MACRO CATCHMENT RAINWATER HARVESTING: OPPORTUNITIES
AND CHALLENGES, A CASE OF MAKANYA CATCHMENT IN
TANZANIA1
Omari Mzirai1, Siza D. Tumbo1, Abeid Msangi1, Henry Mahoo1, Filbert Rwehumbiza1
and Nuhu Hatibu2
1
Soil-Water Management Research Group, Sokoine University of Agriculture,
Morogoro, Tanzania: swmrg@suanet.ac.tz
2
Soil Water Management Research Network (SWMnet),ASARECA Nairobi, Kenya:
n.hatibu@cgiar.org
Rainwater harvesting (RWH) is the process of interception and concentration of
runoff and its subsequent storage either in soil for direct use by plants or in reservoirs
for later application when needed to mitigate dry spells. RWH varies from macro to
micro to insitu systems based on the size of the catchments. Macro RWH systems
with or without storage has shown to be more applicable among communities as
compared to micro catchment RWH systems. This paper describes some of the
opportunities and constraints/challenges for macro catchment rainwater harvesting
systems in Makanya catchment located in the Western Pare lowlands in Kilimanjaro
Region. The study was conducted to assess the potential of runoff and the perception
of farmers on its reliability. Result indicated that crop yields on fields that received
extra water from external catchments (macro RWH) increased by more than 120% as
compared to fields that received rainfall only. The amount of runoff received from
external catchment ranged from 70m3/ha to 300m3/ha, depending on the location of
the field with respect to the command potential of the source of water. However, due
to dynamics on the management of the sources of water, some constraints have been
identified. These include among others difficulties in controlling the runoff (timing
and volume); risk of flooding on the cropped area; lack of infrastructure for equitable
distribution of water and high transaction costs. Results from the study further
indicated that there are opportunities for wider adoption and this include assured
availability of runoff, favourable biophysical conditions and enhanced management
through formation of local institutions.
Keywords:
Rainwater harvesting systems, macro catchment, runoff, risk of
flooding, equitable distribution, transaction cost
1
Paper to be presented in 6TH SYMPOSIUM OF WARFSA/WATERNET/GWP,
EZULWINI, SWAZILAND. 1-4 November 2005