Wairarapa water quality network 1991-92 and macroinvertebrate analysis

Abstract

This report is divided into two sections. The first is a baseline monitoring programme for the Wairarapa Division of the Wellington Regional Council (WRC). This will assist the WRC in meeting the purpose of the Resource Management Act 1991. The second section is a study of macroinvertebrate community indices and sampling methods. The baseline monitoring programme will continue for five years. This report describes the first year results of that report. The baseline monitoring programme was carried out on four rivers in the Wairarapa catchment. These are the Ruamahanga, Waingawa, Waiohine and Tauherenikau Rivers. Physical, chemical and biological spatial and temporal water quality trends were tested at twelve sites. The objective was to introduce an understanding of river water quality dynamics and indicate possible causes of deterioration. Results showed turbidity, nutrients and water quality often failed to meet acceptable standards for aquatic life sustainability, recreational use and aesthetics. Water quality habitat deteriorated downstream and low flows were believed to be a controlling factor in periphyton abundance. Nutrient inputs during summer low flows were of greatest concern due to their impact on periphyton growth. Sources of water clarity deterioration were also discussed and erosion was believed to be largely influential. Trends were generally typical of other parts of New Zealand. Physical, chemical and biological interactions were discussed. Using data from the baseline survey, macroinvertebrate communities and methods were examined in more depth in the second part of this report. Variations of the macroinvertebrate community index were tested against each other and kick and Surber sample methods were compared. There was no consistent preference for a particular MCI method and little significant difference was found between kick and Surber samplers.