Elsevier

Agricultural Water Management

Volume 98, Issue 11, September 2011, Pages 1719-1726
Agricultural Water Management

Water allocation and management in an emerging spate irrigation system in Makanya catchment, Tanzania

https://doi.org/10.1016/j.agwat.2010.07.017Get rights and content

Abstract

Although spate irrigation systems are risk-prone, they can be an important component for livelihood security in semi-arid areas. Spate uses water (flood water), which upstream users often do not require, as rainfall during these periods is more than sufficient. The use of this flood water for spate irrigation is therefore a good opportunity to convert water with a low opportunity cost to high value water. As more rivers are closing, due to socio-economic and climate changes, spate irrigation may become increasingly relevant in semi-arid areas. Spate irrigation systems pose institutional and technical challenges: collective action is challenged by complex upstream–downstream interactions between users within the system, and the high labour demands for regular reconstruction of temporary diversion weirs and intake structures. This paper describes a spate irrigation system in Makanya village, Tanzania that emerged in response to increased upstream water use. We use three of the four dimensions (hydrological, hydraulic and sociological) of spate irrigation proposed by Van Steenbergen (1997) to assess the Makanya spate irrigation system. The Makanya spate irrigation system has an organisational structure that is similar to the canal irrigation (furrow) committees located upstream, and effectively deals with the institutional demands of managing water in spate irrigation systems. Water allocation is reminiscent to the water sharing arrangements existing in the full irrigation system, which previously was in place at the site and in the high- and midlands of the Makanya catchment and therefore set this system apart from the traditional spate irrigation practice elsewhere. Technically, a major challenge is the reconstruction of the head works after each flood. Another aspect is the changes in the river bed. Flash floods carry sediments that deposit on the fields, raising the elevation of the irrigated land every year and making it increasingly difficult for the river water to enter the plots. Improving system efficiency through modernisation of the diversion and distribution structures in this case is not feasible due to the huge amounts of sediments delivered to the system each year. Instead investments in conjunctive use of groundwater could be the solution because it involves a relatively small intervention, minimises the physical disturbance of the system, and therefore is likely to respect the existing locally developed water management arrangements.

Introduction

Spate irrigation has been defined as a system diverting flash floods from the riverbed via canals to bunded fields that may be located some distance from the water source (Lawrence and Van Steenbergen, 2005). The word “spate” refers to flood water originating from episodic rainfall in the upper part of river catchments, which in the lower part is diverted from ephemeral rivers and spread over agricultural land. Spate is often laden with eroded material and thus nutrient rich. Potential relevance of spate irrigation stems from the fact that its water is generated from the hillside during storm events when water is often in excess and of little value at that time to the upstream users. It may therefore be hypothesised that a spate irrigation system uses water with a low opportunity cost for relatively high value purposes.

In areas where rainfall is insufficient and no perennial rivers exist, spate irrigation systems can be a key element in the production of crops needed for the sustenance of livelihoods, providing an enhanced level of food security. It is therefore no surprise that spate irrigation is one of the oldest irrigation methods in arid and semi-arid areas, for instance in the Province of Balochistan, Pakistan spate irrigation is believed to have existed as early as 3000 BC (FAO, 1987). According to Van Steenbergen and Mehari (2008), the area currently under spate irrigation is approximately 2.6 million ha and the number of economically marginal people directly dependent on spate irrigation range between 9 and 13 million. Spate irrigation is practised in West Asia (Pakistan, Iran, Afghanistan), the Middle East (Yemen, Saudi Arabia), North Africa (Morocco, Algeria, Tunisia), the Horn of Africa (Ethiopia, Eritrea, Sudan, Somalia) and East Africa (Kenya, Tanzania) (Mehari, 2007, Oudra, 2008, Van Steenbergen and Mehari, 2008). With increasing global population pressure on land and water resources, the population dependent on spate irrigation is expected to increase.

Despite its potential benefits, spate irrigation has not received the same attention from scholars, governments, non-governmental development organisations and the donor community, as has conventional irrigation systems relying on perennial sources of water (Van Steenbergen, 1997, Mehari, 2007). In a way, spate irrigation remains a ‘hidden’ source of livelihood security (Slater and Twyman, 2003) and is often overlooked in river basin management. In Tanzania, for example, the actual area currently under spate irrigation is unknown, although spate irrigation is being practised in five regions of mainland Tanzania, namely Kilimanjaro, Dodoma, Tabora, Shinyanga and Mwanza regions (Senkondo et al., 2004). In the last three regions spate irrigation is predominantly used for paddy rice production.

Tanzania is endowed with abundant renewable water resources (average renewable water estimated at 2291 m3 cap−1 a−1 in 2007), which are, however, unevenly distributed both spatially and temporally constraining agricultural and other economic development (URT, 2007). Annual rainfall varies from 1600 mm a−1 in the highlands to 400 mm a−1 in the lowlands and semi-arid areas of the country. The distribution of rainfall between the seasons varies significantly. Furthermore, Tanzania currently does not have sufficient installed storage capacity to buffer against the temporal variability of the climate, nor does it have the financial capacity to construct more water storage reservoirs. At present, there are 22 major storage reservoirs with a capacity of 0.5 million m3 or more (URT, 2007). Without expanding the country's storage capacity full irrigation potential may not be realised. Large water storage development, however, is financially and ecologically costly.

In this context, spate irrigation is a potential alternative way of improving food security in the country's semi-arid lowlands areas that receive flash floods in rivers that are most of the time dry (ephemeral). In addition, more rivers are becoming ephemeral, not only due to upstream developments that entail water abstractions (IUCN, 2003, Mul et al., 2006), but also because of the increasing variability in rainfall and thus river flow. Communities are presently adapting to, and will in future have to adapt to these changes, and could learn from existing spate irrigation techniques and practices.

This paper presents a case of a spate irrigation system in the lower part of the Makanya river, which is part of the Pangani river system, in Tanzania. The importance of this case study is that much information is available about biophysical processes and socio-economic developments in the catchment area upstream of the spate irrigation system (see e.g. Mul et al., 2009, Mul et al., this issue, Enfors and Gordon, 2007, Enfors and Gordon, 2008, Enfors et al., 2008). This allows the paper to corroborate the hypothesis that Makanya spate irrigation system converts water with a low opportunity cost into water that has a relatively high social and economic value. Moreover, it fits with the findings of Mul et al. (this issue) that upstream developments aimed at increasing and stabilising crop yields through river diversions have not significantly affected spate water availability downstream.

This paper presents findings of an ongoing research programme on institutions for water resources management in the Makanya catchment, Tanzania (Bhatt et al., 2006). The data is from a field study carried out to understand the emergence and development of spate irrigation system in the Makanya catchment. It focuses on the water management institutions and surrounding technical challenges that can inform decision making for improvement. Section 2 presents the case study catchment and briefly explores water usage in the catchment; Section 3 presents the research methodology and Section 4 describes the functioning of the Makanya spate irrigation system – in terms of biophysical and institutional processes. Section 5 discusses these findings by focusing on the hydraulic, hydrological and social constraints that the spate irrigation system faces, and possible ways for improvement. The concluding section summarises and recommends on the lessons learned for managing spate irrigation systems.

Section snippets

Study area

Makanya spate irrigation system lies at the outlet of Makanya catchment (300 km2), in the south Pare Mountains, mid-reaches of the Pangani river basin in Tanzania (Fig. 1). The catchment represents typical semi-arid to dry sub-humid rainfed agrarian conditions, and manifests strong signs of human induced land degradation resulting from high pressures on soil and water resources. Rainfall distribution in the catchment is bimodal with two rainy seasons. The Vuli season occurs between October and

Research methodology

Data for this paper are based on fieldwork conducted in Makanya catchment, between April 2007 and June 2008. Semi-structured interviews were held to investigate the present institutional arrangements, the water allocation structure and the management of the spate irrigation system. The interviews were held with spate irrigation farmers, village government chairman, and the village agricultural extension officer. Purposive sampling has been used to select farmers for interviews. This was done to

Results

Makanya village is located along the Moshi – Dar es Salaam highway and is home to about 6000 people (URT, 2004), comprising 1255 households. The inhabitants are mainly migrants from other parts of Tanzania who came in search of employment in the nearby sisal estate and gypsum mines. The spate irrigation system is indispensable to the majority of the population, although only an estimated 60 households actually own plots in the spate irrigation area (Mutabazi et al., 2005), many more people rely

Constraints and potential for improvement

The success of spate irrigation depends very much on elements inside and outside of the system to function (see the dimensions mentioned by Van Steenbergen, 1997). This section describes the following three dimensions: the hydraulic dimension, such as sedimentation issues affecting the cross-section of the canals and heightening the plots; the hydrological dimension which relates to the changing conditions in the upstream catchment and resultant changes in flood flows and frequencies; and the

Conclusion and recommendations

Spate irrigation is becoming more important in order to secure livelihoods in small rural communities. This paper describes a spate irrigation system, which emerged as a result of increased water usage by upstream farmers, who mainly use the base flow for supplementary and full irrigation (Mul et al., this issue). The upstream water users have limited capacity to harvest flood flows (Makurira et al., 2007), which currently still reach the spate irrigation system. These floods currently have

Acknowledgements

The work reported here was undertaken as part of the Smallholder System Innovations in Integrated Watershed Management (SSI) Programme funded by the Netherlands Foundation for the Advancement of Tropical Research (WOTRO), the Swedish International Development Cooperation Agency (Sida), the Netherlands Directorate-General of Development Cooperation (DGIS), the International Water Management Institute (IWMI) and UNESCO-IHE Institute for Water Education. Thanks are due to the Soil-Water Management

References (27)

  • P. Lawrence et al.

    Improving community spate irrigation

  • Mehari, A.H., 2007. A tradition in transition: water management reforms and indigenous spate irrigation systems in...
  • A.H. Mehari et al.

    Water sharing and conflicts in the Wadi Laba spate irrigation systems, Eritrea

    Community Spate Irrigation

    (2003)
  • Cited by (29)

    • Seasonal profitability of soil and water conservation techniques in semi-arid agro-ecological zones of Makanya catchment, Tanzania

      2021, Agricultural Water Management
      Citation Excerpt :

      It is mostly practiced in the floodplains with good soil fertility which eliminates the costs of purchase and application of fertilizer. Moreover, the residual soil moisture stored in the floodplains helps to buffer against the impact of intra-seasonal dry spell and reduces the need for frequent irrigation (Komakech et al., 2011). Hence, fertilizer was mostly applied for maize crop grown on terraces (95 %) and borders (59 %).

    • Adaptation strategies to cope with low, high and untimely floods: Lessons from the Gash spate irrigation system, Sudan

      2019, Agricultural Water Management
      Citation Excerpt :

      Mehari et al. (2008) emphasized the importance of flexibility, not only in view of variations in flow, but also to ensure equitable access and fairness of water sharing. Past research into spate irrigation studied local experiences with uncertain water supplies primarily in terms of infrastructure, flexibility in engineering design, and water-sharing rules (Abdelgalil and Bushara, 2017; Haile et al., 2011; Khan et al., 2014; Komakech et al., 2011; Ngirazie et al., 2015; Saher et al., 2014; Van Steenbergen, 1997), ignoring farmers’ and the water user association’s (WUA’s) own coping strategies. Effective strategies can greatly reduce the impact of climate variability and enhance local capacity to adjust and cope with the negative consequences (Cooper et al., 2008).

    • Using smart ICT to provide weather and water information to smallholders in Africa: The case of the Gash River Basin, Sudan

      2018, Climate Risk Management
      Citation Excerpt :

      According to Van Steenbergen and Mehari (2008), the global area under spate irrigation is approximately 2.6 million ha and an economically marginal population between 9 and 13 million are directly dependent on this system for irrigating crops. It is known to be widely practiced in West Asia (Pakistan, Iran, Afghanistan), the Middle East (Yemen, Saudi Arabia), North Africa (Morocco, Algeria, Tunisia), the Horn of Africa (Ethiopia, Eritrea, Sudan, Somalia) and East Africa (Kenya, Tanzania) (Mehari, 2007; Oudra, 2008; Van Steenbergen and Mehari, 2008; Komakech et al., 2011; Mehari et al., 2011; Steenbergen et al., 2011). With increasing population pressure on land and water resources globally, the number of people dependent on spate irrigation is expected to increase.

    View all citing articles on Scopus
    View full text