Making decisions for freshwater resources in the Greater Heretaunga and Ahuriri catchment area
Outline of Presentations • Purpose for this meeting • What the TANK project is about • What do you value about your freshwater? • A few water quality statistics and what they mean for your freshwater values • What we know about sediment, bacteria and nutrient sources • Good Agricultural Practice • Being involved
Why we are here • This meeting is to introduce TANK project and; • Explain the process and outputs • Provide information about key issues • Encourage and support your involvement in this process • TANK Group decisions need to be informed by community involvement and support • Managing water quality requires integrated catchment management
What the TANK project is about • National direction • NPSFM;2014 • Process and requirements • Timeframes • Objectives, limits and methods • Prevent over-allocation • Quality and quantity • Consent expiry
Greater Heretaunga and Ahuriri Land and Water Plan Change (TANK) Catchments defined from surface water boundaries
TANK Plan Development Process • The TANK Group is a community based collaborative approach to developing regional plans. • A process to; • develop a shared understanding about important freshwater values • enable better understanding of the science and the issues • result in more enduring solutions and; • allow collective responsibility for outcomes • reduce areas of contest in Plan Change process
Project Goal: • Identify values, • Recommend draft plan change to provide for those values by end 2017 TANK Group Membership; • Regional Planning Committee to “have particular regard to any wide range of consensus recommendations people and from the TANK Group” interests represented
Freshwater Values • National Values – compulsory • Ecosystem Health • health and mauri of water • Human health – secondary contact • Other important values include; • Swimming • Irrigation • Mahinga kai • Domestic and urban supply • Stock water
Local Freshwater Values • Key issue; • Managing tributaries of the Ngaruroro and Tutaekuri to meet water quality state for swimming; • Other local values? • Accounting also for impacts on estuary and coastal values • Nutrient and sediment loads in freshwater
Climate: Rain, temperature Land Geology Hills / Plains Land use Sediment Nutrients Pathogens Light Water quality Cultural values Habitat Oxygen Human health Recreation Aquatic Ecosystem Health Stream plants Flow River Algae Sediment Contaminants Nutrients Estuary Temperature DIN/DRP Habitat: mussels, Estuary, fish, sea grass Ocean beds, birds
Ngaruroro and Tutaekuri catchments
Nutrients and algae Algal growth depends on: Nutrients: • Phosphorus (DRP) • Nitrogen (DIN) • Light • Temperature • Resetting flows • Substrate size 12
Tutaekuri catchment Mangatutu Patoka Upper Mangaone Tutaekuri Otakarara Rissington Waikonini Lower Tutaekuri Sherenden
Nutrients and algae: Tutaekuri All samples above Very high guidelines Most samples above High guidelines most samples below Moderate guidelines but many Very high DRP above Very high DRP high DIN Most samples below Low Moderate to stringent guidelines high DIN All samples below all Very low guidelines Very low DRP Very low DIN High DRP moderate DIN Very high DRP Low to moderate DIN
Ngaruroro catchment
Nutrients and algae: Ngaruroro All samples above Very high guidelines Most samples above High guidelines most samples below Moderate guidelines but many above Most samples below Low stringent guidelines All samples below all Very low guidelines Very low DRP Very low DIN E. coli no problem Very high DRP except for: Moderate to • high DIN Ohiwa • (Tutaekuri-Waimate) • (Waitio) Slightly higher nutrients, Very high DRP more algae High DIN
MCI Macroinvertebrate Community Index Photos: Landcare Research Factors influencing MCI Organic pollution / oxygen Temperature Habitat (clean gravel, habitat variability) Poor Fair Toxicants (e.g. ammonia, nitrate) Good Excellent Flow
Water clarity and turbidity, deposited sediment Impact on values Clarity/visibility Amount of particles • • Recreation: Safety, aesthetics; Clogging/destroying nets of filter Determines how well you see in the feeders, water • Abrading, damaging gills. • • Ecosystem health, fishery: Visibility Fills stomach of filter feeders with indigestible silt/clay less energy determines success of fish catching prey (visual drift feeders like trout) for growth, reproduction 19
Water clarity and turbidity, deposited sediment Impact on values Tutaekuri at Lawrence Hut Tutaekuri at Brookfields Bridge Mangatutu Impact on values Clean sediment functions: • Spaces between gravel and cobble are (1) habitat, (2) refuge during flood events and high temperature! • Flow between gravel keeps temperatures cool (braided main stems) • Exchange with groundwater • Reaction surface for microorganisms (cleans water) 20
Sediment: Tutaekuri catchment Clarity <1.5 m 17% cover Clarity 6 m Clarity 2 m 3% cover 10 20% cover Clarity 1.5 m 14% cover Clarity 2 m Increasing sediment 25% cover deposited on stream bed
Sediment: Ngaruroro catchment Increasing sediment deposited on stream bed From upstream to downstream Clarity 5 m Clarity 3 m 30% / 5% cover Clarity 1m Clarity 4.7 m 40% cover 15% cover Clarity <2.5 m 35% cover Clarity 1 m 13% cover Clarity <3.5 m 7% cover
Estuary: Water clarity and turbidity Eelgrass Phytoplankton Clarity/visibility/ light penetration Amount of particles in the water: • • Recreation: Determines how well you Clogs and abrades gills of filter see in the water feeders • Filter feeders have to filter more • Ecosystem health: Visibility less energy for growth, reproduction determines success of fish catching prey • Shift from eelgrass and macroalgae to phytoplankton and high turbidity 23
Deposited sediment Impact on estuarine values Ahuriri Estuary Waitangi estuary Waitangi estuary Deposited sediment: • Change in substrate from gravel and sand (slide on left) to mud (centre slide) means change in species (SoE monitoring) • Smothering of eelgrass and intertidal vegetation (left slide) • Smothering of shellfish beds and other infauna (middle slide and SOE data) • Anoxic layer at surface a sign of increasing fine sediment – nothing can live in this (right slide) ! 24
Estuaries - SOE 70 Aonides spp . (abundance per 0.133m2) 60 50 40 30 20 10 0 0 20 40 60 80 100 20% Mud content (% silt/clay)
Summary No issues with • Nitrate and ammonia toxicity • E. coli (except few tributaries) Keep an eye on • Nutrients (particularly P) in tributaries Algae, - lower Ngaruroro • Sediment
Sediment modelling in the TANK catchments Where from, where to and how much?
The SedNet model • Comprised of several sub models • Models takes into account; Land slope Land cover River flows River bank erosion Sediment deposition on river beds & banks
What the model can do? SedNet modelling can; • Identify sources of sediment. • Calculate the area of land (hectares) that is vulnerable to sediment generation. • Estimate the amount of sediment coming from these areas in tonnes. • Estimate catchment and sub catchment loads (tonnes/Year) and yields (tonnes/km 2 /year). • Predict rough particle size of sediment produced e.g. sandy, silty or clay. • Predict the amount of reduction with increasing stock exclusion.
Each Catchment can be quantified (tonnes sediment loss per year) Total sediment loss from the combined TANK catchments of 1.16 million tonnes per year
Tutaekuri catchment - load v Yield Total yield (t/km 2 /yr) Total load (t/yr) t/km2/yr Sediment loss < 0 Tutaekuri Sub-catchments (tonnes) Mangaone 171,884 0 - 250 Average loss of Tutaekuri Corridor 71,635 250 - 500 4.5 tonnes/ha/yr Upper Tutaekuri 51,569 500 - 750 Mangatutu 50,554 Waikonini 17,578 750 - 1000 Otakarara 9,072 1000 - 1250 Tutaekuri Catchment Total sediment loss (Tonnes / year) 372,292 > 1250
Ahuriri catchment - load v Yield Total yield (t/km 2 /yr) Total load (t/yr) t/km2/yr < 0 0 - 250 Average loss of 250 - 500 3.1 tonnes/ha/yr 500 - 750 750 - 1000 1000 - 1250 > 1250
Ngaruroro catchment - load v Yield Total yield (t/km 2 /yr) Total load (t/yr) t/km2/yr < 0 0 - 250 Average loss of 250 - 500 500 - 750 3.5 tonnes/ha/yr 750 - 1000 1000 - 1250 > 1250
Ngaruroro catchment - load v Yield Total yield (t/km 2 /yr) Total load (t/yr) t/km2/yr < 0 0 - 250 Average loss of 250 - 500 500 - 750 3.5 tonnes/ha/yr 750 - 1000 1000 - 1250 > 1250
Karamu sub-catchment sediment loss (t/year) Sediment loss Karamu Sub-catchments (tonnes) Paritua-Karewarewa 27,293 Awanui 5,807 Poukawa 4,748 Havelock North Streams 3,328 Karamu-Clive Corridor 1,058 Mangateretere -148 Louisa -238 Irongate-Southland -521 Muddy Creek -1,726 Hastings Streams -2,398 Raupare -4,201 Karamu Catchment Total sediment loss (Tonnes / year) 33,001 Average loss of 0.6 tonnes/ha/yr
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