The introduction of automatic instruments for precipitation measurements may have resulted in some differences in results from those taken by previous manual instruments. In the station network of the Czech Hydrometeorological Institute (CHMI) this replacement process began in the 1990s, when precipitation measurements taken by the METRA 886 rain gauge gave way to automatic tipping-bucket rain gauges, the MR3H and later the MR3H-FC. Continuous simultaneous measurement by both types of rain gauge at the Brno-Žabovřesky and Ostrava-Poruba stations in the 2000-2019 period enable differences in recorded daily precipitation totals to be compared. Only those days upon which at least one of the two types of rain gauge recorded precipitation are analysed herein. Although the highest proportion of differences in daily precipitation totals lies between −0.1 and 0.1 mm, there is a distinct tendency towards higher totals in positive deviations as measured by the manual METRA 886, that is, tipping-bucket rain gauges generally record lower precipitation totals then the 'standard' manual rain gauge (the MR3H-FC undervalues totals to a greater extent than the MR3H). The design and construction of tipping-bucket rain gauges are reflected in overvaluation of precipitation days with smaller totals and undervaluation of days with high totals when compared with the METRA 886. Series combining measurements by METRA 886 and by tipping-bucket rain gauges (as held in the CHMI database) and series measured by the METRA 886 alone were created, homogenized and analysed in terms of long-term fluctuations and annual variations. Homogenisation of precipitation series based on combined measurements leads to generally undervalued totals compared with those measured only by the METRA 886. Results are discussed with respect to other similar articles, sources of errors in both types of precipitation measurement, and with regard to the homogenisation of precipitation series.

In recent years, two drought monitoring systems have been developed in the Czech Republic based on the SoilClim and AVISO soil moisture models. The former is run by Mendel University and Global Change Research Institute (CAS), while the latter, by the Czech Hydrometeorological Institute. SoilClim is based more on real soil properties and aimed primarily at agriculture, while AVISO complements the system with more theoretical presumptions about soil, showing, rather, climatological potential. Both soil moisture models were complemented by forecasts on a daily basis, taking meteorological inputs from NWP (Numerical Weather Prediction) models and thus giving short-to mid-range outlooks up to 9 days ahead. Validation of the soil moisture and drought intensity prediction was performed and is presented in this article showing its prediction reliability and potential. In the analysis, we focus mainly on the past year, 2017. The tool has strong predictive power for soil moisture and drought intensity so it is suitable for farmers who need to make decisions about irrigation and production activities. The presented system is fully functional and can be applied in the coming years.

The paper deals with the analysis of a river’s regime of a small watercourse and the evaluation of its changes after the construction of a small water reservoir. The aim of the work was to analyse 12 years of flow rate measurements at two profiles of a small watercourse, between which a small water reservoir was built, in the middle of the period of the measurements. The analysis uses traditional characteristics (average flow rate, discharge volume), as well as modern indices from applied hydrology (Richards-Baker flashiness index, hydrogram pulse analysis), which study the variability of the flow rate in hourly and daily intervals. The evaluation showed that at the average flow rate, the effect of the water reservoir was the smoothening of the peak flow rates and prolonging the duration of the discharge waves. At higher flow rates, the water reservoir causes a delay in the culmination and in terms of discharge balance causes a decreased discharge volume, in particular during the vegetation period.

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The agrometeorological model named AVISO is developed and operated at the Czech Hydrometeorological Institute as a tool for calculation the evapotranspiration and soil profile water content. The model uses modified evapotranspiration equation developed by Penman and Monteith. The basic calculated surfaces are water level, bare soil, grass and a few field crops. As part of the research project, some AVISO model procedures and canopy parameters were modified for usage in fruit orchard. Data and observation from apple, cherry and apricot orchards from 2020 to 2022 were used to set up the model and to validate the model results. By determining the hydrolimits of the soil and the characteristics of the root zone of the trees, the water capacity of the model soil profile was estimated. The AVISO model results were compared with measured soil moisture, which was converted to the average soil profile saturation determined in percentage of available water capacity. When tuning the model, emphasis was placed on the decreasing part of the soil water content curve interpreting the intensity of evapotranspiration. In many iterations of the calculation, the results of the model were compared with the measurements using the correlation coefficient, the average bias and the mean absolute error. The average model-measurement correlation values for months in the growing season (April–September) in 2020 and 2021 were between 0.30 and 0.99. The bias error values were between -13.14 and +38.31 mm. The second comparison option was to use the precipitation sums for time periods determined by the almost identical moisture at the beginning and the end of the period. The amount of precipitation in the given section thus theoretically coincided with the sum of evapotranspiration. Correlations of model evapotranspiration and evapotranspiration calculated on the basis of this simple precipitation balance reached values of up to 0.9 for some variants of orchards. Despite some weaknesses, the model results are satisfactory in some experimental stands, especially in apple orchards. The modified model was used to calculate the long term average water balance of apple trees within the territory of the Czech Republic for the growing season for the period 1991-2020. Composition of seven maps was produced - six maps for monthly data and one for entire growing season. The values of water balance for summer months are in range from -77 to +125 mm, sum for growing season is in range from -323 to +563 mm. The lowest values indicating the threat of drought are in the South Moravia region. Among other things, improved model and maps can help to optimize water management and irrigation in orchards.