Oral Presentation Australasian Groundwater Conference 2017

Optimising of Greater Wellington Regional Council’s groundwater monitoring networks using multi-correlational and Kriging based methods (267)

Doug Mzila 1
  1. Greater Wellington Regional Council, Wellington, NEW ZEALAND, New Zealand

Groundwater resources of the Wellington region have a high environmental and cultural value in sustaining freshwater ecosystems and an important social and economic value in meeting water demands for domestic, municipal, agricultural and industrial purposes. Greater Wellington Regional Council (The Regional Council) is in the process of rationalising its groundwater level and quality networks in line with the above mentioned objective values.

This paper presents methods used by the Council aimed at optimising of groundwater level observation networks and the improvement in representativeness of the network. A multi-correlation analysis was undertaken to determine which wells to exclude (or commit lesser monitoring resources) from the current network because they add little or no beneficial information (redundant). A set of key (index) wells were identified and used to generate multi-regression equations to produce data in place of the redundant wells. Kriging based spatially balanced and density sampling algorithms were used to optimise the monitoring network and also identify where new well locations are required. The algorithms were used to find the set of wells whose removal leads to the smallest increases in the weighted sum of the:

  • Mean standard error at all nodes in the Kriging grid where the piezometric surface is estimated (the Kriging grid was modified to include index wells identified from the multi-correlation method)
  • Root-mean-squared error between the measured and estimated water level elevation at the removed sites
  • Mean standard deviation of measurements across time at the removed sites.
  • Mean measurement error of wells in the reduced network

A total of 24 monitoring wells were regarded as redundant and removed or downgraded in terms of monitoring frequency and equipment. However an additional 30 new wells were identified for installation. The final number of additional wells will be dictated by budget constraints and acceptable levels of uncertainties in the data.

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