Spatial Distribution of Kumadugu-Yobe River Basin (KYB) Wetlands
The findings of this study revealed that wetlands of KYB are largely concentrated within the sedimentary formation of the chad basin. The wetlands are predominantly spread along river Yobe, Kumadugu-Gana, small tributaries, famous Hadejia-Nguru wetlands, Oases at the northern parts of the river Yobe and isolated pockets of ponds, as it can be seen in fig 2, plate 1 and plate 2. The wetlands fall within the political boundries of Borno, Yobe, Bauchi, Jigawa and Kano States within Nigeria. Some of Oases of Northern part river Yobe largely falls within the Diffa region of Niger republic. The concentration of the wetlands is largely within the sedimentary formation of the basin, where the relief is below 400m above sea level.
Hadejia-Nguru wetlands which include Nguru Lake, Marma channel complex, Dagona water sentinary are the major hydrological land mark of the basin, which is one of the Ramsar Convention on wetlands sites. The Nguru wetlands is formed by river Hadijia, Jamaare and Budum Gana seasonal flooding. The vast wetland site stretched from Auyo and Kafin Hausa local government areas of Jigawa State to Nguru, Bade, Karasuwa and Jakusko Local Government Areas of Yobe state. This confirmed the report of Blench (2013), that Hadejia-Nguru wetlands falls principally within Jigawa, Yobe and Bauchi States. As it can be seen in plate 5.1, the wetland is a vast jewel in a dryland ecosystem. Map showing the spatial distribution of the KYRB wetlands is presented in Figure 2.
Riparian wetlands are formed along the river bank of river Yobe and its tributaries. The vast flood plain wetlands of river Yobe are largely concentrated at Baderi communities (Dachia, Dagona, Girgir, Gashua and so forth), as it can be seen in Figure 2. After Gashua town, the wetlands form a linear pattern along the river bank up to Lake Chad. Thus there are larger concentrations at Gaidam and Abadam Local Govermnet Areas of Yobe and Borno State respectively. The flood plain wetlands are formed from seasonal flooding but the flood water dry within 3-4 months after the rainfall cession, as it can seen in Plate 3. Thus flooded areas harbour green plants and irrigated crops. Plate 2 and 3 present the flood plain wetland during rainy season and dry season respectively.
The flood plain wetlands of river Kumadugu-Gana are largely concentrated between Zidiwa village of Bauchi state and Dapchi town of Yobe State. The flood plain wetlands along river Kumadugu-gana form on crossing the geological divide between Keri-Keri formation and Chad sedementry formation. The wetlands along this river stretch from Gamawa Local Government Area of Bauchi state and narrowed along few meter around river bank buffer after Dapchi, as it can be seen in Figure 2.
The surface depression wetlands are the widely spread type of wetlands at the down stream part of the basin. They form by small surface flow around the pond. The relative flat terrain of the area enables the formation of the wetlands types. One of the surface depression wetlands site is presented in plate 4
The wetlands distribution map in Figure 2 and 3, revealed that the dry river that has its source from Zandar high lands in Niger republic and flows through Nguru wetlands joins river Yobe at Gaidam also has some wetlands along it banks. The drying of Zandar river affects the continuous flow of river Hadejia beyond Nguru. Oases are formed along the bank of the dry river as it can be seen in Figure 2. The Oases are largely spread at the Northern part of Yobe State and Diffa region of Niger republic. The larger concentration of the oases are within the political boundry of Niger republic specifically Gudumaria Distric of Diffa region. The most prominent Oases sites within the Nigerian boundry includes Tulotulo, Kaska, Sosono, and Maimalari among several others. Some schoolars refer these Oasis as Manga grassland Oasis. Plate 5 present the image of Tulotulo wetland site at Yusufari Local government area of Yobe state. Although previous studies on wetlands of KYRB largely focused on Hadejia-Nguru wetlands. The Oasis as part of the basin hydrological land mark was under reported.