Diffuse Pollution:Groundwater Pathways      Steve Buss
Summary• Groundwater in catchment management• Groundwater in a rural catchment  – Predicting future concentrations  – Miti...
Why groundwater (water supply)? Public water                                                                   Groundwater...
Why groundwater (regulation)?                                                                Rivers                       ...
Groundwater catchments                                                                            !                       ...
Groundwater catchments                                                                            !                       ...
Groundwater catchments                                                   Delay                       Dilution             ...
Groundwater catchments                                                   Delay                       Dilution             ...
Opportunities for mitigation       Nottinghamshire sources: % contribution to groundwater N loading   Yellow =   fertilise...
Cost effectiveness                                        COUNTERFACTUAL             64 mg/l                              ...
TimingUnsaturatedzone thickness(5 to 65 m)                   !                   <Groundwaterflow path length(0 to 9500 m)...
Timing         10 years
Groundwater catchments (2)             2215             #                               #                            10990...
Urban groundwater Ú Û                    Ú                    Û                     Ú                     Û     Ú     Û
Urban groundwater Ú Û                    Ú                    Û                     Ú                     Û     Ú     Û
Conclusions• Groundwater is (mostly):  – Underground and slow-moving  – Unconstrained by catchment boundaries  – Vital for...
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Diffuse Pollution: Groundwater Pathways

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Thoughts on modelling diffuse nitrate pollution, and assessing cost effectiveness of measures.

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Diffuse Pollution: Groundwater Pathways

  1. 1. Diffuse Pollution:Groundwater Pathways Steve Buss
  2. 2. Summary• Groundwater in catchment management• Groundwater in a rural catchment – Predicting future concentrations – Mitigation & cost effectiveness• Groundwater in an urban catchment
  3. 3. Why groundwater (water supply)? Public water Groundwater supply issues (by volume)supply, England OK Other - closure Other - blending & treatment Pesticides - closureSurface Ground- Pesticides - treatment water water Pesticides - blending Nitrate - closure Nitrate - treatment Nitrate - blending 1995-2000 1975-80 1980-85 1985-90 1990-95 2000-05 2005-10
  4. 4. Why groundwater (regulation)? Rivers Lakes Estuaries Coastal waters 0% 20% 40% 60% 80% 100% Percentage of surface water bodies at risk of not achieving WFD objectives: diffuse pollution Results of Water Framework Directive assessment of groundwater bodies at risk of failing to achieve good status in 2015 as a result of nitrate contamination across England and Wales
  5. 5. Groundwater catchments ! < %age of source yield contributed by the model cell Colour scale = 1 – 0.05 % Time & Water Nitrogen N(t) Prediction ! < ! < AttenuationColour scale =1 – 0.05 % Colour scale = 10-80 mg/l
  6. 6. Groundwater catchments ! < mg/l of NO3 in water leaving the soil zone Colour scale = 10 – 80 mg/l Time & Water Nitrogen N(t) Prediction ! < ! < AttenuationColour scale =1 – 0.05 % Colour scale = 10-80 mg/l
  7. 7. Groundwater catchments Delay Dilution ! < Time & Water Nitrogen N(t) Prediction ! < ! < AttenuationColour scale =1 – 0.05 % Colour scale = 10-80 mg/l
  8. 8. Groundwater catchments Delay Dilution ! < Time & Water Nitrogen N(t) Prediction ! < ! < AttenuationColour scale =1 – 0.05 % Colour scale = 10-80 mg/l
  9. 9. Opportunities for mitigation Nottinghamshire sources: % contribution to groundwater N loading Yellow = fertiliser applications to arable land White = areas relevant for change in arable land use
  10. 10. Cost effectiveness COUNTERFACTUAL 64 mg/l COUNTERFACTUAL 64 mg/l concentration vs.  Summary  concentration vs.  Summary  statistics statistics TARGET 50 mg/l TARGET 50 mg/l Reduction required 21.9 % Reduction required 21.9 % 75 75 50 50 25 25 target target 0 0 Peak  Peak  Min ML Max Min ML Max £20,000,000 £20,000,000Engineering vs.  Engineering vs. management  management catchment  catchment  £0 £0 costscosts Min ML Max Min ML Max MEASURES: Light touch scenario Land use change scenario 1. Cover crops before spring cereals …plus… 2. Reduce dietary intake of N and P 7. Convert 50% of arable land to low input 3. Early harvesting and establishment of crops in autumn extensive grazing 4. Use a fertiliser recommendation system 5. Integrate fertiliser and manure nutrient supply 6. Avoid spreading manufactured fertiliser at high risk times
  11. 11. TimingUnsaturatedzone thickness(5 to 65 m) ! <Groundwaterflow path length(0 to 9500 m) ! <Travel time(3 to 60 years) ! <
  12. 12. Timing 10 years
  13. 13. Groundwater catchments (2) 2215 # # 10990 # 20117 Source apportionment # ! < Colour scale = 10 – Treated 0.05 % Surface Urban sewage Colour scale = 10 – 80 mg/l water effluent (other) Sewage treatment works, with population served 103043 # 8777 # 3763 # Groundwater (agriculture) 32870 # 24677 ## 25352 #
  14. 14. Urban groundwater Ú Û Ú Û Ú Û Ú Û
  15. 15. Urban groundwater Ú Û Ú Û Ú Û Ú Û
  16. 16. Conclusions• Groundwater is (mostly): – Underground and slow-moving – Unconstrained by catchment boundaries – Vital for drinking water supply, for aquatic ecosystems, for dilution of sewage effluent in the summer, for industry, for amenity…• Challenging to predict and monitor effectiveness of measures but these can be constrained with simple tools

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