ICRISAT Archival Report 2006 - The seedlings of success in the ...

ii. Long Term Trends In Climate And Runoff In The Limpopo Basin, Zimbabwe And Their Livelihood
Implications David Love, Steve Twomlow, Stefan Uhlenbrook and Pieter van der Zaag - WaterNet, ICRISAT and
UNESCO-IHE,
Rural livelihoods in the Limpopo Basin are made risky by unreliable rainfall, upon which most smallholder farmers
depend. Water resource availability constrains our ability to respond to this challenge and analyzing long term trends
in climate and runoff can help characterize the constraints.
Climate data for 10 stations (time series of 30 – 70 years) and hydrological data from 30 stations (time series of 25 –
50 years), located across the portion of the Limpopo Basin which lies within Zimbabwe, were analysed to determine
the long term trends. Analysis of climate data included evaluation of trends in precipitation and temperature, annual
anomalies, depth duration curves, storm intensity analyses, frequency of rainy days and the occurrence of dryspells.
Analysis of hydrological data (using normalised flows) included flow duration curves (for undeveloped catchments),
flood analyses, days of flow and rainfall-runoff regression analyses.
Results show a decline in rainfall and rise in temperature for some parts of the study area. There is also a decrease in
the number of rainy days per season and an increase in the frequency and duration of dry spells during the rainy
season from some stations. Analyses of flow data show some rivers with a decline in annual runoff and an increase
in the frequency of days with no flow.
The change in rainfall pattern is very significant for rainfed agriculture. The decline in rainfall appears worse for the
better agricultural areas in the north. The increase in frequency of dryspells threatens crop failure even in areas with
higher rainfall. The effects of these changes on maize yield (as the staple crop) will be simulated using the APSIM
model.
Given the significant control of upstream runoff by precipitation received (as shown by the regression analyses),
projected declines in rainfall are likely to result in some declines in water availability in the upstream dams.
Declines in rainfall may translate to more than proportional declines in runoff due to non-linear processes, including
for example interception thresholds. Such a decrease in dam yields will affect both large scale water supply for cities
and small dams which supply water to livestock.
iii. Can drip irrigation improve livelihood of smallholders: lessons learned from Zimbabwe
Paul Belder, Aiden Senzanje, Emmanuel Manzungu, Steve Twomlow, David Rohrbach. ICRISAT and University of
Zimbabwe
In sub-Saharan Africa it is estimated that one third of the rural population is malnourished, yet the continent’s
irrigation potential is poorly developed. One intervention, based on successes from Asia, which has potential to
improve household nutrition in the rural areas through better vegetable production, is small-scale drip irrigation.
This system is said to save water and labour. Since 2002, some 70,000 low-cost, low-head drip irrigation kits have
been distributed through humanitarian relief initiatives throughout the rural areas of Zimbabwe.
In the dry season of 2006 a country-wide survey was undertaken to determine the impacts of drip kits that had been
delivered to needy households. Survey results showed that disadoption of drip kits occurred as a function of time,
and after 3 years only 16% of the kits that had been distributed were still being used (Table 9B9). Reasons for
disadoption included lack of water; lack of understanding of the drip kit concept, and more importantly a lack of
technical support and follow-up by the Non Government Organizations who distributed the kits and the extension
services. A cost-effectiveness analysis showed that drip kits are only more cost-effective than traditional hand
watering if potential water savings are achieved (Table 9B10) . This was, however, hardly the case due to lack of
knowledge on crop water requirements with the kits, and a beneficiary perception that the soil surface should be wet.
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