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.