Macquarie Aquatic Environment Assessment
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Water Assessment Hydrology Report Series Surface Water Hydrology of the Ringarooma River Catchment November 2010 I S S N : 1835- 9531 (Revised Report No. WA 10/11 ) 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: Dr Shivaraj Gurung, Senior Hydrologist Preferred Citation: DPIPWE (2010). Surface Water Hydrology of the Ringarooma River Catchment. Water Assessment Hydrology Report Series, Report No. WA 10/11 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: Overlay of Ringarooma River catchment with subcatchment boundaries. 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 revised hydrological information supporting the development of a water management plan for the Ringarooma 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 Ringarooma River catchment lies in the northeast corner of Tasmania and covers an area of approximately 922 km2. Annual rainfall in the catchment varies from 600 mm in the low lying coastal areas to up to 1800 mm in the highlands. Most of the rainfall occurs in the southern and southeast headwaters of the upper catchment. The annual average rainfall in the catchment is around 1100 mm while annual evaporation averages at around 1000 mm. The total annual rain water input into the Ringarooma catchment is approximately 1014 GL. The total natural flow yield at the catchment outlet estimated from surface water model is around 414 GL/year and comprises about 41% of the total annual rain water input into the catchment. This simple water budget indicates that a significant proportion of (59%) of rain water input into the catchment is lost into the system from surface retention, evaporation and recharge into local groundwater aquifers. The highest recorded flood at the Ringarooma River stream flow measurement site at Moorina was approximately 486 m3/s. Average floods (1 in 2 year floods) at the Moorina gauge peak at approximately 100 m3s-1 and are about twice the size of base-flow level in the river. Peak floods generally take approximately 2 days to recede to sustained river flow of 50 m3/s. Low flow probability analysis indicated that within a given year the likelihood of occurrence of average flows falling below 100 ML/day over a period of five consecutive days is around 60%. Currently, surface water resources are allocated solely on surface water information, with only cursory regard for groundwater influences. While it is recognised that the flow data for this catchment suggest a significant groundwater influence, there is little understanding of groundwater influence in the catchment. Water allocation is presently based on the premise that water is being allocated from surface water only, when in fact it may be drawing indirectly on the groundwater resource. Conversely, the level of groundwater extraction is largely unknown and may be having some impact on the surface water resource. With increasing demand for better management of the State’s water resources, greater emphasis must therefore be put into implementing an holistic approach to understanding surface and groundwater connectivity within this and other catchments in Tasmania. 3 Table of Contents EXECUTIVE SUMMARY ................................................................................................ 3 TABLE OF CONTENTS ................................................................................................. 4 1.0 INTRODUCTION ..................................................................................................... 5 2.0 CATCHMENT LOCATION AND DESCRIPTION ............................................................. 6 2.1 DRAINAGE DISTRIBUTION .............................................................................................. 7 3.0 CLIMATE AND STREAM-FLOW ................................................................................ 8 3.1 RAINFALL AND EVAPORATION ....................................................................................... 8 3.2 STREAM-FLOW MONITORING .......................................................................................11 3.3 STREAM FLOW CHARACTERISTICS ...............................................................................13 3.4 FLOW DURATION ........................................................................................................15 3.4 FLOOD FREQUENCIES .................................................................................................16 3.5 LOW FLOWS ...............................................................................................................17 3.6 FLOW RECESSION .......................................................................................................19 3.6 WET AND DRY SEASON COMPARISON ..........................................................................20 4.0 RINGAROOMA CATCHMENT WATER BALANCE MODEL ........................................... 21 4.1 OVERVIEW OF CATCHMENT MODEL .............................................................................21 4.2 MODEL CALIBRATION AND ACCURACY .........................................................................24 5.0 NATURAL FLOW CHARACTERISTICS ..................................................................... 26 5.1 NATURAL FLOW STATISTICS........................................................................................26 5.2 FLOW DURATION ANALYSIS.........................................................................................26 6.0 CATCHMENT WATER BUDGET ............................................................................. 28 SUMMARY ........................................................................................................................29 7.0 CLIMATE CHANGE AND FUTURE DEVELOPMENT IMPACT ........................................ 30 7.1 CLIMATE CHANGE IMPACT ...........................................................................................30 7.2 FUTURE FORESTRY DEVELOPMENT .............................................................................30 7.3 FUTURE IRRIGATION DEVELOPMENTS ..........................................................................31 REFERENCES ........................................................................................................... 31 4 1.0 Introduction This report provides a revision of the relevant hydrological information that supports the development of a water management plan for the Ringarooma River catchment. The key features of this report are characterisation of stream flow data from selected gauges in the catchment, and outputs from a catchment water balance model to provide hydrological information for environmental flow assessments and calculations of a catchment water budget. This report information on: Hydrological characterisation of the catchment; Climate and Stream flow characteristics; Development of catchment hydrological model; Catchment water budget; Climate change and future