**1. Introduction**

Over the long period of operation of the country's largest Nizhnekubansky water management complex, the operational characteristics of a significant part of its hydraulic structures (HS) have changed significantly in comparison with the design ones, and some of them have lost their management functions. The need to consider the current technical HS condition is due to the fact that they are the main structural and functional elements of an integral system of the reclamation and water management complex designed to provide water resources to 215 thousand hectares of irrigated rice lands. The reclamation water management complex of the Lower Kuban includes, in addition to the Krasnodarsky one, the Kryukovskoye, Varnavinskoye, and Shapsugskoye reservoirs, the Fedorovsky retaining and Tikhovsky water distribution

waterworks, more than 100 functioning pumping stations and over 550 HS, more than 3 thousand km of irrigation and discharge channels, up to 156 thousand hectares of natural fishery reservoirs [1].

Irrigation systems and hydraulic structures of the agricultural complex of the Lower Kuban are shown in **Figure 1**.

The Krasnodarskoye reservoir is the main source of irrigation and performs a number of other important functions: population protection from floods, high water control with discharges up to 1200 m<sup>3</sup> /s. The main function of the reservoir is to provide water for 12 rice irrigation systems, the needs of fisheries, and navigation conditions for shipping. As a result of siltation, the capacity of the Krasnodarskoye reservoir decreased, and the value of the temporary operation level dropped below the design by 90 cm. Failures in the technical condition are also noted at other reservoirs, waterworks and HS, including pumping stations, and water supply and drainage channels, which negatively affect the water supply of rice systems. Reduction of the total volume of flood water in reservoirs, which previously, according to design parameters, made it possible to avoid a shortage of irrigation water at the most stressful time in terms of agrometeorological conditions. The low efficiency of channels, pumping stations, and other HS as a result of their unsatisfactory technical condition are also the cause of water scarcity [2].

In recent years, the area of rice crops in the Krasnodar Territory has grown to 130 thousand hectares. The average yield in the region is about 7 t/ha, with a total water intake for rice irrigation of more than 2.5 km<sup>3</sup> [3]. An increase in air temperature and a decrease in precipitation in the rice-growing area during its growing season, associated with climate change in the Kuban, lead to an increase in irrevocable water consumption. High irrigation rates of rice, reaching an average of 20 thousand m<sup>3</sup> /ha or more, on saline soils, additionally cause a shortage of irrigation water.

The current state of the water management complex, characterized by transformation and degradation of operational characteristics, is mainly due to the processes of wear of engineering systems and their destruction under the influence of natural

**Figure 1.** *Irrigation systems and hydraulic structures of the Lower Kuban.*

#### *Theoretical Approaches to Water Use Optimization for Rice Irrigation Systems in the Lower… DOI: http://dx.doi.org/10.5772/intechopen.105521*

and industrial factors, it is impossible to return to the previous design parameters. In the current situation, one of the productive ways to reduce risks and damages from systematically observed water scarcity is not only an obvious direct opposition to degradation factors, repair and replacement of HS, reduction of rice acreage, new rice varieties resistant to water scarcity, and low-volume irrigation methods, but also a flexible management system for resource distribution and use. Adaptive properties of the rice agro complex, as an integral result of the agricultural and agro-industrial (agricultural producers) complexes' water users operational and production activities can be achieved with the management system organically combining strategic and tactical goals. First of all, these are combined into single regional and local levels of monitoring the elements state of the rice agro complex and the distribution of water resources, static long-term, and real-time dynamic operation modes of water management and hydro-reclamation systems elements.


Calculations done periodically using this tool allow you to quickly respond to the supply of agricultural producers with water, adjusting the irrigation regime during the vegetation period, as well as through local redistribution and adjustment of water use. The analysis of the results obtained using the above approach at the end of the irrigation season following the harvest results will make it possible to form a water use schedule for the next year adapted to the expected environmental conditions, making the management system trainable.

The need for such an analysis arose due to the fact that, on the one hand, water demands are formed by agricultural producers, and their adjustment and implementation are carried out by the Federal State Budgetary Institution "Kubanmeliovodkhoz" management department, while the indicators of the

operation service are rice yields and gross output from the entire territory of the reclamation and water management complex, forcing to control water consumption. On the other hand, water demands by agricultural producers are based on the principle of "from what has been achieved," i.e., the more, the easier it is to carry out the technological process of cultivation, which, on the contrary, creates conditions for increasing the risk of developing water scarcity.
