Hadejia-Nguru Floodplains

Hadejia-Nguru 8. floodplains Hadejia-Nguru is famous, not so much among ecologists or conservationists, but among socio-economists. It fi g- ured prominently in an extensive study on the hidden, economic values of wetlands. The costly irrigation schemes, made possible by construction of upstream dams, have been computed as economically just feasible: its net value amounted to 20-31 $/ha of irrigated land, or 0.03-0.04 $ per million litres of water. This calculation was inaccurate, however, because it disregarded the reduction of the river fl ow and the consequent loss of income for fi shermen, farmers and other people living downstream. Barbier & Thompson (1998) concluded that “the increased irrigation benefi ts can only partially replace the lost agricultural, fi shing and fuelwood values from reductions in fl oodplain downstream” and therefore “further expansion of large-scale irrigation should be avoided”. However, the political reality is that “the focus on birds that constitutes one element of the HNWCP (Hadejia-Nguru Wetland Conserva- tion Project) has proven an important stick to beat almost any project set up in the region. Typically, Government offi cials accuse externally funded programmes of being interested only in European birds and not in the welfare of resident populations. Such dogma has no empirical support from the published and grey literature emerging from these projects but as political rhetoric it plays extremely well to a Nigerian audience”. 1 1138 Livvinng onn thee edge Hydrology A NIGER Lake Chad Nguru Gashua Yobe river The Hadejia-Nguru floodplains are situated in the Komadugu-Yobe Basin in NE Nigeria, along the fringes of the Hadejia and Jama’are NIGERIA Hadejia rivers (Fig. 83). The rivers rise on the Jos plateau and the hills around Katagum Kano Hadejia river Kano. In 1960-2000, the annual rainfall in the catchment area varied Challawa Gorge between 250 and 850 mm. The rivers are seasonal, with little flow dam Tiga a'are river dam in the dry season between October and May. Depending on rainfall, Jam the floodwater level rises between 3 and 5 m from early July to mid site of Kafin September, followed by gradual decline from October to February. Zaki dam The maximal extent of flooding in September once was as much as 2500-3000 km2 in the wet 1960s and early 1970s, but declined 20 km to 700-1000 km2 thereafter, only 300 km2 being flooded in the dry Jos disaster year of 1984 (Fig. 84). The annual extent of the Hadejia- B Nguru Nguru floodplains varies in synchrony with the flooding of the Inner Gashua Niger Delta. 2 Upstream of the Hadejia-Nguru floodplains, there are 20 dams, of which in the Upper Hadejia River two that are large. The Tiga dam (1974) was constructed to provide water to the city of Kano and to source the Kano River Irrigation Project (670 km2 planned, of which by 2000, 140 km2 had been completed). The Challawa Gorge Dam (1992) was built to facilitate irrigation 200 km downstream in the Hadejia river Hadejia Valley (125 km2 planned, of which 75 km2 had been realised Hadejia in 2000). Both reservoirs are large compared to the natural annual flooded in 1987 flow of the Hadejia River, even when the wet 1960s are taken as a + flooded in 1974 Keffin Haussa river reference point (2.7 km3 at Wudil): the storage capacity is 1.99 km3 Jama'are river 5 km for the Tiga (but for safety reasons reduced to 1.43 km3 in 1992) Katagum and 0.97 km3 for the Challawa. The Tiga dam reduces the peak Nguru Gashua flow of the Hadeija River by 30-40% (Goes 2002). As a consequence, C the Hadejia-Nguru lost 200 to 500 km2 of their floodplains (Hollis & Thompson 1993). The relative impact was highest in dry years. In 1984, for instance, the flooded area was only 300 km2 when otherwise 600 km2 would have been inundated had it not been for the Tiga dam. The water stored in both reservoirs is partly released in the dry period. Under natural conditions, only 2% of the annual runoff would have passed the town Hadejia between November and Hadejia May, but this increased to 16% once the Tiga Dam was on line, and to 32% after the Challawa Dam had been completed (Goes 2002). At present, the Hadejia-Nguru floodplains depend largely on the runoff of the near-natural Jama’are River, especially since the KKatagumatagum hydrological interventions in the Upper Hadejia. The proposed 5 km construction of the Kafin Zaki Dam, intended to facilitate a large irrigation scheme near Katagum, will have a considerable impact on flow of the Jama’are River. Fig. 83 The Rivers Hadejia, Jama’are and Yobe in NE Nigeria with the The hydrology of the Hadejia-Nguru wetlands has changed Challawa and Kafin Zaki dam is planned (map at top). The flood extent markedly in the aftermath of dam building. Water management of the Hadejia-Nguru floodplains is shown on map, middle, for years of the two newly created reservoirs reduced peak flood level, but with high (1974) and low river discharges (1987). From: Hollis et al. increased water level in the dry period. Seasonal wetlands have (1993). The Google Earth satellite composite shows the same area as become much smaller, to be replaced by permanent marshes the top map during peak flooding (24 September 2003). Note the parel- densely vegetated by Cattail, which caused blockage of the Hadejia lel (NE-SW) ridges of fossil sand hills between which the rivers meander, River in the floodplains, thus further enlarging the extent of stagnant and the dry floodplains along the Kafin Hausa, in the past normally water-covered even in relatively dry years. Hadejia--NNgguru flooodplains 139.

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