Question On Notice No. 1856 asked in the Legislative Council on 1 February 2024 by Hon Dr Steve Thomas

Question Directed to the: Parliamentary Secretary to the Minister for Water Parliament: 41 Session: 1  

Question  

I refer to the Vasse River as it flows though Busselton, and I ask: 

(a) what plan does the Government have in place to improve the water quality in the Vasse  River; 

(b) what budget does the Government have in place to improve the water quality in the Vasse  River; 

(c) is the Government measuring the level of phytoplankton in the Vasse River; (d) if yes to (c), in what locations is the testing occurring and at what frequencies; (e) please table the results of the testing in part (c) for 2021, 2022 and 2023; (f) to which Government department(s) is any testing from part (c) being reported; (g) are these reports made publicly available; 

(h) what dredging has been done in the Vasse River to improve water quality and what  dredging is planned in the future; 

(i) how is the success of the dredging being measured; 

(j) how much phoslock has been used in the river and how much is planned to be used; (k) how is the success of the use of Phoslock being measured and please table those  measurements; 

(l) has any used Phoslock been removed from the river; and 

(m) how many toxic algal or phytoplankton blooms have been recorded in the Vasse River in  2021, 2022 and 2023? 

Answered on 12 March 2024  

(a) The Vasse Wonnerup Wetlands and Geographe Bay Water Quality Improvement Plan  (2010). In addition, the multiple agency Vasse Taskforce coordinates water quality  improvement actions in the Vasse Geographe catchment including the Lower Vasse River. 

(b) The Revitalising Geographe Wetlands project budget has been around $1.6 million  annually since 2015. The specific budget on the Lower Vasse River varies annually  depending on remediation works undertaken. 

(c) Yes. 

(d) Fortnightly at three locations (upstream of Bussell Highway, downstream of Strelly  Street Bridge and downstream of the Causeway Bridge). 

(e) Data below are summarised by both biovolume which relates to the guideline and cell  counts which relate to the actual number of phytoplankton cells counted in each sample. 

Please note VASR1 is Vasse river 1 measuring site, which is located downstream of Strellly  St and upstream of the Causeway bridge. VASR2 is Vasse River 2 measuring site at the  footbridge between the Causeway bridge and Camilleri St. Data from the third measuring site  was not included due to no algal or phytoplankton bloom activity.

Year Site Total Cyanobacteria Biovolume (mm3/L) 

Winter Minimum Summer Maximum 

2021 VASR1 0 93 

2022 VASR1 0 47 

2023 VASR1 0.01 171 

2021 VASR2 0 134 

2022 VASR2 0 34 

2023 VASR2 0 183 

Year Site Total Cyanobacteria Counts (cells/mL) 

Winter Minimum Summer Maximum 

2021 VASR1 94 810,000 

2022 VASR1 25 5,000,000 

2023 VASR1 148 1,800,000 

2021 VASR2 32 690,000 

2022 VASR2 34 6,200,000 

2023 VASR2 47 1,700,000 

(f) Department of Health and the City of Busselton 

(g) No. 

(h) Stage 1 and 2 dredging undertaken by the City of Busselton in 2022 and 2023 with Stage  3 proposed for 2024. 

(i) Water quality monitoring in the river. 

(j) Forty tonnes of phoslock has been applied to the Lower Vasse River over two periods in  November and December 2023. 

(k) Water quality and phytoplankton monitoring. 

(l) Phoslock is not removed from the river once it has been applied. The phoslock remains in  the sediment where it can continue to bind phosphate. 

(m) In each of those years there has been an ongoing blue-green algae bloom lasting several  months over summer. It is not practical to divide this continuous presence into separate  blooms although the species composition changes over time in response to changes in supply  of nutrients, light, temperature and salinity change.