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2.3.3 Regeneration Water
Use of regeneration water involves the indirect reuse of water that has
already been used, primarily in the agricultural sector. In some
instances, this water is utilised for urban purposes. The objective of
this technology is to augment the available water through reuse.
In irrigation, excess irrigation water applied to the land surface
drains via subsurface drains to open channels where it is conveyed away
from the fields to prevent waterlogging of the crop roots. Traditionally,
such water is discharged to the nearest surface water course, where it is
effectively removed from the irrigation system. In contrast, this
technology conveys the drainage water to collection areas where it is
pumped into reservoirs, mixed with fresh water and reused for irrigation.
Extent of Use
In Zimbabwe, use of regeneration water is currently practised on the
sugar estates of Hippo Valley, Chiredzi and Triangle, and in other
agricultural areas. For example, the Town of Glendale, Zimbabwe, depends
for its water supply on regeneration water emanating from the irrigation
of large citrus plantations in the Mazowe Valley.
Operation and Maintenance
Regular inspection, repair and maintenance of pumps and accessories is
Level of Involvement
Depending on the scale of the irrigation operations, government, large
and small farmers, and other institutions may make use of this technology.
For irrigation purposes the major cost is pumping. The amounts of money
involved depend on the size of the pumps, which, in turn, is dependent on
how much water is available. Therefore, cost of this technology is very
much a function of the size of irrigation operation. Irrigation pump
installation costs in Zimbabwe are about $2 000/ha.
Effectiveness of the Technology
Water from the drains is put to use instead of being "wasted".
Additional water for irrigation is made available. With flood irrigation,
water collected in the drains accumulates at as much as 3 l/s from a 400
ha section. This water is enough to irrigate an additional 3 ha of
cropland. In the case of Glendale, the water requirements of the small
town, 32 l/s, are more than covered by the volume of regeneration water
recovered through this technology.
This technology is appropriate wherever water shortages are experienced.
The use of regeneration water may not be appropriate where the
regeneration water has a high concentration of dissolved salts.
Additional water is made available for many other purposes through the
use of this technology. Extra hectares may also be cropped as a result.
Regeneration water has been found to be extremely saline, having
electrical conductivity values greater than 4 million mS/cm at 250C , in
some situations. This leads to salinity problems where applications of
regeneration water are of high volume and/or prolonged. In cases where the
regeneration water is utilised in the area where it is generated, there
are usually some increased costs due to the extra pumping required to lift
the regenerated water to the head of the irrigation scheme.
No cultural problems relating to the use of this technology have been
Hippo Valley Estates, Post Office Box 1, Chiredzi,
Zimbabwe, tel. 263-96-2381, fax: 263-96-2554.
Triangle Limited, Private Bag 801, Triangle, Zimbabwe,
tel. 263-96-6221, fax: 263-96-6513.