**2. Study area**

Two river basins, with at least five consecutive hydrological years record, over the period 1958–2015 were selected. River selection are from Global Runoff Data Center (GRDC)'s [23] available collection of West African basins. Gauges of the rivers are located in North-central and North-east (**Figure 1**) of Nigeria. Besides, the location of the gauges covers the vast tropical savannah climatic region, which covers most of the country (west to centre Nigeria) and the Arid climatic region found in the North [24]. Climate change impacts in Nigeria has been identified as disastrous due to the country's vulnerability and deficient coping capability [25]. The consequences are evidenced in rising temperature, variable precipitation, sealevel rise and flooding, desertification and drought, altered water resources, and biodiversity loss [26]. Moreover, the ecological system, agricultural systems, and livelihoods that these basins support are susceptible to the reality of climate change. The selected basins are briefly described in **Table 1**.

**The Niger river basin:** is the longest catchment in West Africa. The Niger watershed stretches over an expanse of terrain that spans ten west African countries, covering an area of around 2,156,000 km2 , with nearly 1,270,000 km2 hydrologically active [27]. The Niger river comprises of different hydrographic regions uniquely identified by drainage and hydrological characteristics. The Guinea highland is the river source, flowing to the Sahara into Mali through the Inner Delta. From

#### **Figure 1.** *Study area map.*


#### **Table 1.**

*Description of selected rivers and gauges.*

the Inner Delta, it flows southeast, and join with its major tributary, River Benue and eventually enters the Atlantic Ocean by the Niger Delta within Nigeria [28]. 28.3% (424,500 km2), of the hydrologically active basin falls within Nigeria (the lower Niger) and stretches over 20 of the country's 36 states. Within Nigeria, the Niger river constitutes two major rivers (the Niger and Benue) and more than half of its major rivers. Approximately 60% of the Nigerian population lives in the basin area. 71% of over 100 million people inhabiting the Niger basin live in Nigeria [28]. Agriculture, particularly rain-fed agriculture, supports most of the inhabitants' livelihood and is therefore susceptible to impacts of climate variability. The gauging station on the Niger river in this study is Lokoja at the confluence of the river Niger and Benue.

**The Hadejia-Jama'are Komadugu-Yobe Basin (HJKYB)** is a combined basin of the Komadugu-Yobe river and the Hadejia-Jama'are River System located in the north-east part of Nigeria. The Hadejia and Jama'are river are the two main rivers of this basin that meet at the Hadejia Nguru Wetlands (HNW) to form the Komadugu-Yobe Basin [29]. The Hadejia river has its source in the Kano highlands, while the Jama'are river rises from the Jos plateau in Nigeria. The combined catchment of the

*Future Climate Change Impacts on River Discharge Seasonality for Selected West African River… DOI: http://dx.doi.org/10.5772/intechopen.99426*

HJKYB discharges into Lake Chad, and it is the major recharge into the lake from Nigeria. The HJKYB is one of the essential basins in Nigeria that support over 15 million people, which mostly rely on agriculture, fishing, livestock rearing, and water supply [30] for their livelihoods. An essential part of the HJKYB is the HNW which was the pride and joy of the north-eastern part of Nigeria for many years. The research site on the HJKYB is at the Gashua gauge station on the Komadugu-Yobe River, Bunga gauging station on the Jama'are River, and the Wudil on the Hadejia river.
