Low Flows Regionalization in North-Western Italy

Abstract

Prediction of low flows in ungauged catchments is needed in many branches of water resources management, including water availability and river ecology studies. In this paper we analyze the regional variability of q 95 , i.e., the specific discharge that is exceeded 95% of the time, in North-Western Italy (Piemonte and Valle d'Aosta Regions). Multiple regressions with morphoclimatic catchment characteristics are applied in subregions obtained through four classification methods: Seasonality Indices (SI), Classification and Regression Trees (CRT), Residual Pattern Approach (RPA) and Weighted Cluster Analysis (WCA). All the classification methods separate the South-Eastern Apennine-Mediterranean area from the rest of the study domain (the Alps mountain range), even if they use different criteria to carry out this division (e.g., the percentage of forest, seasonality of low flows, combination of several parameters). In the Apennine-Mediterranean part of the area, low flows occur in summer with a long period of drought and are mainly due to dry climate, moderate snowpack storage and high evapotranspiration. In Alpine catchments low flows occur in winter and vary according to precipitation, elevation, interactions with aquifers and land cover. Within the Alpine mountain range the CRT algorithm identifies a number of small high-elevation catchments in which the intense drought period during winter has the soil freezing processes as the driving force. From a statistical point of view, the CRT model outperforms the P. Vezza (B) · M. Rosso P. Vezza et al. models obtained by the other classification techniques in terms of explained variance (69%). Because of this, and given the meaningful hydrological interpretation of the results, we use the CRT model for the regionalization of q 95 in Piemonte and Valle d'Aosta. Lastly, as operational procedure for future low flow regionalization studies, we suggest that more classification methods should be applied to assist the critical analysis of the results.

Random forests to evaluate biotic interactions in fish distribution models

“…The CART technique splits a learning sample using an algorithm known as binary recursive partitioning, by which the data set is divided into two parts by maximizing the homogeneity in the two child nodes. This splitting or partitioning starts 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 10 from the most important variable to the less important ones and it is applied to each of the new branches of the tree (Vezza et al, 2010).…”

Catchment classification based on characterisation of streamflow and precipitation time series

“…Haines et al, 1988;Holmes et al, 1999;Viglione et al, 2006) or low flow percentiles (e.g. Nathan and McMahon, 1990;Laaha and Bloeschl, 2006;Vezza et al, 2010) or the entire flow duration curve (e.g. Singh et al, 2001;Ley et al, 2011;Patil and Stieglitz, 2011;Sauquet and Catalogne, 2011).…”

Índices de sazonalidade para regionalização hidrológica de vazões de estiagem no Rio Grande do Sul

“…Vários pesquisadores têm proposto metodologias para identificar regiões homogêneas no contexto de regionalização de vazões de estiagem e, dentre essas metodologias, Laaha & Blöschl (2006) destacam as medidas de sazonalidade, as quais têm sido aplicadas com sucesso em diversos estudos (Burn et al, 1997;Young et al, 2000;Laaha, 2002;Laaha & Blöschl, 2006;Vezza et al, 2010).…”

“…Among the three seasonality measures, SI and SH were more appropriate due to specific hydrological characteristics in the state, therefore, they can be considered as relevant methodologies to delineate hydrologically homogeneous regions for the regionalization of low stream flows. ISSN 1807ISSN -1929ISSN v.18, n.7, p.748-754, 2014 Introdução A determinação de vazões de estiagem em rios e as frequências que lhes são associadas, apresentam inúmeras aplicações na área de recursos hídricos, tais como: planejamento para abastecimento de água, projeto de reservatórios, manutenção de quantidade e qualidade de água para irrigação, recreação e vazão ecológica para conservação de espécies animais (Vezza et al, 2010).…”