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.
Your Growth Partner.
Available at:
Greenhouse Technologies- Johannesburg MULTIFLORA FLOWER MARKET CNR VICKERS & FIG PLACE CITY DEEP JOHANNESBURG T: 011 613 3103- F: 011 613 2095 sales @ ghtech. co. za- www. ghtech. co. za