Water-saving technologies and irrigation facilities

Agricultural crops and animal husbandry are key branches of the Kazakhstani economy. These sectors of agriculture, which are priorities for development of the republic's economy, have good potential for expansion. Kazakhstan currently faces the problem of serious impairment of natural resources and its environment, in all major economic sectors. Almost one-third of all agricultural land has been or is about to be degraded, and more than 10 million hectares of potentially arable land have been abandoned. The economic losses suffered as a result of low land capacity in the country are estimated to have cost the economy between 1.5 and 4 billion USD annually, and may increase by 2030, resulting in severe social consequences for the agrarian sector. Between 30 and 45% of the population are employed in the agricultural sector in the North-Kazakhstani, Almaty and South Kazakhstani regions (Concept of Kazakhstan transition to ‘green economy’ 2013).

The Kazakhstan economy as a whole and the agriculture sector in particular will be developing under conditions of acute water resources deficiency. Water scarcity is already common in the Aral, Balkhash, Ural, Shu, Talas, Assy, Saryssu, Turgay, and Nury inland basins. For instance, the annual volume of surface runoff available is expected (in a pessimistic scenario) to fall by 15–18 km³ (by 2020), of which 10–12 km³ will arise because of increasing water use outside Kazakhstan and 5–6 m³ because of the predicted effects of climate change.

The hydrologic data indicate that water discharge will be 81 km³/a by 2020 and 76.3 km³/a by 2030, at a state consumption rate of 88–90 km³/a (III – VI National Message 2013).

To achieve water saving in agriculture (6.5–7 billion m³ by 2030) initiatives are needed in three directions:

• - the introduction of up-to-date irrigation techniques and water-efficient technologies, which will enable the saving of 1.5 billion m³ by 2030;

• - the cultivation of crops requiring less water (enabling the saving of 3.5 billion m³ by 2030);

• - reduction of water loss during transportation to irrigated fields (enabling the saving of 1.8 billion m³ by 2030). (Concept of Kazakhstan transition to ‘green economy’ 2013).

Water saving under current conditions involves the complex reconstruction and modernization of both irrigation and collector networks, as well as hydro-technical facilities, and the introduction of water-saving technologies, and contemporary water control and distribution equipment, enabling rational use of available water resources

The wide use of contemporary water-saving technologies in various branches of the economy, improvement of interstate water relations, and inter-basin and trans-border river flow transfer, can become a basis for water security in Kazakhstan.

An important means of solving agricultural water supply problems in many countries is increasing efficiency of water utilization for irrigation. On average, irrigation efficiency is about 38% throughout the world and, according to scientific estimates, will reach 42% by 2030.

Up-to-date water resource utilization technologies involve a set of strategic recommendations for the improvement of available water resources toward their increase (Kireicheva 2013):

• - development of facilities designed to accumulate and store rain water under extreme climatic conditions, such as floods, deglaciation, high intensity showers, etc., by replenishing groundwater. This approach is wide-spread in India, Holland, Canada, South Africa, etc.;

• - use of sewage for irrigation. Ten percent of irrigated lands in developing countries use this resource, the restrictions on such use relate to health risks, and the high cost of treatment and preparation;

• - establishment of new-generation irrigation systems with low-capacity irrigation (drip, mist and combined), water-circulation systems with units for sewage treatment and conditioning. This enables savings of up to 20% of natural fresh water.

Modern irrigation technologies are operated under extensive restrictions, as they require complex and expensive technical facilities.

A number of points should be noted with respect to irrigation technologies.

Standard sprinkling provides regular accumulation of water in the topsoil, moisturizing both soil and plants. Frequent watering using small volumes affects the micro-climate of the topsoil during irrigation, improves the plants’ water regime and increases crop yields (Liu & Kang 2006; Hassunizadeh 2010; Liu et al. 2013; Mutiro & Lautze 2013).

Impulse sprinkling provides a non-stop water supply to the plants and soil, and enables establishment of the required micro-climate in the plants’ environment to activate physiological processes under conditions of high air temperatures and low moisture content. Compared to standard sprinkling, this technique increases crop yield by 120–180%, and reduces discharge by 30–40% (Lebedev 1998; Albaji et al. 2010; Shuravilin & Khrabrov 2011). This technology is recommended for use in foothill areas, where other irrigation techniques are seldom applicable. Such systems enable the introduction of soluble mineral fertilizers and chemical protective agents during irrigation (Zeinalova 2013).

Drip irrigation supplies water constantly to plant roots through sprinklers, enabling the introduction of soluble fertilizers and providing significant water saving and increasing plant yield. However, it cannot be used in salinized soils, among other restrictions (Hassunizadeh 2010).

Mist (aerosol) irrigation provides regular moistening of leaves and stems with water volumes, while reducing air temperatures and increasing photosynthesis. It is designed for irrigating crops cultivated in both open soil, and plastic and winter greenhouses. It can be used effectively for chemical protection, foliar fertilization and finely dispersed moistening of fruit crops, in intensive highland and piedmont gardening (Figure 1).

Mist irrigation of a pear garden in the Kabardino-Balkar republic contributed improvements in micro-climate, and an increase in 1-year whips and the harvest. The harvest increase made up 5.63 tonnes/hectare compared to the non-irrigated land plot (Khazhmetov et al. 2006).

The technology is used in combination with other irrigation techniques.

Subsurface irrigation provides a continuous water supply for plants and capillary moistening of the topsoil that maintains a fixed moistening depth, as well as reducing surface evaporation significantly.

Use of this technique on cotton in West Texas (USA) improved water use efficiency when groundwater reserves were low (Enciso-Medina et al. 2002). Research into subsurface irrigation of maize in north-west Kansas (USA) confirmed that careful management of such systems reduces water consumption by almost 25% while soil moisture remains stable (Lamm et al. 1995). The efficiency of use of subsurface irrigation on pastures has also been proved, although its high economic cost is also noted (Finger et al. 2015).

Impulse sprinkling is consistent with the trend of sprinkler improvement by reducing precipitation intensity and increasing the use of dual-sprinklers, in particular.

It facilitates the supply of water to plants in a regime close to their natural water consumption cycle during the entire period of growth. At the same time, optimal soil moisture levels are achieved by reducing the air temperature and increasing its moisture content during vegetative periods with high temperatures.

Impulse sprinkling is carried out using sets that can cover 1 hectare.

The main units in a set comprise (Figure 2): pump 1 with remote control 2, pressure pulse generator 4, distribution pipes 6 and emitters 7; pulse sprinklers 9 and pulse sprinkler control 10, with feedback 8. Water flow in the distribution pipes and pulse sprinkler activation time are controlled by valves 3 and 5.

An impulse sprinkler (Figure 3) incorporates an accumulation tank in the form of hydro-accumulator 1, with limiting sphere 2 and membrane 3, shut-off device 4, and sprinkler unit 5.

The system is triggered to operate when water is ‘requested’ by a soil moisture signal or in accordance with the pumping program, and the pump is activated. The required volume of water is stored in the hydro-accumulator tanks of the impulse sprinklers. When they are full or on a time relay signal, an automatic command is given by the remote control to the impulse generator. The valves are activated and the water is moved by compressed air, etc., to the sprinklers. The sprinkler valves close on a pressure increase signal in the pipeline. The frequency of the working cycles depends on the time taken to fill the hydro-accumulator and is controlled by the valves. The average intensity of impulse sprinkler rain precipitation is less than 0.02 mm/min (Shtepa et al. 1990). Impulse sprinkling enables daily watering to be done at night and/or all-day irrigation. Typical specifications for an impulse sprinkling system are provided in Table 1.

The use of impulse sprinklers is preferable in hilly areas where use of other techniques is difficult. This type of system enables the addition of soluble mineral fertilizers and plant protection agents during watering.

This technology (Zharkov et al. 2000) is designed for the irrigation of crops cultivated in the open, or under plastic or in winter greenhouses.

It is installed as modular systems with carousel-type sprinklers or fine spray nozzles. A typical system consists of a water source 1, pump 2, pipeline networks 3, 7 and 9, water meter 4, adaptors 7 for connecting pipes of different diameters, T-joints 8, and risers 10 with sprinklers 11, valve 5. Plugs 12 are equipped for pipe washing. Mist irrigation systems enable irrigation in areas where the slopes are up to 12%, at wind speeds up to 5 m/s.

Figure 4 provides the scheme of a module with carousel-type sprinklers (6 pieces) (Figure 4(a)) and a module with fine spray nozzles (12 pieces) (Figure 4(b)).

The specifications for typical, modular, mist irrigation systems with carousel-type and fine spray nozzles are given in Table 2.

Subsurface irrigation – was developed for the cultivation of trees, small fruit and similar crops. Such systems use the condensed scheme of sapling placement in facilities to provide optimal water and nutrition regimes, and facilitate the formation of high-quality root systems to increase plant yield per unit area.

A typical subsurface irrigation system (Figure 5(a)) consists of a water source 1, pump 2, feed 3, distribution 4 and irrigation 5 pipelines, and plant irrigation devices 6. Pipeline length corresponds to the planting scheme.

The irrigation device 6 consists of a container 7, irrigation pipe 8, and inlet 9 and outlet 10. The container holds soil 11 and a plant 12, and the pipe outlet can be closed with a plug, if required, 13.

Subsurface irrigation is relatively simple. Water is pumped from the source through the irrigation pipelines to the subsurface pipes. The plant watering scheme is designed to obtain optimum water and nutrition conditions in the soil. When the plants’ root systems are fully formed, the containers and pipes are put into the open soil and connected to the irrigation and distribution networks.

Subsurface irrigation increases plant yield per unit area, despite the close proximity of the containers in the nursery, and enhances crop quality. At the same time, the amount of good quality potting soil required is reduced, because of the use of containers, labor costs are reduced and working conditions are improved.

The use of up-to-date water-saving technologies in irrigated agriculture enables increase in the efficient use of water and improved amelioration regimes for irrigated land. The technologies described briefly above – impulse sprinkling, mist sprinkling and subsurface watering – are intended to save water in irrigation and enable the establishment of optimal conditions for plant development. This should lead, almost always, to increased efficiency in the use of irrigation water as well as increases in crop yields per unit area.