Surface Water Reports 2011 - includes Rai Catchment Management Plan

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Surface Water Reports 2011 - includes Rai Catchment Management Plan

2011 Monitoring Summary - Surface Water Quality

Monitoring is carried out at 54 sites across the region. Some sites are monitored monthly and some annually. A mixture of physical, chemical and biological measurements are taken at each site. Approximately 50% of sites are graded as good or excellent and 20% of sites are graded as poor or very poor.

Monitoring is carried out at 54 sites across the region as shown in the above map. Some sites are monitored monthly and some annually. A mixture of physical, chemical and biological measurements are taken at each site.

Key points

  • 54 river sites are monitored across Marlborough.
  • Chemical, physical and biological components are measured and analysed to determine water quality grades.
  • High concentrations of suspended solids, bacteria and heavy metals occur after heavy rainfall, particularly in urban and agricultural catchments.
  • Diffuse pollution is the main cause of river pollution in Marlborough.
  • Approximately 50% of sites are graded as excellent or good.
  • Approximately 20% of sites are graded as poor or very poor.

2011 Surface Water Report

Surface water sampling of rivers and streams is carried out in order to assess the current state of water quality in our surface waters and to allow for changes or trends in water quality to be detected over time. Water quality results are summarised and grades (Excellent – Very Poor) are assigned to each site.

Why we Monitor Water Quality

  • To assess the current state of our freshwaters for the region
  • To identify trends in water quality over time
  • To assess the effectiveness of land management practices
  • To ensure the values of our rivers and streams (ie: recreational, ecological, fish spawning etc) are not compromised by existing and changing land use practices
  • To monitor the effectiveness of our plans and policies.

Rai Catchment Management Plan

Prepared for Marlborough District Council by NIWA. Although water quality in the Rai River and its tributaries is generally quite good – on an average annual basis – there are times of the year when this is not the case (notably during summer low-flows) when inputs from pastoral agriculture adversely affect the river system.

River water and habitat quality in Marlborough’s Rai River catchment has, at times, become degraded as a result of inputs from farming in the catchment.

Marlborough District Council engaged NIWA to review and report on the current water quality situation in the catchment with a view to providing analysis and guidance as to practical and effective future actions that can be taken to address the water quality issues in this catchment.