PERFORMANCE OF IRRIGATION SYSTEMS IN SOUTH AFRICA - Management, Performance, and Applications of Micro Irrigation Systems - page 68

The possible reason for the low percentage of dragline systems that comply with
the norms, can be attributed to the incorrect system pressure (of the 20 dragline sys-
tems which were tested only six of them operated within the acceptable pressure
range), worn nozzles, incorrect spacings and the climatic conditions, where relatively
high wind speeds prevailed during testing. The wind speeds varied from 1 to 11 m/s.
The wind also affected the performance of the fl oppy system but not as much as with
the dragline systems. The CU and DU values were in the same order as was found
with this project (Table 4), in a research project by the ARC-IAE [1] where impact
sprinklers and fl oppy systems were evaluated.

TABLE 4 Results of research on impact sprinklers and floppy systems (WRC report, 5).

Parameter Impact

Sprinkler A

Impact
Sprinkler B

Floppy

CU% 78 76 78

DU% 68 63 71

Figure 5 shows the performance of the micro systems (M 28 and M 29 ) and the drip
systems (from M 30 to P 38 ). None of the micro irrigation systems exceeded the EU, DU
and SU norms and only 11% of the drip systems exceeded the EU, 33% the DU and
22% the SU. Pressure variation and clogging is the mayor problem. Especially system
K32 and U34 were severely clogged. The results of the uniformity of the micro and
drip irrigation systems were similar to that of the other irrigation systems. This is con-
trary to the common belief that micro and drip systems have much higher uniformities
than other irrigation systems.

5.6 CONCLUSIONS
Although most of the systems performed lower than the accepted norms, yet it is
within the range of what is normally found under in-field evaluations. It is however
of the utmost importance that the irrigation systems should be properly maintained
and operated within their specified design parameters to ensure optimal efficiency and
operation of the system. The results showed that well maintained and correctly oper-
ated systems can achieve or exceed the uniformities, which are considered reasonable
and acceptable.
In order to conserve water resources, close attention must be paid to the perfor-
mance of irrigation systems. The frequent evaluation and maintenance of irrigation
systems are imperative to keep the performance on a high level and to optimize water
use effi ciency.