A.N.Morozov.

ZONING THE IRRIGATED LANDS OF UZBEKISTAN ACCORDING TO SPRINKLING USE.
(The article has been published in the transactions of the Central Asian Research Institute for Irrigation SANIIRI "Development of the water economy and reclamation of the Republic of Uzbekistan during the transition to the market economy", Tashkent, 2006).

Introduction
Under the conditions of the increasing shortage of irrigation water, the matter of changing for water-saving crop irrigation technologies is becoming more and more urgent. A few ends can be gained at that, such as: saving of water, increasing productivity of the irrigated lands, improvement of the reclamation and ecological situation. Out of the well-known irrigation methods (flooding, overlapping strips and furrows, sprinkling, drip irrigation), only sprinkling is considered herein. The purpose of zoning is making easy the practical selection of one or another type (construction) of sprinkling machine for irrigation of crops at specific environmental and economical situation, which could ensure the following: saving of water resources at the expenses of the reduction of the unproductive water losses to depth and surface outlets; lowering specific water consumption per unit of the production being produced owing to possible strict keeping irrigation regime and increasing irrigation evenness and, as a result, rising crop productivity; improvement of reclamation and ecologic state on the adjacent territories.Zoning factors.

Water permeability of the soils. Water sprinkler must be chosen in such a way so that to bar the emergence of surface flow, therefore the main factor that conditions the expedience of using sprinkling for crop irrigation is soil permeability which determines permissible rain intensity. Also the extent of water saving with using sprinkling irrigation depends upon soil permeability, since water losses to depth and surface outlet (under interchangeable ways) directly depend on this factor. Water permeability degree is unambiguously defined only by the filtration factor under total saturation; however, this value is not constant for the soils with high rate of clay particles and organic matters and changes even during the carrying out of an experiment. As to the process of unsteady absorption, which essentially is irrigation, it depends on a number of the following parameters:
" state of soil surface (in natural state, loosened, rolled with agricultural machinery etc.);
" pre-irrigation moisture and moisture profile in soil depth;
" way and rate of water supply to the soil surface.
By convention, to the accuracy sufficient for practice, the classification offered in work [1] can be adopted, which is given in table 1.

Table 1. Adaptability of various sprinkling types for the soils of different permeability

Characteristic of permeability Absorption rate	(K1), mm/hour	Types of sprinkling machinery according to sprinkling feature
		fine-dispersed		of middle fineness			of large fineness
		Rain intensity, mm/hour
		0.4	0.8	2.0	4.0	6.0	10.0	15.0	20.0
Strong	15	*	*	*	*	*	+	+	*
Higher	8	*	*	*	*	+	+	*	*
Medium	4	*	*	*	+	*	*	*	*
Lower	2	*	*	+	*	*	-	-	-
Weak	1.5	*	+	+	*	-	-	-	-

Here and in other tables some restrictions are applied, marked with the signs as follows:
" types which practically cannot be employed (-);
" types which can be employed, but for economical reasons are hardly applicable (*);
" types which are completely proper for use (+) .

Surface geometry. For sprinkling irrigation, the field's topography (microrelief) so important at surface irrigation method is of no practical importance. The governing factor here becomes macrorelief which determines the possibility of the machine movement over the field [2]. In table 2, preferable machine types are suggested usable at one or another relief.

Table 2. Usability of sprinkling machines subject to the mobility degree at different relief types.

Relief	Type of sprinkling machines
	Stationary	Portable	Movable
Level	*	*	+
Slightly hilly	*	*	*
Hilly	*	+	-
Foothill	+	+	-

Note: At present, there are machines operating afoot and on highly hilly relief, however they require highly trained servicing.
Hydrogeological conditions. Depending on natural and artificial, created by irrigation and/or drainage, hydrogeological conditions, they distinguish three principal types of the soil-forming process: automorphic, with stably deep (3 m and deeper) underground water of any salinity virtually not influencing on the soil; semi-automorphic, with underground water at depth of 2-3 m, which noticeably influences on the soil layer and its salinity degree, in the case of high saltiness; hydromorphic, with close underground water, which greatly effects soil water and salt regimes. In table 3, possibility is shown for using sprinkling for each of the abovementioned types of soil-forming processes.

Table 3. Usability of all types of the sprinkling machinery subject to hydrogeological conditions and exposure to salinization.

Natural or artificial drainage degree Hydromorphic property	Where UWD means underground water depth
	Automorphic (UWD > 3 m)			Semi-hydromorphic (UWD = 2-3 m)			Hydromorphic (UWD = 1-2 m)
	Fresh	Low-salted	High-salted	Fresh	Low-salted	High-salted	Fresh	Low-salted	High-salted
High	+	+	+	+	+	+	+	*	*
Medium	+	+	+	+	+	+	+	*	-
Low	+	+	*	*	*	-	*	-	-

Here, one should notice several fundamental circumstances, such as:
" salinity presence or its potentiality does not hinder in using sprinkling irrigation, since the salts carry-over efficiency at sprinkling is twice as much than washing by other methods, and this is experimentally proved;
" although use of sprinkling at hydromorphic soils no prone to salinization is possible, it is ineffective for two reasons: first, it doesn't bring to considerable water saving, since the losses to depth outlet are constrained by small free capacity of the soils and lower layers; second, it improves not enough the uniformity of soil moistening which is high as it is under the current conditions due to close level of underground water;
" use of sprinkling under hydromorphic conditions, at saline soils or those prone to high salinization, as well as other irrigation ways, is not reasonable without carrying out of hydroengineering reclamation (decrease of the inflow from outside and losses in sections of the network, increase of artificial drainage degree). Moreover, local using perfect irrigation technologies under these conditions, as well as lower water entry, will cause its overflow from the adjacent territories, irrigated by normal way, by underground; that will inevitably result in the intensification of salinization processes.
" using sprinkling at automorphic soils (generally, adyrs) having huge losses to depth outlet at normal irrigation ways is the most profitable and allows reducing water supply by several times, thanks to which the costs of the purchase and exploitation of sprinklers can totally be repaid [2], also refer to the page ABOUT USABILITY ASSESSMENT OF IMPROVED IRRIGATION METHODS UNDER PRESENT CONDITIONS UNDER THE CURRENT SITUATION. Characteristics of climate. Climate conditions overall need in irrigation water. Notwithstanding the seeming differences in the climatic peculiarities of the irrigated lands on the territories of the Republic of Uzbekistan, the ones are not so big during the vegetation period. Variation of the extreme values of the characteristics according to moisture deficit amounts to only 25 % between the zones S-II-G (�-II-�), the northernmost point at the mountainous zone and Y-II-A (�-II-�), the southernmost point at the desert zone [3]. Relative water saving compared to the interchangeable irrigation way is more significant. It is known that wind can influence upon water losses at sprinkling irrigation. However, even this influence is appreciable for the territories with abnormally high wind speed and frequency (for instance, Bekabad, Havast, and so on). The experience of sprinkling use under the working conditions of the Kyzyl-Kum desert [4] has shown that even under such extreme conditions sprinkling is the most reasonable irrigation way for high-permeability soils both by technical and economical parameters, which ensures uniform irrigation, saving of water resources, and reclamation condition for the lands highly subjected to salinization. The only climatic indices which are significant when justifying sprinkling and selecting the type of sprinkler under Uzbekistan's conditions are the speed, frequency, and length of wind during the vegetation period. In table 4, proposals are presented made for various types of sprinklers according to the permissible speed and frequency of wind.

Table 4. Restrictions on sprinkling usability subject to the speed, frequency, and length of wind.

Characteristics of wind activity			Types of sprinklers according to rain characteristic
Speed, m/s	Frequency during vegetation period, days	Maximum length, days	Fine-dispersed		Of medium rain fineness			Of big rain fineness
			Rain intensity, mm/h
			0.4	0.8	2.0	4.0	6.0	10.0	15.0	20.0
< 2.0	Any	Any	+	+	+	+	+	+	+	+
2-5	< 10	< 10	*	+	+	+	+	+	+	+
	10	10-15	*	*	+	+	+	+	+	+
	>10	> 20	*	*	*	+	+	+	+	+
5-8	5	< 5	*	*	*	*	+	+	+	+
	5	5-10	*	*	*	*	*	+	+	+
	>5	>10	*	*	*	*	*	*	+	+
> 8	< 3	< 3	*	*	*	*	*	*	*	+
	5	3-5	*	*	*	*	*	*	*	*
	> 5	> 5	*	*	*	*	*	*	*	*

Note: It should be noted that nowadays the leading foreign companies have developed sprinkling nozzles for surface water atomization, for which the risk of drop drifting is less than for common those by several times.

At that, the following considerations were taken into account: the lower the wind frequency and length during the vegetation period, the less the effect of its speed on the irrigation regime, since sprinkling can be stopped while wind is blowing with no significant detriment to the crop; and the larger and more intensive the rain, the less wind influences on raincloud drifting, with other equal states [3].

Crop types. Different crops make special demands of soil moisture (inter-irrigation period) and relative air humidity. When selecting a sprinkler construction, the type of crops being grown is of practical importance, and, at that, the plant height is a deciding factor. In table 5, the criteria for the selection of a proper sprinkler construction are given depending on the crop type and plant height.

Table 5. Usability of sprinkler for different crops.

Crop type	Types of sprinkling machine according to the sprinkler design and position
	Far-range	Medium-range, raised above plants	Medium-range, at the soil level	Short-range, put down in the inter-row space	Short-range, at the soil level
Gardens, vineyards	+	+	-	-	+
Tall-stalked (corn, kenaf etc.)-	+	+	-	+	-
Low (cotton plant, vegetables etc.)	+	+	+	+	*
Grain-crops, spiked (wheat and so on)	+	+	+	+	+

Sprinkler types according to a water withdrawal way. Use of the sprinkler in irrigation systems originally designed for surface irrigation ways becomes complicated due to difficult water withdrawal from the existing network. To zone sprinkling, the existing systems can be divided as follows: in earth bed; coated; with flexible pressure hose; rigid conduit with hydrants. In order to avoid great financial expenses for the alteration of the network in question with the sprinklers connected, one should follow the guidelines given in the certificate of the machine being used.
Water supply to the system. To attain the highest effect of using the sprinkling machinery, preference should be given to the irrigation systems with the least water supply where it is impossible to provide normal crop irrigation regime under the current conditions. Among such systems are those where water supply limit does not exceed 80 %.
Forms of land utilization and the maintained area. When selecting areas, the preference should be given to farms and the associations of land-users, on the lands with difficult water delivery (machine water lifting), where particularly the advantages of water saving and rational use can become apparent. The area being maintained should be selected in accordance with possible capability of the sprinkler. At the same time, minimum inter-irrigation periods must be provided at the designed irrigation rate. That is to say, it is advisable that the machine is continually used during the vegetation period and in the three-shift working regime, with stopping only for the maintenance works.
Power supply. From the economical point of view, the most reasonable way is using sprinkling in the systems with mechanical water lifting, where the water value is high. One of the preferable conditions for the sprinkling machine to be arranged is the availability of district power supply from the state power system involving approximate power transmission lines and needed stand-by power in the system, since the water delivery cost by diesel machines is higher by far than by electrified ones.
Economical criteria to select machines. With the existing scope of choice between a few types of machines according to all the aforementioned parameters, one must employ the machines of the lowest normalized expenditures (NE).
NE = E * C + EC --> min
where, E is the standard factor of depreciation of capital investments
C is capital investments
EC - annual exploitation costs

References
1. Departmental Construction Standards VSN 3.3-2.2. Interfarm network with the surface irrigation way. M., 1987
2. A.N.Morozov. On the use conditions for perfect irrigation ways in the current situation. Transactions of paper abstracts for the conference "Problems and ways of forming economic interrelations in the water industry and agriculture under the conditions of the market reforms development", Central Asian Research Institute for Irrigation SANIIRI, Tashkent, 2004, pp. 176-181.
3. V.R.Shreder, V.F.Safonov, I.K.Vasilyev, R.I.Parenchik, A.R.Riftina. Design values of the crop irrigation rates in the basins of the Syrdarya and Amudarya rivers. State Design Institute for Water and Cotton Projects "Sredazgiprovodhlopok", Tashkent, 1970, p.292.

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