Smooth regional estimation of low-flow indices: physiographical space based interpolation and top-kriging

Castiglioni, S.; Castellarin, A.; Montanari, A.; Skøien, J. O.; Laaha, G.; Blöschl, G.

doi:https://doi.org/10.5194/hess-15-715-2011

S. Castiglioni¹, A. Castellarin¹, A. Montanari¹, J. O. Skøien^2,5, G. Laaha³, and G. Blöschl⁴ ¹School of Civil Engineering (Dept. DICAM), University of Bologna, Italy
²Department of Physical Geography, University of Utrecht, The Netherlands
³Institute of Applied Statistics and Computing, University of Natural Resources and Life Sciences, BOKU Vienna, Austria
⁴Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Vienna, Austria
⁵Institute for Environment and Sustainability, Joint Research Centre, European Commission, Italy

Received: 10 Sep 2010 – Discussion started: 23 Sep 2010
Revised: 22 Feb 2011 – Accepted: 28 Feb 2011 – Published: 04 Mar 2011

Abstract. Recent studies highlight that spatial interpolation techniques of point data can be effectively applied to the problem of regionalization of hydrometric information. This study compares two innovative interpolation techniques for the prediction of low-flows in ungauged basins. The first one, named Physiographical-Space Based Interpolation (PSBI), performs the spatial interpolation of the desired streamflow index (e.g., annual streamflow, low-flow index, flood quantile, etc.) in the space of catchment descriptors. The second technique, named Topological kriging or Top-kriging, predicts the variable of interest along river networks taking both the area and nested nature of catchments into account. PSBI and Top-kriging are applied for the regionalization of Q₃₅₅ (i.e., a low-flow index that indicates the streamflow that is equalled or exceeded 355 days in a year, on average) over a broad geographical region in central Italy, which contains 51 gauged catchments. The two techniques are cross-validated through a leave-one-out procedure at all available gauges and applied to a subregion to produce a continuous estimation of Q₃₅₅ along the river network extracted from a 90m elevation model. The results of the study show that Top-kriging and PSBI present complementary features. Top-kriging outperforms PSBI at larger river branches while PSBI outperforms Top-kriging for headwater catchments. Overall, they have comparable performances (Nash-Sutcliffe efficiencies in cross-validation of 0.89 and 0.83, respectively). Both techniques provide plausible and accurate predictions of Q₃₅₅ in ungauged basins and represent promising opportunities for regionalization of low-flows.

Citation: Castiglioni, S., Castellarin, A., Montanari, A., Skøien, J. O., Laaha, G., and Blöschl, G.: Smooth regional estimation of low-flow indices: physiographical space based interpolation and top-kriging, Hydrol. Earth Syst. Sci., 15, 715-727, https://doi.org/10.5194/hess-15-715-2011, 2011.

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