Abstract

Abstract. The effect of plantations on mean annual streamflow is well understood and, there are robust methods available for assessing the impact. Plantations also affect streamflow regime, leading to reductions in low flow and increased number of zero-flow days. Understanding changes in streamflow regime following plantation expansion is important for developing water resources and environmental flow strategy. This study evaluated the impacts of plantations on streamflow regime from 15 catchments in Australia. The selected catchments range in size from 0.6 to 1136 km2 and represent different climatic conditions and management practices. The catchments have at least 20 yr and in most cases 35 yr of continuous daily streamflow data and well documented plantation records. Catchments with perennial streamflow in the pre-treatment periods showed relatively uniform reductions in most flows after plantation expansions, whereas catchments with ephemeral streamflow showed more dramatic reductions in low flows, leading to an increased number of zero-flow days. The Forest Cover Flow Change (FCFC) model was tested using the data from the selected catchments and comparison of predicted and observed flow duration curves showed that 14 of the 15 catchments have coefficients of efficiency greater than 0.8. The results indicate that the model is capable of predicting plantation impacts on streamflow regime.

Highlights

  • Our understanding of the vegetation impact on mean annual water yield is well advanced, and there are robust methods available for assessing the impact (Bosch and Hewlett, 1982; Zhang et al, 2001; Brown et al, 2005; Zhao et al, 2010; Wei and Zhang, 2010)

  • Proportional reductions are small in high flows and large in low flows

  • The Forest Cover Flow Change model (FCFC) was developed to adjust a time series of observed or simulated daily flow to account for significant changes in forest cover

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Summary

Introduction

Our understanding of the vegetation impact on mean annual water yield is well advanced, and there are robust methods available for assessing the impact (Bosch and Hewlett, 1982; Zhang et al, 2001; Brown et al, 2005; Zhao et al, 2010; Wei and Zhang, 2010). The flow duration curve (FDC) approach has been adopted as it provides a statistical method for describing flow distribution and more importantly allows for identification of differences between two streamflow time series (Smakhtin, 2001; Brown et al, 2005, 2006). Another useful feature of an FDC is the ability to display flow variability and its direct application in water allocation analysis (Brown et al, 2007)

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