New Water Policy and Practice Issue 4, Number 1, Fall 2017 | Page 47

Risk-Based Pesticide Monitoring in Drinking Water Catchments in Western Australia
The project has focused on three operational drinking water catch-
ments in WA, each with different agricultural land uses and pesticide risk to
water quality. These include two surface water sources and one superficial
groundwater source. At each catchment, a two-year pesticide sample pro-
gram was developed to investigate the most suitable time and location in
the catchment for monitoring. This required a confident understanding of
catchment land uses and characteristics, and historical rainfall data. Addi-
tionally, pesticide risk modelling has been developed to direct efforts with
pesticide risk assessments and sampling at these catchments. The model-
ling has been investigated and designed to utilize tools already available and
routinely used by the Corporation, including Pesticide Impact Risk Index
(PIRI), developed by the CSIRO (Kookana et al. 2005), and Geographical
Information System (GIS).
The aim of the project is to provide the Corporation with confidence
that pesticide risks to drinking water sources are understood, and assurance
that they are being effectively managed. However, the major challenges for
the Corporation to manage pesticide risk includes the diversity of crops and
pesticide applications sometimes on a small spatial scale, the rapid change
and rotation of crops, the introduction of new pesticides to market, the fact
that not all catchment land is owned or managed by the Corporation, and
the complexity of pesticide transport that is dependent on many variables.
The information below provides an overview of how land-use planning and
management in drinking water catchments is organized and undertaken in
WA, to provide the context in which the pesticide research project is being
undertaken.
Drinking Water Quality Management in Western Australia
The ADWG provides the framework for good drinking water quality man-
agement in Australia and -is based on the best available scientific evidence
(NHMRC 2017). As such, the ADWG provides an authoritative reference for
the Australian water industry to ensure the continual safe supply of drinking
water to end users. This is true for the Corporation, the largest drinking wa-
ter supplier in WA. The Corporation must meet the requirements as stipu-
lated in their Memorandum of Understanding (MoU) with the State’s p ublic
health regulator, the Department of Health (DoH), to continue to supply
drinking water (Water Corporation 2007). To ensure the protection of pub-
lic health, this MoU includes the Corporation’s commitment to continual-
ly meet the objectives of the ADWG, including taking a catchment to tap,
multi-barrier, risk-based approach to drinking water quality management.
Therefore, the first barrier to drinking water quality management is effective
source selection and protection. Pesticide risk has a high profile in the MoU.
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