Agricultural-Driven Eutrophication

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Diane Dixon
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1 Agricultural-Driven Eutrophication Professor Louise Heathwaite Department of Geography University of Sheffield Phosphorus Loading to UK Waters Land Leaks! P P load load -1 yr -1 Kg Kg ha ha-1 yr-1 Agriculture Agriculture % % Loch Leven Lough Neagh Lough Erne.5 73 Slapton Ley Phosphate Concentration in Rivers in England & Wales National P Loss Model estimates Environment Agency data DEFRA NT136 <2 µg P l mg P l-1 no data Louise Heathwaite Eutrophication Forum Presentation 11th October 21 1

2 Towards a National Consensus on of Phosphorus Loss to Water from Agriculture Louise Heathwaite University of Sheffield, Penny Johnes & Dan Butterfield University of Reading, Andy Fraser NSRI, Paul Withers, Eunice Lord & Mike Hutchins ADAS P Loss-potential soil nutrient status fertiliser/manure input P Transfer HER erosion vulnerability hydrological pathways P Delivery Delivery ratio! surface/drainflow! sediment /P flux! P loss from farm infrastructure Drivers land cover/use livestock numbers/ fertiliser needs DEFRA PE15 Drivers climate soil physical & chemical properties topography Drivers hydrology (drainage density, stream order, return period & connectivity) artificial flow routing Agricultural Issues Manure recycling & Fertilizer use Soil nutrient status & Land Management Increased potential for nutrient loss? Temporal issues Phosphorus load varies with source & annual runoff Horticulture Rural Forest Urban Sewage Grazing Wet year: 154,kg total P Source: CSIRO National Eutrophication Management Programme Dry year: 2,kg total P Louise Heathwaite Eutrophication Forum Presentation 11th October 21 2

Scaling Issues Surface runoff P is related to soil P 2.5 Dissolved P in surface runoff (mg l -1 ) 2. 1.5 1. r =.

5 2 4 6 8 Soil P (mg kg -1 ) Comparing P loss in surface runoff at plot (2m 2 ) and field (2ha) scales.42.3.29.4.44.

3 Scaling Issues Surface runoff P is related to soil P 2.5 Dissolved P in surface runoff (mg l -1 ) r =.73 clay silt loam fine sandy loam Soil P (mg kg -1 ) Comparing P loss in surface runoff at plot (2m 2 ) and field (2ha) scales All units mg l -1 Case Studies Evaluating the relative contribution from point & diffuse sources for catchment studies Louise Heathwaite Eutrophication Forum Presentation 11th October 21 3

4 Phosphorus in Irish Lakes Neagh Upper Erne Lower Erne Derg Sheelin Macnean (lower) Macnean (upper) Melvin Ennell Corrib Mask Leane Conn Total P concentration (µg l-1) OECD eutrophic lakes limit -1 Phosphorus (tonnes P yr ) Lough Neagh point source P load Major towns Other towns 2 Industry Source: DARDNI Agricultural Phosphorus balance Northern Ireland 1998 Phosphorus (tonnes P yr -1 ) Source: DARDNI Input P a P time bomb? Rain P Fertiliser P Diffuse P Pigs* Poultry* crops Grazing* systems Output P *Denotes concentrate P Long-term trends and diffuse P loads in Lough Neagh River phosphates (tonnes P y -1 ) Diffuse loading Diffuse trend Flow River Flow (*1 9 m 3 yr -1 ) Cumulative Phosphorus (kg P ha -1 ) Cumulative soil P Diffuse river soluble phosphate Water phosphorus (kg P ha -1 ) River discharge and diffuse Soluble P sources Soil P accumulation and diffuse P loss rates Source: DARDNI Louise Heathwaite Eutrophication Forum Presentation 11th October 21 4

5 Pistern Hill Research Catchment Cattle shed P concentration (mg P l -1 ) Sources Reception pit Silo Manure heap Point Sources Drinking trough Gateway VSA Precipitation Grass leachate Grassland topsoil Parent material Diffuse Sources Total particulate P Dissolved organic P Dissolved inorganic P Jan-Mar Apr-Jun Jul-Aug No flow Sept-Dec P concentration (µg l -1 ) Timeframe Base flow (.5 L min -1 ) Feb Mar Sep Jan Storm flow (1-5 L min -1 ) Oct Nov Dec Total particulate P Dissolved organic P Dissolved inorganic P Louise Heathwaite Eutrophication Forum Presentation 11th October 21 5

P concentration (µg l -1 ) 2 4 6 8 1 12 Pathways Overland flow Matrix flow Macropore flow (-15 cm) Macropore flow (15-3 cm) Macropore flow (3-45 cm) Drainflow (base flow) Drainflow (storm flow) Total

6 P concentration (µg l -1 ) Pathways Overland flow Matrix flow Macropore flow (-15 cm) Macropore flow (15-3 cm) Macropore flow (3-45 cm) Drainflow (base flow) Drainflow (storm flow) Total particulate P Dissolved organic P Dissolved inorganic P The Chesapeake Bay Catchment 3-6% soils high P status >6% soils high P status Land Use and P Export to the Chesapeake Bay Sources Non-Point Forest Agriculture Urban Point Area % --- P export Louise Heathwaite Eutrophication Forum Presentation 11th October 21 6

7 Introducing Complexity Spatial Heterogeneity The same P can have different impacts in different parts of the transport system Towards a National Consensus on of Phosphorus Loss to Water from Agriculture Universities of Sheffield & Reading, ADAS, NSRI P Loss-potential soil nutrient status fertiliser/manure input P Transfer HER erosion vulnerability hydrological pathways P Delivery Delivery ratio Source Transport Critical Source Areas Concept Louise Heathwaite Eutrophication Forum Presentation 11th October 21 7

VARIABLE SOURCE AREAS Riparian Zones 1 km Topographicallycontrolled VSAs Convergence Zones CRITICAL SOURCE AREAS routing along tramlines 1 km Land managementcontrolled CSAs Study Catchment, NE

8 VARIABLE SOURCE AREAS Riparian Zones 1 km Topographicallycontrolled VSAs Convergence Zones CRITICAL SOURCE AREAS routing along tramlines 1 km Land managementcontrolled CSAs Study Catchment, NE Pennsylvania Flumes CSA monitoring site Catchment boundary (4 ha) Stream channel 9% of annual P export comes from 5% of land area Louise Heathwaite Eutrophication Forum Presentation 11th October 21 8

9 Generation of CSAs during storms Saturation sensors Saturated area Maximum Initial Stream flumes Delineating the risk of P transport Risk Transport negligible low medium high very high Targeting areas at risk from P loss Source Source Factors P loss risk low medium high Source and Transport Factors Louise Heathwaite Eutrophication Forum Presentation 11th October 21 9

We need a holistic, integrated approach Multi-scaling Approach point scale 1-D physically based models, properties in each layer plot scale hillslope & small catchment scale 3-D physically based

10 We need a holistic, integrated approach Multi-scaling Approach point scale 1-D physically based models, properties in each layer plot scale hillslope & small catchment scale 3-D physically based models, properties in each cell Quasi-physical probability distribution function model 1 km river basin or regional scale simple models based on statistical distributions for each sub-catchment Met station Flow & water quality gauge Plot experiments Source: The SEAL Project Louise Heathwaite Eutrophication Forum Presentation 11th October 21 1

July, International SWAT Conference & Workshops

July, International SWAT Conference & Workshops Analysis of the impact of water conservation measures on the hydrological response of a medium-sized watershed July, 212 212 International SWAT Conference & Workshops ANALYSIS OF THE IMPACT OF WATER CONSERVATION