Regional estimation method of rivers low flow from river basin characteristics

Low flow characteristics are usually estimated from flow gauge stations. However hydrological data are not always available at the site of interest: regional frequency analysis is commonly used for the estimation of flow characteristics at sites where little or no data exists. The study is applied to Tuscany rivers discharge dataset. The area is subdivided into homogeneous regions using an L-moments procedure. The low flow indices Q(7,2) and Q70 at ungauged basins are evaluated with deterministic (Inverse Weighted Distance) and geostatistical (Ordinary Kriging) methods. In order to improve the capability of low flow statistics in ungauged sites a multivariate model, based on geomorphoclimatic characteristics, is also assessed. For each sub-region a relation connecting low flow indices and geomorphoclimatic characteristics is found.