refereed paper
Study Area
N
In-field Testing Program
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The Leichhardr River was dammed Lake Al, Fe, and Cu elements were also in 1957 ro create Lake Moondarra reseed in rhe field using the Palintesr Main ro capture runoff from rhe Selwyn lagoon outlet Photometer 7000. Measurements Range ro provide potable water for were found ro be within ± 10% Site 4 Mount Isa City (population 20,369 variabi lity of the laboratory results ABS census 200 1) and Mount Isa obtained by Simmonds and Bristow Mines. The lake (20° 34' S, 139° Pry Ltd (in field and laboratory 35' E) is located some 19 km results respectively: Fe 260 and 210 downstream of the City and Mount µm/L, Al 28 and 30 µm/L; Cu 64 Isa Mines (Figure 1), and has a µm/L and 60 µm/L). As a result, the maxim u m capacity of 106,830 ML Palintesr Photometer was considered (Finlayson, 1980). At the dam wall, ro be adequate for testing un filte red the Lake Moondarra-Leichhardr heavy metal concentration (Al, Cu, River catchment is approximately Fe), colour and turbidity for rhe l, 113 km 2. The drainage network is !00 Legend sampling program. Dissolved located in rhe semi-arid tropical • Sample locations 0 Hydrillo oxygen, cond uctivity, temperatu re zone of northwest Queensland • Typho Reeds (Figure 1), where rwo seasons exist: and pH, were measured using a YSJ a dry season fro m April ro 556 Ha ndheld Monitoring System. Figure 2. The Clea r Water Lagoon site and principa l September and a wee season from The equipment was recalibrated components of the reed bed system. Ocrober ro March. Not only does prior ro each sample ru n. In all the river have ephemeral flow cases, the data deri ved from water characteristics, ru noff is also highly variable include Hydrilla verticiflata, Potamogeton samples (Table 1) represent unfiltered tricarinatus, Typha orientalis and Vallisneria over inter-annual scales due to fl uctuations values. Normally, samples are fil rered using in monsoonal rai nfall. spiralis as well as the less desirable Salvinia a 0.45 µm fi lter prior ro analysis bur here molesta. T he distribution of the two main CWL was originally constructed in 1968 as che 'raw' sample was analysed . The results species Hydrilla verticillata and Typha a alternative water supply to Lake may therefore be considered ro reflect orientalis is illustrated in Figure 2. Wrigley Moondarra, which becomes highly turbid maximum values. T his approach was used et al. (199 I) argued char these macrophyres during rhe wet season (values up ro 100 because the drinking water derived from are instrumental ro the water clarification NTU recorded, Wrigley et al. , 199 1). Clear Water Lagoon is not filtered between process as th ey act co trap suspended matter, Sedimen t and water quality in Lake extraction and delivery to customers. altering micro-scale flow velocity patterns Moondarra may be influenced by discharge Therefore, rhe val ues presented herei n around the foliage and prompting from the town's sewerage system (Finlayson, reflect rhe actual quality of wate r being settlement on the bed of the lagoon. 1980) as well as sediment-bound heavy delivered ro reticulation system fo r the metals derived from historic and Methods township of Mount Isa. contemporary mining activities (Taylor and Water and sediment samples and associated MJNITAB statistical software (versio n 13.2, Hudson-Edwards, 2005; submitted) In environmental measurements were raken MINITAB Inc, 2000) was used ro evaluate 1982, water quality was observed ro improve from CWL during the wetter months of (ANOVAs) the relatio nship between sample so greatly after passing through CWL char ir January and February 2006. Water quality days and sample sires. Descriptive statistics was decided to permanenrly divert all parameters (colour, conductivity, dissolved as mean, standard deviation and such drinking water supplies drawn from Lake oxygen, metals, nutrients, pH and turbidity) min imu m and maximum values were also Moonda rra through che lagoon prior ro were measured at seven sires across the calculated. T he underlying assumptions for chlorination and transfer to Mount Isa lagoon system (Figure 2) . Sedi ment samples normal ity were determ ined using a Terminal Reservo ir. Water from Lake were also collected from sires I , 3, 5 and 7 Kolmogorov-Smirnov rest, where data were Moondarra is pumped into the CWL system and analysed fo r rheir total extractable As, nor normally distributed they were via an open-earth flume which directs flow Cd, Cu, Fe, Mn, Ni and Pb concentrations. successfully log-transformed prior to via a settling pond, th rough reeds and ocher Unfiltered water samples were collected analyses. macrophyres, and finally into the primary from each of rhe study sires (Figure 2) in holding lagoon (F igure 2). Clear Water nitric acid washed boccies for heavy metal Sediment Sampling Lagoon is considered an integral part of the resting and were scored on ice for transport Bulk sediment samples were collected using water supply system and supplies around to Simmonds and Bristow Pry Led a 2.5 m polyp ropylene pipe in the seeding 18,000 ML annually ro Mount Isa's laboratory (NATA accredited). T hese po nd and by scuba divers within the reed populatio n, mining, industry and commerce. preliminary samples were reseed fo r Al, As, beds and main lagoo n adjacent to the ourThe lagoon has a coral operating capacity of Cu, Ca, Fe, Mg, and Ni ro decipher if the rake Col Popple Pump Station (Figure 2). 2,800 ML, with an average depth of 5 m elements altered in concentration The samples were stored in polyethylene although pumping only occurs over rhe top throughout the system. Al, Fe, and Cu bags and transported ro Simmonds and 0.5 m of CWL. This is equivalent ro around revealed significant changes in concentration Bristow Pry Ltd (Brisbane) where they were 400 ML of accessible water or 8 days supply chroughou r the sys rem and were selected for analysed by Inductively Coupled Plasma at curren t average usage races (Mount Isa furt her study. The remaining elements were Mass Spectroscopy (ICP-MS Perkin Elmer Water Board, personal communication) . significanrly below ANZECC/ARMCANZ Elan 6100 DRC) for coral extractable The dominant macrophyres in the lower (2000) guidel ine values and thus were not metals. Duplicate samples were all fo und ro fl ume, seeding pond and main lagoon considered for fu rther study. be withi n ± 15%. Journal of the Australian Water Association
Water
DECEMBER 2006 73