Jiménez E. E .E. , González B. P. , Domínguez G. M. Relationship between irrigation uniformity parameters in center pivot machines
Agricultural Technical Sciences Magazine , ISSN -1010-2760 , RNPS -0111, Vol 21, No. 3 , July- September, pp . 18-22, 2012.
Research Institute of Agricultural Engineering, Project Sugar Institute , Havana, Cuba .
The parameters Coefficient of uniformity by Heermann and Hein, the uniformity coefficient of variation by Bremond and Molleand and distribution uniformity and its relationship with the Appropriately Irrigated Area with the aim of assessing the irrigation uniformity was determined. The study was conducted in Cuba in 16 pivots machines , which used the type emitters Nelson D3000 Spray , Spray Senninger , Super Spray Nozzle and Diffuser IIRD of Research Institute of Agricultural Engineering . Relations between the above parameters and the wind speed were also established . High values of coefficient of uniformity , except for six machines , which could be associated with the wrong nozzle distribution were obtained . Although there is high association between the parameters of irrigation uniformity and Properly Irrigated Area, it is imposed to study the uniformity by sections to identify in which areas of the machine there are problems in water distribution. Bad, regular and well irrigated area, for a center pivot machine, can be determined taking account of the percentage of Properly Irrigated Area
In 16 pivot machines at 6 municipalities and 4 different brands, in order to determine the uniformity of irrigation, were made field trials in Artemisa, Mayabeque and Matanzas , the most productive provinces of the country were selected. The standard used for the tests was the NC ISO 11545 (2005 ) . These tests were conducted with emitters Nelson D3000 Spray , Spray Senninger , Super Spray nozzle and diffuser IIRD latter produced in Cuba . The height above the ground of the same ranged between 0.9 and 1.2 m .
The irrigation uniformity indicators identified were the following :
– Uniformity coefficient ( CUh ) by Heermann & Hein (1968 ) :
Where: n – number of collectors ;
C i – amount collected by the collector ( with i varying from 1 to n );
Di – irrigated area by collector i or distance from the center of pivot to collector i ;
Mc – weighted average of the amounts collected by n collectors
– Uniformity coefficient of variation ( CUV ) according Bremond & Molle (1995 ) :
– Distribution uniformity UD – 25%: average high in 25 % of the area less irrigated / average high in entire area x 100 %
Besides other parameters was determined as :
Properly Irrigated Area ( ARA) : based on the sheet which is within the range of 10 % above and below the middle high .
Excessively Irrigated Area (ARE ) : based on the sheet that is above 110% of the middle high.
Insufficiently Irrigated Area (ARI): based on the sheet is below 90 % of the middle high.
– Also the graphic relations were established between the following indicators :
ARA- CUh ; ARA- CUV ; ARA -UD 25 % ; CUh – speed ( V.V ); CUV- V.V ;
UD 25% – V.V ; ARA- V.V
RESULTS AND DISCUSSION
In Table 1 the results of irrigation uniformity are showned . High uniformity of machines equipped with rotator issuers , except the evaluation 4 that was associated with the inclination of the downspouts. So did the rest of the downspouts on assessments 3, 10 , 13, 15 and 16.
Favourable values uniformity parameters of emitting for range 0.9-1.2 m height , confirms criteria others . Cardenas (2000 ) observed that increased the CUh with decreasing height . The author obtained the highest values of this parameter with the issuers located at 1m height. Heinemann et al. ( 1997 ) and Tarjuelo ( 2005 ) , suggest the reduction of the height of the emitter to the ground , to reduce drift and evaporation losses , without impairing the quality parameters of irrigation . According to Kincaid (1996 ) , the spray nozzles should be at least 1m above the ground . But Montero et al. (1997 ) obtained a different results for the conditions of Spain recommends 2 m high.
An interesting element is the percentage Properly Irrigated Area (ARA ), where its show , in some cases, contradictions with uniformity coefficient of Heermann and Hein ( CUh ) , uniformity coefficient of variation of Bremond and Molle ( CUV ) parameters and uniformity of distribution ( UD25 % ) , ie , significantly different values ARA are reflected.
Table 1. 1 Ratio of data from different machines brands tested and their parameters of irrigation uniformity
Table 1. 2 Relationship of data from different machine brands tested and their parameters of irrigation uniformity
Jiménez ( 2008) , scored significantly higher correlations to conduct this study except between ARA- UD25 % relationship, because this indicator represents 25% of the lowest values , and precisely these fall outside in the ARA. Then he proposed criteria employed by Tarjuelo of irrigated area (2005 ) , using the percentage of Properly Irrigated Area(Table 2).
TABLE 2. Criteria irrigated area based on percentages of ARA
Criteria irrigated area according Tarjuelo (2005 )
Percentage of properly irrigated area ( ARA)
Área very well irrigated Major to 66%
Área well irrigated Between 57% and 66 %
Area inadequately irrigated Low of 57%
Source : Jimenez (2008 ).
This is associated with the distribution of the water sheet along the machine. If the length of the side that you are applying water with high variability , is near to the pivot , the ARA will be higher, and while more far is the section that distributes water bad of the pivot, will be more small the ARA. It is imposed to study the uniformity by sections, which coincides with the author of reference , whereas the distribution of the sheet along the machine is homogeneous, or that alterations in the distribution of water are in the first stages of the machine.
Also Tornés et al. (2009 ) conducted piecewise uniformity pivot machines and scored infrairrigated areas (low height of 0.85 Media Collection ) in the last sections , yet high uniformity coefficients ( 90 % higher ) .
It can be summarized that the uniformity coefficient should not be the indicator governing the quality distribution of water in the center pivot irrigation machine , it is the percentage of Properly Irrigated Area
Generally speaking , satisfactory uniformity coefficient values Heermann and Hein , uniformity coefficient of variation and distribution uniformity for different types of emitters studied were obtained.
– Although dependence percentage of Properly Irrigated Area with the parameters of irrigation uniformity is found , does not mean they always be the case , since it is not the same present problems of distribution of irrigation in the start that in the end of the machine, because they represent different areas . Therefore, it imposes uniformity analyze deliver water by sections .
– Under the conditions studied , there is no impact of wind speed on the parameters Properly Irrigated Area, uniformity coefficient Heermann and Hein, uniformity coefficient of variation and uniformity distribution.
– The coefficient of uniformity should not be the parameter that determines if the area is well irrigated or not, it is the percentage of Properly Irrigated Area .
– The area criterion bad, regular and well irrigated , for a center pivot machine , can be established taking account of the percentage of Properly Area Irrigated, based on the fact that the distribution of the sheet along the machine is uniform or changes in the distribution of water can find in the first sections of the machine.