Looking Further Downstream: Flood Based Farming

My previous posts have focused on small scale irrigation which can be carried out by small-holder farmers at a local level through the use of technology. This week, I will be discussing an alternative method, flood based farming, which does not require such use of technology.

(Source: econotimes.com)

Flood based farming (FBF) is regularly carried out across sub-saharan Africa, particularly in west Africa. FBF occurs in regularly flooded areas and essentially takes advantage of the natural flood patterns to grow crops throughout the year. There are typically two distinct seasons – the wet season and the dry season. During the wet season, rivers have high flow which leads to extensive flooding, allowing the growth of water-intensive crops such as rice, maize and millet. The remaining alluvial soil during the dry season is used to grow pumpkins and sweet potatoes (Barbier et al, 1998).

For many African countries, wetlands play a large role in the economy and provides fundamental (and somewhat sustainable) income for the local population. Surplus food that is produced is especially important during times of food insecurity. It is common for crop diversification to occur in the same field to spread risk as different crops have different ecological requirements. This is particularly common in growing rice where several varieties of rice are planted together to account for unanticipated low or high water levels (Adams, 1993). FBF also allows farmers to produce more crops in a year in comparison to other methods of irrigation as it maximises land use during both wet and dry season and can cultivate a large range of crops to better suit the agriculture market.

In more recent years, FBF patterns have been disrupted by the building of dams along rivers. Dams have been built along the majority of Africa’s rivers to store water which provides “insurance against uncertainty due to climatic variability” (Schultz, 2002). 70% of all dams use the stored water for irrigation purposes, though some are multipurpose in their uses. The construction of dams further upstream has had detrimental effects on FBF as river control reduces both the quality and quantity of water. The timing of flood patterns is especially important for farmers and with dams in place, they become less frequent and predictable (Adams, 1993). One thing to note is that the majority of these irrigation schemes only serve to irrigate a small amount of land, in comparison to the extensive floodplain that would otherwise be flooded.


The Case of Sokoto Valley

The Sokoto valley is located in north-west Nigeria and serves as an invaluable agricultural resource for local communities. The Sokoto river is dammed at Bakalori (see figure 1) to store water for the irrigation of 30,000 ha. The main purpose of the dam was to control extreme flooding in the lower floodplain region and an irrigation scheme was only of secondary importance (Adams, 1985). However, after further research, the irrigation scheme was expanded to become the dam’s primary use.

Figure 1: The Sokoto Valley

(Source: Adams, 1985)

Since the construction of the dam in 1974, the average discharge of the Sokoto river during 1977-1980 was 461Mm3 but pre-dam discharge reached around 750Mm3 (Adams, 1986). With the irrigation scheme in full flow, a reduction in both the duration and the regularity of flooding is clearly visible. In a study undertaken by Adams, it was found that local villagers in the floodplain were demanding greater releases of water in the wet season as many of the farmers relied heavily on FBF (Adams, 1985). The period of surface flooding during the wet season is crucial as soil moisture is fundamental for cultivation in the dry season.

In the Sokoto valley, rice is the most planted crop in the wet season with over 20 varieties to diversify risk. A few other crops are also grown which display different levels of flood tolerance including sorghum and millet. During the dry season, a larger variety of crops are grown including tomatoes, sweet potatoes and peppers (Adams, 1986). Cropping strategies were fine-tuned to allow for maximum yield. However, the Bakalori dam reduced flooding downstream and as a result, the dry conditions made it almost impossible to grow crops which were more water-intensive. Table 1 shows the change in plots before and after the construction of the dam. For all the dry season crops, there has been a distinct fall following the construction of the dam which has had adverse effects for the farmers as this is their source of livelihood.

Table 1 – percentage of plots under dry season plots

(Source: Adams, 1985)

It is clear that the farmers downstream are very knowledgeable in cropping and have a progressive level of adaptation. Irrigation schemes have hindered farmers from achieving their maximum yields and it seems as though Sokoto valley’s economy would be better off without the dam in place. The dam is an expensive to build and maintain and the irrigation scheme is set to irrigate only 30,000 ha of land. Given the present circumstances, it would seem that regulated flooding would be the best option in Sokoto valley. Farmers would be able to adjust their farming patterns and floodplain losses would be reduced.

The example of Sokoto Valley is unfortunately not the exception. For many FBF systems across Africa, they face the same issue of dam construction restricting flooding further downstream. The potential for FBF would be much higher had these dams not been constructed in the first place. The real economic benefits are often overlooked and as a result, farmers are often the ones who are most disadvantaged. With climate change, the future for flood based farmers remains unclear and it is up to those who are in charge to find solutions which are fair for all parties including the local farmers.