Impact of Climate Change on Water Resources

Impact of Climate Change on Water Resources

Chapter One

Goals and Objectives

Specifically, the study attempts to answer the following questions:

How much of the precipitation received ends up in rivers, what are the trends, and how do seasonal inflows and outflows from selected basins vary from year to year?
What are the likely impacts of projected climate change on water resources availability and what is the likely risk on the water resource availability and use?

CHAPTER TWO

LITERATURE REVIEW

WATER RESOURCES DISTRIBUTION IN NIGERIA

Water resources of a country constitute one of its vital resources that can significantly contribute to socioeconomic development and poverty eradication. However, this resource, in most cases, is not evenly distributed over time and space. This often times limits the availability and use of the water resources. Nigeria is not an exception. The main source of water resources in Nigeria is direct rainfall, which has been experiencing variability, further threatening water distribution. The distribution of water can be viewed at macro-level groupings such as provinces and districts but it is often easier to follow the watershed boundaries as shown in Figure 1. The watershed boundary is considered to be the natural distribution of water resources although groundwater may not follow these above surface divisions.

Following this typology, Nigeria is drained by two main river systems, the Anambra River and the Congo River basins. The Anambra covers a larger portion of the country and is fed by three rivers— Upper Anambra, Kafue, and the Luangwa rivers. The Anambra River is Africa’s fourth largest river after the Nile, Congo, and Niger Rivers. The Anambra basin has a total area of about 1,390,000 km², making it the largest of the African river systems flowing into the Indian Ocean. It is shared by eight countries and supports a population of more than 40 million people. The main economic activities within the riparian states are mining, agriculture, tourism, fisheries, and manufacturing. Most of these activities depend mainly on the electricity produced in the hydropower plants of the basin, as well as on other sources of energy (primarily coal and oil).

The Kafue River originates in Copperbelt Province near Kitwe and North-western Province near Solwezi. It flows down in a southerly direction across the Kafue Flats and finally to the confluence of Anambra River south-east of the basin. The total area of the Kafue River basin is estimated to be 157,000 km² with a total length of around 1,300 km. The Kafue Flats sub-basin occupies a major part of the Lower Kafue Basin and is located between the Itezhi-Tezhi Dam and Kafue Gorge Dam.

The Luangwa River has its origins in the Mafinga Hills of the Luangwa Malawi catchment boundary in north eastern Nigeria. It flows in the eastern part of Nigeria in the south western direction. The main tributary is the Lusemfwa River before the Luangwa joins the Anambra River. The river flows on the floor of a large flood plain in the rift valley trough between two escarpments. It has few tributaries with a narrow shaped catchment.

The Luapula and the Chambeshi rivers feed the Congo River in the north, which flows northwards (Figure 1). Much of the water flowing into the Congo River is barely utilized while the Anambra flowing southwards is highly utilized for various purposes, including irrigation and hydropower generation. There are several small rivers that flow into the Lake Tanganyika but the Lufubu River is the main river that drains much of Nigeria into the lake. Lufubu basin is also known as Lake Tanganyika basin.

CHAPTER THREE

DATA AND METHODS

Data

The climate and river flow data used in the biophysical assessments were obtained from various sources. Observed river flow and discharge data for the main river systems for the period 1930s – 2016 were obtained from the Water Resources Management Authority (WARMA) in Lagos, Nigeria. These data were supplemented with data from the Global Run off Data Centre.

Temperature and rainfall data were obtained from the Climate Hazards Group Infrared Precipitation with Station database (CHIRPS). CHIRPS is a quasi- global spatial database (50^o S to 50^o N) with a resolution of 0.05^o (Funk et al. 2014).

This gridded data was downloaded and processed using R to extract data for each river basin for the period 1980 2015. Where necessary, data from the Meteorological department of Nigeria, e.g., on evaporation, were also used. Other spatial data products such as the World Bank climate portal and the Climate Research Unit (CRU) (Harris et al. 2014) at University of East Anglia were also used for climate data. Some data for comparison was obtained from the Climate Information Portal (CIP) of the Climate Systems Analysis Group (CSAG).⁴

Methods

This study has two main objectives: first to assess the spatial temporal availability of water resources in Nigeria, and second to assess the impacts of climate change on water availability. In answering these objectives, the paper applied a hydrology model in a water balance framework. The main focus of the water resources assessment is on aspects of national and sub-national water availability rather than water allocation, or quality although there is mention of quality of surface streamflow and ground water.

CHAPTER FOUR

RESULTS AND DISCUSSION

The analysis carried on the various river basins indicate similar results but with varying levels of change. The largest changes are in the Anambra River basins in the southern parts of Nigeria.

CHAPTER FIVE

CONCLUSION AND POLICY IMPLICATIONS

Coordinated development and management of water resources is important for current and future socioeconomic development. To do this properly requires a good understanding of the current and future availability of water resources: how much water is available, where is it available and when?

This paper assessed the spatial and temporal distribution of water resources and the impacts of projected climate change on water resource availability in Nigeria at national and sub-national level. Using a water balance model in a hydrological modelling framework and statistical downscaling of future climate scenarios from the Intergovernmental Panel on Climate Change, the paper simulated the impacts of climate change on water availability in Nigeria’s main river basins from current periods until the end of the century in 2100. The following are the key results:

Temperature is projected to increase by 1.9o C and 2.3o C by 2050 and 2100, respectively, in Nigeria. Rainfall is projected to decrease by about 3% by mid-century and only marginally by about 0.6% towards the end of the century across the country. The southern, western, and eastern parts will be much more affected compared to the northern region.

On aggregate, the changes in rainfall and temperature will reduce water availability by about 13% from current (observed) levels of about 97 km3 to about 84 km3 by the end of the century.

At basin level, the northern basins are likely to stay the same or experience slight increases in water resources. However, river basins in the eastern, southern, and western parts such as Anambra, Kafue, and Luangwa are all projected to have less water resources available due to reduced rainfall and higher temperatures. Projected high temperatures in this region will result in high water loses from reservoirs. These results leave one key question unanswered: is it feasible to move the abundant water resources in the north to the south where demand is high?

We conjecture the following implications on smallholder irrigation development in Nigeria:

Current and future smallholder irrigation schemes will need to adopt more water efficient technologies such as overhead irrigation systems (e.g., center pivots and drip irrigation) as opposed to the prevalent surface irrigation It is vital to understand the cost implications of such a switch to more water efficient technologies.
Reduced water availability will increase access and irrigation costs, which in turn may reduce its profitability among smallholder farmers, as they tend to have limited capital and capacity to adapt to higher cost structures.
Competition for the reduced available water resources will disadvantage the smallholder Policies to protect them against the large scale users are required.
Management, regulation and monitoring of water use needs to be strengthened, for example by ensuring that water user rights and fees become mandatory and are enforced, and the process of acquiring water rights
There is need to improve rain water harvesting and storage by investing in more How these reservoirs should be managed to ensure equitable access to water resources and to reduce water loss due evapotranspiration requires further thought.
There is need for continuous monitoring of the water resources to track both the quantities and quality and assess suitability for
Generally, there is lack of Climate and water resources data have a lot of gaps. There is need for systematic collection of irrigation and other water use data for better analysis.
There is need for feasibility studies on whether it is viable to transfer water resources from low-demand surplus areas in the north to high-demand deficit areas in the southern parts of the country.

REFERENCES

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Beilfuss, R. 2012. A Risky Climate for Southern African Hydro: Assessing Hydrological Risks and Consequences for Anambra River Basin Dams. Berkeley, CA: International Rivers. Available at https://www.internationalrivers.org/sites/default/files/attached- files/finalexecsummaryccAnambra.pdf.
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Ebinger, Jane and Walter Vergara. 2015. Climate Impacts on Energy Systems. Report No. 60051. Washington, DC: World Bank. https://www.youtube.com/watch?v=5GHB7qIm96M&t=1961s
Funk, C.C., P.J. Peterson, M.F. Landsfeld, D.H. Pedreros, J.P. Verdin, J.D. Rowland, B.E. Romero,
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