PERFORMANCE FIELD EVALUATION OF DRIP IRRIGATION SYSTEMS UNDER CONDITIONS OF THE DESERT REGION IN WESTERN IRAQ

A field experiment was carried out at Al-Saqlawiya township Al-Anbar governorate at north in latitude 33°24 ́57" and east longitude 43°41 ́23", during period from 15/10/2018 to 15/1/2019 in order to evaluate the performance of 5 units of surface drip irrigation system, components and periods of use, by the steps recommended by the American Agriculture Engineers Association, at 50 kPa operational pressure. Results showed that there was a disparity in values of emitters actual discharge, uniformity coefficient, emission uniformity and variation percent of discharge. Although the similarity of most measurement conditions such as land area, design, management and the operational pressure except of the periods of using these systems which ranged 2-5 years. The decrease percent of actual discharge values 8.06%, 8.74%, and 19.04% when comparing the actual discharge for the system 1 with the values of systems 2,3 and 4, respectively. While the increase percent of the actual discharge value reached 29.74% when comparing of system 1 with system 5. Uniformity coefficient of system decreased were 5.32%, 19.95%, 3.81% and 7.21%, respectively, and 10.73%,37.25%,7.51% and 14.36% for the decrease percent of emission uniformity comparing the system 1 with the systems 2, 3, 4 and 5, respectively, as for the increase percent for the variation emitters discharge, it were 7.70%, 118.73%, 7.70%, respectively. Noncompliance of users of these systems with regular maintenance of the end of agriculture seasons, poor storage conditions, not maintained at high temperature or cold conditions and increase use periods, all had caused the expansion of emitters' holes, which affected negatively in some values of the followed evaluation standard.


INTRODUCTION
The problems of limited available water for agricultural purposes in Iraq and particularity in Al-Saqlawiya, Al-Anbar, are considered of the main issues that challenge the water resources planners and the researchers. The demand for water for agricultural purposes has increased significantly last years, especially that the agricultural sector has become one of the biggest sectors consuming water. Studies have shown that the water allocated for irrigation purposes is not exploited property due to the increase of water losses percent as well as the poor usage for these resources. The attention of using the modern systems has increased in order to rationalize the water use and to reduce the demand, Subsequently, the use of drip irrigation systems has increased in the agricultural fields and greenhouses of most of Al-Saqlawiya areas, which led to import big amount of the components of drip irrigation systems different companies with non-standard specifications. the use of these components available in markets which often come without data or specification from their companies, in addition to the lack of sufficient expertise by their manufacture resulting in significant reduction in their design standards, and an increase in the costs of their maintenance and management. (5) have found that there was a variation in the actual emitters discharge at their design discharge with a differences in water distribution rates along the emitters deployed on the distribution line. (16,17,18) showed that the emitters and emitters tubes are often made from polyethylene, and when they are put on ground they are affected by the climate conditions such as temperature and cool, where this effects on the hydraulic properties of the emitters. (4) indicated in a study, that the energy loss may sometimes reach 30% from the total loss as a result of protrusion in the emitter that may encounter the route of water flowing. Whereas (11), and (15) showed that emitters sensitivity for clogging is one of the most important considerations when choosing the emitters with different characteristic, and they described the emitters according to their ability for clogging, so when their holes diameters is bigger than 0.7 mm they are very cloggingsensitivity, when the diameter is ranged between 0.7 to 1.5 mm they are sensitive, while they are not sensitive relatively when the diameter of their holes is bigger than 1.5 mm. (14) indicated that the poor design for system and the not responsible maintenance and management result in irregular emitters discharge, and that's a result of many factors such as the hydraulic difference. The same researchers above showed that the hydraulic differences along the emitters line are affected by the slope, length and diameter of the tube as well as the relationship between the applied operational pressure and emitters discharge. Also they indicated that the uniformity coefficient depends on the variable properties of system that are shown at the evaluation. (1) have obtained the actual discharge 4.00, 4.43 and 4.81 L h -1 when using operational pressure from 50, 70 and 100 kPa by using emitters whose design discharge 4 L h -1 . The actual discharge percent increased 10.75% and 20.25% for 70 and 100 kPa depended values above by the effect of operational pressure 50 kPa with the 70 and 100 kPa, respectively, (3) indicated that the 50 kPa operational pressure is the best to operate the irrigation system, where an actual discharge of 3.94 L h -1 was obtained and it's the nearest to the design discharge 4 L h -1 . (8) noted that the regularity of irrigation water to the plant by drip irrigation system has a big significance for design and operating the system. (10) found that the most factor effective in the regularity of irrigation water exiting the emitters is the variation in pressure regulators used in the system and the sensitivity of these emitters to change in pressure and temperature. (20) classified the variation value of discharge to preferable when its equal to 10% acceptable when its 10 to 20% and not acceptable if it exceeds 20%. (3) obtained the best values for uniformity coefficient, emission uniformity and percent of discharge variation, when they were about 96.77, 96.69 and 9.64%,respectively, at 50 kPa operational pressure and emitters whose 4 L h -1 discharge. Whereas (19) classified the value of uniformity coefficient as follow: UC ˃ 90% is "excellent", 80% ˂ UC ˂ 90% "good" , 70% ˂ UC ˂ 80% "satisfactory" , 60% ˂ UC ˂ 70% is "poor" and UC ˂ 60% is " not acceptable". (12) have defined the emission uniformity as in another alternative criterion, were it represents the ratio between the rate of the minimum quarter of emitters discharge over the rate of the overall discharge of emitters. (2) concluded that not conducting the regular maintenance for some apparatus led to clog some nozzles, which affected negatively in values of uniformity coefficient and low water depth as well as the nozzles discharge for some apparatus used in the study, and not joining the nozzles in their proper places had a negative effect on the regularity of water distribution and the performance of these system, and therefore this study aims to: 1-Evaluating performance and regularity of added water for drip irrigation systems in a set of agricultural fields in Al-Saqlawiya sector. 2-Evaluating the properties for the emitters commonly(Actual discharge, Uniformity coefficient, Emission uniformity and Variation percent of emitters discharge) used and then judging their quality and matching for the requirements of the drip irrigation system design.

MATERIALS AND METHODS
The questionnaire was evaluated, data and information were collected about the use of drip irrigation system under field operating conditions in agricultural fields in Alsaqlawiya sector (5 fields),. Where in the beginning scan was conducted to determine the cites and places of the fields that use these systems. The study included determining the places of designing and installing drip irrigation systems, and this was done in fall season 2018/2019. Table 1 shows periods of using irrigation systems used in the study.   Table 2 shows some physical and chemical characteristic of field soil according to (7,15). Five drip irrigation systems were evaluated in this study (600 m 2 area for each) each one has included :the main unit which consist of a steel tank with 2 m 3 capacity, pumping crew composed of a gasoline pump with 5.5 Hp and gives 30 m 3 h -1 discharge, a disk filter, pressure gage meter, switches to on and off the water and a set of tubes for water distribution, length of lateral tubes with 16 mm diameter were used that interposed with emitters type GR whose 4 L h -1 design discharge and 0.40 m the distance between them on one lateral line. The drip irrigation systems were installing in their allocated areas in order to the field preparation and evaluation for potato crop cultivating.

Field evaluation for drip irrigation system
In order to conduct the field evaluation for each drip irrigation system in each farm the steps recommended by the American Agricultural Engineer Association were followed, therefore the performance of each system in the field was evaluated by measuring the water distribution regularity of the irrigated area, where operational pressure 50 kPa was used. Distribution uniformity of the units was determined according to the equation mentioned in (8): Where: q=emitters discharge (L h -1 ). t= operating time (hr). v = Water volume received in the cans (L).  Table 3 shows the water volume compiled in collection cans according to the drip irrigation systems that are being studied, at 4 minute time and 50 kPa operational pressure. The emission uniformity was calculated by the equation mentioned in (12):

Where:
Ʃ= Summation Xi = Water volume compiled in each cans (ml). X ˉ = Average of water depths compiled in the cans (ml). n= Number of water collection cans. Therefore the distribution uniformity can be calculated according to the following equation:

Fig. 3. Emission uniformity values for the surface drip irrigation systems at 50 kPa operational pressure
The decrease percent of emission uniformity are 10.73%, 37.25%, 7.51% and 14.36% when comparing emission uniformity for system for system 1 with the systems 2, 3 and 4, respectively. The values of emission uniformity for the surface drip irrigation systems and their decrease in percentage are identical to that of uniformity coefficient, and this is consistent with what mentioned by (12) Emission uniformity is an another alternative criterion for uniformity coefficient of water distribution of emitters because it represents the ratio between the rate of minimum quarter of emitters discharge and overall discharge. Variation percent of emitters discharge Fig. 4 shows percent variation emitters discharge for the surface drip irrigation systems used in the study. variation percent of discharge were 37.14%, 40.00%, 81.25%, 40.00% and 54.65%, for system 1, 2, 3, 4 and 5 respectively, the minimum value for system 1 is 37.14% and 81.25% for system 3 is the maximum 1. Also noticed that the variation percent of emitters discharge have increased gradually for the systems 1,2and 3 then decreased to 40.00% for the system 4 and again increased to 54.65% for the system 5. The increase percent's of variation of emitters discharge reached as follows: 7.70%, 118.77%, 7.70% and 20.73% when comparing the discharge variation for system 1 with the systems 2, 3, 4 and 5 respectively. It's shown from Fig.4.

Fig. 4. Variation of emitters discharge values for surface drip irrigation systems at 50 kPa
operational pressure That most of the values of variation percent are not acceptable in the field and performance evaluation for the drip irrigation systems except of system 1 which is nearest one to be acceptable, and this agrees with the classification of (20) that the variation percentage of discharge are preferable at 10% or less, acceptable at 10% to 20% and not acceptable at 20% or more, and this agrees with (14) that the poor design, management and maintenance for the system result in an irregularity the emitters discharge of the field. Conclusions -From the results of this study, we concluded that the regular maintenance for the drip irrigation systems is essential especially at the end of the season for each crop in order to remove the precipitations and to fix the broken parts there save them in an appropriate conditions such as temperature and cool. -Conducting the regular evaluation for these systems according to the recommended criteria in order to know the good and appropriate qualities under the conditions of the study area.
-In form all users (of these systems) of the need to rationalize water consumption, achieve a high irrigation efficiency and distribution as well as a rise water unit value in order to increase the production and improve its quality.