Abstract
This study discusses a dataset of water stable isotopes from precipitation (4 rain gauges) and surficial water (9 rivers) from the northern Italian Apennines, an area in which clay-rich bedrocks widely outcrop and the runoff response to precipitation events is very rapid. The dataset has been compiled starting from existing data that had previously been published in the literature and consists of monthly values of stable isotopes oxygen-18 (18O) and deuterium (2H) lasting over the period from January 2003 to December 2006 (precipitation) and from January 2006 to December 2007 (surficial water). For this period, mean residence times estimated by means of a sine-wave fitting technique make evident the significant differences over time spent by water molecules within the 9 catchments. Moreover, isotopic compositions of rivers deviated from those of precipitations revealing the influence of some catchment characteristics in differentiating the isotopic composition in rivers. Further correlations between mean residence times of river water and selected catchment characteristics reveal the role of orography and bedrocks in delaying the water molecules during their flow-paths. In addition, time series and cross–correlation analyses indicate a certain control by the main watershed divide on the isotopic composition of river waters, which is reflected in a progressive isotopic variation with longitude. The study shows that, despite using a short-time dataset (2-years for surficial water) of sparse stable isotopes can provide remarkable indications for depicting hydrological processes in large catchments made up of clay-rich bedrocks.
Highlights
Catchments are complex hydrological systems in which the understanding and quantification of the several processes participating in the final runoff is a challenge [1]
In all the rain collectors, dE -MW was higher than the corresponding MA values as they ranged from 10.3%
This study shows that a short-time series of scattered water isotopes can be useful in order to depict hydrological processes occurring in large catchments composed of clay-rich bedrocks
Summary
Catchments are complex hydrological systems in which the understanding and quantification of the several processes participating in the final runoff is a challenge [1]. This is because the hydrological processes are heterogeneous and their full understanding is not achieved even on small scales (i.e., that of the slope). They have been extensively used to understand the runoff mechanisms by collecting isotopic data from the different components participating in the hydrological cycle. In glacierized catchments, the isotopic data of the snow and glacier melt water, in addition to those of precipitation and runoff, are essential [4,5]
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