The value of floodplains and how that's being threatened

In a similar way that I have illustrated the potential of groundwater as a source of water, I will use this post to discuss the value of floodplains as an environment. Floodplains already play a massive role in supporting the lives of many Africans. The Niger Delta for instance supports 550,000 people, such as through supporting 17000 hectares of rice (Adams 1993). There are also a variety of ways in which they can support human activities. During the wet season, fish will migrate towards the floodplain, supporting fisheries. At the same time the soil also tends to especially fertile for agriculture. These benefits have significant economic value, with the Hadejia-Nguru wetlands in North-East Nigeria providing between 849 and 1277 Nigerian Naira per hectare through agriculture, fishing and fuelwood. (Thompson and Hollis 1995). As in my other posts, I wish to highlight variability, as the benefits of the floodplain depending on location and as well as on socio-economic groups. In Kilombero Valley, Tanzania for instance, over 60% of "intermediate" wealth households rely on wetlands for fuel wood, compared to less than 50% for "better off" wealth households, while the proportion for poor households is under 60%, compared to over 80% in Bumbwisudi, also in Tanzania (Rebelo et al. 2010). Floodplains also play a crucial ecological role. For instance, the movement of water can determine nutrient transport, flooding, erosion and sediment (Rebelo et al. 2010). They can have less quantifiable benefits, such as by supporting groundwater recharge (Thompson and Hollis 1995) and I have already covered in an earlier post, just how valuable groundwater can be. 

Figure 1: A table showing the present value of benefits of the Hadejia-Nguru wetlands. (Thompson and Hollis 1995)

However, the value of floodplains is under threat. Hydrological projects, such as dams, for instance impact the flow of water into the floodplain, such as the timing and volume of flooding, which will therefore have ecological and socio-economic impacts. There has in particular been a rise in projects to expand agriculture within the floodplains, as a result of rising populations and efforts to increase food security (Rebelo et al. 2010). Analyses of such projects however have suggested that they may not produce the same level of value as the floodplain. The Kano river irrigation project on the Kano river, a tributary of the Hadejia was begun due to attempts to achieve self-sufficiency in food. Yet, the upper estimate for the benefits of it were 233 Naira per hectare- not even a fifth of the benefits of the Hadejia-Nguru wetlands (Thompson and Hollis 1995). This can be due to how such projects can end up having adverse downstream effects. The Bakolori dam in Nigeria for instance reduced the extent and depth of flooding and meant that some areas were to dry for rice but got waterlogged too easily to support dry-land crops. As such the area of rice reduced by 7000 hectares and dry season crops reduced by 5000 hectares (Adams 1993). Despite this, the complex ways in which floodplains can provide values also means that measuring the benefits is not straightforward. For example, an engineering study in 1987 suggested that benefits of the Manantali dam in Senegal through hydroelectric power generation outweighed flood-cropping (Adams 1993). However, a follow up study in 1991, stated that the benefits of the flood, especially with regard to fishing and livestock production, were underestimated and so actually the benefits of the dam were not greater (Adams 1993). 

Given the uncertainty of the benefits that these schemes can produce there is a need for improvement of the usage of hydrological and economic analysis to determine whether they are truly beneficial (Barbier and Thompson 1998). As was the case with community management and privatisation, large scale hydrological projects show how the current strategies in Africa regarding water and food do not always lead to improvements and do not sufficiently consider differences with regard to stakeholders. This emphasises, as I discussed in my last post,  just how crucial it is for Africa to adopt concepts, such as IWRM, that do address Africa's complexities.