Response of the groundwater regime of the South Fergana river basins to global warming

The article presents the results of assessing the response of the groundwater regime in the river basins of South Fergana to global warming.

VARIABLE RHYTHMS IN GROUNDWATER REGIME AND THEIR RELATIONSHIP WITH CLIMATE FACTORS

Due to the anomalous changes in the groundwater regime over the past 5 years, the question arose about the adequacy and effectiveness of existing methods for predicting their level. The data of monitoring observations from 1951 in the upper part of the Southern Bug river basin are analyzed. The specific underground runoff to the river in the site of Khmilnyk was calculated by the finite difference method. It is established that at the end of the 80s of the last century a 7-8 year cycle began to appear in the fluctuations of the groundwater level (GWT) and groundwater runoff. It correlates well with the cyclicity of the air temperature, and, to a lesser extent, with the cycles of the monthly amount of precipitation. Instead, such rhythms are not at all typical of solar activity, which is characterized by 11-year and 5-6-year cycles. It is in connection with them that the heliosynoptic method of long-term prediction of RGV is based. It is likely that temperature changes occurring on Earth may change the "sun-induced" cyclicity of GWT, so this method of forecasting becomes ineffective. As there is no clear link between temperature changes and solar activity, it is possible that temperature changes are caused by human activity.From 2013-2015, with the beginning of the low water cycle in the study area, the anomalous minima in the GWT mode became more frequent and the cycles were transformed in the direction of their reduction (up to 5-6 years), which may indicate sharp changes in the nature of groundwater storage recovery. Deviations from 8-year cycles and differences in their duration in different parts of the same catchment area are primarily related to differences of GWT. Wavelet analysis was used as the main method of cyclic selection. Using multiple correlation analysis, it was found that in recent decades the temperature has reached a dominant position in terms of the impact on the groundwater regime (at their levels from 1.5 to 4.0 m). As a result, it was noted that our 7-8 year cycles are well traced during the relatively multi-water period caused by increased infiltration of groundwater due to increasing winter thaws (one of the most significant manifestations of global warming), and 5-6 year cycles correspond to low water periods.

Assessment of the impact of clearcutting on groundwater regime in swampy habitats

The aim of the study was evaluation of clearcutting effect on water regime in a tree harvesting area. The results was made on the basis of the study carried out in Rakowski Ditch catchment, in Wielkopolska lowland in Poland. It was found that a more useful method to establish the effects of clearcutting is to is to compare the groundwater table level in the post-clearcutting area with that in a control area than to analyze the groundwater table level changes in the same area before and after the clearcutting. Regression analysis is a particularly useful tool in groundwater regime analyzes. The results obtained in this study indicated that the groundwater regime changes in the post-clearcutting area were manifested as an increase in the average groundwater levels. The major changes in the groundwater table after clearcutting were observed in the minimum levels, while the lowest changes took place in the maximum groundwater levels. The variation in groundwater levels was higher in the period after clearcutting than in the period before it. The analysis of linear regression of groundwater levels in the well located in clearcutting and that in the control area confirmed the change in the groundwater regime in the post-clearcutting area. Stronger relations in the period before clearcutting were observed. Key words: clearcutting, groundwater, forest catchment, swampy habitats

Modeling and forecasting of groundwater regime for rice systems as one of the main indicators of ameliorative state of the territory

Relevance of research. An important factor of the formation of the soil state of modern rice irrigation systems is water-salt, nutrient and groundwater regimes. Ground water level is one of the indicators of the technical state of rice irrigation systems. Direct correlative dependence of rice yield on the ameliorative state of the field is proved by many researchers. Maintaining of soil fertility when growing rise at a constant level is ensured by sustentation of the ground water level not less than 1,5 m from the surface in the inter-vegetation period. Measures to combat flooding in the territory are developed based on monitoring dates. GIS technologies should be used to quickly perform the assessment of conditions when man-made factors change. Objective of research is to develop the forecast models of the mail indicators of the hydro-ameliorative state of rice irrigation systems, particularly for ground water levels, for saving their fertility and increasing their efficiency. Research methods. Mathematical-statistical, comparative and retrospective methods were used for analyzing the data base. The data from the Kakhovska hydrogeological and reclamation section of the Lower Dnieper BWMA as well as the data of own research over 28- year observations were used for model developing. The model of groundwater regime for the conditions of rice irrigation system was developed using the method of three-parameters smoothing, which takes into account seasonal fluctuations, in the program Statistica 10.0. The forecast was made for the period of 5 years for every month. The forecast models were developed for the experimental and production conditions. Results. The difference in groundwater level during a year at rice irrigation systems ranges from 0,5 to 1,0 m from the surface. Maximum actual value of ground water level in experimental conditions was 4,25 m from the surface, minimum actual value was 0,15 m from the surface during the research period and they did not differ much from the model values. The sampling interval was 4,19 m for the actual data and 3,88 m for the model. Close relation between the model of ground water regime for experimental conditions and the actual data is confirmed by the correlation coefficient 0,96. The forecast of ground water regime of rice irrigation system for the experimental conditions shows that the groundwater level will decrease in the period of 2019-2024 years and will vary in the range of 1,20-2,23 m from the surface. Maximum actual value of ground water level in the production conditions was 3,78 m from the surface, minimum one was 1,39 m from surface. Model data do not much differ from the actual values. The reliability of the developed model of ground water regime for the production conditions of rice irrigation systems is confirmed by the correlation coefficient 0,96. The forecast model of the groundwater regime developed for production conditions shows that the indicator will increase in the period of 2018-2023 years and will change in the range of 2,13-2,85 m from the surface. Conclusions. Forecast modeling of ground water regime of rice irrigation systems shows that ground water level will be deeper than 2,0 m from surface in inter-vegetation period in experimental and production conditions. The results of forecasting have proved that it is unlikely the occurrence of negative soil process due to ground water regime and a good hydrogeological-ameliorative state of experimental and production rice irrigation systems during the forecast period.

Hydraulic Assessment of the Impacts of Gate Realization on Groundwater Regime

Presented paper deals with the hydraulic assessment of groundwater flow in the area affected by the realization of the hydraulic gate on the Klátov branch and in the adjacent territory of a dike, which is located on the right-side of Little Danube. This hydraulic assessment is part of the project of the Slovak Water Management Enterprise, which also aims to increase the height and seal the dike on the right-side of the Little Danube. Generally, the project is divided into three phases (Phase I, II and III) to implement different technical measures to protect the area from flooding. The assumption for the execution of the technical measures of the mentioned three project phases is a continuous flood protection of part of the Žitný ostrov area around the Little Danube and the Klátov River branch in the reach from Kolárovo to Jahodná town. Therefore, a 3D mathematical model was created to simulate groundwater flow by changing boundary conditions of surface water flow during flood periods.

MONITORING AND EVALUATION OF GROUNDWATER LEVELS AT LADNÁ HYDROPEDOLOGICAL PROFILE

The planned construction of Oder-Danube canal was one of the largest activities, which led to the realization of research projects, which also included construction of boreholes for monitoring groundwater levels. Hydropedological profiles (HP) consist of boreholes, which are situated usually across the route of the canal and across longitudinal axis of valleys or flat Moravian hollows. They belong to basins of Oder, Bečva, Dyje (Thaya) and Morava rivers. First observations started back in 1933, subsequent followed after 1940. Nowadays these objects serve for obtaining general idea about the groundwater regime in valley profiles of these rivers. From geological perspective, these HP profiles are in an area of Quaternary sediments. Groundwater level monitoring at HP is important especially because of relating the profile to a particular watercourse and duration of the continuous monitoring. It can be used for determination of hydraulic link between surface water and groundwater. These values can be very useful especially in the determination of spread of potential groundwater pollutants via surface waters. Aim of the work is to assess course of groundwater levels at the Ladná profile of interest and to evaluate the effect of river engineering of the Dyje River on the groundwater regime, taking into account the drought period. Next aim of the work was to show the relationship with surface waters and evaluate the relationship between individual boreholes and the watercourse in the entire profile. In addition, long-term data series of groundwater level monitoring were used to perform evaluation of course of groundwater levels during various time periods, in particular during the individual reference periods, as specified by the CHMI, i.e. 1931-1960, 1931-1980 and the current reference period 1981-2010. Subsequently, the period 1991-2018 was also analyzed as a period associated with the current situation and finally also the entire period of monitoring, i.e. 1948-2018, a total of 70 years.