Gosford City Council Historical Water Quality Review & Analysis

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RESULTS OF WATER QUALITY DATA ANALYSIS 3-7 3.1.1.6 Dissolved Oxygen Median annual dissolved oxygen for the Gosford waterways is presented in Table 3.10, while mean quarterly dissolved oxygen is presented in Table 3.11. Dissolved oxygen within the water is consumed by respiration of organic matter. Heterotrophic conditions within the waterways result in reducing oxygen levels. The quarterly analysis suggests that the dissolved oxygen levels are at least quasi-seasonal, with notable decreases over the summer months, only to return to high levels during the last quarter. Catchment runoff during the last quarter (as evidenced by monthly rainfall records and associated salinity levels) probably contributed to the sudden increase in dissolved oxygen at most sites, particularly Kincumber Creek, Avoca Lagoon and Cockrone Lagoon. Possible reasons for the seasonal variation in dissolved oxygen could be related to the boom and bust cycle of algae, where elevated temperatures in the summer make conditions ideal for algal growth, but when nutrients become limiting, the bloom dies off, and the organic matter decay (consuming oxygen in the process). Table 3.10 Annual Medians for Dissolved Oxygen Dissolved Oxygen (mg/L) Site No. and Location 2001/ 2002 2000/ 2001 1999/ 2000 n=11 n=12 n=9 Trend Site : 77 - Booker Bay 6.71 7.18 7.30 Site : 78 - Narara Creek Entrance 5.76 6.60 6.25 Site : 79 - Erina Creek Entrance 5.51 6.37 6.30 Site : 80 - Kincumber Creek Entrance 5.50 6.53 6.80 Site : 81 - Cockle Creek 6.56 8.14 7.40 Site : 82 - Woy Woy Creek 5.60 6.00 5.25 Site : 83 - Wamberal Lagoon 6.90 9.40 7.50 Site : 84 - Terrigal Lagoon 6.84 7.30 6.35 Site : 85 - Avoca Lagoon 6.20 8.10 6.65 Site : 86 - Cockrone Lagoon 7.17 8.22 7.65 Average Rainfall at Gosford 1248mm 1038mm 1228mm Table 3.11 Quarterly Means for Dissolved Oxygen Dissolved Oxygen (mg/L) Site No. and Location Apr - Jun Jan - Mar Oct - Dec Jul - Sep Apr - Jun 2002 2002 2001 2001 2001 n=4 n=1 n=3 n=3 n=3 Trend Site : 77 - Booker Bay 6.87 5.84 6.72 6.92 6.93 Seasonal Site : 78 - Narara Creek Entrance 6.12 4.56 5.86 5.80 6.93 Seasonal Site : 79 - Erina Creek Entrance 6.16 4.80 5.65 6.22 6.84 Seasonal Site : 80 - Kincumber Creek Entrance 5.50 2.76 3.40 6.68 5.99 Seasonal Site : 81 - Cockle Creek 7.50 4.46 5.68 6.96 8.72 Seasonal Site : 82 - Woy Woy Creek 6.35 4.03 4.55 5.87 6.26 Seasonal Site : 83 - Wamberal Lagoon 7.22 4.71 5.91 7.34 9.48 Seasonal Site : 84 - Terrigal Lagoon 7.27 5.58 5.87 7.22 7.33 Seasonal Site : 85 - Avoca Lagoon 7.53 2.60 5.69 7.19 8.16 Seasonal Site : 86 - Cockrone Lagoon 8.86 2.02 6.96 7.70 7.54 Seasonal Average Rainfall at Gosford 150mm 735mm 189mm 174mm 445mm D:\R.N0754.002.01.DOC 7/11/03 16:11
RESULTS OF WATER QUALITY DATA ANALYSIS 3-8 3.1.2 Chemical Parameters 3.1.2.1 Ammonia Annual median concentrations of ammonia in the Gosford waters is shown in Table 3.12, while the quarterly averages of ammonia for the past 15 months is shown in Table 3.13. The annual data suggests that there has not been any notable trends in ammonia concentrations, except possibly for Avoca Lagoon, where the median concentration essentially halved between 1999/2000 and 2001/2002. The reason for this reduction is not known, and was not consistent with trends at other locations, or with overall rainfall / runoff patterns. The quarterly analysis shows that high concentrations were recorded in the Brisbane Water sites during the last quarter (Apr-Jun 2002), however, notably higher ammonia concentrations were recorded in the coastal lagoons during the preceding quarter (Jan-Mar 2002, although only one record was taken in this period, so caution is required in interpreting the results). It is likely that the variable nature of ammonia concentrations is closely linked with catchment runoff (given that significant runoff occurred between February and Apr 2002), however, the chemical processes within the waterways would obscure this connection to some degree. Table 3.12 Annual Medians for Ammonia Ammonia (mg/L) Site No. and Location 2001/ 2002 2000/ 2001 1999/ 2000 n=11 n=12 n=9 Trend Site : 77 - Booker Bay 0.011 0.013 0.005 Site : 78 - Narara Creek Entrance 0.019 0.027 0.015 Site : 79 - Erina Creek Entrance 0.019 0.021 0.028 Site : 80 - Kincumber Creek Entrance 0.026 0.029 0.019 Site : 81 - Cockle Creek 0.013 0.014 0.010 Site : 82 - Woy Woy Creek 0.027 0.025 0.020 Site : 83 - Wamberal Lagoon 0.015 0.016 0.024 Site : 84 - Terrigal Lagoon 0.013 0.017 0.019 Site : 85 - Avoca Lagoon 0.012 0.016 0.024 Site : 86 - Cockrone Lagoon 0.010 0.010 0.008 Average Rainfall at Gosford 1248mm 1038mm 1228mm Table 3.13 Quarterly Means for Ammonia Ammonia (mg/L) Site No. and Location Apr - Jun Jan - Mar Oct - Dec Jul - Sep Apr - Jun 2002 2002 2001 2001 2001 n=4 n=1 n=3 n=3 n=3 Trend Site : 77 - Booker Bay 0.022 0.008 0.010 0.010 0.013 Variable Site : 78 - Narara Creek Entrance 0.046 0.017 0.017 0.018 0.024 Variable Site : 79 - Erina Creek Entrance 0.047 0.019 0.018 0.015 0.024 Variable Site : 80 - Kincumber Creek Entrance 0.067 0.028 0.022 0.021 0.034 Variable Site : 81 - Cockle Creek 0.034 0.013 0.012 0.011 0.015 Variable Site : 82 - Woy Woy Creek 0.048 0.027 0.027 0.015 0.024 Variable Site : 83 - Wamberal Lagoon 0.018 0.049 0.022 0.010 0.019 Variable Site : 84 - Terrigal Lagoon 0.019 0.044 0.012 0.011 0.015 Variable Site : 85 - Avoca Lagoon 0.023 0.116 0.012 0.009 0.021 Variable Site : 86 - Cockrone Lagoon 0.020 0.132 0.010 0.008 0.011 Variable Average Rainfall at Gosford 150mm 735mm 189mm 174mm 445mm 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 27: 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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