This paper gives the results of the investigation of the operation of a pumping unit equipped with a frequency converter. As a rule, it is widely assumed that when changing the speed up to 50 %, the pump efficiency almost does not change, and the possibility of decrease of its efficiency is not taken into consideration when calculating the economic efficiency of the operation of the pumping unit equipped with a frequency converter. However, failure to take account the efficiency decrease may cause inaccurate assessment of the economic efficiency of the use of the frequency converter and, consequently, improper selection of the method of control of the operation of the pumping units. This is particularly important for irrigation pumping plants the operation of which is characterized by large volume of the pumpable volume and less severe requirements for provision of the water pressure required for the consumer. The purpose of this paper is to carry out experiments on a test-bed equipped with a pumping unit, parameter measuring instrument, and a frequency converter, and detection of the pattern of efficiency variation with speed. The paper presents the results of the carried out experiments, the obtained characteristic curves of the variation of different types of the efficiency at variation of the pump shaft speed, as well as their analysis.

In Uzbekistan, as well as in many other countries of the world, pumping units operate in parallel into a common pressure pipeline at some pumping stations of the irrigation system. This was done mainly to save on the capital costs of the pipeline. Analysis and hydraulic calculation of the existing large irrigation pumping stations with pumping units operating in parallel showed that at some of them the conditions of parallel operation of pumping units were impaired. As a result, a negative hydraulic process arises, in the form of self-induced vibrations of the water flow in the pipeline, which leads to various damage and deformation of the pressure pipeline and pipeline supports. The calculations showed that with different modes of pumping units operating together, the power consumption at the Amu-Bukhara-1 and Namangan pumping stations, accounting for one unit increases by 0.72 ... 6.53%, and at the Amu-Bukhara-2 and Amu-Zang-2 pumping stations, this index, on the contrary, decreases by 0.32 ... 1.67%. Therefore, a properly selected operating mode of parallel-connected pumping units will lead to a decrease in operating costs, i.e. decrease in the prime cost of raised water.

Currently, 78% of all irrigated land in Uzbekistan is provided with water by pumping stations and installations. The water sources of most pumping stations are rivers and irrigation channels that transport a large amount of bottom and suspended sediments. Due to the lack of consideration of bottom sediments moving in the form of ridges, when installing the pumping units suction pipeline, during their operation, these bottom pumps flow from the water intake source in the interior of the units. As a result, intensive waterjet wear of the flow part and the impeller of the pumps occurs. This leads to an intensive reduction in the main parameters of the pumps, as well as reduces their repair period. Currently, this is one of the major problems of pumping stations that take water from the Zarafshan river, as well as those operating on the Karshi, Amu-Bukhara, Amu-Zang and Jizzakh main channels. Laboratory studies were carried out on the experimental installation to determine the height of ridges with different granulometric composition of bottom sediments. As a result, a formula was obtained for determining the height of the ridge, taking into account the heterogeneity of ridge forms. Based on the obtained formula, a method for setting the height of the pumping unit suction pipe inlet relative to the riverbed bottom is recommended. The application of the proposed method does not allow bottom sediments to enter the inner part of the pumps, as a result of which their intensive abrasive wear decreases, the inter-repair period increases, while maintaining its main parameters for a long time.

Among the Central Asian republics, Uzbekistan is unique in that approximately 80% of its territory lies within a plain, characterized by an arid geographic zone and dry climate. Agricultural production in these regions is possible only through artificial irrigation. In recent years, global climate change and challenges related to transboundary water use have led to a reduction in water availability. The average annual water allocation to Uzbekistan is estimated at 51–53 billion m³, of which 90–91% is consumed by the agricultural sector. Due to the uneven distribution of water resources and the complex topography of irrigated lands, water supply is supported by numerous pumping stations operated by the state, water users associations, farms, and clusters. Additionally, well-based pumping systems are employed to maintain groundwater levels and ensure irrigation. On average, these facilities consume around 8.0 billion kWh of electricity annually. The agricultural sector faces several critical challenges, including crop water deficits caused by water shortages, slow adoption of water-saving technologies, and limited implementation of drip irrigation on household plots, dachas, and greenhouses that play a key role in food supply. Moreover, the delivery of water to fertile lands situated far from main power lines and water sources remains problematic. This article aims to explore the integration of solar energy solutions to support drip irrigation in both large-scale agricultural lands (ω = 1.0–100.0 ha and above) and small-scale areas such as homestead plots, dachas, and greenhouses (ω = 0.01–1.0 ha), as well as their application in small- to medium-sized pumping stations. Based on the research and experimental design work carried out, three mobile photovoltaic units—MPPU-8-500-4000, MPPU-2-550-1100, and MPPU-4-500-2000—were developed and implemented to address water and energy shortages in agriculture.

This study addresses the challenges of online monitoring of water metering in irrigation systems in Central Asia, specifically in the Republic of Uzbekistan. The importance of this study lies in improving water management and energy efficiency in a region where water resources are critical for agriculture. Uzbekistan, with 2.3 mln ha of irrigated land – 53% of the total agricultural area – is dependent on 1,693 pumping stations that annually pump over 50 mln m3 of water. These stations consume between 8 to 8.2 bln kWh of electricity each year, representing about 11% of the nation’s total electricity generation. Currently, energy consumption at these irrigation pumping stations is monitored manually, and most stations lack accurate water metering devices, which hinders the ability to account for sediment in the water and prevents real- time energy efficiency monitoring. Additionally, 1–3% of the electricity used by these stations is consumed by auxiliary systems, contributing to increased overall energy consumption. The primary goal of this study is to scientifically substantiate, develop, and implement a system for monitoring the energy efficiency of irrigation pumping stations in real time. This includes providing real-time data on electricity consumption and supply, as well as integrating photovoltaic systems to meet the internal energy needs of the pumping stations. The implementation of such a monitoring system is expected to optimise energy use, reduce operational costs, and enhance sustainable water management practices in Uzbekistan.

Uzbekistan is one of few countries in the world where more than 50% of the irrigated lands are provided with water by pumping stations. The main water sources are the transboundary rivers, the Amu Darya, and the Syr Darya, which transport a large amount of bedload and suspended sediments. In these water sources, the average annual turbidity is up to 5-7 kg/m3, and the average monthly turbidity reaches 10-12 kg/m3. The content of abrasive particles with the Mohs hardness of 5 and more reaches 50-60% of the total amount of suspension. When these sediments pass through the pumping units, their hydro-abrasive wear is observed; this leads to a change in the main parameters of the pumps. Bedload sediments with the size of more than 1 mm cause the most intensive pumps hydro-abrasive wear. Therefore, in our research, much attention was paid to developing methods to prevent the ingress of bedload sediments into the flow part of pumping units. For this purpose, based on laboratory tests, taking into account the heterogeneity of bottom sediments, the dependence for determining the ridge forms' height was revealed. On the basis of this dependence was developed methods for determining the height of the threshold damless intakes and the height of the inlet of the suction pipe pumping unit relative to the riverbed bottom. The developed methods reduce abrasive wear of pumping units and increase their repair period.