Freely available mean daily discharge series from Czechia: what can be inferred from them?

Abstract

Abstract. Most hydrometeorological data from Czechia are still provided for a fee. This especially applies to time series with a finer step than monthly. The fact that the data must be paid with respect to an expert's appraisement and that the proper licence agreement ratification has to be performed causes a considerable delay in the data transfer to potential customers, unfortunately including scientists as well. Naturally, this timeconsuming process is unpleasant to the experts on both sides. Due to a substantial rise of university students' requests for data, the Czech Hydrometeorological Institute's hydrologists launched a website from which long mean daily discharge series representing ten selected watergauging stations can be downloaded. Besides other assessments, the series may play an important role when studying climate change impacts on water resources in Czechia. Therefore, the objective here was to extract from these series some preliminary information on long-term changes such as abrupt and gradual trends caused either by the construction of reservoirs or by climate variability itself. The main tool used was nonparametric trend analysis. Mainly different months were of interest so as to determine if there have been recorded some changes in seasonality. The results may be easily expanded by students.

Freely available daily hydrometeorological data from Czechia: further insights

“…For the hydrological data sets composed of discharge, the source was the same as in [1] (i.e. the website of the Czech National Committee for Hydrology, CNCH; http://cnvh.cz/).…”

“…Thus, although the series of discharge could have different starting points, the end point was always 31 December 2016. Having prior information about the homogeneity and the missing values within the series, we proceeded with five selected water-gauging stations that were subjected to the stationarity and unit root tests in [1] (i.e. stations 091000, 151000, 240000, 294000 and 421500).…”

“…In the case of air temperature and precipitation, we assumed that the tests of homogeneity were carried out by climatologists before offering them online. For the next analyses, the series should be deseasonalized, as emphasized, for example, in [1,12,13]. Observing suspicious patterns in wavelet spectra after the wavelet-based deseasonalization suggested by [14] (not shown), we decided rather to employ classical deseasonalization outlined in [12,15,16].…”

“…In 2017, the academia and other researchers or scientists from around the world were informed about the existence of freely available mean daily discharge series from Czechia [1]. The author of that paper briefly demonstrated how the data set could be used especially in relation to the study of possible influences of climate change (CC) on water resources monitored by the Czech Hydrometeorological Institute (CHMI).…”

“…On the one hand, the stationarity of the offered discharge series was tested, but on the other, values of the Hurst exponent (i.e. a key indicator of long-range dependence, otherwise called long-term persistence, LTP) were not reported in [1]. This exponent is closely related to the fractional differencing parameter d of the models characterizing stochastic processes typical of LTP (i.e.…”