Aquifer Test at Woolston/Heathcote, Well M36/1160 in the Riccarton
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The quality of coastal waters between Kaikoura and Pegasus Bay July 1993 – June 2006 Report U07/16 Lesley Bolton-Ritchie March 2007 Report U07/16 58 Kilmore Street PO Box 345 Christchurch Phone (03) 365 3828 Fax (03) 365 3194 75 Church Street PO Box 550 Timaru Phone (03) 688 9069 Fax (03) 688 9067 Website: www.ecan.govt.nz Customer Services Phone 0800 324 636 The quality of coastal waters between Kaikoura and Pegasus Bay Executive Summary This report presents and interprets the water quality data collected by Environment Canterbury at sites located from Kaikoura to south Pegasus Bay between July 1993 and June 2006. The data were collected for varying periods of time, over different time periods and the sites sampled changed over time. For the purpose of this report the coastline from Kaikoura to Pegasus Bay was divided into three geographic areas. These areas were Kaikoura (from just north of Kaikoura township to Haumuri Bluffs), Hurunui (from Haumuri Bluffs to just north of the Waipara River mouth) and Pegasus Bay (from just north of the Waipara River mouth to Scarborough Beach). Samples were collected from nine Kaikoura, six Hurunui and eight Pegasus Bay sites. Sites were typically sampled monthly over a year-long period but the year/s of sampling at the sites varied. Some sites were only sampled for a year while other sites were sampled for two or more year-long periods. In the Kaikoura area nutrient and other determinand concentrations differed between sites and were also more variable at some sites than others. The results indicate that the rivers, creeks and streams that discharge to the coast in this area impact on coastal water quality, with: • Lyell Creek affecting coastal water quality at the site located just right of the creek mouth • The Kowhai River affecting coastal water quality in South Bay • The Ote Makura stream affecting coastal water quality in Goose Bay • The Oaro River affecting coastal water quality at Oaro Oxidation pond seepage in particular, but also dairy factory wastewater and Middle Creek water, could account for the variability in TN and TP concentrations in the sea water 1 – 2.5 km south of these inputs. The coastal water in Ingles Bay is not impacted by any significant nutrient inputs. In the Hurunui area the variability in nutrient concentrations at some sites indicated site specific, localised influences on coastal water quality. These localised influences are more than likely the surface water bodies that discharge to the coast in the vicinity of each sampling site. In Pegasus Bay the near shore salinities were lower than those further from the shore which suggests that all of the nearshore water in Pegasus Bay is slightly diluted. The freshwater sources are the Waimakariri, Waipara and Kowai rivers, Ashley Estuary and Avon-Heathcote Estuary/Ihutai and stormwater outlets. The nutrient data indicate that water flowing out of the Avon-Heathcote Estuary/Ihutai affects the sea water nutrient concentrations to at least 6.2 km north and 1.8 km south of the estuary mouth. Avon-Heathcote Estuary/Ihutai water has a greater impact on nutrient concentrations at the waters edge in Pegasus Bay than the Waimakariri River does. This should change once sewage is no longer discharged into this estuary. The data suggests that Waimakariri River water affects the salinity but not the nutrient concentrations at Woodend Beach (5.5 km north) and Spencerville Beach (4.6 km south) of the river mouth. To determine the along-shore extent of the impact on the Waimakariri River on nearshore nutrient concentrations will require sampling at sites located close to and at increasing distances away from the river mouth. The stormwater discharged at Waimairi Beach likely affects enterococci and chlorophyll-a concentrations in the sea water at this beach. The information in this report provides: • a baseline against which any large changes in water quality as a result of the discharge of treated sewage directly into Pegasus Bay (from the Waimakariri District Council outfall and the Christchurch City Council outfall) can be assessed. • a baseline against which any large changes in water quality as a result of lower nutrient concentrations in the Avon-Heathcote Estuary/Ihutai (once sewage is no longer discharged into the estuary) can be assessed. • information that will be useful to resource managers in assessing the suitability of water quality for the uses and values associated with this part of the coast • information that will be useful to future resource consent applicants for, for example, aquaculture or discharges to the coast. Environment Canterbury Technical Report 1 The quality of coastal waters between Kaikoura and Pegasus Bay 2 Environment Canterbury Technical Report The quality of coastal waters between Kaikoura and Pegasus Bay Table of Contents Executive Summary...........................................................................................................1 1 Introduction .............................................................................................................7 1.1 The study area ..........................................................................................................................7 1.1.1 Kaikoura...........................................................................................................................7 1.1.2 Hurunui.............................................................................................................................8 1.1.3 Pegasus Bay....................................................................................................................9 1.2 Kaikoura to Pegasus Bay water quality ....................................................................................9 1.3 Objectives of this study..................................................................................................................10 2 Methods .................................................................................................................10 2.1 Sites and depths ............................................................................................................................10 2.2 Sampling regime............................................................................................................................10 2.3 Sample collection....................................................................................................................10 2.4 Sample analyses.....................................................................................................................11 2.5 Data analyses ................................................................................................................................11 3 Kaikoura results and discussion .........................................................................12 3.1 Results ...........................................................................................................................................12 3.1.1 Between sites.................................................................................................................12 3.1.2 Over time .......................................................................................................................16 3.2 Discussion.....................................................................................................................................16 3.2.1 Influences of creeks, streams and rivers .......................................................................17 3.2.2 Other influences.............................................................................................................21 3.2.3 Site K3 in Ingles Bay......................................................................................................21 4 Hurunui results and discussion...........................................................................21 4.1 Results ...........................................................................................................................................21 4.1.1 Between sites...............................................................................................................21 4.1.2 Over time .......................................................................................................................24 4.2 Discussion.....................................................................................................................................24 4.2.1 Influences of creeks, streams and rivers .......................................................................24 4.2.1 Other influences.............................................................................................................27 5 Pegasus Bay results and discussion ..................................................................28 5.1 Results ...........................................................................................................................................28 5.1.1 Between sites...............................................................................................................28 5.1.2 Over time .......................................................................................................................33 5.2 Discussion...............................................................................................................................36 6 Future investigations and monitoring.................................................................38 7 Acknowledgements...............................................................................................39