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Pine Creek region surface water resources assessment Vol 1 - Study report Vol 2 - Geotechnical report



Pine Creek region surface water resources assessment Vol 1 - Study report Vol 2 - Geotechnical report


Willing & Partners; Dames & Moore; Earl James & Associates


E-Publications; E-Books; PublicationNT; Report no. 55/1989







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Northern Territory Government

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Report no. 55/1989

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Attribution International 4.0 (CC BY 4.0)

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Northern Territory Government



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Technical Report WRD89055 Viewed at 15:07:05 on 29/07/2010 Page 27 of 45. 10 10.1 YIELD ANALYSIS OF FINAL SITES General In the study area, dam storages are required to meet the future demand for mine process water and other uses. The storage capacity to sustain a specific demand is dependent on three factors. the variability of the dam inflows the size of the demand the degree of reliability of the demand being met Inflow variability can be determined by rainfall-runoff modelling. Dam storage capacity, the magnitude of the demand and the demand reliability are interelated and an assessment of how these parameters interact can be made by simulating a range of reservoir operations. 10.2 Rainfall Runoff Modelling The Monash Daily Catchment Model (porter and McMahon, 1971) was selected to determine dam inflows. It models the rainfail-runoff process by simulating the distribution of moisture in the soil subject to severai governing parameters. A process of model caiibration and verification was done to determine appropriate parameter values for the study area. Three gauged catchments were used in the calibration process; Harriet Creek dO\vnstream of El Sherana Road, McKinlay River at Burrundie and Bridge Creek at Railway. Long term daily rainfall data for Pine Creek was assumed to be representative of the region. A trial and error approach was used in model caiibration by adjustment of parameter values to get the best overall fit between recorded and simulated streamflows. The total runoff volume, variability of daily flows and the reproduction of high and low flows were used as measures of fit. A satisfactory calibration was achieved although there were some shortcomings due to the reliance on the use of the Pine Creek rainfall record. Within the region, the incidence of rainfall is highly variable both temporally and spatially. As a result, the Pine Creek data may not be fully representative on a regional basis. In the absence of long term records at other sites, greaterrefinements to the model calibration could not be achieved. Given the preliminary nature of the study, the model results were considered sufficiently reliable. Extended sequences of daily streamflow data were derived for the three gauged catchments. The sequence, as restricted by the available historical rainfall record, was for the period of 99 years from 1890 to 1988. This data was used as input for the reservoir operation studies as detailed in the next section. Full detail of the rainfall runoff modelling is compiled in Volume 2. 10.3 Reservoir Operations Study of Final Sites RESERVOIR OPERATIONS MODEL A simple operations model was developed using a monthly water balance technique. The governing equation that fo=ed the basis of the model was as follows: ST2 where STl ST2 - STI + INF - NE1LOSS - SPILL - DRAFT - reservoir storage at the start of month = reservoir storage at the end of month PINE CREEK REGION SURFACE WATER RESOURCES ASSESSMENT Page 18