Hydro-geo-chemical streamflow analysis as a support for digital hydrograph filtering in a small, rainfall dominated, sandstone watershed

The aim of the present study is an analysis of the ability of digital hydrograph filtering tools for the characterization of the baseflow source contributing to total streamflow for a typical, small, sandstone, rainfall dominated catchment. Daily streamflow and electrical conductivity data for an experimental catchment, the Ciciriello catchment, a 3km(2) watershed located in Southern Italy, have been collected to the purpose since 2012. The application of a mass balance filter (MBF), using electrical conductivity as tracer data, has pointed out a seasonal characterization of the baseflow pattern, contributing to total streamflow by 90% during the low flow period and up to 40% during the high flow period. The Lyne and Hollick one parameter and the two parameters Eckhardt digital filters have been furthermore processed, both in an uncalibrated and calibrated application. Providing a preliminary total streamflow and baseflow recession analysis, the one parameter filter appears particularly suited for ungauged cases, as the uncalibrated and calibrated applications are almost identical, with relative prediction errors, compared to MBF, smaller than 5%. The uncalibrated two parameters filter generates instead large relative error of about 35%. To improve the baseflow description, in particular during the low flow period, and to correct large (28%) underestimation of the minimum baseflow value, a seasonal calibration for the BFImax parameter (the maximum BaseFlow Index that can be modeled by the filter algorithm) is in fact needed. (C) 2016 Elsevier B.V. All rights reserved.