SABI Magazine Volume 9 Issue 3 | Page 37

SAPWAT
for the estimation of crop irrigation requirements by irrigation engineers , planners , agriculturalists , administrators , teachers and students . The development of the SAPWAT3 and SAPWAT4 programs is based on the FAO published Irrigation and Drainage Report No . 56 , Crop evapotranspiration . Guidelines for computing crop water requirements ( Allen , et al ., 1998 ).
Figure 3 Variables taken into account when estimating irrigation water requirements
This intuitive and comprehensive document is highly acclaimed and has become accepted internationally . As the calculation of crop evapotranspiration is the first and essential element
of any routine for estimating crop irrigation requirement , SAPWAT4 has at its core the computer procedures contained in FAO 56 . Extensive use was also made of FAO Irrigation and Drainage Report No . 66 , Crop Yield Response to Water ( Steduto , et al ., 2012 ) for reviewing crop coefficients .
Figure 4 Weather stations included in SAPWAT4 , each dot represents a weather station
The irrigation requirement of crops is dominated by climate , particularly in the yearly and seasonal variation in the evaporative demand of the atmosphere as well as precipitation . SAPWAT4 has included in its installed database comprehensive weather data that is immediately available to the user ( Figure 4 ).
Weather data base
Firstly , it includes the complete FAO CLIMWAT weather data base ( Smith , 1993 ) encompassing not only South Africa , but many other countries in the world where there is irrigation development . CLIMWAT comprises 3 262 weather stations from 144 countries , and contains long-term monthly average data for calculating Penman-Monteith ET0 values as well as rainfall . While CLIMWAT weather data output is monthly averages , SAPWAT4 calculations are based on daily values requiring interpolation . This has been facilitated in SAPWAT4 by statistically fitting a cosine curve to the monthly ET0 values .
Secondly , the installed set of weather data in SAPWAT4 also includes derived weather stations , presently only applicable to South Africa . This database was developed from the South African Atlas of Climatology and Agrohydrology by the team from the School of Bioresources Engineering and Environmental Hydrology , University of KwaZulu- Natal ( Schulze and Maharaj ,
2006 ). The derived weather stations are located at the centroid of the polygon that represents each quaternary drainage region of the country and provide not only comprehensive coverage , but also 50 or more years of historical and predicted ( 1950- 1999 for most cases ) daily weather data . This capability has major implications for planning and for strategy development .
SAPWAT4 provides facilities for importing additional weather station data , including data produced by the New LocClim Climate Estimator , an FAO program that produces monthly climate data for any place on earth .
Figure 5 Köppen-Geiger climatic system for Southern Africa

We ’ ve Received a lot of Flattery for Our new Drippers .

D1000
Thin Wall Drip Line with
A
ActiveFlexTechnology
The Rivulis D1000 Drip Line with the ActiveFlex™ technology combines the best of drip irrigation technologies into this next generation product . The D1000 Drip Line is manufactured with an 8 mil wall and a slit outlet that is ideal for sandy or subsurface applications . Because the D1000 Drip Line utilizes a molded dripper , it produces very accurate flow rates and superior plug resistance . With all its features , the D1000 Drip Line with ActiveFlex™ technology delivers on enhanced performance of a thin wall drip line in your field .
Most Advanced Flat Dripper Technology
The Rivulis D1000 Dripper slit outlet opens to emit the water and then closes . The slit outlet remains closed when the drip line is not pressurized . The advantage of an outlet that closes is its resistance to particle ingestion during installation , system shutdown , retrieval , and use in subsurface applications .
Product Options
Diameter
Wall
Flow Rate
Standard Dripper Spacing
( mm )
( mil )
( mm )
( l / h )
cm
16
6
0.15
16
8
0.20
1.0 , 1.5
15 , 20 , 25 , 30 and 40
22
8
0.20

D2000 Drip Line

Product Options
Diameter
Wall
Flow Rate
Standard Dripper Spacing
( mm )
( mil )
( mm )
( l / h )
cm
16
30 , 35 , 40 , 45
0.76 , 0.89 , 1.02 , 1.14
1.0 , 1.5 , 2.0 , 4.0
20 *, 25 *, 30 , 33 , 40 , 50 , 60 , 75 ,
20
40
1.02
1.0 , 1.5
100 cm (* only for 1,0 and 2,0 l / h )
The Rivulis D2000 Drip Line , with medium to heavy wall thicknesses , has innovative flat drippers that minimize resistance of the water flow in the main channel , allowing growers to use longer lateral runs than with similar cylindrical shaped drippers . The design of the dripper incorporates features such as an expansive filtration area , large dripper channel , and sharp teeth to create a turbulent flow for better clog resistance .

D5000 Flow Regulated Drip Line

Product Options
Diameter
Wall
Flow Rate
Standard Dripper Spacing
( mm )
( mil )
( mm )
( l / h )
cm
16 , 17 , 20 , 22 , 23 15-47 0.38-1.19 0.65 , 1.0 , 1.5 , 2.0 20 , 30 , 40 , 50 , 60 , 75 and 100 cm
The Rivulis D5000 Flow Regulated Drip Line utilizes a universal flat dripper that can be integrated in several diameter and wall thickness configurations . Engineered to resist clogging , the Rivulis D5000 ’ s design incorporates both multiple inlet filters and a dripper labyrinth with a large cross section . With the added feature of flow regulation , the Rivulis D5000 Drip Line is the ideal choice for long runs or sloping terrains .
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