Stitt River Stream Flows Proposed Rosebery WWTP Outfall

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1 Cradle Mountain Water Stitt River Stream Flows Proposed Rosebery WWTP Outfall

2 Macquarie Franklin was formed in April 2011 by the merger of two Tasmanian based consulting firms - Agricultural Resource Management (ARM) and Davey & Maynard. Macquarie Franklin Head Office 112 Wright Street East Devonport Tasmania 7310 Phone: Fax: info@macfrank.com.au Web: Report author: Alistair Brooks An appropriate citation for this report is: Macquarie Franklin,, Stitt River Stream Flows Proposed Rosebery WWTP Outfall Document status: Final Version This report has been prepared in accordance with the scope of services described in the contract or agreement between Macquarie Franklin and the Client. Any findings, conclusions or recommendations only apply to the aforementioned circumstances and no greater reliance should be assumed or drawn by the Client. Furthermore, the report has been prepared solely for use by the Client and Macquarie Franklin accepts no responsibility for its use by other parties. i

3 Contents 1 Background Scope of Report Site Investigation Location of Stitt River Stream Flow Sites Collection of Data Flow Gaugings Results Overview of Results Summary Figure index Figure 1- Location of the temporary and permanent stream flow sites on the Stitt River... 4 Figure 2 Odyssey data logger with one metre probe... 5 Figure 3 Flow gauging no Figure 4 Velocity Profile for Gauging no Figure 5 Flow gauging no Figure 6 Velocity Profile for Gauging No Figure 7 Rosebery BOM Daily Rainfall for March... 8 Figure 8 Flow data for both monitoring sites for total period of data collection... 9 Figure 9 shows the low flow data for both monitoring sites for part of the data collection period... 9 ii

4 1 Background This report has been developed for Cradle Mountain Water (CMW), which is planning to relocate the outfall of the Rosebery Waste Water Treatment Plant (WWTP) into the Stitt River upstream of Lake Pieman Macquarie Franklin was engaged by CMW to establish a typical low flow and river level hydrograph for the Stitt River at the proposed Rosebery WWTP outfall location. This data will be used to help determine the hydrodynamics of the Stitt River in the vicinity of the proposed outfall. In particular that data will be used to characterise the critical low river level hydrodynamics at the outfall location (data has been supplied to CMW in excel format). 1.1 Scope of Report The scope of this report includes: The description of two field visits that included installing level data loggers /probes in the river at the outfall location, and the undertaking of flow gaugings; A description of the level and flow data collected; and A correlation between the Stitt River upstream of Rosebery site (Entura Site) and the Stitt River at the WWTP proposed outfall location. 2 Site Investigation An initial site visit was undertaken of the Stitt River on 4 th of March An onsite meeting was conducted with David Krushka of Cradle Mountain Water. The proposed WWTP outfall location was inspected and a 1 metre range data odyssey logger/probe was installed at this location to collect river height data. A cross sectional survey of the river control at this section of river was also undertaken to determine the river cease to flow level and to determine the data odyssey logger/probe level in relation to the cease to flow level. A flow gauging using a flowtracker was also undertaken to ascertain the flow and velocity rate of the river for the river height at the time of the site visit. The data logger/probe was left installed in the river for 21 days to collect 15 minute interval logged river level data over that period. A second site visit was undertaken on the 25 th March 2013 and the data logger was downloaded and removed. A second flow gauging was also undertaken for the river height at the time of the second site visit. 3

5 2.1 Location of Stitt River Stream Flow Sites The location of the temporary and permanent stream flow sites on the Stitt River are shown below. Figure 1- Location of the temporary and permanent stream flow sites on the Stitt River Stitt River at Proposed WWTP outfall (Temporary Site) Stitt River upstream of Rosebery (Entura Site) Stitt River at Proposed WWTP outfall (Temporary Site) Stitt River upstream of Rosebery (Entura Site) 4

6 3 Collection of Data Level data was collected at the proposed WWTP outfall location (temporary site) using an Odyssey data logger with a one metre probe (as shown in figure 7). Data was recorded at 15 minute intervals and downloaded at the end of the three week data collection period. A depth/discharge rating curve was developed for the temporary site using the two flow gaugings undertaken, the cease to flow level, and a correlation with the Entura upstream site. The collected level data was then converted to flow data using this rating curve. Flow data was also sourced from the Entura site (permanent site) for the same period of time. Figure 2 Odyssey data logger with one metre probe 4 Flow Gaugings Two flow gaugings were undertaken at the proposed WWTP outfall location using a FlowTracker acoustic doppler measuring instrument (results shown in figures 3 and 5). These measurements were taken at different river heights. The first flow measurement ( m 3 /sec) was taken during a period of extremely low flows in the river which appear to be lower than typical summer flows. The velocity profile for this flow measurement (as shown in figure 4) shows low velocities at the proposed WWTP outfall. 5

7 The second flow measurement ( m 3 /sec) was taken during a higher flow event which appears to be more typical of the types of flows that occur down the river during the summer period. The velocity profile for this flow measurement (as shown in figure 6) shows velocities at the proposed WWTP outfall to be in the vicinity of 0.4m/sec to 0.5 m/sec across the river. Figure 3 Flow gauging no.1 Figure 4 Velocity Profile for Gauging no. 1 6

8 Figure 5 Flow gauging no.2 Figure 6 Velocity Profile for Gauging No. 2 7

9 5 Results 5.1 Overview of Results Flow data was collected at both monitoring sites from 4th of March 2013 to 25th March Varying weather conditions occurred over this three week period with very dry conditions occurring in February and the first week of data collection in March. A small amount of rainfall (see figure 7 below) occurred in the second week, and increased in the third week which resulted in flows in the Stitt River increasing substantially. Figure 7 Rosebery BOM Daily Rainfall for March Flow data for both monitoring sites is shown below in figure 8. The black trace shows the permanent Entura site data and the green trace shows data collected at the proposed WWTP outfall. A very good correlation occurs between each site. Figure 5 shows the low flow data for the first two weeks of the data collection period. The trace on the temporary site shows the effect of the pump station between the two sites that supplies water for the mine and the Rosebery Township. For future comparison of very low river flows between these two locations, it should be noted that the pumps for the town water supply and mine are downstream of the Entura site, therefore there will be less flow in the river at the proposed WWTP outfall compared to the permanent Entura site when the flows in the river are very low. However, as the flows in the river increase and the town pumps have less effect on the percentage of flow in the river, flows at the temporary site end up being greater than the Entura site due to the larger catchment area at the WWTP outfall location. 8

10 Figure 8 Flow data for both monitoring sites for total period of data collection Figure 9 shows the low flow data for both monitoring sites for part of the data collection period 9

11 6 Summary Based on the site inspection and collection of stream flow data: Over the three week data collection period a very good flow correlation occurred between the Stitt River upstream of Rosebery site (Entura site) and the temporary installed site at the proposed WWTP outfall; At the start of the data collection period velocities in the river at the WWTP outfall location appeared much lower than normal typical summer velocities due to the very low rainfall period leading up to this date. However, the velocity in the river at the end of the data collection period appeared more typical of summer velocities for the Stitt River; For future comparison of very low river flows between the two locations, it should be noted that the pumps for the town water supply and mine are downstream of the Entura site, therefore there will be less flow in the river at the proposed WWTP outfall compared to the permanent Entura site when the flows in the river are very low. However, as the flows in the river increase and the town pumps have less effect on the percentage of flow in the river, flows at the temporary site end up being greater than the Entura site due to the larger catchment area at the WWTP outfall location. 10

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