Region-specific multiple-approach separation of river hydrograph using the GrWat R package

River hydrograph separation is one of the most important operations applied to the streamflow data. Numerous separation techniques and and their software implementations have been developed so far. In operational practice of Russian hydrological organizations and research institutes an event-based approach is commonly used for the hydrograph separation. Different meteorological events such as temperature transition through zero and rains are recognized in meteorological data, and then the corresponding changes in river hydrograph are identified, which eventually helps to attribute each peak in hydrograph with corresponding genetic component. The base flow component is traditionally defined according to Kudelin’s approach, taking into consideration different schemes of surface-ground water runoff interaction. In contrast, the most widespread separation approach in Western school is filtering-based. Lyne-Hollick, Maxwell, Boughton, Jakeman, Chapman and some more sophisiticated filters can be applied to separate the flow into quick and base. Results of two approaches are quite different, especially in terms of the baseflow component. In current study we present the updated open-source grwat R package, which puts both worlds together. It contains both the genetic event based and filtering-based hydrograph separation approaches with the ability to mix them together. In particular, applying the filtering-based separation inside the detected genetic events provides curve of the baseflow well corresponding to tracer-based studies. The second novelty of the package is the intellectual procedure for determination of the second-order events that complicate the freshet (seasonal) flood, such as rain floods. Finally, the updated package contains the internal spatial database of hydrograph separation parameters which is obtained over the European territory of Russia through experimental work. This database allows automated selection of the optimal separation parameters based on the location of the river gauge supplied by package user. The database can be extended to other regions of the world through collaborative work of package users.

The study was supported by the Russian Science Foundation grant No. 19-77-10032