HR: 1330h
AN: H32C-0595    [PDF]
TI: A methodology for predicting the impact of vegetation on flow duration curves
AU: * Best, A E
EM: alice.best@csiro.au
AF: CSIRO Land and Water, P.O. Box 1666, Canberra, ACT 2601 Australia
AU: * Best, A E
EM: alice.best@csiro.au
AF: Department of Civil and Environmental, The University of Melbourne, Victoria, 3010 Australia
AU: * Best, A E
EM: alice.best@csiro.au
AF: Cooperative Research Centre for Catchment Hydrology, P.O. Box 1666, Canberra, ACT 2601 Australia
AU: Zhang, L
EM: Lu.Zhang@csiro.au
AF: CSIRO Land and Water, P.O. Box 1666, Canberra, ACT 2601 Australia
AU: Zhang, L
EM: Lu.Zhang@csiro.au
AF: Cooperative Research Centre for Catchment Hydrology, P.O. Box 1666, Canberra, ACT 2601 Australia
AU: McMahon, T A
EM: t.mcmahon@civenv.unimelb.edu au
AF: Department of Civil and Environmental, The University of Melbourne, Victoria, 3010 Australia
AU: McMahon, T A
EM: t.mcmahon@civenv.unimelb.edu au
AF: Cooperative Research Centre for Catchment Hydrology, P.O. Box 1666, Canberra, ACT 2601 Australia
AU: Western, A W
EM: a.western@unimelb.edu.au
AF: Department of Civil and Environmental, The University of Melbourne, Victoria, 3010 Australia
AU: Western, A W
EM: a.western@unimelb.edu.au
AF: Cooperative Research Centre for Catchment Hydrology, P.O. Box 1666, Canberra, ACT 2601 Australia
AB: While the impact of vegetation on the mean annual water balance is well understood, there is a need to be able to predict the impact of vegetation changes on the magnitude and frequency of daily flows. A flow duration curve (FDC) displays the relationship between any given flow and the percentage of time that flow is exceeded. This paper provides a method for linking the current understanding of the impact of vegetation on the mean annual water balance to changes in the daily FDC. The FDC is described by five parameters, the conditional median (median flow for days when flow exceeds a given threshold), the cease to flow percentile and three curve fitting parameters. The parameters of FDC model are then linked to a mean annual water balance model using daily rainfall data, thus allowing the FDC to be adjusted to changes in vegetation. Two methods are proposed for linking the mean annual water balance model to the FDC model. The first method is appropriate for gauged catchments where daily flow data under existing vegetation are available (i.e. the FDC under current conditions is known). The second is appropriate for ungauged catchment and relies on the regionalisation of the FDC model parameters. The gauged catchment method has been tested on data from 16 paired catchment studies. These catchments are generally small head water catchments and provide an excellent source of data for catchments undergoing large percentage changes in vegetation. The regionalisation of the FDC model parameters is based on data from 23 catchments in the upper and middle Murrumbidgee basin, NSW, Australia. These data were divided into calibration and validation data sets. The calibration data set was used to develop regional relationships, while the validation data set tested how well these regional relationships predicted the observed FDCs under current vegetation conditions. The methodology for the gauged catchments was able to replicate the observed changes in FDC for the paired catchment studies and is considered appropriate for the adjusting a known FDC for changes in vegetation. The regionalisation of the model parameters revealed the sensitivity of the FDC model to the predictions of the conditional median and the cease to flow percentile. The results of the regionalisation indicate the further work is required to improve the regional predictions of the FDC model parameters, particularly the conditional median.
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2003 Fall Meeting