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Low-gradient or horizontal plane irrigation

Dead furrow irrigation by crosscut circuit

Spur (or dead) furrows with cofferdams at the end section lines are used on gentle-slope (up to 0.003) land plots, so that the difference between the elevations of the head and end cross-sections of furrows should not exceed 1/3 of their depth.

The crosswise scheme of irrigation on horizontal plane. This scheme is used in gentle-slope areas with poor meliorative conditions. In the main, it differs from the longitudinal scheme only in that the direction of irrigation (of furrows) is perpendicular to the routes of delivery ditches. Concentration of water distribution on a single route makes easier automation and observation over the irrigation process, as well as enables slightly simplifying the structure and reducing the costs.

This scheme is better to be used when slope gradient of the site in the direction of delivery ditches is more than transverse grade along which furrows are cut, because the length lf is always more than the width of the land plot.

Source: Laktaev, N.T. Cotton irrigation, 1978

Counter irrigation

If a field has horizontal relief, i.e. it is levelled, counter irrigation simultaneously from the both ends of furrows (from the head and end of the furrow or border strip) can be used. This allows somewhat halving the furrow length.

Efficiency of counter irrigation is determined experimentally. This irrigation method will allow increasing specific water consumption per unit of product and reducing seasonal accumulation of salts in the soil. This irrigation method is recommended to be applied by farmers.

Source: water-salt.ru

A levelled horizontal plot can be irrigated by the counter irrigation method. Water application is carried out by simultaneous water supply from the both sides from two water outlets. Counter irrigation by furrows is carried out. Water streams join approximately in the middle of the field, and horizontal water surface is formed. A possible area of the plot will double. This is a suggestion by the Turkmenistan Research Institute of Hydraulic Engineering and Land Reclamation (TurkmenNIIGiM) and Uzbekistan State Institute for Designing of Water Development and Land Reclamation Projects (Uzgiprovodkhoz).

Under the procedure of improvement of this irrigation method, Uzbekistan State Institute for Designing of Water Development and Land Reclamation Projects has developed the project of automated irrigation for group of irrigated plots. The project provides for the installation of special outlets-automatic machines of tailrace channels that ensure stable water discharge by a specified water horizon. The group delivery ditch serving several plots is equipped with automatic machines of headrace channels.

A single-side irrigation ditch (hollow) supplies water to all furrows over the whole width of field in accordance with the above-mentioned irrigation schemes; at that, a dropdown curve inevitably occurs in it, because variable-discharge hydraulic regime takes place. No matter how little is the difference between the elevations of this flow at its beginning and end, it is comparable with the depth of furrow filling, which causes some non-uniformity in watering of the field across its width (irrigation front). In addition, in case of water supply from two water outlets by these schemes, we can observe undesirable soil erosion at field corners at the beginning of the hollows just behind the outlets. These problems will not take place, if water is supplied not from two but from four corners. Counter water supply to the hollow will provide horizontal water surface along the length of the hollow, and water discharge lowered twofold will prevent soil erosion.

At counter irrigation, it is recommended to have dead furrows in the middle of the land plot (field). When running by furrows, water reaches the half of the plot not simultaneously: by the furrows compacted with tractor wheels it reaches the half somewhat more quickly, while with non-compacted ones, its lags behind. By the dead furrow, water can spread to the neighboring dry furrows, moving in the opposite direction. This method allows making even watering of the field.

The land plot can be as wide or the hollow can be as long as it is enough for uniform water distribution among the furrows on irrigation front. The higher the discharge at the hollow head section and traveling discharge of distribution, i.e. discharges to the furrow, the less the irrigation front. According to experiments carried out by the Turkmenistan Research Institute of Hydraulic Engineering and Land Reclamation, the width of the irrigated plot should not exceed 125, 150, 175, 200 and 250 m for soils of A, B, C, D and E [in Russian] , , , ) (soil permeability indices) types, respectively.

Source: Laktaev, N.T. Furrow irrigation on horizontally leveled land plots (theory, recommendations).
Tashkent, SANIIRI, 1987. [in Russian]

Check irrigation by furrows

In 1964, S.M. Krivovyaz suggested carrying out irrigation on very gentle slope saline-prone lands by the following method: during the growing season, carry out check irrigation on horizontally levelled surface by deep furrows (by the crosswise scheme); during the non-growing season, by flooding with water supply to the field from open network or with low-pressure irrigation reinforced-concrete pipelines 600-800 mm in diameter. In 1967, they started preparatory works for testing that suggestion in the Golodnaya Steppe.

Wide field use of such a combination of irrigation methods, but from open irrigation network and by the longitudinal scheme together with other reclamation works was implemented for the first time in the kolkhoz named after Kalinin of the Ilyailinskiy district of the Turkmen SSR in 1969. Water was delivered to the field from permanent field drain irrigation network in earth bed. Irrigated fields of 200x200 m (each one is of 4 ha) are staggered along the main slope. The planting system represents narrow (0.6 m) spaces between rows. A permanent field irrigation ditch with a water discharge of 150-160 l/s with reinforced double-sided outlets is installed at the head of each pair of irrigated fields. There are roads to embankments to the left and right of the field irrigation ditch. The surface inside every irrigated field is levelled thoroughly with gradient of no more than 0.0001.

Preparation and treatment of soil including all types of mechanized works during the growing season are carried out in two adjacent inclined fields with furrow length of 400 m. Cotton is irrigated at every irrigated field separately. For this purpose, a bund is cut with bund former (checker/landshaper) at the head of each field across the irrigation furrows opposite the water outlet of the field irrigation ditch prior to the first water application. At that, water-distributing and water-regulating furrows are formed. After opening of the water outlet of the field irrigation ditch, water runs through the water-distributing furrow initially by small stream (15-16 l/s), gradually covering the entire irrigation front. As soon as the water in the water-distributing furrows rises above the bottom of the irrigation furrows, its discharge is to be raised up to 70-80 l/s, and water application goes on. At the end of the irrigation furrows, water stream is blocked by a bund with water-regulating furrow that enables regulating the uniformity of watering of the field.

Each field irrigation ditch at water discharge of 150-160 l/s simultaneously water two irrigated fields with an area of 8 ha. Irrigation of one field takes 1-1.5 days. One irrigator carries out simultaneous watering on an area of 4 ha. The irrigator waters 2 ha per shift. After watering, prior to cultivation, the bund with water-regulating and distributing furrows is levelled and a cultivation area of 8 ha is formed. An irrigated field 4 ha in area is a large irrigated check plot for winter-spring leaching or charging irrigation. The irrigators job during both the growing season and at period of leaching or charging irrigation consists in opening and closing of the slide valves of the permanent water outlets.

Source: Bezuevskiy, I.L. Improvement of cotton irrigation means techniques.
Moscow, Publishing House Kolos, 1982, p. 48, with pictures
(breakthrough technology for all kolkhozes and sovkhozes) [in Russian]

Permanent irrigation site irrigation

During the development of saline-prone lands, researches of irrigation of levelled and gentle-slope land plots by permanent irrigation plots (V.A. Dukhovny) started in 1971. Watering was carried out by crosswise scheme, i.e. furrows are cut perpendicularly to the irrigation network. The irrigation network is made from precast reinforced concrete flumes or closed pipelines; dense network of closed horizontal drainage is laid on the plots. The width of the spaces between rows is 0.9 m. The width of the irrigated plot is 100-200 m, and its length is 300-400 m.

The enclosing bunds formed after passing of a bund former (checker/landshaper) serve as the boundaries of the irrigated plot at check flooding irrigation by furrows. When watering by breaking down into permanent irrigated plots, small earth dams built with mechanisms (scrapers) serve as the boundaries of the irrigated plot. The researches were carried out in new sovkhozes of the Golodnaya Steppe.

Permanent irrigation sites are represented by separate irrigated fields of up to 7 ha (200x350 m). The fields have only one slope gradient (0.001) at the direction of watering. A small bounding dam is built around the periphery of the irrigated field. At that, along the longitudinal boundary between the fields, this dam is arranged on over-drain border strip. The dam is 0.3-0.5 m high and 6 m wide. The irrigation network is made from reinforced concrete flumes, elevation of water in which have are higher than the elevation of the field by 0.5-1 m. Irrigation scheme is of crosswise pattern. The furrows on the site are cut along the main slope. Prior to water application, a border strip or single-side furrows are made with a bund former (checker/landshaper) or grader at the head and end of the furrows; this strip or one-sided furrows are used for water distribution over the site. Water is supplied to the strip just like it is supplied at check flooding irrigation by furrows, viz. with a flexible T-pipe. Water is diverted from the flume network by means of usual water outlets installed at every 50-60 m.

On-the-farm researches of the method of irrigation by permanent irrigated land plots made it obvious that this method is a sort of replication of flooding checks by furrows. The only difference between them consists in the boundaries of the irrigated plot: in the first case, these are represented by dams built with machines; in the second case, by temporary bunds with strips along them, formed after the pass of a bund former (checker/landshaper).

The suggested size of the irrigation plot is 7 ha, 200 m wide and with furrows 350 m long). To provide evenness of watering of the site, its slope gradient along the length should not exceed 0.0005.

The irrigation equipment used can easily be transferred by human force; if it is replaced by permanent outlets, the labor of the irrigator will become still easier.

Source: Bezuevskiy, I.L. Improvement of cotton irrigation means techniques.
Moscow, Publishing House Kolos, 1982, p. 48, with pictures
(breakthrough technology for all kolkhozes and sovkhozes) [in Russian]

Selected bibliography