Gosford City Council Historical Water Quality Review & Analysis

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RESULTS OF WATER QUALITY DATA ANALYSIS 3-15 Table 3.23 Water Quality Index for Gosford Waters, 1999 - 2002 Location 2001 / 2002 2000 / 2001 1999 / 2000 Booker Bay 1.43 1.43 1.14 Narara Ck entrance 1.71 1.86 1.57 Erina Ck entrance 1.86 2.00 2.00 Kincumber Ck entrance 2.14 1.71 1.57 Cockle Broadwater 1.29 1.86 1.00 Woy Woy Creek 1.71 2.43 1.86 Wamberal Lagoon 1.57 2.00 1.57 Terrigal Lagoon 1.43 2.14 1.86 Avoca Lagoon 1.71 1.71 1.43 Cockrone Lagoon 1.29 1.14 1.14 Table 3.24 Basic Scorecard Index 1.00 – 1.09 10/10 1.10 – 1.24 9/10 1.25 – 1.49 8/10 1.50 – 1.74 7/10 1.75 – 1.99 6/10 2.00 – 2.39 5/10 2.40 – 2.79 4/10 2.80 – 3.19 3/10 3.20 – 3.59 2/10 3.60 – 4.00 1/10 Table 3.25 Scorecard for Gosford Waters, 1999 - 2002 Location 2001 / 2002 2000 / 2001 1999 / 2000 Booker Bay 8/10 8/10 9/10 Narara Ck entrance 7/10 6/10 7/10 Erina Ck entrance 6/10 6/10 6/10 Kincumber Ck entrance 5/10 7/10 7/10 Cockle Broadwater 8/10 6/10 10/10 Woy Woy Creek 7/10 4/10 6/10 Wamberal Lagoon 7/10 6/10 7/10 Terrigal Lagoon 8/10 5/10 6/10 Avoca Lagoon 7/10 7/10 8/10 Cockrone Lagoon 8/10 9/10 9/10 D:\R.N0754.002.01.DOC 7/11/03 16:11
RESULTS OF WATER QUALITY DATA ANALYSIS 3-16 The dissolved oxygen concentrations measured by the probe are difficult to interpret and are of limited value. The reason for this is the fact that the probe appears to have been affected by biological fouling. The results show a slow decline in dissolved oxygen concentrations between changeover periods. At changeover, the levels increase suddenly, indicating that prior to changeover, recorded levels were incorrect. Turbidity levels measured at Koolewong were highly variable, with values up to 160 NTU recorded regularly. A comparison of the turbidity and salinity plots indicated that higher turbidity levels were not always corresponding to catchment runoff events (as depicted by a reduction in salinity levels). Therefore, other factors also affect turbidity levels at the Koolewong datasonde. By way of example, it may be possible that wind waves cause resuspension of finer bottom sediments in the vicinity of the Koolewong probe. Also, the turbidity probe appears to be affected by biological fouling, with sudden reductions in turbidity occurring at instrument changeover (and coinciding with sudden changes in dissolved oxygen levels). 3.2.2 Avoca Lagoon The results of the Avoca Lagoon datasonde show that the Avoca Lagoon entrance broke out 14 times between March 1996 and June 2002. On most occasions tides returned to the lagoon following breakout for a period of a few days before closing once again. When closed, water levels in the lagoon respond to periods of catchment runoff (with sudden increases in water levels) and evaporation from the water surface (with slow reductions in water level). In most cases, salinity follows a reverse trend to water level, with dramatic increases in salt concentration associated with entrance breakout, followed by a gradual reduction in salinity as the lagoon hydrology is subsequently dominated by freshwater catchment inputs. Temperature showed a strong seasonal trend, with temperatures peaking in January / February at about 25 – 30 °C, and reaching a minimum in June / July at about 10 – 12 °C. pH varied considerably within Avoca Lagoon, between about 7 and 9.5, although some values greater than 10 were also recorded. In general, higher pH levels appeared to occur during the early summer months (Oct – Dec) with levels generally about 9 or greater. Levels would then reduce to about 7.5 during late spring / winter months. It is suggested that the pH levels within Avoca Lagoon are influenced by the seasonal cycles of phytoplankton and macroalgae growth. Although chlorophyll-a monitoring has not been conducted to measure the amount of primary productivity within the lagoon, it is likely that the increasing temperatures associated with the early summer months would initiate higher amounts of productivity in the waterway, resulting in increasing pH levels. When pH levels are elevated, entrance breakout can also have an impact on pH, as most of the phytoplankton and macroalgae would be removed or detrimentally affected by the sudden change in lagoon hydrology. Dissolved oxygen levels in Avoca Lagoon vary between 16 mg/L and zero. Oxygen levels can be influenced by several different factors in mostly closed lagoons, including phytoplankton and macroalgae growth (photosynthesis), organic decay (respiration), entrance breakout, and catchment runoff. The DO probe also shows some signs of biological fouling of the sensor, so all information derived from the data should be used with caution. D:\R.N0754.002.01.DOC 7/11/03 16:11
Page 1 and 2: Gosford City Council Historical Wat
Page 3 and 4: CONTENTS I CONTENTS Contents List o
Page 5 and 6: LIST OF FIGURES III 4.4 Outcomes fr
Page 7 and 8: LIST OF TABLES V Table 3.23 Water Q
Page 9 and 10: INTRODUCTION 1-2 locations in Brisb
Page 11 and 12: INTRODUCTION 1-4 aquatic ecosystems
Page 13 and 14: INTRODUCTION 1-6 Default trigger va
Page 15 and 16: GWQ: A DATA MANAGEMENT AND ASSESSME
Page 23 and 24: RESULTS OF WATER QUALITY DATA ANALY
Page 35: RESULTS OF WATER QUALITY DATA ANALY
Page 43 and 44: FUTURE DIRECTIONS FOR WATER QUALITY
Page 67 and 68: MHL DATASONDE RESULTS: AVOCA LAGOON
Page 69: MHL DATASONDE RESULTS: KOOLEWONG C-

Gosford City Council Historical Water Quality Review & Analysis

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