The composite weir-gate structure is considered an important hydraulic structure. This is because of its widely used in civil engineering hydraulic works especially in an irrigation system to measure, control, divert and keep the required water level. This study focuses on the influence of barrier existence on the hydraulic parameters that described the hydraulic characteristics of composite weir-gate hydraulic structure. In this study, several experimental runs were conducted to determine the effect of barrier's location, spacing and number on the water level and depth at the downstream region of flume, discharge coefficient of composite hydraulic structure, and flow rate throughout the flume. Our experiments indicated that the turbulence intensity, inlet effect, and position, gap, and number of barriers have affected the hydraulic behavior of weir-gate structure. This appears clearly by obtaining different results of discharge coefficient and flow rate that cross the weir-gate structure comparing with same cases without barriers. Also this study gives some insights on the significance roles of fluid separation, eddies generation near the barrier, fluid resistance and overlap between overflow and underflow velocities and their effects on hydraulic factors that dominate the problem. These hydraulic factors must be considered in the design and construction of barrier/barriers in open channel to prevent any fluctuation or drop in discharge, water elevation and the required water depth at downstream region.

A sediment core, 350 cm long recovered from Młynek Lake, northern of Poland (Warmia and Masuria Region) was analyzed with respect to their content of diatoms and chrysophyte cysts. The aim was to reconstruct the lake water level and climatic changes during the past 2500 years. The recognized diatom assemblages displayed marked floristic changes along the sediment core samples. The main change in diatom composition consists of a shift from an assemblage dominated by benthic Fragilaria sensu lato species through marked intervals to a planktonic one in distinct zones. A high proportion of benthic to plankton taxa has been reported as indicative for a lowering of the lake level with long ice cover in a cold dry climate and a shift from benthic to planktonic diatom taxa reflects arising water level with longest growing season and reduced ice cover on the lake during a warm wet climate. Multivariate statistical analysis included hierarchical ascending clustering distinguished four diatom ecological groups. The analyzed core section was divided into 11 diatom zones according to a distribution of ecological groups and variation in abundance of dominant species supported by 14C data. The results displayed a developmental history of the Młynek Lake that can be divided into 6 main phases of alternating warm wet and cold dry shifts. A distinct dominance of planktonic eutrophic indicator diatoms accompanied by a low abundance of chrysophyte cysts indicates increased lake trophicity and a general trend for the increasing anthropogenic impact.

The runoff coefficient is one of the fundamental hydrological characteristics of a catchment. It indicates a share of the precipitation water that runs off from the catchment.

The results of the runoff coefficient calculation based on measurements carried out continuously in the Cerhovický Stream catchment over a considerable period of time, i.e. from 1988 up to 2006 are presented. The precipitation and runoff data in the catchment were used. Mean value of the runoff coefficient and the runoff coefficients for the agricultural and forest parts of the catchment are presented. The total mean runoff coefficient for the Cerhovický Stream is 0.19 with the standard deviation of 0.06. Mean runoff coefficient for the forest part is 0.13 and for the agricultural part – 0.24.

Differences between the years with a higher and a lower precipitation were followed as well. We also statistically evaluated possible hydrological changes caused by the construction of the highway and the market centre. For another possible explanation of quite high standard deviation of the mean annual runoff coefficient we followed the monthly runoff coefficient dependence on water temperature and of ground water table depth.

The aim of the study was to determine the influence of the load on the water accumulation embankment crown on changes in the course of the filtration curve in its body. The study was carried out with a medium-size filtration apparatus. We made a model of hydrotechnical embankment with the following dimensions. Width: base 2.0 m, crown 0.5 m. Slope inclination: waterside 1:1.5, landside 1:1. Embankment height 0.6 m, width 1.0 m, weight 900 kg. The construction mater-ial included a homogeneous mineral subsoil classified as silty medium sand (siMSa). The embankment model made in a medium-size apparatus kept the accumulation level at a height of 0.5 m. With data from the recording systems, we deter-mined the course of the filtration curve. Next, we kept on loading and relieving the embankment crown using an actuator and a VSS plate with a diameter of 300 mm. During this process, we recorded changes in the level of the water table inside the embankment. A decrease in the water table was observed as a result of increased load. Once the load on the embankment crown was reduced, the water level inside the embankment increased. The embankment model built from natural soil works well as a structure that keeps damming water in a continuous manner. The use of drainage in the form of a stone prism at the foot of the landside slope allows protecting the slope against the negative influence of filtration (piping, lique-faction).

The results of a long-term water level monitoring in three forest ponds are presented in the paper. The ponds are locat-ed in the Wielisławice and Laski forest districts in South Wielkopolska, Poland. Two of the analysed ponds are natural ones supplied by precipitation and the third now is disused artificial fishpond of throughflow water management. Systematic water level measurements, as well as measurement of basic meteorological conditions – precipitation and air temperature – were carried out in the 2000–2016 hydrological period. The basic statistics as well as the trends in long-time changes in water levels, were determined using the nonparametric Mann–Kendall test were calculated. The results obtained were sta-tistically inconclusive, but they indicated downward trends in water levels in the natural ponds and upward trends in water levels in the artificial pond. Although a statistically significant downward trend was observed in only one natural pond, it may suggest some negative changes occurring in the catchment of ponds in general.