Whangamarino Wetland Study and Ongoing Monitoring
Client: Waikato Regional Council
PDP was first engaged in 2015 by Waikato Regional Council to undertake a sedimentation and water quality survey for the Whangamarino Wetland, which is part of the Lower Waikato Flood Control Scheme. The purpose of the study was to understand the flux of suspended sediment into the Whangamarino Wetland. The information obtained from the study supported a Waikato Regional Council application to renew its resource consent for the Lower Waikato Flood Control Scheme.
The field investigation consisted of:
- Sampling 10 monitoring sites during three different scenarios: at baseflow, when the Waikare control gates were partially open, and when the Waikare control gates were fully open.
- Continuous physio-chemical monitoring (pH, electrical conductivity, turbidity, temperature and dissolved oxygen) using hand held water quality instruments, and flow gauging.
- Water quality samples collected at each of the monitoring locations and analysed for nutrients (nitrate, nitrite, dissolved reactive phosphorus, pH and electrical conductivity.)
- Total Suspended Sediment (TSS) sampling was carried out using a DH48 depth integrated sampler to allow average sediment loading to be calculated and to help understand sediment processes within the wetland.
- Sediment cores were taken at each of the monitoring locations using an Ogeechee sediment core sampler, to help understand the sediment quality and to identify the source of the sediment.
- Trace metal analysis of the suspended sediment (total dissolved metals) within the water column were used to characterise a chemical fingerprint at each sampling location. The purpose was to identify the source of the sediments within the Whangamarino Wetland.
- Continuous water quality monitoring
- Sediment flux monitoring
- Field validation monitoring
- Data management and reporting
- Council liason
Client: Waikato Regional Council
Since the initial study, PDP has continued to undertake a number of maintenance and monitoring packages for Waikato Regional Council. This has required the design and management of several remote continuous water quality/hydrometric monitoring stations within the Whangamarino Wetland. Continuous monitoring of water flow, water level, water velocity, temperature and turbidity is a requirement of the consent in order to understand the flux of suspended sediment into the Whangamarino Wetland.
Key features of the ongoing monitoring include:
- Field validation monitoring of flows, suspended sediment concentrations, turbidity readings and dissolved oxygen concentrations.
- Visual inspections of installed staff gauges to validate water level data obtained by continuous monitoring.
- Collection of samples for water quality analysis (Total Nitrogen, TKN, Ammoniacal-N, Nitrate, Nitrite, Total Phosphorous and Dissolved Reactive Phosphorous) using a Van dorn bottle.
- Flow gauging using an M9 Acoustic Doppler Current Profiler (ADCP) (for high flow monitoring) and a handheld Acoustic Doppler Velocimeter (ADV) (for low flow monitoring) to develop flow rating curves.
- Development of sediment rating curves for each monitoring site and correlating sediment concentrations with turbidity measurements.
- Data quality assurance and management using HYDSTRA. All measurements and quality assurance checks are undertaken in accordance with the requirements of the National Environmental Monitoring Standards (NEMS).
- Preparation of detailed annual reports and more frequent (i.e. monthly to 6 monthly) brief data summary reports for submission to Waikato Regional Council, reporting the results of the above investigations.
The continuous monitoring has required the physical installation of instrumentation at each of the Whangamarino monitoring sites. PDP reviewed a range of instrumentation types that would both meet the project objectives and conform to NEMS standards. It was determined that the most suitable long-term instrumentation included:
- Side looking Acoustic Doppler Profilers (ADP) to allow for continuous measurement of water flow, water level, water velocity and temperature. The ADP can also provide estimates for suspended sediment concentrations.
- Turbo Turbidity Sensors to produce a Formazin Nephelometric Unit (FNU) output that can be used to estimate sediment concentrations within the water column.
- Pressure Transducers to provide water level measurements.
- Staff Gauges to facilitate quality assurance assessment for water levels obtained.
- D-Opto Dissolved Oxygen Sensors capable of measuring dissolved oxygen concentration, dissolved oxygen saturation and temperature and is equipped with an anti-bio-fouling mechanism.
- An INW barometric pressure logger, which has allowed Waikato Regional Council to meet the NEMS requirement to have a continuously deployed barometer within 30 kilometres of all monitoring sites.