Abstract

Abstract. An assessment of regional similarity in catchment stream response is often needed for accurate predictions in ungauged catchments. However, it is not clear whether similarity among catchments is preserved at all flow conditions. We address this question through the analysis of flow duration curves for 25 gauged catchments located across four river basins in the northeast United States. The coefficient of variation of streamflow percentiles is used as a measure of variability among catchments across flow conditions. Results show that similarity in catchment stream response is dynamic and highly dependent on flow conditions. Specifically, within each of the four basins, the coefficient of variation is high at low flow percentiles and gradually reduces for higher flow percentiles. Analysis of the inter-annual variation in streamflow percentiles shows a similar reduction in variability from low flow to high flow percentiles. Greater similarity in streamflows is observed during the winter and spring (wet) seasons compared to the summer and fall (dry) seasons. Results suggest that the spatial variability in streamflow at low flows is primarily controlled by the dominance of high evaporative demand during the warm period. On the other hand, spatial variability at high flows during the cold period is controlled by the increased dominance of precipitation input over evapotranspiration. By evaluating variability over the entire range of streamflow percentiles, this work explores the nature of hydrologic similarity from a seasonal perspective.

Highlights

  • A number of problems in hydrology require estimation of regional similarity in catchment stream response

  • The flow duration curves (FDC) are plotted as streamflow value vs. the streamflow percentile

  • In all the four basins, CV is high at low flow conditions and trends lower for high flow www.hydrol-earth-syst-sci.net/15/989/2011/

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Summary

Introduction

A number of problems in hydrology require estimation of regional similarity in catchment stream response These include: regional flood frequency analysis (Acreman and Sinclair, 1986; Burn, 1997; Merz and Bloschl, 2005), parameter regionalization for lumped hydrologic models (Burn and Boorman, 1993; Merz and Bloschl, 2004), regional low flow predictions (Nathan and McMahon, 1990; Laaha and Bloschl, 2006), and water quality assessment (Wolock et al, 2004). Acreman and Sinclair (1986) grouped 186 catchments in Scotland into five homogeneity regions based on six basin characteristics, viz., drainage area, stream frequency, channel slope, mean annual rainfall, fraction of basin covered by lakes and soil type index. One widely used approach involves the use of similarity in catchment physiographic characteristics. Acreman and Sinclair (1986) grouped 186 catchments in Scotland into five homogeneity regions based on six basin characteristics, viz., drainage area, stream frequency, channel slope, mean annual rainfall, fraction of basin covered by lakes and soil type index. Wiltshire (1986) grouped 376 British catchments into five homogeneous regions based on catchment attributes such as basin area, average annual rainfall and urban fraction. Burn and Goel (2000) grouped catchments in central India for flood frequency estimation using attributes such as catchment area, stream length and main channel slope. Wolock et al (2004) used the hydrologic landscapes concept of Winter (2001) to group 43 931 catchments in United States into 20 regions based on identification of similarities in topography

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