT Clayey Peat Boulder Clay WATER Wilkesley Halite Formation 40 Groundwater flow from Halite Figure drawn by Sarah Scott

61 Conclusion - Wybunbury The sand and gravel aquifer is not in direct connectivity with the water beneath the peat raft There is no evidence that the site is being damaged as a result of a chemical pressure acting through the groundwater body. Hence the site is not significantly damaged So, the site is OK for now, BUT Source Pathway Receptor

62 Wybunbury conclusions (2) Continued risk from ongoing application of chemical fertilisers of causing an increasing trend and subsequent damage to the site Important to take positive measures early to reduce diffuse groundwater pollution (e.g. nutrient management plans) Investigations help target individual farms Identify source areas for chemical pressures Agriculture teams working with farmers and nature conservation officers

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64 Lessons learned chemical pressures Targeted ecological surveys can indicate impacts Can t rely on low P preventing damage In-combination effects may be important in causing actual ecological damage to GWDTEs e.g. aerial deposition of nitrates

65 Quantitative (abstraction) pressures Soley, R., et al. (in press) Groundwater abstraction impacts on river flows - predictions from regional groundwater models. In: Shepley, M.G., Whiteman, M., Hulme, P., Grout, M. (eds), Groundwater Resources Modelling: a case study from the UK. Geological Society, London, Special Publications Whiteman, M., et al. (in press) Origin, development, and status of the regulatorled national groundwater resources modelling programme in England and Wales. In: Shepley, M.G., Whiteman, M., Hulme, P., Grout, M. (eds), Groundwater Resources Modelling: a case study from the UK. Geological Society, London, Special Publications,

66 Water quantity variables Discharge of groundwater to the site via springs and seepages Maintenance of an upward hydraulic gradient from the groundwater body to the near surface deposits Maintenance of an upward flow of groundwater from the groundwater body to the near surface deposits Impacts on groundwater levels in the GWDTE Water saturation of the soil or soil moisture characteristics as a result of inputs from groundwater

67 Quantitative thresholds Buxton Heath

68 Appraisal of scenarios groundwater heads at the feature of interest Breaches (1974 and 76)

69 Water Quantity risk from abstractions Risk Category Criteria Low Medium High Performance against model-based hydrological criteria Scale of breach for water levels (drought summers) Frequency of breaches for water levels (drought summers) Timing of breaches < 5 cm < 10 cm > 10 cm 1 out of 10 droughts only < 5 out of 10 > 5 out of 10 droughts only and non droughts only droughts and nondrought periods Impact on overall hydrological functioning hardly impacted impacted in some years significantly impacted in most years

70 Possible Actions Risk category General action Changes to licences Implications for public water supply abstractions Monitoring Low Affirm licences n/a No change to deployable output n/a Medium modify licences presumption to maintain licensed quantities but achieve more control over actual abstraction Deployable output may be affected by restrictions in drought years continue hydrological monitoring, set up routine ecological monitoring High modify or revoke licences presumption to modify licensed quantities Deployable output may be affected by reductions to licensed quantities continue hydrological monitoring, set up routine ecological monitoring

71 Lessons learned - methodology Importance of risk-based approach, local conceptual understanding For proper risk-assessment we need: location of GWDTE s, sensitivity to pressures and magnitude of pressures Local knowledge is key to risk screening/characterisation Impact assessment step (Tier 3) is always site specific

72 Lessons learned investigations Cost effective techniques Soil Augering Hydro-ecological walkover survey Dipwells (with dataloggers) Chemical sampling Ecological quadrats? Nitrogen Isotopes/age dating? Geophysics (resistivity, GPR.)? Deep piezometers Cheaper More expensive

73 Challenges for ATV for Denmark for Europe For risk screening we are improving the chemical threshold /trigger values we are working on this We need co-operation from other EU Member States to compare knowledge/databases on water quantity and quality requirements of GWDTEs (use for setting threshold values) this might require a common categorisaton of GWDTEs across Europe Receptor-focused monitoring of GWDTEs Hydrogeologists and ecologists working together

74 What next? Writing up results of investigations EU Working Group C (Groundwater) paper on GWDTEs (April 2011) Revise methods for second cycle of WFD (2011/12)

75 Acknowledgements Dr. Andrew Brooks (Entec UK Ltd.) Iain Diack (Natural England) Sarah Scott (Environment Agency for England & Wales) Dr. Peter Jones (Countryside Council for Wales) Contact Details: Thank you for listening! mange tak for opmærksomheden!