Surface Water Quality in South West Otago
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Surface Water Quality in South West Otago June 2004 Surface Water Quality in South West Otago ISBN 1-877265-15-2 June 2004 Surface Water Quality in South West Otago i Executive Summary Water quality monitoring in the Wairuna Stream, Waipahi River, Heriotburn and Crookstonburn began in 1996 as part of the state of environment monitoring programme. In response to concerns that water quality may be deteriorating, a more intensive six month surface water quality monitoring programme commenced on the Wairuna Stream in April 2000. Poor water quality results from this programme led to the Waipahi/Clydevale monitoring programme, which encompassed a larger catchment, this ran from October 2002 to October 2003. The third water quality monitoring programme began in May 2000 in the Heriotburn and Crookstonburn catchments. Otago Regional Council has also been working with landowners and farmers in the area to minimise the potential impacts of high density farming in an area which is predominantly tile drained. Water quality monitoring focused on six sites in the Wairuna Stream, ten sites in the Waipahi/ Clydesvale and 14 sites in the Heriotburn and Crookstonburn. Spot water sampling was conducted at all sites with water samples tested for a range of physico- chemical and microbiological parameters. Periphyton and macroinvertebrate sampling was also conducted. The monitoring results indicate that water quality in all three catchments is poor with a deterioration in water quality with distance downstream. For example there was a marked increase in Eschericia coli with distance downstream in all watercourses other than the Kaihiku and Waipahi. In addition, the Heriotburn and Wairuna catchments had extremely high median concentrations of indicator bacteria, all sites exceeding MfE/MoH action/red mode levels (550 E.coli/100ml). Nutrient concentrations were also found to be high, nitrite-nitrate nitrogen exceeds Australia and New Zealand Environment and Conservation Council (ANZECC) 2000 default trigger values at all monitoring sites other than the headwaters in the Crookstonburn, Wairuna and Kahiku Stream. Nutrient enrichment is of concern as at many sites both median dissolved phosphorus and median dissolved inorganic nitrogen concentrations exceed the ANZECC 2000 default trigger values for lowland river ecosystems, suggesting that excessive weed growth or algal blooms are likely to occur. Macroinvertebrate values followed the same trend as water quality, showing a decline with distance downstream, although differences in physical habitat may be a contributing factor rather than a decline in water quality. Poor water quality at most monitoring sites is attributed to various factors, one being tile drains, which are widespread throughout South Otago, these rapidly remove excess surface water to provide better conditions for grass, however they also quickly and efficiently convey farm surface runoff to receiving watercourses. Allowing stock access to water and riparian margins will also degrade water quality through deposition of sediment (bank erosion), increased nutrient input, increased faecal contamination and reduced water clarity. Otago Regional Council’s Land Resource section are working closely with farmers and landowners to improve water quality. Field days, catchment group meetings and sampling at property boundaries all play a part in encouraging landowners to adopt best management practices. On the other hand the Compliance section ensure that breaches of Council rules are investigated and appropriate measures taken. Surface Water Quality in South West Otago Surface Water Quality in South West Otago ii Surface Water Quality in South West Otago Surface Water Quality in South West Otago iii Table of Contents Executive Summary........................................................................................................... i 1 Introduction ........................................................................................................ 7 1.1 Aims and Objectives ............................................................................ 7 1.2 Background Information ...................................................................... 7 1.3 Physico-chemical, Microbiological and Biological Monitoring.......... 7 1.4 Sampling Methods............................................................................... 7 1.5 Monitoring Analytes ............................................................................ 7 1.6 Data Analysis ....................................................................................... 7 1.7 Results .................................................................................................. 7 2 Wairuna Catchment Surface Water Quality Monitoring.................................... 7 2.1 Catchment Description......................................................................... 7 2.2 Water Quality Monitoring:................................................................... 7 2.3 Monitoring Results............................................................................... 7 2.4 Biological Sampling............................................................................. 7 2.5 Discussion ............................................................................................ 7 3 Waipahi/Clydevale Catchment Monitoring Programme.................................... 7 3.1 Catchment Description......................................................................... 7 3.2 Water Quality Monitoring:................................................................... 7 3.3 Monitoring Results............................................................................... 7 3.4 Waipahi River ...................................................................................... 7 3.5 Waiwera River and Tributaries ............................................................ 7 3.6 Kaihiku Stream and Tributaries ........................................................... 7 3.7 Washpool.............................................................................................. 7 3.8 Biological Monitoring.......................................................................... 7 3.9 Discussion ............................................................................................ 7 4 Heriotburn / Crookstonburn Catchment Monitoring Programme ...................... 7 4.1 Catchment Description......................................................................... 7 4.2 Water Quality Monitoring.................................................................... 7 4.3 Monitoring Results............................................................................... 7 4.4 Heriotburn ............................................................................................ 7 4.5 Crookstonburn...................................................................................... 7 4.6 Key Tributaries..................................................................................... 7 4.7 Pomahaka River................................................................................... 7 4.8 Biological Monitoring.......................................................................... 7 Surface Water Quality in South West Otago Surface Water Quality in South West Otago iv 4.9 Discussion ............................................................................................ 7 5 General Discussion............................................................................................. 7 6 Conclusions ........................................................................................................ 7 7 References .......................................................................................................... 7 Appendix 1 ....................................................................................................................... 7 Appendix 2 ....................................................................................................................... 7 Appendix 3 ....................................................................................................................... 7 Appendix 4 ....................................................................................................................... 7 List of Figures Figure 1.1 Location of physico-chemical and microbiological water quality monitoring sites sampled between April 2000 and October 2003............ 7 Figure 2.1 Location of physico-chemical, microbiological and biological water quality monitoring sites. Tributaries 1 and 2 and School Road 1 and 2 were sampled for physico-chemical parameters only............................... 7 Figure 2.2 Box and whisker plot of E. coli concentrations at various sites in the Wairuna catchment between April 2000 and February 2002 ................... 7 Figure 2.3 E. coli bacteria concentrations (back transformed means and confidence intervals, using ANOVA on log scale, alpha 0.05) recorded at various locations in the Wairuna between April 2000 and February 2002 ........................................................................................... 7 Figure 2.4 E. coli bacteria concentrations recorded at various locations in the Wairuna between April 2000 and February 2002, total rainfall mm recorded at Warepa over the preceding 48 hours and total mean flow recorded in the Waipahi River at Waipahi................................................ 7 Figure 2.5 Box and whisker plot of median turbidity concentrations recorded in the Wairuna