“Environmental and economic foundations of system optimization of operational, technological and construction parameters of rice irrigation systems”

The paper substantiates the necessity to carry out system optimization of operational, technological and construction parameters of water regulation in the operation of rice irrigation systems, lays out methodological approaches and results. This research formulates approaches to the selection of project criteria and conditions of economic and environmental optimization during the construction of complex optimization models in the projects of their reconstruction and operation taking into account climatic management strategies of such objects. The proposed set of measures as a result of system optimization is focused on improving the natural and amelioration state of rice irrigation systems, improving their technological and technical parameters, introducing of water and resource saving regimes of rice irrigation and related rice crop rotations.


Introduction 10 
Problem statement. At the present stage, one of the strategically important and urgent tasks of development of the agrarian sector in Ukraine is the restoration of productivity and resource potential of the rice growing branch, which is impossible without improving the overall technical, technological, economic and environmental efficiency of the existing rice irrigation systems (RIS). The worsening of environmental problems in irrigated agriculture and, especially, in rice growing requires coordination of economic and environmental goals when the most comprehensive ecological and economic results are achieved. This is possible through the introduction of measures aimed at the formation of agricultural systems, which are characterized by ecological stability of the environment and high reproductive capacity based on the use of scientifically-founded and resource-saving technologies of irrigated agriculture.

Analysis of the recent research and publications.
The purpose of the modern amelioration of lands should not only be an increase in agricultural production, but also the preservation and This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International license, which permits re-use, distribution, and reproduction, provided the materials aren't used for commercial purposes and the original work is properly cited. improvement in soil fertility under the conditions of the rational use of natural resources and environmental protection (B. S. Maslov, I. V. Minaev, 1985).
Rice systems have a number of features that distinguish them from classical reclamation objects. These features are caused by complex soil, geological and hydrogeological conditions of the territories and the dominance of flooded rice in the rotation of crops. A peculiar feature of the water regulation technology in the growing of flooded rice is the creation and maintenance of the required flushing water regime as a prerequisite for the use of agricultural land ensured by the appropriate modes of water supply and water disposal used to create a layer of water on rice fields according to the biological characteristics and needs of rice culture, as well as filtration and transpiration losses. The essence of the flushing water regime is the reduction of seasonal accumulation of salts in the upper layers and washing out of them by descending water currents into the lower layers and the drainage network. It is important to ensure the necessary level of flushing of rice fields both during the creation and maintenance of a layer of water on them and during their draining for increasing the productivity of rice growing and improving the ecological and amelioration state within the system and in the surrounding area.
In light of the current economic and environmental requirements to such objects, it is necessary to carry out a transition from the usual practice of considering rice irrigation systems not as purely technical, but as complex natural and technical systems with a corresponding change in the whole methodology, technical and technological strategy of their creation and functioning, as well as consideration of the changing in time and uncertain climatic conditions, because they, along with the reclamation factors, have a decisive influence on the overall natural and amelioration mode of rice irrigation systems and on the resulting environmental and economic benefits (V. G. Gusakov, A. N. Rokochinskyi, 2016).
As practice and accumulated experience show, the solution of such complex problem for the existing rice irrigation systems, which essentially are also ecological and economic objects (M. I. Romaschenko, A. M. Rokochinskyi, 2010), requires the use of appropriate system solutions to optimize their natural and amelioration regime. show that the most significant impact on the natural amelioration regime of the existing rice irrigation systems is affected by the waste drainage network, which in the rice systems determines the intensity and orientation of filtration processes that occur during the prolonged over-wetting of soils under the conditions of irrigation flooding. The natural amelioration network of rice irrigation systems is aimed at the formation of water and salt regimes and, to a significant degree, is a determining factor of productivity of agricultural lands and a guarantor of maintaining a proper environmental and reclamation state of irrigated lands of the rice system.

Goal, objectives and methodology of research.
The goal of the paper is to improve the efficiency of rice irrigation systems by optimizing their natural reclamation regime.
To achieve the stated goal, the following problems were solved:  development of theoretical foundations and modern approaches to system optimization of technical and technological solutions to water regulation of rice irrigation systems on the environmental and economic principles and taking into account different time periods of their reconstruction and operation;  research, analysis and assessment of operational, technological and technical aspects of water regulation in rice irrigation systems in their relationship with the changing natural and agro-amelioration conditions;  development of general principles regarding the implementation of models for optimization of technical and technological solutions of water regulation in rice irrigation systems according to the environmental and economic principles;  improvement of methods of calculation and optimization in solving a complex of forecasting and optimization problems of water regulation in rice irrigation systems in the projects of their construction, reconstruction and operation, implementation and evaluation of their effectiveness. Optimization of the natural reclamation regime of rice irrigation systems, based on the need to create and maintain a flushing water regime on the irrigated saline lands as a main factor of ensuring their favorable land improvement conditions, as well as improvement of the general technical, technological, economic and environmental effectiveness of the system, may be reduced to optimization of the intensity of filtration in surface irrigation of rice culture through appropriate relationship between the supply and drainage of water with appropriate irrigation mode. It is the filtration regime, which is formed on the irrigated rice fields during the maintenance of the layer of water in rice cultivation and in the subsequent period, which determines their general environmental and amelioration condition and evaluates the technological efficiency of the drainage network in different periods of operation of rice irrigation systems.

Research results
According to such indicators as compared to their maximum values and according to the specific conditions of soil reclamation, it is possible to predict the processes on the rice fields and in the system in general, thereby implicitly evaluating the environmental effect of the reclamation activities. Formally, this can be represented in the complex model (1) or in more detail Justification of the optimal natural reclamation and groundwater regimes, the relevant technological and technical parameters of project solutions for rice irrigation systems according to the integrated assessment of indicators of their environmental efficiency can be done quite effectively on the basis of the method proposed by B. Karuka (1989).
According to this approach, the characteristic of environmental reliability of variants of reclamation projects can be represented as vector Н with components z SZ H -the relevant standard, critical or permissible value that corresponds to j Ẑ .
This approach to the assessment of ecological safety of the project is different from the classical theory of reliability, which features probability values, but it is quite simple and universal in nature, since depending on the formulation of the problem it makes it possible to use different, mostly expert methods of assessment and different sets of diverse indicators.
Therefore, according to the studied methodology, environmentally optimal general natural reclamation and ground water regimes are provided subject to the restriction that the coefficient of ecological safety of the reclamation project is within the range 0 , The proposed scheme of evaluation of environmental reliability of reclamation projects is quite versatile, because, as a constituent element of reliability, it can have any set of both quantitative and qualitative factors characterizing the state of environmental reclamation of a certain territory. Optimization of optimal parameters for drainage was carried out considering the optimal parameters of the speed of vertical filtration on rice fields, which reflect the operational and technological aspects of water regulation in rice irrigation systems and the optimal indicator of the share of rice in crop rotation -50 ... 60%.
Calculation of economic indicators was carried out in prices and rates of 2015.
Generalized results of this assessment are summarized in Tables 1, 2. The expediency of the proposed project solutions, which are aimed at improving the level of drainage of rice fields as the main condition for the creation of the flushing water regime, which is related, in general, to the effective functioning of rice irrigation systems, is confirmed by the assessment of their environmental safety. Thus, the coefficient of environmental reliability in the creation and maintenance of the necessary level of flushing on rice fields during the period of vegetation 6 ... 8 mm/day is 0.80 ... 0.87, which meets the necessary requirements.

Conclusion and recommendations for further research
System optimization of the natural reclamation regime of rice irrigation systems on ecological and economic principles makes it possible to improve the general efficiency in the functioning of rice irrigation systems taking into account economic and environmental requirements through the coordination of parameters, the level of structural and environmental reliability and the cost of these solutions with the level of the generated effect during their realization.
Undoubtedly, the obtained general recommendations should be clarified for the conditions of each real object, which would be considered according to the relevant technical, economic and environmental indicators.