Water Assessment Hydrology Report Series Characterisation of the Surface Water Hydrology for the Macquarie River above Lake River Catchment July 2010 ISSN: 1835-9531 (Report No. WA 10/02) Water Assessment Branch Water and Marine Resources Division Department of Primary Industries, Parks, Water and Environment. Copyright Notice: Material contained in the report provided is subject to Australian copyright law. Other than in accordance with the Copyright Act 1968 of the Commonwealth Parliament, no part of this report may, in any form or by any means, be reproduced, transmitted or used. This report cannot be redistributed for any commercial purpose whatsoever, or distributed to a third party for such purpose, without prior written permission being sought from the Department of Primary Industries, Parks, Water and Environment, on behalf of the Crown in Right of the State of Tasmania. Disclaimer: Whilst DPIPWE has made every attempt to ensure the accuracy and reliability of the information and data provided, it is the responsibility of the data user to make their own decisions about the accuracy, currency, reliability and correctness of information provided. The Department of Primary Industries, Parks, Water and Environment, its employees and agents, and the Crown in the Right of the State of Tasmania do not accept any liability for any damage caused by, or economic loss arising from, reliance on this information. Prepared by: Suzanne Witteveen, and Bryce Graham Preferred Citation: DPIPWE (2010). Characterisation of the Surface Water Hydrology for the Macquarie River above Lake River Catchment. Water Assessment Hydrology Report Series, Report No. WA 10/02 Water and Marine Resources Division. Department of Primary Industries, Parks, Water and Environment, Hobart, Tasmania. Contact Details: Department of Primary Industries, Parks, Water and Environment Water Assessment Branch 13 St Johns Avenue, New Town. Phone: 03 6233 6833 Web: www.dpipwe.tas.gov.au Email: [email protected] Cover Page Image: The Macquarie River at Morningside (photo C.Bobbi) The Department of Primary Industries, Parks, Water and Environment The Department of Primary Industries, Parks, Water and Environment provides leadership in the sustainable management and development of Tasmania’s resources. The Mission of the Department is to advance Tasmania’s prosperity through the sustainable development of our natural resources and the conservation of our natural and cultural heritage for the future. The Water and Marine Resources Division provides a focus for water management and water development in Tasmania through a diverse range of functions including the design of policy and regulatory frameworks to ensure sustainable use of the surface water and groundwater resources; monitoring, assessment and reporting on the condition of the State’s freshwater resources; facilitation of infrastructure development projects to ensure the efficient and sustainable supply of water; and implementation of the Water Management Act 1999 , related legislation and the State Water Development Plan. 2 Executive Summary This report provides relevant hydrological information supporting the development of a water management plan for the Macquarie River catchment. Water management plans provide a framework for managing catchment water resources in accordance with objectives of the Water Management Act 1999 , and the State Policy on Water Quality Management 1997 . The Macquarie River catchment described in this report lies upstream of the Lake River junction in the Midlands region of Tasmania and covers an area of approximately 2,697 km 2. Major tributaries of the Macquarie River include the Elizabeth, Tooms, Blackman and Isis rivers. Lake Leake, Tooms Lake and the Blackman Dam are the major man-made storages in the catchment. The Macquarie catchment experiences medium to dry climatic conditions influenced by the prominent tiers in the west and east of the catchment. The average annual rainfall varies from 500 mm in low lying areas to 1,200 mm in the highlands. The catchment-wide average rainfall is approximately 580 mm. The annual average evaporation in the catchment is approximately 1,000 mm. Average floods (1 in 2 year) in the lower Macquarie River downstream of Elizabeth River peak at around 115 m3s-1. Large floods (magnitude greater than 755 m3s-1) observed in the lower Macquarie River have an average recurrence interval of more than 1 in 100 years. Peak discharges after a major flood event in the lower Macquarie River take approximately 10 days to recede to base flow level. Low flows in the Macquarie River and its major tributaries are common throughout the year. In the lower Macquarie the likelihood of occurrence of flows less than 35 ML/day over a five day consecutive period in a given year is around 80%. The observed annual average yields for the Macquarie River at Trefusis and Morningside gauges are 54789 and 118319 ML respectively. These are not natural yields as they represent what remains in the river following releases from lakes Leake and Tooms Lake, natural catchment pickup and extractions from the system. The Tasmanian Sustainable Yields Project provides a range of climate change projections for the catchment out to 2030. A future wet climate outcome indicates an increase in annual yield by 6%, a median future climate indicates a decrease in annual yields by 6% and a future dry climate indicates a decrease in annual yields by 11%. 3 Characterisation of the Surface Water Hydrology for the Macquarie River above Lake River Catchment EXECUTIVE SUMMARY ......................................................................................... 3 1 INTRODUCTION ............................................................................................. 5 2 CATCHMENT DESCRIPTION ............................................................................ 6 2.1 DRAINAGE ........................................................................................................................ 7 2.2 LAND USE ........................................................................................................................ 8 2.3 WATER USE ..................................................................................................................... 8 3 CATCHMENT HYDROLOGY ............................................................................ 9 3.1 RAINFALL AND EVAPORATION ........................................................................................ 9 3.2 RIVER FLOW MONITORING ............................................................................................. 11 3.3 GAUGED FLOW CHARACTERISTICS ............................................................................... 13 3.4 SPECIFIC YIELD ............................................................................................................... 16 3.5 FLOODS .......................................................................................................................... 18 3.6 FLOW RECESSION .......................................................................................................... 19 3.7 LOW FLOWS ................................................................................................................... 20 3.8 WET AND DRY YEAR COMPARISONS .............................................................................. 21 4 CLIMATE CHANGE AND TASMANIAN SUSTAINABLE YIELDS PROJECT ........ 23 5 REFERENCES ................................................................................................ 25 4 1 Introduction This report provides a hydrological characterisation of the Macquarie River above Lake River catchment, supporting the development of a water management plan for the Macquarie River catchment. A complementary report for the catchment, describing a water balance model, potential yields and current allocations has also been prepared in support of the water management plan for the Macquarie River above Lake River catchment. Water management plans provide a framework for managing catchment water resources in accordance with objectives of the Water Management Act 1999 , and the State Policy on Water Quality Management 1997 . This report presents analyses of rain, evaporation, and streamflow data from various locations around the catchment. The Macquarie River stream-flows have been analysed to show general variation in gauged flows, as well as potential flood frequencies, low flows, and flow recessions. 5 2 Catchment description The Macquarie River catchment is located in the Midlands region of eastern Tasmania and makes up part of the Tamar River Basin. The catchment extends from Tooms Lake in the south to Longford in the north and has a total catchment area of 4,241 km 2. The Macquarie River catchment described in this report lies upstream of Lake River and covers an area of approximately 2,697 km 2. The catchment has an oblong shape 84 km long and 64 km wide at its longest axis lengths. The upper reaches of the catchment consist of rugged terrain dominated by dolerites and related rocks while the low lying areas contain mainly quaternary sediments with common outcrops of basaltic rocks. The dominant vegetation types in the highland areas of the catchment are dry Eucalypt forests and woodlands. Vegetation and landscape in the low lying areas are extensively modified by agricultural activities. Major tributaries of the Macquarie River include the Elizabeth, Tooms, Blackman and Isis rivers. Lake Leake, Tooms Lake and the Blackman Dam are the