Reducing risks to drinking water supply by prioritising catchment investment

Seqwater invests in programs to reduce risks to the drinking water supply 

Seqwater is South East Queensland’s (SEQ’s) Bulk Water Supply Authority. It operates over 30 water treatment plants which provide safe, secure and cost-effective drinking water to over 3 million people across the region.  

Seqwater operates an extensive program of on-ground, catchment management interventions, to protect source water and to reduce the risks to water treatment plants.  

The primary hazards to water quality targeted by Seqwater’s catchment investment program are fine sediment and microbial pathogen pollution (bacterial, protozoa and viruses). These primary hazards are generated from 19 different hazardous processes like streambank erosion and feedlots. 

Interventions that target these hazardous processes are inherently land-based activities (e.g. riparian revegetation and cattle exclusion fencing). Seqwater only owns around 5.4% of the drinking water supply catchments. This means that they must work in close partnership with many organisations and landholders to implement their program of on-ground interventions for source water protection. A key challenge is how to develop and communicate catchment investment programs that deliver the best return on investment for Seqwater and provide a rigorous scientific basis to engage with partner organisations.  

CIDSS helps decide what to do and where to do it to most effectively reduce risks  

In collaboration with Seqwater, Truii has developed the Catchment Investment Decision Support System (CIDSS), a web-based spatial optimisation application that creates portfolios of potential on-ground, catchment management interventions.  

The CIDSS uses base data of the current level of 19 hazardous processes across approximately 1500 mini catchments in the region, along with a library of more than 60 alternative on-ground interventions, which can be delivered to address those hazardous processes and ultimately reduce the risk of pollution to the water treatment plants.  

The importance of the location of the intervention within the catchment, relative to the water treatment plant, is managed by calculating the attenuation in pollution abatement throughout the river and lake system.  

Each of the water treatment plants may have different capacity to treat polluted water (plant risk profiles), which must be taken into consideration when developing potential investment strategies. 

The CIDSS considers the multiple downstream water treatment plants from any place in the landscape to develop potential investment portfolios that give the greatest risk reduction for a given investment. 

A key feature of the CIDSS is the ability to ‘review and refine’ these portfolios by allowing the user to adjust the alternative interventions to develop pragmatic investment strategies that fulfill partner expectations as well as Seqwater’s needs. 

The results of the potential investment strategies are presented for comparison and communicated in terms of the change in risk at each of the water treatment plants.