IJERD – International Journal of Environmental and Rural Development (2023) 14-1

Research article
erd

Simple Weir Types and Their Prospects for Small-Scale
Irrigation Development in Northern Zambia
ALEX LUSHIKANDA KABWE*
United Graduate School of Agricultural Sciences, Tottori University, Tottori, Japan
Email: d21a3003k@edu.tottori-u.ac.jp

MASAHIRO HYODO
Faculty of Agriculture, Tottori University, Tottori, JapanHIDEHIKO OGATA
United Graduate School of Agricultural Sciences, Tottori University, Tottori, JapanYOSHIHIRO SAGAWA
Sanyu Consultants INC, Tokyo, JapanYOSHINAO ADACHI
Sanyu Consultants INC, Tokyo, Japan

MASAYUKI ISHII
Academic Assembly, Shimane University, Shimane, Japan
Receive 19 January 2023

Accepted 8 May 2023(*Corresponding Author)

Abstract In Zambia, simple weir technology is increasingly gaining popularity as analternative method for river water diversion among rural small-scale farmers. The now widelyadopted technology was first introduced in the Northern Province region of Zambia to promotesmall-scale irrigation in local communities. These small-scale facilities are constructed acrossthe width of the river using forest materials such as poles, twigs, thatching grass, and tree bark
strips. These types of irrigation structures produce an adequate head of water enough for thediversion of water from the river into a canal conveying water for irrigation. However, simple
weirs that farmers have been constructing with forest materials are observed to experiencechallenges such as breaching, and often break down and collapse within six to seven months.
Therefore, the objective of this research was to investigate the characteristics of simple weirs
constructed by farmers on a self-help basis for community-based small-scale irrigation
schemes in the Luapula, Muchinga, and Northern Province regions of Zambia. We observed
the simple weirs constructed before the start of irrigation season (May) and simple weirs built
in the operational phase (May-November) and we characterized simple weirs as 1) single-line
weir, 2) inclined weir, 3) trigonal weir, and 4) double-line weir. The results show an
improvement in the irrigated area by small-scale farmers since the introduction of simple weirs.
The findings revealed that challenges that were often encountered on the simple weirs were
not solely caused by river flooding, but also by compromises in the construction,
inconsistencies in maintenance, and lack of measures to sustain and protect the weirs. It wasalso observed that simple weirs in operation were regularly maintained and repaired during
the irrigation season. Despite the challenges farmers were experiencing with the simple weirs,
farmers persistently conducted maintenance activities, replaced worn-out poles and thatchinggrass and de-silted before the start of the irrigation season.
Keywords simple weir types, small-scale irrigation, river water diversion, arid land

INTRODUCTIONⒸ ISERD

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Most of the smallholder farmers live in rural areas in sub-Saharan Africa (SSA) and constitute about
70% of the continent’s population in the bracket of poor people (Sakaki and Koga, 2013). This groupof farmers is viable, but marginalized and vulnerable since they entirely depend on seasonal rainfall
for their agricultural activities. Rainfed farming practiced by small-scale rural farmers produces a
low agricultural yield that is frequently influenced by weather-induced changes. The problems
associated with rainy season farming are numerous and not limited to 1) farming within 3-4 months
in which to produce enough food crops to last up to the following harvest and 2) during the dry
season, there is a prevalent shortage of fresh and nutritious crops. Based on the mentioned challenges,
smallholder irrigation is promoted in SSA as a strategic intervention to enhance agricultural
production, productivity, and farm household incomes (Osewe et al., 2020). To acceleratesmallholder irrigation development in rural areas in SSA, low-cost irrigation technologies like river
diversion simple weirs have been widely promoted for gravity irrigation. One of the gravity irrigation
methods that has become popular in rural areas in SSA is river water diversion. The Southern Africa
region is cited with a potential irrigable area of more than 3 million hectares (Xie et al., 2021) forriver water irrigation schemes.
Simple weirs have been used in establishing community irrigation schemes in rural areas inSouthern African countries such as Malawi, Mozambique, and Zambia (Lautze et al., 2017). In thenorthern region provinces of Zambia, small-scale local farmers construct simple weirs on the rivers
in the dry season (May-November). The simple weir irrigation technology has increasingly become
one of the irrigation methods among smallholder irrigation farmers in the rural areas in Zambia(Luapula, Muchinga, and Northern provinces) (Colenbrander et al., 2012). This is because simple
weirs are community demand-driven technologies, relatively cost-effective, and adaptable to rural
environments with the potential for gravity irrigation (suitable topography and surface flowing
rivers). In Zambia, surface water from rivers and springs are the primary sources of water accessedby farmers for small-scale irrigation. Farmers have been accessing irrigation water using manuallyoperated technologies like watering cans, buckets, and 20-25ltr plastic containers. However, this typeof irrigation has less impact on the irrigated area expanded and irrigation production. Simple weirs
have been introduced to develop small-scale irrigation in Zambia. The simple weir irrigation
technology has attracted the attention of the majority of small-scale farmers in the rural area.
However, most of the simple weirs constructed by farmers themselves do not continuefunctioning throughout the irrigation season as many of them are either breached, partially destroyed,or washed away and needed to be either repaired, rehabilitated, or reconstructed after the annual
floods. Farmers claim that, based on their experiences with simple weirs, the contributing factors to
the challenges experienced include high peak discharges, weakness of structures, small canal intake,and excessive accumulation of sediment particles upstream of the weirs. Since the introduction of
simple weirs as an alternative method of irrigation in the northern region of Zambia a decade ago, todate little information has been disseminated on the performance and challenges of these types ofsmall-scale irrigation facilities.
OBJECTIVE
To explore the prospects of the simple river water diversion weirs constructed by local communities
for small-scale irrigation in the northern region of Zambia by 1) characterizing the simple weirs
structures, construction, and materials 2) studying the challenges of simple weirs, 3) assessing theeffectiveness of simple weir maintenance during and before the irrigation seasons, and 4) assess theimpact of the simple weir on small-scale irrigation development.
METHODOLOGY
Study Area and Data Collection
The study was conducted in Zambia’s northern provinces shown in Fig.1. Geographically, Zambia
lies in the tropics at an elevation of 1,200m above sea level with a sub-tropical climate due to itsⒸ ISERD

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latitude and high-altitude location. The climate in Zambia is characterized by three distinctive
seasons all year, dry and hot (August to November), dry and cool (May to August), and a wet rainyseason (December to April). Zambia is divided into three agroecological zones with Zone III,
covering the northern region of Zambia, receiving the highest amount of rainfall between 1,000 mm
to 1,500 mm per year (Brigadier et al., 2015). The rainy season increases both in intensity andduration from the southern region to the northern region. In Zambia’s northern region, surface
flowing water is sufficient to support dry-season irrigation.

Fig. 1 Location of Luapula, Muchinga, and Northern Provinces in Zambia
The collection of primary data was conducted through discussions and interviews with
agricultural extension officers, farmer groups, and simple weir users. The study reviewed theliterature on small-scale irrigation development, focusing on low-cost irrigation technologies in rural
areas in Zambia. The primary data used in this study was collected from 55 sites in three provinces.
The study area was clustered into three provinces and 55 simple weirs were randomly selected from
Luapula province 22 sites (72 participants), Muchinga province 15 sites (31 participants), andNorthern province 18 sites (69 participants). 172 simple weir users participated in the discussion in
Table 1. The data was collected between August 20th and November 30th, 2022.
Table 1 Location of simple weir sites, number of simple weirs, and users who participated
Province

Number of simple weirs andsites

Number of simple weir users
who participated

LuapulaMuchinga
Northern
Total

22
15
18
55

72
31
69
172

Simple Weirs Small-Scale Irrigated Agriculture
During the seven-month dry season, small-scale farmers resort to irrigation to supplement rain-fed
agricultural production. Vegetable growing is the common system of agriculture between May andDecember in rural areas in Zambia. This type of agriculture during the period is the principal
livelihood for the majority of the people in the region. Crops that are produced using simple weirirrigation include cabbage, tomatoes, onions, watermelons, carrots, and Irish potatoes. These crops
are generally irrigated and widely cultivated on sites supplied with river water diverted by simple
weirs.
RESULTS AND DISCUSSIONSⒸ ISERD

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Characteristics of the Simple Weir Types
In Zambia, simple river water diversion structures are usually constructed of simple materials ofpoles, thatch grass, and clay soil bunds (Food and Agriculture Organization, 2014). Although simple
weirs are generally constructed for one irrigation season, they are viable facilities. Farmers areusually advised to dismantle the weirs as a coping strategy to flood damage and store material to
avoid depletion of forest for the reconstruction in the following irrigation season. Figure 2 shows
four simple weir types that are conventionally used for irrigation and are part of improved methods
for small-scale irrigation (Bekele et al., 2006).

(1) Single-line weir: It
consists of a single
line of wooded poles
constructed across thewidth of a river. Thisweir type is suitable
for rivers which arewider and shallower.
It is recommended on
hard riverbed
foundations.

(2) Inclined weir: Thisweir has one mainpole placed
horizontally across thewidth of a river andsupported byriverbanks ofrelatively the sameheight. It is
recommended onrivers which areslightly deeper andnarrow with stony(3) Trigonal weir: The
weir consists ofseveral tripod stands
constructed withround poles. The
tripod stands arealigned across thewidth of the river toform a weir. This weirtype is suitable on
rocky riverbeds.

(4) Double-line weir:This weir type has twoparallel lines of poles
constructed across theriver, spaced at 0.20.5 m. The space
between the parallellines is filled with clay
soil to minimise water
loss by seepage.

Fig. 2 Characterization of simple weir types and constructions methods:(1) single-line weir, (2) inclined weir, (3) trigonal weir, (4) double-line weirSingle-Line Weir
Single-line simple weirs are constructed using round forest poles (0.8-0.1 m diameter) and adultwrist-size bundles of thatch grass (Fig. 2-1). A single row of poles is embedded vertically into theriverbed across the width of a river. According to available data, the intra-spacing of poles ranges
between 0.5 to 1 meter from each other across the river. The wooden poles are connected by purlins
tied across using tree bark strips. The weir is reinforced at the base of the pole line by ramming clay
soil. Thatching grass is used to reduce water seeping through the weir. The weir causes the waterlevel to rise upstream and diverted into the canal off-taking on its upstream side.
Inclined Weir
The inclined weir is constructed where the narrow and straight river section has a good formation ofriverbanks on both sides and relatively the same height. One pole (0.2-0.3 m diameter) is used as across member where slanted poles (about 0.1 m in diameter) are supported (Fig. 2-2). The crossmember pole is placed horizontally across the river to the preferred flood height and anchored by theriverbanks. The slanted fixed poles are approximately inclined at 600 angles to the river flow. The
slated poles are connected using the purlins and covered with thatching grass to minimize water loss
downstream. Clay soil is compacted at the base to provide anchorage and reduce seepage. The waterrises above the historical flood level and is diverted into the canal conveying irrigation water.
Trigonal WeirⒸ ISERD

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This type of weir is recommended on riverbeds with stones or hard rock foundations. A single tripod
is constructed using 3 by 2 m (approximately) long poles and tree bark strips. The three poles areconnected at the top of one end. The front with two long poles covered with thatch grass faces
upstream, the other pole shunts downstream to provide stability. Several tripods are constructed andlater aligned in a single line across the river to form a weir (Fig. 2-3). Water is prevented from being
lost through seepage using the thatching grass. Depending on the width of a river two or more tripods
can be erected across. During the rainy season, the tripods are removed from the river channel andstored for use in the following irrigation period.
Double-Line Weir
The double-line weir has two parallel rows of round poles placed vertically into the riverbed (Fig. 24). The space between the two parallel rows of poles across the river is approximately 0.2 to 0.5
meters (Food and Agriculture Organization (FAO), 2015). The space between the two rows of polesis filled with clay soil to reduce water loss through leakage. The double-line weir impounds flowing
river water in a small earth pond formed upstream. Water is diverted from the ponds and supplied
downstream to the fields. The double-line weir can also be used as a fishpond. Apart from divertingwater for irrigation, the double-line weir can also be used as a crossing point.
Analysis of Reasons for Adoption of Simple Weirs for Irrigation
Information and farmers’ experiences in Figs. 3 and 4, were collected from different sites between
2014 and 2017. Figure 3 summarises the reasons farmers expressed about the simple weir as atechnology for irrigation. The findings of this study included exploring the motivation and interestof the local farmers in simple weir irrigation. The results show multiple reasons presented in Fig. 3
for using simple weirs for small-scale irrigation development. The responses presented are based on
the information collected from the farmers. It was found that about 26% of the population of smallscale farmers using simple weirs stated easy construction, and 19% mentioned the use of local
materials of forest products like poles and thatch grass in the construction of simple weirs as amotivating factor. 15% of simple weir users’ interest in simple weir was about enhancing household
livelihood while 14% of the farmers stated agricultural activities throughout the year, a vital reason(Bjornlund et al., 2019). About 13% of the farmers expected improvement in the area irrigated whileother farmers stated a reduction in manual labor required to lift water for irrigation from the source
to the crops. The reasons given by farmers for adopting simple weirs for irrigation purposes
substantially varied. These responses were noted during the site visits and interviews. The responses
farmers advanced according to (Colenbrander et al., 2012) represent the solutions seen by farmers as
most promising for developing low-cost irrigation systems in rural areas. According to the responsesof the farmers interviewed, easy construction, livelihood diversification, and increasing land underirrigation have been the basis for adopting simple weirs in the northern region of Zambia.

Fig. 3 Farmers' responses on the adoption of simple weirsⒸ ISERD

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Analysis of the Attributing Factors to Stagnant Development of Small-Scale Irrigation and
Low Adoption of Simple Weirs in the Northern Region
Figure 4 summarises the responses of the farmers from the study sites with simple weirs used for
irrigation in the northern region province of Zambia. The responses varied with 18% of the farmers
stating weir breaching challenges, 17% of the farmers expressing weir leakages as their concern, and
27% of the farmers mentioning high labour demand for repair and maintenance as challenges(Dakpalah et al., 2018). While 5% of the farmers stated deforestation as more poles are required tobe harvested for construction from the forest. Fig. 4 Farmers' responses collected from simple weirsites.

Fig. 4 Farmers' responses collected from simple weir sites
Analysis of the Maintenance Activities of Simple Weirs by Farmers
Figure 5 shows the flood damage control strategy farmers practice at the end of the irrigation period(December). Based on the observation during the site visits, it was observed that about 7% of thetotal number of weirs were deliberately dismantled, 47% partially dismantled and 50% of the total
number of the weirs remained un-dismantled. Though dismantling of weirs during the off-season isrecommended as a flood damage control measure, it is not implemented on all simple weirs because
weirs are sometimes used to divert river water to supplement rainfall during dry spells.

Fig. 5 Maintenance activities carried out on simple weirs by farmers
Simple Weir Impacts in Promoting Small-Scale Irrigation in Northern Region
Figure 6 refers to the period between 2014-2016, in which 876 hectares were brought under irrigation
using simple weirs. In 2014, 2015, and 2016, the land expanded for irrigation in hectares was 292,
214.6, and 369.4 respectively. In 2016, there was a significant increase in the area brought underirrigation largely due to farmers’ increasing interest in simple weirs and farmer-to-farmer knowledge
sharing and skill transfer (Japan International Cooperation Agency (JICA), 2017).
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Fig. 6 Number of hectares irrigated by diverting river waterusing the corresponding number of simple weirs
CONCLUSION
This study focused on the simple weirs that have been introduced in the northern region of Zambia.
Simple weirs characterized by four types single, line, double line, inclined, and trigonal weirs are
increasingly becoming popular in small-scale irrigation development in the northern region rural
areas in Zambia. The use of simple weirs to divert river water for irrigation is relatively ‘’new’’ inZambia. The use of locally available materials of forest materials and the need to supplement
household income and food requirements has motivated the majority of small-scale farmers in thenorthern region to engage in dry season irrigation (May-December). Despite the promising results inenhancing irrigation water accessibility, there are still some structural challenges with simple weirs.
This study suggests the need for improvement in the construction and selection of construction
materials for simple weirs.
ACKNOWLEDGEMENTS
The authors would like to thank the Ministry of Agriculture staff in Luapula, Muchinga, and Northern
provinces of Zambia for their contributions to this study. Furthermore, we would like to thank theInternational Platform for Dryland Research and Education of Tottori University and are also gratefulto Japan International Cooperation Agency for its support.
REFERENCES
Bekele, Z. and Tilahun, K. 2006. On-farm performance evaluation of improved traditional small-scale
irrigation practices, A case study from Dire Dawa area, Ethiopia. Irrigation and Drainage Systems, 20 (1),
83-98, Retrieved from DOI https://doi.org/10.1007/s10795-006-5754-y
Bjornlund, H., Zuo, A., Wheeler, S.A., Parry, K., Pittock, J., Mdemu, M. and Moyo, M. 2019. The dynamics
of the relationship between household decision-making and farm household income in small-scale irrigation
schemes in southern Africa. Agricultural Water Management, 213, 135-145, Retrieved from DOI
https://doi.org/10.1016/j.agwat.2018.10.002
Brigadier, L., Barbara, N. and Bathsheba, M. 2015. Rainfall variability over northern Zambia. Journal of
Scientific Research and Reports, 6 (6), 416-425, Retrieved from DOI https://doi.org/10.9734/JSRR/2015/16189
Colenbrander, W., Kabwe, A. and van Koppen, B. 2019. Agricultural water management technology adoptionin Zambia, Findings of a household survey. Gates Open Research, 3, 12558, Retrieved from DOI
https://doi.org/10.21955/gatesopenres.1116188.1
Dakpalah, S.S., Anornu, G.K. and Ofosu, E.A. 2018. Small scale irrigation development in Upper West region,
Ghana, Challenges, potentials, and solutions. Civil and Environmental Research, 10 (3), 85-97, Retrieved
from URL https://iiste.org/Journals/index.php/CER/article/view/41817/43067Ⓒ ISERD

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IJERD – International Journal of Environmental and Rural Development (2023) 14-1

Food and Agriculture Organization (FAO). 2014. Irrigation techniques for small-scale farmers, Key practices
for disaster risk reduction for implementers. Rome, Italy, Retrieved from URL https://www.fao.org/3/i3765e/i3765e.pdf
Food and Agriculture Organization (FAO). 2015. Main water intake structures. Rome, Italy, Retrieved from
URL https://www.fao.org/3/i3765e/i3765e.pdf
Japan International Cooperation Agency (JICA). 2017. Technical cooperation project on community-based
smallholder irrigation in the Republic of Zambia. JICA, Tokyo, Japan.
Lautze, J., Phiri, Z., Smakhtin, V. and Saruchera, D. 2017. The Zambezi river basin, Water and sustainable
development (1st ed), ISBN 9781315282053, London, UK.
Osewe, M., Liu, A. and Njagi, T. 2020. Farmer-led irrigation and its impacts on smallholder farmers’ crop
income, Evidence from southern Tanzania. International Journal of Environmental Research and Public
Health, 17 (5), 1512, Retrieved from DOI https://doi.org/10.3390/ijerph17051512
Sakaki, M. and Koga, K. 2013. An effective approach to sustainable small-scale irrigation developments in
Sub-Saharan Africa. Paddy and Water Environment, 11, 1–14, Retrieved from DOI https://doi.org/10.1007/
s10333-011-0287-x
Xie, H., You, L., Dile, Y.T., Worqlul, A.W., Bizimana, J.-C., Srinivasan, R., Richardson, J.W., Gerik, T. and
Clark, N. 2021. Mapping development potential of dry-season small-scale irrigation in Sub-SaharanAfrican countries under joint biophysical and economic constraints, An agent-based modelling approachwith an application to Ethiopia. Agricultural Systems, 186, 102987, Retrieved from DOI https://doi.org/10.1016/j.agsy.2020.102987Ⓒ ISERD

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