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Catchment pathways and mitigations at the land/water interface
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Issues vary among catchments
B C Nutrient issues: A > B > C Sediment issues: B > A > C Pathogens issues: B > C > A
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How “stuff” was getting into WW streams
with water Pasture & track runoff (Sed, N, P bugs) Groundwater, seeps (N&P) with sediment (bugs, P) Erosion, streambank damage stock dung & urine (bugs, N & P) fertiliser application (P)
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N and P Pollutant Forms Key sources Nitrogen
(1) urine patches, (2) fertiliser, (3) effluent irrigation Phosphorus (1) fertiliser, (2) soil erosion, (3) animal excreta/effluent irrigation total nitrogen (excluding nitrogen gas) organic nitrogen inorganic nitrogen dissolved particulate ammonium nitrite nitrate Note: total Kjeldahl N = organic N + ammonium total phosphorus dissolved/ soluble / filterable (<0.45 µm) particulate reactive organic inorganic
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Sediment Aggregate Floc
(1) grazed pasture, (2) stream bank/bed erosion, (3) animal excreta, (4) animal tracks, (5) unpaved roading suspended sediment organic mineral clay silt Aggregate Floc Source: Droppo et al. (2005) Source: Liss et al. (1996)
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Faecal microbes Crytosporidium Rotavirus Campylobacter
(1) grazed pasture, (2) effluent irrigation, (3) wild and feral animals, (4) livestock in, or close to waterways faecal microbes viruses bacteria protozoa Indicator: enteroviruses, phages Pathogens: human enteroviruses and adenoviruses, noroviruses, rotaviruses, hepatitis A Indicator: E. coli Pathogens: E. coli, Campylobacter, Salmonella Indicator: Clostridium perfringens spores Pathogens: Giardia, Cryptosporidium Crytosporidium Rotavirus Campylobacter
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With the water? surface runoff subsurface floodplain inundation
infiltration excess saturation excess subsurface groundwater seepage matrix flow – slow preferential flow – fast e.g. tile drains floodplain inundation hyporheic exchanges Artificial drainage Flooding Surface runoff Seepage Hyporheic exchanges continuous Subsurface flow Stream Groundwater flow
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Hill-land sources P fertiliser P to stream P N in urine N as gas
Rock mineral P N in urine N as gas Leached N Atmospheric N N fixation N slips & soil erosion bank & gully erosion Runoff livestock excreta sediment bugs
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Sediment systems diagram- Hill farms
Goals
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Nutrients systems diagram – Hill farms
Goals
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Lowland sources dairy effluent irrigation or discharge
sediment, N, P, bugs P, N fertiliser runoff sediment, N, P, bugs N fixation N in urine leached N drains sediment, N, P, bugs
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Pastoral mitigation toolbox
match land use to capability trees vs livestock vs fodder crops livestock type/system nutrient management budgets, timing, targeting, DCD?; soil carbon target farm hotspots (80/20 rule) e.g. erosion control tree planting raceway/track runoff managed fence seeps and wetlands treatment wetlands on tile drains & catchment outlets grass filters/hedges in swales wintering pads/herd shelters dairy effluent treatment, storage and irrigation riparian setbacks for cultivation fish-friendly culverts & flood gates riparian management
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Livestock exclusion fencing
Maths: dairy cow faeces/urine inputs 0.3 kg P/ha/y (20% Toenepi yield) 4 kg N/ha/y (13% Toenepi yield) 50 kg SS/ha/y (30% Toenepi yield) 10 billion E coli/ha/y input Plus Bank erosion Sediment re-entrainment Vegetation damage 5 Catchment studies-Before and after exclusion SS loads – 30-90% reductions mostly attributed to reduced erosion E. coli conc % reductions nutrients variable Williamson et al., 1996; Owens et al. 1996; McKergow et al., 2003; Line et al. 2000, 2003; Meals & Hopkins 2002, 2003.
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Resuspension fine material re- entrained cattle entered stream
50 100 150 200 250 00:00 04:48 09:36 14:24 19:12 Time (24 h) Turbidity(NTU) Upstream Downstream cattle entered stream fine material re- entrained Stassar and Kemperman, 1997
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Damage +5 y +3 y Matarawa and Waikakahi
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NZ reach scale studies (a small sample)
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Buffers & contaminants
Filtering surface runoff RIPARIAN ZONE LIVESTOCK STREAM RIPARIAN ZONE LIVESTOCK STREAM Filtering subsurface flow Stream bank stabilisation RIPARIAN ZONE LIVESTOCK STREAM RIPARIAN ZONE LIVESTOCK STREAM Setback
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Performance comparison
Riparian fencing Subsurface flow filtering Grass filter strips % low medium high sediment phosphorus nitrogen Seepage wetlands
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Generalised widths to provide riparian functions
livestock excreta/damage fish habitat bank stabilisation flood control shade leaf input overland flow filtering wood input plant nutrient uptake wildlife habitat After: Dosskey et al. (1997)
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Generalised vegetation types and Riparian functions
Grass /sedge Shrubs Trees Bank stabilisation low high Overland flow filtering sediment & sediment bound medium soluble Nutrient uptake - Denitrification med ium Shading Wood input Leaf litter input Enhancing fish habitat Sp. specific Controlling downstream flooding Human recreation Aesthet ics Modified from Dosskey et al & Yuan et al 2009
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Riparian costs (incl. labour) & some direct benefits
Farmer benefits Avoid stock loss, ease management Paddock subdivision Better farm water Stock browse medicinal plants e.g. flax Shelter Aesthetics Timber, carbon credits…. Bridges and crossings Culverts $2,500-$25,000 ea1 Bridges several $ 1000 ea Fencing – Dairy2 single wire electric $2-3/m 3 wire electric $5/m Fencing – Sheep & beef2 wire post + batten $18/m Alternative water supply Variable, big issue in hills sheep/beef Planting with trees/shrubs $1200/ha pines to $10-20,000/ha natives3 Lost farm land Loss of 1 cow at $1000 = cost of fencing 325 m of both sides of stream with single wire electric and 100 m with 5 wire post and batten fence 1 2 3 including labour Quinn et al Cheaper from seedlings and incentives available in some regions
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Targeting livestock fencing
cattle and deer > sheep small streams highly accessible FW tidal inanga spawning sites lake and estuary margins wetland seeps – especially cattle and deer
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Whatawhata headwater expt: 36% pine exclude cattle (not sheep) + poplars
Reduced temp and macrophytes Increased clarity, wood cover and invert health 2002 2011 Quinn et al. (2009). NZJ Mar FW Res 43(3):
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6. Riparian reforestation
Natural forested habitat Fish cover Wood Microclimate Shade control of stream temp Shade control of algae Natural food resources Enhances biodiversity Terrestrial & aquatic Faster in smaller streams 2002 2011
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Riparian forest regrowth cools small streams faster than large ones
10 10 B A Summer Max Summer Max Rate of decline in average summer temperature difference from reference (˚C/yr) 1 1 Summer Mean Summer Mean 0.1 10 100 1000 10000 1 10 100 Catchment area (ha) Channel width (m) Source: Quinn & Wright-Stow 2008
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Dairy effluent management
Ox ponds need high dilution Mudstone geology low diln in summer Wetlands polish somewhat# SS c %, BOD 35-50%, N 15–35%, E. coli 80% Advanced Pond System 50% lower N, P, BOD than 2 ponds; fold more E. coli removal Deficit irrigation best if* low rate, even spread application over wide area, Code of Prac used storage during wet on heavy soils #Tanner and Kloosterman *Monaghan, Houlbrooke et al. (2010). NZJAgRes53:
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MITIGATING direct FDE losses with deficit irrigation
Source: Dave Houlbrooke, AgResearch
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Stock & headwater wetlands
cattle grazing of small/shallow wetlands high E. coli load, especially in storms (6M/100 ml) increases N exports tracks/ channelisation BUT grazing by sheep may stimulate plant growth
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Taupo wetland & cattle 1700 m2 grass, rushes, sedges Exports
baseflow 32 g TN/d cattle 306 g TN/d cattle 9% of time => 34% of TN export
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Headwater wetland benefits at Whatawhata: 1. trap sediment
10 100 Native forest Pasture HW wetlands Pasture no wetands SS (g/m3)
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Whatawhata wetland Mean & S.D Inflow Outflow Inflow Outflow
Wetland: 60 m2 grazed headwater wetland 9 ha catchment mean Q = 0.4 l/s Mean & S.D Inflow Outflow Inflow Outflow
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Stock & headwater wetlands
cattle grazing of small/shallow wetlands high E. coli load, especially in storms (6M/100 ml) increases N exports tracks/ channelisation BUT grazing by sheep may stimulate plant growth
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3. Artificial wetlands Tile drains Outlets of small catchments
1-5% of catchment N 20-50% SS ca.80% E. coli ca.90% low P retention Lake Okaro inflow wetland Tanner, et al (2010). NZ guidelines: Constructed wetland treatment of tile drainage. McKergowet al (2007). Stocktake of diffuse pollution attenuation tools...
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4. Grass filter strips band of managed grass that provides a buffer between a source and a water body
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what makes a GFS work? barrier dense vegetation
causes runoff to pond and deposit material dense vegetation slows water and creates tortuous paths sieves runoff unsaturated uncompacted soils allows infiltration to occur
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GFS & pasture runoff Waikato (Smith, 1989)
200 150 100 50 Particulate P (mg m-3) 50 100 150 1500 1000 500 Nitrate (mg m-3) Particulate N (mg m-3) 25 50 75 SS (g m-3) Grazed no filter Grazed with grass filter (6% of hillslope)
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Matching GFS form with purpose and location
paddock-edge GFS filter surface runoff lower paddock boundary contour GFS filter surface runoff mid paddock (strip grazed pasture) grass hedge intercept concentrated flow and filter surface runoff concentrated flow paths
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How wide: GFS widths for SS control
Modelled# as Fn of slope angle & length, soil clay content and drainage: low (<7%) slopes, GFS widths of mostly 1-5% of hillslope predicted to remove 80-95% SS med (7-20%) slopes, widths 2-15% of hillslope - remove 50-95% SS International review*: 5m usually removes 80% SS #Collier et al *Yuan, et al . (2009).. Ecohydrology 2(3):
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