A.N.Morozov

Open Join-stock Company "Ghidroproject"

ABOUT USABILITY ASSESSMENT OF IMPROVED IRRIGATION METHODS UNDER PRESENT CONDITIONS UNDER THE CURRENT SITUATION

The main cause of the irrigated lands reclamation crisis in the Central Asian republics are the problems associated with the decrease of soils fertility, irrigation water deficit, salinization of those, as well as pollution of the sources with drainage-waste effluents which is due to imperfect irrigation means [1, 2].
Lack of incentives to saving of water on the level of a field, its free delivery and consump-tion were not conducive to solution of the irrigation technology problems, especially since perfect irrigation technique is expensive and requires for relatively high maintenance cost, and high level of the maintenance itself and manpower training.
As a result, for a half a century of intensive reclamation of new lands a situation arose when out of the total water supply to the systems, 40-50 % of that was performed by means of pumps, about 30 % was efficiently used on fields and the rest 70 % created meliorative problems which reclamation specialists hardly solved, maintaining the drainage and exporting its effluents back to water sources (80 %) and depressions (20 %) [3].
On figure 1, the analysis of water consumption in different functional elements of modern irrigation systems is shown, according to the data of [3]. In the picture, one can see that only just 19 km3, or 33 %, of water taken, including return water, arrive the fields.

Fig 1. Water consumption by the branches of the Uzbekistan national economy.

That problem came to the crisis point for a century, and that was studied insufficiently, and consequences of a number of decisions taken were not so apparent as it is today; nevertheless, it is necessary to look for realizable way outs from the deadlock arisen.
Water reclamation is needed to make up for natural moisture deficiency and control salt conditions of soils subjected to salinity at growing crops in the view of gaining crop production. Water supply in excess of the amount necessary for that brings to the need for drainage, that causes incidental, artificially created problems, diametrically opposite to the first and paradoxical to an arid zone.
Major effect on uniformity of fields' moistening and regulation of salt conditions of soils is made by means of water distribution to fields.
The examples of reclamation of the Surkhan-Sherabad, Karshi, Kirkkiz, Golodnaya Steppe and Djizzak objects with level of conducting systems close to the world one, but without proper means for water distribution to fields showed that water saving there (according to research data by SANIIRI) amounted on the average to 2000 m3/ha, but that did not give any significant improve-ment of the reclamation state. Everywhere, irrigation by imperfect means resulted in waterlogging or salinization of lands.
Analysis of the experience with testing or production use of sprinkling equipment, subsoil and drip irrigation in Uzbekistan allows drawing the conclusion that in spite of efficiency of those irrigation methods, in respect to water economy and specific water consumption to unit of yield, which do not raise doubts, their application in the practice of irrigated agriculture, some time or other, ended in the same way - an utter fiasco, although the conclusion that improvement of the irrigation technique is priority from macro-economical perspective has been confirmed on the whole by the world practice of irrigation and reclamation development.
In our opinion, the main reason for disinterestedness of relevant subjects (farmers or their associations, like Water Users Associations) lies in unobviousness of economic and ecological ad-vantages of perfect irrigation technology.
Let us determine the conditions under which today the application of that technology is possibly economically efficient on the level of a specific farm.
First of all, irrespective of irrigation technology applied, scheduled water use must be rees-tablished on irrigation systems, so that every farmer is sure that he will take at least limited amount of water for irrigation, strictly according to the preset plan. Without getting this, it is vain at all to speak about efficient water consumption.
Now, we shall enumerate, to the point, conditions of perfect irrigation technology applica-tion:
1. Economic interests of farmers to gain additional production of plant cultivation. (This condition seems evident from the position of market economy, however it is not met everywhere and always on first stages of the agrarian reform carried out in Uzbekistan).
2. Actual water resources deficit in the system. (Otherwise, under the conditions of free water consumption, the farmer has no obvious reason for saving water).
3. Technical expediency and opportunities of using one or another irrigation means. (At this point, we mean that irrigation technology, replacing the traditional furrow irrigation or any other imperfect method of irrigation, should correspond with natural and eco-nomic characteristics of the object under consideration: soil permeability extent; drain-age degree and slopes of the territory; kinds of agricultural crops being cultivated; sizes of the farm.
4. Paid water consumption determining attitude of farmers to perfect irrigation technology, especially if water supply involves expenses to purchase and maintenance of pumping equipment.
In work [4], estimation technique of efficiency of perfect irrigation technology application is given. In that [5], it is viewed in detail how to estimate the advisability of using perfect irrigation technology from the standpoint of its economic efficiency; in that [6], it is shown that using perfect irrigation technology, despite its comparatively high cost, results in more productive operation of irrigation systems from the economic and ecological standpoints.
In the present statement, we are not considering concomitant positive effects on the system and macro-economic levels, connected with application of perfect irrigation technology. We shall touch just on consideration of expediency criteria of its use on the lowest level, namely by farmers or Water Users Associations (WUA).
The main criterion for an individual farmer or WUA will be the saving of means that they gain owing to reduction of expenses to water delivery (in particular, water lifting by engines) and the profit that they have due to improved field moistening uniformity and normalization of irriga-tion mode, using perfect irrigation technology. The means, saved at that, should cover the costs connected to the purchase and maintenance of perfect irrigation technique, otherwise diseconomies are inevitable.
For immediate using perfect irrigation technique, one can suggest, at first, low-water-supplied systems, to those water delivery is carried out by means of pumps (especially all systems at foothills, on so-called adyry). Besides, it is necessary that soils and lower layers must be of high and very high permeability (in Uzbekistan, there are somewhat more than 1 mln.ha, or 25 %, of such irrigated lands see table 1).

Table 1 Classification of Uzbekistan soils according to water permeability, ths.ha.

Out of those, today, most perspective for using perfect irrigation technique are the lands with deep-located groundwater, where losses to deep spillage with furrow irrigation are maximum (the areas of such lands amount to 80 % of the highly water-permeable lands of Uzbekistan, i.e. around 0.8 mln.ha).
We'll consider a particular case of most evident, effective perfect irrigation technique appli-cation which now may awake interests of both individual farmers and WUAs holding irrigated lands on adyry and incurring sizeable expenditures to operation of pumping stations performing wa-ter lifting of volume much exceeding both the biological need of cultivated agricultural crops and the rates set.
In table 2, the machine-irrigation areas in the republic's regions and pumping stations' out-puts set are shown. These data give the estimate of the problem's dimension.

Table 2. Areas of machine irrigation and set output of pumping stations in the regions of Uz-bekistan (the Republic of Karakalpakstan is not considered), according to data of "Vodproject".

 

Under these conditions, ensuring of the reasonable irrigation mode with the furrow irrigation technique is connected with the great over-expenditure of irrigation water to deep spillage, which becomes here much noticeable due to high water permeability and low water-retaining ability of those soils. It is extremely hard to gain high irrigation uniformity over a field under such conditions, and losses to deep spillage, taking place under automorphic conditions much deeper the topsoil, cannot be used by plants.
From the agritechnical standpoint, to such conditions, perfect is making frequent irrigation within the rates of water-retaining ability of soil's root-existing layer, that is the classic irrigation mode set according to soil moisture lowering down to 0.5-0.7 of the maximum irrigation moisture. It is actually impossible to carry out such an irrigation mode without using perfect irrigation tech-nology.
We'll present the principal positions of such calculation in somewhat simplified way so that any competent farmer could make regarding his specific conditions.
Under such natural conditions, economic subjects are concerned in that how one can reduce the costs associated with the lifting of surplus irrigation water and in what way one can improve water supply to the planted being cultivated. In order that a farmer can decide whether he needs a perfect irrigation technique, he needs to compare, in value terms, costs of water withdrawal with imperfect irrigation technique to ones with perfect irrigation technique and allow, at that, for yield increase thanks to improved irrigation uniformity and water distribution over the field.

This expression can be written in the form as follows (all the calculations are made for 1 ha of irrigated area):

C1> C2 - Vy + C3

(1)

Here, C1 - costs of water lifting and irrigation under the existing conditions, ths.Sum/ha;
C2 - costs of water lifting and irrigation with the designed conditions, ths.Sum/ha;
Vy - value of yield increase owing to perfect irrigation technology application,
Vy = VС* Y, ths.Sum/ha;
VС - cost of hundred kg yield, ths.Sum/hundred kg;
Y - yield increase due to perfect irrigation technology application (in the calcula-tions, it may be suggested to accept 30-40 % of the actual), hundred kg/ha;
C3 - costs associated with harvesting, storing and transporting extra-production gained, ths.Sum/ha;

We'll develop expression (1).
The costs in the first considered case are formed of the costs of:
- Water delivery to a farmer's plot or to WUA's boundary:

яwd = Vwd*W1

(2)

here, Vwd-delivery value, ths.Sum/1000 m3,
W1 - irrigation water amount for a season, ths.m3/ha (if water is delivered for free, for the time present, then жДБ = 0);

- Water lifting by pumps

яwd = W1*H*Ce

(3)

here, м - lifting height, m;
- pump efficiency, at small pumping stations - around 0.6; at large - 0.7-0.8;
Ce - electricity charges, ths.Sum/йW.

- Amortization costs of pumping equipment (е*й1ps), wages of the pumping station mainte-nance staff (MS1ps) and irrigators staff (IS1);
Then, costs in the first case will be:

C1 = W1*(Vwd+ H*Ce / *367.2) + A*й1ps + MS1ps + IS1

(4)

here, A - factor of annual assessments to amortization;
й1ps - balance cost of pumping stations available, ths.Sum;
367,2 - conversion factor.

In the second (designed) case, costs of delivery and lifting by pumps decrease down to nor-mative ones (when calculating, one can accept those, at the least, by 30 % less than the normative ones for furrow irrigation technique). Amortization costs of new irrigation technique and its main-tenance are added instead of costs of irrigators' wages and carrying out irrigation at the existing situation. If the pumping equipment is replaced by less powerful one, then the liquidation value of the existing pumping equipment is taken into account (i.e., in that case, in the calculations, value й2 of the new pumping stations' equipment reduces by the amount of the existing equipment's liquida-tion value). So, one can write:

C2 = W2*( Vwd + H*Ce/ *367.2) + A*й2ps + MS2 + A*йpit + IS2

(5)

 

here, A*й2ps + MS2 - depreciation charges and maintenance of new pumping stations, and keeping its staff as well (if the pumping stations are not replaced, then those are accepted the same as in the first case, namely A*й1ps + MSps1), ths.Sum;
A*йpit - amortization costs of perfect irrigation technique, ths.Sum;
IS2 - wages of perfect irrigation technique operators staff, ths.Sum;
Substituting the terms into expression 1, one can write:

W1*(Vwd+ H*Ce/ *367.2) + A*й1ps + MS1МЯ + IS1 > W2*( Vwd + H* Ce / *367.2) + A*й2ps + MS2 + A*йpit + IS2 + VС* Y - C3

(6)

Every farmer or WUA, having made calculations and comparing the left and right sides of inequality (6), is able to estimate to a first approximation if the perfect irrigation technique is profitable under the existing conditions.
One can evaluate the payback period of perfect irrigation technique through the following formula:

Pp = йpit + й2ps /(C2 + C3 - C1)

(7)

If the existing pumping stations are not replaced by new ones, then expression (7) becomes simpler:

Pp = йpit /(C2 + C3 -C1)

(8)

The data stated allow unbiased approaching to the selection of areas for introduction of per-fect irrigation technique and determining economic efficiency of its use under the current condi-tions.
Successful application of perfect irrigation technique in one or two farms at low-water dis-tricts will exemplify to other farmers concerned with saving of means to water supply.

References:
1. N.I.Parfenova, N.Reshetkina. Ecologic principles of irrigated lands' hydro-geological irrigation mode control. Hydrometeoizdat. 1995, 360 pp.
2. E.I.Pankova, I.P.Aydarov, I.A.Yamnova, A.F.Novikova, N.S.Blagovolin. Natural zon-ing of salted lands of the Aral Sea basin (geography, genesis, evolution). M., 1996, 180 pp.
3. General Scheme for complex use and protection of water-land resources of the Re-public of Uzbekistan for the period up to 2005. "Vodproject", Tashkent, 1992.
4. V.M.Zavgorodniy, V.G.Kovalenko. Comparative system analysis of efficiency of irrigation technology being used. In the book "Use of system analysis in irrigation and drainage". M., "Nauka", 1976, pp. 19-23.
5. N.F.Bonchakovskiy. Use of system analysis in water management. In the book "Use of system analysis in irrigation and drainage". M., "Nauka", 1976, pp. 10-18.
6. V.E.Raynin, B.I.Koshovets. Selection of antifiltration and drainage measurements when designing irrigation systems. Hydraulic engineering and reclamation, 1977, # 5, pp. 44-51.

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