In-River’ Nutrient Loads
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What do we currently know? …about ground & surface water quality… & land use… in the Waiau River catchment Gathering current knowledge with the Science Stakeholder Group: 16 November 2016, Amberley Purpose • Share what we (the whole SSG) know • Find, & plan to fill, knowledge gaps • Reach a level of comfort with messages …to inform ZC & wider community Outline topics for today 1. Groundwater quality (20 mins) 2. Surface water quality / ecology (60 mins) 3. Current land use & N loads (20 mins) 4. Next steps… Waiau catchment groundwater quality Maureen Whalen – Groundwater Science Key messages • Groundwater quality is good overall • Vulnerable to bacteria impacts • Some wells with elevated nitrate • Note upward nitrate trends in the Culverden Basin • Useful to compare to data from other organisations Groundwater uses in the catchment Primary use is irrigation and drinking water supply Long-term groundwater quality monitoring wells • Good spatial coverage • New Emu Plains well • Variable length records (<2 to >20 years) Median E. coli counts • Groundwater is vulnerable to bacteria impacts Maximum Nitrate-Nitrogen concentrations • Generally, maximum nitrate concentrations are lower than NZ drinking-water standards • A few wells have sufficient long- term records to determine trends Nitrate-Nitrogen trends (2006 – 2015) • Most wells have no clear upward or downward trend • Hanmer Plain wells don’t have long enough record to see trends Amuri Plains area well 18 Increasing nitrate trend since 2006, 16 possibly land-use intensification 14 12 10 MAV (11.3 mg/l) 8 6 4 2 0 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 Parnassus area well (10m) 9 Decreasing trend since 2008, nitrate seems 8 to respond to large recharge events 7 6 5 4 3 2 1 0 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 Parnassus area well (22m) 14 12 MAV (11.3 mg/l) 10 8 6 4 • No increasing or decreasing trend since 2006 • Increasing from 1995 to 2006 2 • Near MAV 0 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 Phosphorus concentrations (2016) Hanmer well - May be due to naturally occurring conditions Groundwater quality comparison with NZ drinking water standards Community drinking water supplies – protozoa test results • Protozoa (giardia and cryptosporidium) are not removed by most drinking water treatments (such as MIOX). • Tests for protozoa are done regularly for HDC on: – Amuri community drinking water scheme (Well 6.7m deep connected to Waiau River); – Cheviot community drinking water scheme (Well 13m deep connected to Waiau River). • No protozoa have been detected. Key messages - recap • Groundwater quality is good overall • Vulnerable to bacteria impacts • Some wells with elevated nitrate • Note upward nitrate trends in the Culverden Basin • Useful to compare to data from other organisations Questions Surface Water Quality in the Waiau River Catchment Adrian Meredith – Principal Surface Water and Ecology Scientist Kimberley Dynes – Ecology Scientist Environment Canterbury • Waiau River (3 sites) 2004-Present • Mason River and Leader River: 2005-Present • Home Stream, Rotherham Stream, Lowry Peaks Drain – monitored by AIC Home Stream Rotherham Stream Lowry Peaks Drain Outline of Water Quality Topics • Life supporting capacity – Temperature, DO, sediments • Overall Ecosystem Health • Periphyton – Biomass, cover, green algae, cyanobacteria • Drivers of Periphyton – Nutrients and flow • Swimmability Life-supporting Capacity Water Temperature 2011-12 2012-13 2013-14 2014-15 2015-16 Mason River SH70 20.1 16.9 22.2 25 21.4 Leader River SH1 21.5 19.1 22.9 22.9 20.8 Waiau River Leslie Hills Road 15.2 14.3 13.9 17.6 15.2 Waiau River at Waiau 18.3 15.4 18.8 21.1 17.1 Waiau River SH1 18.6 16.9 18.2 23.2 18.1 Dissolved Oxygen (% Sat) 2011-12 2012-13 2013-14 2014-15 2015-16 Mason River SH70 93 97 92 95.8 97.6 Leader River SH1 97.4 91.7 92.4 84.7 96.2 Waiau River Leslie Hills Road 94.5 96.8 95 98.2 98.7 Waiau River at Waiau 95.3 94.5 99.4 94.6 100.9 Waiau River SH1 91.8 94.6 92.4 94 85.9 • Water temperature <20 OC; DO >90% to support aquatic species (particularly salmon and trout) • Waiau River water temp OK most years • Max water temp exceeds plan objectives in hill-fed rivers • All rivers well oxygenated environments Life-supporting Capacity Sedimentation 2011-12 2012-13 2013-14 2014-15 2015-16 Mason River SH70 15 10 20 90 40 Leader River SH1 15 5 20 30 30 Waiau River Leslie Hills Road 10 80 15 35 50 Waiau River at Waiau 10 5 - 40 15 Waiau River SH1 20 5 10 50 10 • Sediment is a parameter of growing concern • Sediment smothers benthic habitats (20% cover) • Waiau and tributaries can exceed maximum • More commonly a problem in streams and drains Aquatic Ecosystem Health • Monitoring of aquatic invertebrate species as an indicator of overall water quality and stream habitat • QMCI = a grading system based on the relative sensitivity of a species to water quality and habitat degradation. Macro-invertebrates (bugs) • Macro-invertebrates (>0.5 mm) are the most commonly researched and monitored EPT 670 species – follow the keys 9 8 7 Plan Minimum 6 Outcome QMCI 5 4 3 2 Waiau River Hanmer Road Hanmer River Hope River SH7 Boyle River SH7 Leslie Hills Road Waiau River SH1 Mason River SH7 Leader River SH1 Mason River SH70 Waiau River at Waiau • All sites except the Leader River at SH1 achieve the minimum plan Objective Key Messages: Aquatic Ecosystem Health • All sites, except the Leader at SH1 meet the minimum plan objective • Leader River impacted by low flow, sedimentation/embeddedness, nuisance periphyton growth and warm temps • Streams like Lowry Peaks and Rotheram Stream? Periphyton Monitoring • Total Biomass • Total cover % • Filamentous algae • Cyanobacteria mats • Didymo • Rivers different susceptability Total Periphyton - biomass • NPS-FM National Objectives Framework – Benthic Periphyton – chlorophyll ‘a’ • indicates benthic periphyton is: – Target <50 mg/m for Waiau River at Leslie Hills – Only have suitable data at 2 sites • Waiau River at Leslie Hills generally good • Mason River variable and not suitable all years Chlorophyll a No. samples National Bottom line CBA SQ34704 Waiau River Leslie Hills 3 yr 36 0 0% 0 0% 1 3% 28 78% 2011-12 12 0 0% 0 0% 1 8% 8 67% 2012-13 12 0 0% 0 0% 0 0% 8 67% 2013-14 12 0 0% 0 0% 0 0% 12 100% SQ34869 Mason River SH70 3 yr 36 2 6% 3 8% 2 6% 22 61% 2011-12 12 2 17% 3 25% 1 8% 3 25% 2012-13 12 0 0% 0 0% 1 8% 10 83% 2013-14 12 0 0% 0 0% 0 0% 9 75% Filamentous Algae periphyton cover Periphyton (long filament) 2011-12 2012-13 2013-14 2014-15 2015-16 Mason River SH70 15 10 30 15 20 Leader River SH1 30 20 45 40 85 Waiau River Leslie Hills Road 0 0 4 1 10 Waiau River at Waiau 0 0 - 2 0 Waiau River SH1 0 0 0 1 2 • elevated green filamentous algae in tributaries • negligible green filamentous algae in Waiau River • Different susceptabilities Potentially toxic cyanobacteria (algae) mats in rivers • Alternative algae growth form: – Black/Brown mats – Potentially toxic to livestock, dogs and people – Odorous and taints food • May have different drivers to filamentous green algae – Water temperature tolerances – Nutrient concentrations – Nitrogen and Phosphorus high nitrates, low dissolved phosphorus Phosphorus sourced from fine sediment – Stable bed, reduced flushing flow frequency, often more common in riffles cyanobacteria mat cover in rivers 80 70 60 50 40 Max % Cover Max Cover % cyanobacteria 30 20 10 0 Mason River SH70 Leader River SH1 Waiau River Leslie Waiau River at Waiau River SH1 Hills Road Waiau 2012-13 2013-14 2014-15 2015-16 Public Health Alert Guideline LWRP Objective/Action Guideline - Most problematic in Leader River - Present in Waiau River – Highest at upstream site? - Waiau River may be more susceptible to black mats. cyanobacteria mats in rivers • No public health warnings have been issued • Leader River exceeded levels but is not a recognized bathing site • Local observations suggest side braids of Waiau at SH1, and immediately below drains and streams have a denser cover of mats (than the main braid) • Waiau River more susceptible to mat growth, but flow (floods) currently limits growths Water quality drivers of periphyton • Targets are periphyton growths and state of the rivers • Nutrients and water quality measured as a driver of growths • Not as a target in themselves Nutrients and their impact on water quality • Nutrients – At low concentrations - Beneficial in encouraging thin growths of algae in rivers (food for aquatic life) – At higher concentrations – encourage conspicuous nuisance growths of algae – At very high concentrations some nutrients (Nitrate-N, Ammonium-N) can be toxic • Different guideline address different effects Nutrient impacts on periphyton – Nitrogen • Increase in nitrogen at SH1 – indicating moderate- high risk of nuisance periphyton blooms 1.2 1.0 0.8 Probability of nuisance growth 0.6 DIN (mg/L) High 100% 0.4 Moderate 70% 0.2 Adequate 50% 0.0 Limiting 30% Waiau River Waiau Leslie Road Hills Leslie Waiau RiverSH1 Waiau Leader River SH1 Leader Mason Mason River SH70 Waiau River Waiau Waiau at Nutrient impacts on periphyton – Phosphorus - Tributaries show moderate increase in risk of nuisance growths - Risk not increasing down the Waiau River 0.045 0.040 0.035 0.030 Probability of nuisance growth 0.025 0.020 High 100% DRP (mg/L) 0.015 0.010 Moderate 70% 0.005 Adequate 50% Limiting 0.000 30% Waiau River Leslie Hills Road Waiau River SH1 Leader River SH1 Mason River SH70 Waiau River at Waiau Nutrient impacts on periphyton – Phosphorus • Phosphorus concentrations for all