Four variants of damming water in a projected storage reservoir were examined for their effects on groundwater levels in the surrounding area. The extent of reservoir’s influence on the ground waters under stable motion conditions was determined, and the effects of a short-term damming up to the crest level and of increased seepage from the aeration zone were assessed. An author’s mathematical model based on a two-dimensional non-stationary Boussinesq equation was used. The differential equation was solved by finite element method. It was found that the level to which water is dammed has a significant impact on the extent of the reservoir’s influence on ground waters, while neither a short-term damming in a flood period nor higher seepage from the aeration zone during a wet summer results in a significant increase in groundwater levels. The computer simulations made it possible to adopt a safe variant of damming, posing no threat to the structures in the reservoir’s surrounding, already at the planning stage.

In the hydrological years 2000-2004, studies were conducted in the Mała Wełna river catchment (up to the Kiszkowo gauging section) having a high lake density index. The water balance was used to establish the changes in water retention in the catchment. Then, relationships were established between the retention changes and the precipitation totals and the changes in groundwater levels. It was found that the monthly and yearly retention changes were positively correlated with the monthly and yearly precipitation totals and groundwater level changes in two observation wells situated at a distance of 135 and 250 m from a girdling ditch. Therefore, the changes in groundwater levels in these wells may provide a basis for estimating the retention changes in the catchment.

Based on the monthly measurements performed from April to September 2005 in the layers 0-10, 20-30, 40-50, 65-75 and 90-100 cm of four characteristic soil profiles, the study assessed the soil moisture conditions in the left-bank part of the Odra river valley upstream of the Malczyce dam under construction. The changes in water reserves were analysed in relation to precipitation, depth of groundwater table, and stage of water in the Odra river. The basic physical properties of soils were determined and the water retention curves were drawn, then the moisture ranges corresponding to the characteristic moisture conditions were established. The precipitation of the study period was close to normal. Because of the quite deep groundwater table near the soil profiles (deeper than 1.5 m in all measuring points, deeper than 4 m in part of the area) the upper soil layers studied were supplied only from precipitation and their moisture did not depend on the level of ground waters. Profiles No. 7 and 10 had more favourable moisture conditions: for most of the study period, the water reserves in the layer 0-50 cm ranged between the field water capacity and the drought water capacity. The moisture conditions of profiles No. 8 and 9 were worse; in the former, the total water reserves both in 0-50 and 0-100 cm layer were most often lower than the value corresponding with the wilting point.

The paper discusses the hydro-morphological changes in the mountain stream Targaniczanka caused by the violent flood flow on the 24th August 2005. The flood destroyed or damaged road bridges located in the middle and lower reaches of the stream and affected buildings situated too close to its channel. The course and effects of this event were analysed on the basis of stream basin parameters, rainfall, flood wave travel, stream cross-sections, rating curves, and the grain-size distribution of bed material. Since the Targaniczanka Stream catchment is uncontrolled, the discharge during the flood was described using a rainfall-runoff model. The grain size measurements made it possible to determine the bed stability conditions which, combined with the measurements of cross-sections, provided the basis for establishing bed roughness and the discharge capacity curve. The hydraulic parameters of the stream bed after the flood were compared with the results of simulation run for a stable cross-section. The frequent occurrence of rapid outflows in the stream may be attributed to the morphology of its basin. The flow that occurred on the day in question substantially exceeded Q1%. The fact that the hydrodynamic stability of the stream was upset and many bridges were damaged suggests that the infrastructure of the stream should be redesigned.

The study provides the results of research on the uniformity of sewage flow from drain pipes of a soil infiltration system. The research compared two types of pipes with holes drilled in the bottom: type I - with holes spaced at 0.50 m, type II - with holes spaced at 0.25 m, and used six levels of hydraulic loads from 24 to 120 dm3. Laboratory experiments were carried out in a ground bed from medium sand, using water in place of sewage. The flow from the drain pipe type I, with a larger spacing of holes, was found to be more uniform than that from the drain pipe type II. For both types, the uniformity of flow decreased with the increasing load of pipes.

The study examines the potential applications of artificial neural networks in predicting the time series of water levels and river flows. The data for computations comprised the time series of daily water levels and river flows at the gauging sections in Gdów and Stróża on the Raba river and in Marwin on the Krzyworzeka stream from the hydrological years 1979-1981 and the daily precipitation totals from 1978–1981 recorded at the meteorological station in Dobczyce. Two separate neural networks were created for the time series of water levels and river flows. It was decided to build perceptron networks differing in architecture. An analysis showed that the efficiency of a perceptron network in predicting water levels and river flows at the gauging section in Gdów on Raba is higher when the water levels and river flows at the Stróża gauging section on Raba and the Marwin gauging section on Krzyworzeka along with the daily precipitation totals in Dobczyce are assumed as input parameters than in the case in which the model takes no account of precipitation. Slightly better results of prediction were obtained for river flows than water levels, which may be due to somewhat different factors determining the former.