The paper presents the results of computational experiments for evaluating the impact of different evapotranspiration assessment methods usage on the accuracy of soil moisture dynamics simulation for the conditions of sprinkling irrigation. We consider a differential one-dimensional model of moisture transport stated in terms of water head which uses as an initial data the estimates of evapotranspiration according to the methods of Ivanov, Shtoiko, Penman-Monteith and SEBAL. The differential moisture transport model was discretized using the finite-difference scheme. Its unknown parameters values were found by solving an inverse problem using the metaheuristic particle swarm optimization algorithm. We perform water head modeling accuracy assessment using different methods of evapotranspiration evaluation along with their linear combination. The Ivanov’s method was found to be the most accurate in the conditions of soybean growing in the south of Ukraine under sprinkling irrigation while linear combination of four considered methods gives an additional increase of accuracy by 6.5%.

The formation of optimal crop rotations is virtually unsolvable from the standpoint of the classical methodology of experimental research. Here, we deal with a mathematical model based on expert estimates of “predecessor-crop” pairs’ efficiency created for the conditions of irrigation in the forest-steppe of Ukraine. Solving the problem of incorporating uncertainty assessments into this model, we present new models of crop rotations’ economic efficiency taking into account irrigation, application of fertilisers, and the negative environmental effect of nitrogen fertilisers’ introduction into the soil. For the considered models we pose an optimisation problem and present an algorithm for its solution that combines a gradient method and a genetic algorithm. Using the proposed mathematical tools, for several possible scenarios of water, fertilisers, and purchase price variability, the efficiency of growing corn as a monoculture in Ukraine is simulated. The proposed models show a reduction of the profitability of such a practice when the purchase price of corn decreases below 0.81 EUR∙kg –1 and the price of irrigation water increases above 0.32 EUR∙m –3 and propose more flexible crop rotations. Mathematical tools developed in the paper can form a basis for the creation of decision support systems that recommend optimal crop rotation variations to farmers and help to achieve sustainable, profitable, and ecologically safe agricultural production. However, future works on the actualisation of the values of its parameters need to be performed to increase the accuracy.

For integrated water management in river basins in Ukraine, there is no toolkit for system modeling and selection of management structure in river basins according to environmental and economic criteria, which corresponds to the creation of water management systems under conditions of sustainable development. Therefore, the urgent task is to develop a system model of integrated water management on the example of the Ingulets River basin. The purpose of the work is to create a system model of integrated water resources management in Ingulets River basin, which provides scenario modeling of technological solutions, their evaluation and optimization of economic criteria for efficient water use under environmental constraints and criteria for achieving a good or excellent ecological status of the river basin. The system model is used as a toolkit, the method of decomposition of the river basin into subsystems, analysis of subsystems and their composition into a holistic model of integrated management by the basin principle. Telecommunication methods are proposed to improve monitoring. A method of scenario analysis is proposed, which performs simulation modeling of prospective management scenarios at the first level of the hierarchy, and at the second level - options are evaluated according to the criteria of cost-effective water use with environmental objectives and regulatory restrictions. For simulation modeling, a system of balance difference equations for the dynamics of water masses, mixing and spreading of pollution in rivers and reservoirs is formalized. A system of combined control for the impulse method of river washing was developed. Multicriteria optimization of variants of the control structure is carried out on the Pareto principle. A system model has been developed for integrated water resources management in the Ingulets River basin that meets the requirements of the EU Water Framework Directive on the establishment of cost-effective water use while ensuring good or excellent ecological status of rivers. The structural and functional diagram of the system model includes the subsystems: the water supply subsystem of the Dnipro-Ingulets canal; a subsystem for flushing the Ingulets River from the Karachunivske reservoir and displacing the saline prism into the Dnipro River; subsystem of environmental safety when discharging pollution into the river Ingulets; subsystem of water supply for irrigation in the Ingulets irrigation system, prevention of soil salinization. A system of technological, economic and environmental criteria for evaluating integrated management by the basin principle has been developed. They include maintaining the water level in reservoirs, displacement of salt water prism and limitation on water quality, ensuring the ecological condition of the river, and the dynamics of water resources consumption. Technological criteria determine the maintenance of water levels in reservoirs. Cost-effective water use is estimated on the basis of the dynamics of water consumption for river washing and irrigation. The formalized integrated management system in the Ingulets River basin includes operational water resources management and structure management. Integrated management is carried out according to subsystems, types of management and a system of criteria. For operational management the balance differential equations of water exchange in reservoirs are formalized. A two-layer model of water masses dynamics, pollutants distribution and mixing when flushing rivers from reservoirs is used. Scenario analysis is offered to select the optimal structure of the management system. Simulation scenarios are being simulated. Scenario optimization is performed on the Pareto principle. An example of evaluating the effectiveness of the proposed system and its comparison with the existing regulations for Ingulets River flushing is given.

The paper provides an overview of models and software used in decision support systems in irrigation. The models of biomass accumulation or evapotranspiration are the base of decision support systems in irrigation. The overview of the most famous systems is given, as well as an innovative irrigation control system "Irrigation online" is presented. The objective of the work is to share the experience of development and implementation of irrigation management systems and outline the ways of their improvement. The "Irrigation online" system consists of hardware and software components. The part of the system's hardware is located in the field consisting of iMetos or Davis weather stations, as well as of own-developed equipment. The software part, intended for storing, processing and providing recommendations, is hosted and run on a server. It sends the recommendations about start watering and necessary irrigation rates to a user’s computer or mobile device. The system is based on modelling of moisture transfer, automated measurements of soil moisture and meteorological indicators in the field and weather data from automated forecast web-sites. Water retention curve of soil and the dependence of the moisture transfer coefficient on the head, which are the input parameters of the model, are given for every layer according to the van Genuchten-Mualem Model. The application of the system took place in 2019 in SE EF“Askaniiske” Kherson region and LLC “APC “Mais” in Cherkasy region. The system "Irrigation Online" provided the recommendations on watering winter rape, wheat, corn, soybeans, alfalfa and potatoes. The system provided the recommendations on watering winter rape, wheat, corn, soybeans, alfalfa and potatoes. It was specified that the use of the system "Irrigation Online" enables to schedule irrigation regimes, the implementation of which requires watering with less (by 15-25%) in comparison with the current irrigation rates, due to which more favourable conditions for the maximum realization of crop varieties and hybrids potential are created. It is accompanied by enhancing the environmental safety of irrigation as a result of minimization of irrigation water losses for infiltration. Irrigation control system "Irrigation Online" uses a range of soil moisture suction pressure rather than a soil moisture range as an optimum moisture supply range for plants. For setting up irrigation terms and rates, the value of suction pressure, which corresponds to the part of water field capacity when it is determined by water retention curve of soil, is taken. The pre-irrigation threshold of suction pressure is the value, which at non-irrigation for some short period will not cause water stress for plants Monitoring of meteorological parameters and soil moisture level in the "Irrigation Online" system allows daily adjusting irrigation terms and rates for next 5 day period and significantly improves the accuracy of their forecasting.