Mechanical water lifting is used both for irrigating the entire given area as a whole, and for irrigating individual, elevated areas within the gravity irrigation area (moreover, water rises from a river or from irrigation canals). This combination of gravity irrigation and irrigation with mechanical lifting of water in many cases is quite reasonable.
Irrigation, in which water from a source is supplied to the system using water-lifting mechanisms, is called machine (mechanical water lifting). The head structure is a water-lifting installation that pumps water to the irrigated area through a pressure pipeline. Water from the source is raised to the highest marks of the entire irrigated area or its individual zones, and from there it is distributed by gravity channels or pressure pipelines.
Machine water lifting is used both for irrigation of the entire area, and for individual elevated areas with gravity irrigation.
In sprinkling irrigation, pumping stations not only supply the specified flow rates, but also create the necessary water pressure.
The disadvantage of irrigation with a machine lift is the need for complex pumping and power equipment, electricity, and high operating costs. All this increases the cost of water supplied to the fields.
However, pumped irrigation, despite the high operating costs and high cost, is often economically feasible and cost-effective.
Routes of main irrigation canals and pumping stations with machine water lifting can be located according to four schemes.
First scheme. The entire irrigated area is located in one zone, irrigated by one main main canal that receives water from a pumping station through a pressure pipeline.
Second scheme. The same irrigated area as in the first scheme, but water is supplied not through one, but through several channels. The area is divided into several zones of water rise and each is served by its main main canal, which is routed along the highest marks of the corresponding zone, and receives water through separate pressure pipelines, but from a common coastal pumping station.
Third scheme. The irrigated area is also divided into zones, but each zonal canal is fed by independent pumping stations that sequentially supply water from the underlying to the overlying zones.
The first coastal pumping station NS-1 delivers to the height of the first zone the water flow required for irrigation of all three zones. Station NS-2 delivers to the height of the second zone the water flow required for irrigation of the second and third zones, station NS-3 - to the highest elevations of the third zone.
Fourth scheme. The irrigated area is divided into zones, and each has its own water supply, independent of other zones; Each zone is supplied with water by an independent coastal pumping station. This scheme is used in the operation of mobile pumping stations.
The correct solution of the problem of mechanical irrigation is associated with the establishment of the number of swing zones. At the same time, the division of the irrigation area into separate zones is of great importance. The power of pumping stations decreases with the increase in swing zones, and vice versa. Therefore, when designing, such a combination of the location of channels and pumping stations is found that gives the lowest construction and operating costs for pumping stations and main channels.
When designing pumping stations, the expediency of irrigating a given area with one large water-lifting installation or several installations of smaller capacity is established.
For machine water supply, stationary and mobile pumping stations and installations are used. Stationary pumping stations are more widely used than mobile ones. Stationary stations include a complex of hydraulic structures: water intake, supply channel, intake basin, station building, pressure pipelines, pressure intake basin.