Regionalization Methods for Low Flow Estimation in Ungauged Catchments – A Review

Abstract

Aim of the study The purpose of the paper is to look at the topic of estimation of the low flow characteristics at ungauged catchments in a balanced and systematic way, to provide a recent documentation of the subject and trace the most recent trends in low flow regionalization. The review focuses on methods, which are based on diverse methods that is the statistical, seasonal approach which are commonly used for the estimation of low flow characteristics in ungauged sites and which can be adopted in Polish conditions. Material and methods The paper examines the variety of literature sources published primarily during the last two decades. The most popular approaches to regionalization of watersheds are described: methods of residuals pattern approach, multivariate statistics such as cluster analysis, Classification and Regression Tree (CART) models or seasonality of low flows. Results and conclusions The described regional regression approach for low flow estimation in ungauged catchments, which correlates low flow indices and catchment characteristics, is the most widely used method. The methods were chosen because they differ in terms of methodological approach to using statistical methods. Also, the methods described in the article are "universal", which means that they can be adopted for different regions, countries, including Poland; they are interdisciplinary, and can be adopted for low flow calculation as well as average or flood flows.

Journal of Water and Land Development

“…The first applied method was the residual pattern approach (RPA), in which the residual, between the low flow values, calculated from the global regression model, and the observed values, was estimated. Geographically contiguous regions are then plotted manually on a map [CUPAK 2020]. In the RPA, in the first step, a global regression model should be determined using stepwise regression, and then the residuals obtained from the global model should be plotted on a map in geographical space.…”

“…For controlled catchments, this problem does not occur. For these, the most reliable statistical methods should be used [CUPAK 2020;WAŁĘGA et al 2014].…”

“…Another aspect of empirical formulas is the year of their development, e.g. Punzet's formula was developed by the author in the 1980s [CUPAK 2020;WAŁĘGA et al 2014]. They, therefore, need to be verified using data now coming from much longer observation sequences [WAŁĘGA et al 2014].…”