Estuaries and Catchments team, Water Wetlands and Coasts Science Branch, Science Division, Office of Environment and Heritage

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1 Impact assessment of Berkeley Vale subcatchment pollutant loads in nearshore zone of Tuggerah Lakes Rebecca Swanson, Aaron Wright, Peter Scanes and Angus Ferguson Estuaries and Catchments team, Water Wetlands and Coasts Science Branch, Science Division, Office of Environment and Heritage

2 Overview Berkeley Vale, Tuggerah Lakes / local issues Objectives Sampling sites - water quality Catchment model MUSIC Groundwater inputs - survey Review of stormwater network/sqid Recommendations / future research

3 Central Coast NSW Central Coast approximately 50km north of Sydney Tuggerah Lakes are three shallow interconnected lagoons (max depth 3 m) Tuggerah Lake Some exchange with ocean water at The Entrance 3

4 Click to edit Master title style Click to edit Master text styles Berkeley Vale Tuggerah Lake Southern basin The Entrance 4

5 Tuggerah Lakes Catchment and Lake Processes Overland runoff from rural catchments dominates annual freshwater flow to the lakes Biological recycling controls nutrient dynamics in the lake 5 Urban stormwater and groundwater seepage have significant impacts on the ecology of nearshore zones Winds cause sediment to be stirred up into the water column Ocean exchange is minimal relative to lake volumes and freshwater runoff 5

6 Marine plants In the water column (400x magnification) On the bottom Phytoplankton-microalgae Primarily use dissolved inorganic nutrients - ammonium, nitrates, phosphates from catchment inputs Macroalgae Primarily use recycled nutrients and localised sources in near-shore zone Seagrasses Primarily use recycled nutrients and localised sources in near-shore zone Benthic microalgae Use dissolved inorganic nutrients from catchment (nitrates, phosphates) 6 Bacteria in sediment 6

7 Migration of seagrass Urban stormwater is trapped in nearshore

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9 Wrack Black Ooze Decaying macroalgae Macroalgal bloom Eutrophication

10 The bloom The collapse

11 Tuggerah Lakes Restoration Project 1990s

12 Reclaimed foreshore / STZs / open drains

13 Objectives Identify pollution sources and pathways from Berkeley Vale subcatchment to nearshore zone Water quality sampling (creeks, STZs, open drains, nearshore) Groundwater inputs? Catchment model Assess the effectiveness of stormwater network and SQIDs Recommendations to reduce ooze in nearshore

14 Berkeley Vale A discrete subcatchment not connected to main drainage lines 14

15 Water quality - snapshot Sampled in dry and wet conditions Grab samples collected from STZs / open drains / nearshore Total suspended solids Nutrients Chlorophyll What is the water quality in open drains and nearshore? Physicochemical parameters multiprobe EXO Salinity Temperature Dissolved oxygen ph fdom (dissolved organic matter) 15

16 BV4 16 BV9 BV7

17 BV4 BV10 BV1 BV3

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19 19

20 Salinity dry wet Berkeley Creek Salinities in Wet Sampling Freshwater influence from creek inflows is apparent at northern and southern sites Localised catchment inputs greater influence in mid section Groundwater influence at BV5? BV1 BV2 BV3 BV4B BV5 Drain #1 outlet BV7 BV8 Drain #2 outlet BV9 BV10 Tumbi Creek Bridge Tumbi Creek Salinity psu

21 Nitrogen TN = full bar DON Particulate N NOT readily taken up by plants NH4+ NOx Readily taken up by plants ANZECC guidelines TN 300 µg/l

22 Phosphorous TP = full bar DOP Particulate P NOT readily taken up by plants DIP = phosphates Readily taken up by plants 22 ANZECC guidelines TP 30 µg/l

23 BV5 poorest water quality of all sites 23

24 Water Quality Summary Water quality was worse during the dry sampling run than the wet Median Turbidity, 20NTU vs 5NTU Median Dissolved Oxygen, 40% saturation vs 90% Chlorophyll range, µg/l vs 5-15 µg/l High to extremely high concentrations of ammonium, phosphate at some sites during dry. High to very high nitrate, high phosphate at many sites during wet 24

25 Catchment Model - MUSIC Subcatchments Model setup Model output

26 Subcatchment Catchment Model Estimates Flow (ML/year) Peak Flow (m3/s) TSS Load (kg/year) TP Load (kg/year) TN Load (kg/year) % of total (Flow) , , , , , , , , , , , , ,

27 Groundwater Inputs? 27

28 Are GPTs effective?

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30 Conclusions Berkeley Vale foreshore drains and nearshore zone are eutrophic Stormwater inputs are trapped Groundwater inputs? Stormwater improvement devices/treatment zones 30

31 Recommendations/ Future research Calibrate catchment model Reduce quantity/ improve quality of stormwater Community engagement / behavioural change Redesign stormwater treatment zones / saltmarsh wetlands Improve flushing of nearshore zones strategic wrack harvesting channels through barrrier 31

32 32 Questions???