A Standard Approach to Baseflow Separation Using The Lyne and Hollick Filter

Abstract

The digital filtering approach to baseflow separation suggested by Lyne & Hollick (1979) has been widely used and is available in a number of computer packages. However, details of the approach used by different authors vary and so do the results. This means baseflow volumes and indices reported by different authors, and at different times, are difficult to compare. We propose a standard method for baseflow separation using the Lyne and Hollick digital filter. This includes reflecting the flow series at the start and end of the record to reduce “warm up” effects and the adoption of specific starting values for each filter pass.

Key Words:

• Baseflow separation
• digital filter
• Lyne
• Hollick
• baseflow index

Additional information

Notes on contributors

A R Ladson

Tony Ladson has more than 25 years’ experience in hydrology and river management and has worked on projects throughout Australia, the US and Taiwan. He has a PhD from the University of Melbourne, a Master of Science from the University of Minnesota and also studied at Uppsala University in Sweden. He is a director of Moroka Pty Ltd, an honorary fellow at the University of Melbourne and a teaching fellow in the Department of Civil Engineering at Monash University, where he delivers post-graduate courses on water resources, urban drainage infrastructure and flood management. One of Tony’s main interests is the application of hydrologic principles to improve the environmental condition of Australia’s rivers. Tony has more than 90 refereed publications and has completed a book on Australian hydrology for Oxford University Press.

R Brown

Rachel Brown is a water resources engineer with SKM, and has qualifications in environmental engineering, botany and water resource management. She has worked on a Natural Heritage Trust study into groundwater and surface water condition change, which involved hydrologic analysis of data to identify user-friendly approaches to baseflow separation from streamflow data, trend analysis to understand baseflow contribution to streamflow, and the development of a tool (Basejumper) to support water resource managers in understanding changes in baseflow trends. Rachel was also involved in a project for the update of the Australian Rainfall and Runoff guidelines that developed a simple approach to estimate baseflow contribution to design flood events based on readily available catchment characteristics. Rachel is also actively involved in the water engineering community and is currently Chair of the Victorian Water Engineering Branch of Engineers Australia.

B Neal

Brad Neal is SKM’s practice leader for water resource planning and has 18 years’ experience in hydrology and water resource management. In the area of groundwater and surface water interaction, Brad has provided technical input and review to the development of guidelines for groundwater trend analysis for coal seam gas activities, the development of the Basejumper software for baseflow separation and trend analysis, the contribution of baseflow to design flood peaks and the estimation of baseflow indices in unregulated rivers across the whole of Victoria, the Murray-Darling Basin and tropical northern Australia.

R Nathan

Dr Rory Nathan is the Practice Leader for Hydrology with SKM. He holds degrees in different aspects of engineering hydrology from the universities of Melbourne and London, and has around 30 years’ experience in academic and consulting positions. Rory’s technical interests are in the modelling of hydrological processes, environmental hydrology, and the analysis and simulation of extreme events.