Small-scale v Large-scale

First of all, what is irrigation? Irrigation is the controlled amount of water to plants at timed intervals, depending on the plant’s needs. In developed countries, a common type of irrigation are lawn sprinklers systems, often seen in parks and golf courses which turn on automatically using an irrigation controller, in less developed countries irrigation can be as simple as ‘surface irrigation’ (see figure 1) where gravity distributes the water and there is no technology involved.  

Figure 1, surface irrigation

In this blog post, I’m going to discuss two types of irrigation; small-scale irrigation & large-scale irrigation and and give examples of schemes which have succeed and failed. In Westernised countries large-scale irrigation is prevalent, and incredibly efficient due to technological advancements, but Africa lags behind as it has the lowest agricultural productivity in the world, so is large-scale irrigation the answer? Africa has an abundance of potential for irrigated land, the IFPRI discussion paper states that Africa could increase its agricultural productivity by 50% if adequate irrigation schemes were employed, which would make a substantial contribution to food security, especially during periods of drought. So why not use more large-scale schemes?

A brief history of irrigation in Africa

During the first or second millennium BC irrigation in SSA was used predominantly during wet season flooding and rainwater harvesting. From BC until independence most SSA countries used SSI for agriculture, however post-colonialism (1960s+) many SSA countries were given large aid budgets to develop large-scale irrigation projects in order to boost development. However large foreign debts also accrued during this period, so although large-scale irrigation expansion had occurred, these debts forced agricultural budgets down, and the maintenance of these irrigation projects declined. This refocused attention back to small-scale irrigation schemes which are cheap and easy to maintain, highlighted by the statistic that 95% of Africa’s crops today are still rainfed.

Large-Scale Irrigation (LSI)

The major advantage of irrigation is a continuous supply of water to plants, even during the dry season. As rainfall in Africa is sporadic and temporal, being able to store water and use it later when needed is important. This will increase in importance as climate change intensifies extreme weather events, making droughts and floods worse, so irrigation is essential not just for increasing, but maintaining food security.

While this sounds all lovely, LSI in practice, is riddled with problems in many African countries. For example, the Ngezi mamina irrigation in Zimbabwe was built as part of aid project in 1994. Since construction the project has failed to perform well as farmers were not initially consulted about the scheme and have therefore been reluctant to take over the responsibility of running the scheme, complaining that the design was poor and they wouldn’t have approved of the project in the first place. Some key takeaways from this failure:

1)    Farmers need to be consulted during project planning, not just treated as beneficiaries

2)    Only projects that have been built to a high technical standard should be transferred to farmers, otherwise problems will ensue

3)    Governments need to produce regulation and strategy for the transfer of LSI schemes to farmers

Additionally LSI schemes such as these often deplete local water sources used for sanitation, hygiene and drinking which can negatively affect quality of life and increase the prevalence of disease.

Small Scale Irrigation (SSI)

SSI refers to the management and supply of water for an area of land no bigger than 10ha. It is increasingly being recognised that small-scale irrigation schemes are lower cost and often more efficient than large scale irrigation schemes in Africa. Studies have shown that traditional farming methods and indigenous technical knowledge relating to SSI often outweigh large industrial size irrigation projects. But why?

First of all, the initial cost of SSI is lower, a treadle pump for example costs from $20 - $100 which is affordable, and if farmers can grow one extra crop in the dry season, this results in more profit which can then be spent on further irrigation.
Kenyan agriculture is a prime example of how SSI has been successful in increasing irrigation potential. Farmers in Kenya use a mix of SSI techniques, such as rainwater harvesting, bucket irrigation, treadle pumps and motorised pumps. Inexpensive pump sprinkler systems have been profitable investments for horticultural crops and local ‘Jukali’ sprinkler units are used by farmers to tap into the piped systems for additional sprinkler systems. A local NGO called Approtech redesigned a treadle pump into a pedal pump which is lighter and more portable which they sell for $70 and is used mostly by smaller, subsistence farmers to expand their irrigation plots by 50%. This pump was so popular that within 2 months demand had outstripped supply and Approtech had to raise production capacity.

Successful SSI project in Tanzania

The Iganjo Irrigation scheme was started in 1967 as a private farmers initiative. Originally it consisted of an 800m-long earth canal and a weir made of stones and sand-filled bags. In 2006 the Iganjo farmers secured government funding to replace the sand and stone weir with cement, and were able to line 75% of their canal.

Today the Iganjo farmers benefit from an aqueduct, 4 culverts and 2km of lined secondary canals. The scheme supports 1,016 farmers and outputs for crops such as potatoes, tomatoes and peas has almost tripled. So why has this scheme succeeded?

1)    The scheme was farmer-led, the farmers had a history of practicing irrigation and sought government-support instead of the government deciding what irrigation the farmers should use

2)    Proximity to market, Iganjo is only 16km to Mbeya city, so they are able to easily sell their crops and save 20% of profits to reinvest in the scheme

To conclude, while there is definitely potential for Africa to increase its irrigation potential using LSI, the above case study demonstrates that Africa should not be wholly dependent on LSI due to its shortcomings. SSI schemes have much untapped irrigation potential and it is now essential that African governments and institutions make supporting SSI a priority if they want to ensure food security for their nations.