ARTICLE

Impact of Climate Variability on Reservoir Based Hydro-power

Impact of Climate Variability on Reservoir Based Hydro-power
Generation in Jebba Dam, Niger State, Nigeria

Hadiza Muhammad Liman Peace Nwaerema Jacob Yisa

Department of Geography, Ibrahim Badamasi Babangida University, Lapai, Nigeria

ARTICLE INFO

Article history
Received: 12 January 2021
Accepted: 8 March 2021
Published Online: 30 April 2021

ABSTRACT

Keywords:
Evaporation
Hydro-power
Rainfall
Reservoir
Temperature

This study examined impact of climate variability on reservoir-based hydropower-generation in Jebba dam, Niger State of Nigeria. Data of rainfall,
temperature, evaporation, reservoir inflow and outflow and power output
for thirty-one years were obtained from Jebba Hydropower Station \[JHP\].
The Man-Kendall and Pearson’s Product Moment Correlation Coefficient
(PPMCC) were used to establish the influence of weather parameters on
the reservoir inflow and outflow. Findings showed increased electricity
generation during dry season than wet season. The highest annual mean
amount of the electricity generated was in 2016 having mean of 689.12
mwh, dry season (352.26 mwh) and wet season (336.86 mwh). Reservoir
inflow showed a negative trend with severe fluctuations in 1998 (1436.42
M3/Sec), 1999 (1581.08 M3/Sec) and 2010 (1641.08 M3/Sec) with a steady
increase in 2016 (1556.0042 M3/Sec), 2017 (1556.4242 M3/Sec) and 2018
(1635.7542 M3/Sec). The reservoir outflow pattern showed tremendous
and negative trend in fluctuation with increase in 1998 (1421.75 M3/Sec)
1999 (1581.58 M3/Sec) and 2010 (1641.16 M3/Sec) and a steady increase
in 2016 (1535.00 M3/Sec), 2017 1558.83 M3/Sec and 2018 (1632.00 M3/
Sec). Thus, rainfall and reservoir inflow had strong relationships with the
amount of power generated than temperature and evaporation. Therefore,
the government should increase the water carrying capacity of the reservoir
construction by storing water to be used during dry periods.

1. Introduction

Climate is the average atmospheric condition of a particular place at a particular time over a long period of time
\[1\] \[2\]
ranging from 30-35 years . Also, reveals that climatic
conditions of a geographic location will determine the
availability of water resources from 30-35 years. Rainfall,
evaporation and temperature have more influence and
affect hydroelectricity performance since they are inter-re-
\[3\]
lated with other elements of weather . It is predicted that

in the world, energy consumption will double between the
\[4\]
years 2007 and 2035 . Researchers have projected that
the population of the world will be above 10 billion persons around 2050 and will rise above 11.2 billion in the
\[5\]
year 2100 . Thus, it is very clear that the present population of people is severely demanding energy service
and water resources resulting from the rise in population.
However, the next four decades will witness pressure in
energy and water resources as various dams will influence
power demand and control water supply in some regions.

Department of Geography, Ibrahim Badamasi Babangida University, Lapai, Nigeria;
Email: [pnwaerema486@gmail.com](mailto:pnwaerema486@gmail.com)

* * *

However, evaporation, temperature, rainfall pattern alters global hydropower production. The changes in these
patterns are mostly caused by climate change. The rise in
demand for electricity will continuously put pressure on
electric power decision for countries, especially with the
\[6\]
increased pollution by the greenhouse gas .
\[7\]
According to temperature and reservoir inflow are

increased pollution by the greenhouse gas .
\[7\]
According to temperature and reservoir inflow are
also important in the generation of electricity; due to the
fact that rise in temperature will result in higher evaporation from water bodies thereby reducing the quantity of
available water. When the rate of evaporation is greater
than the rate of precipitation, it will result in water scarcity. Thus, this process needed to be investigated in a
drainage basin where hydroelectric power dam is usually
hosted by the reservoir as there is suspected loss of water
through evaporation and their effects in loss of water. The
phenomena of evaporation and water loss are very crucial
in understanding the amount of reservoir discharge and
energy supply in the study of dams. These have yielded to
the interest in the study of climatic systems and biophysical modifications of drainage basins in order to cope with
the problems of electric power generation and management.
However, hydropower stations are facing tremendous

ment.
However, hydropower stations are facing tremendous
challenges as a result of climatic change; communities,
companies and businesses are affected because of the
fluctuation of electric power. This has effects on smalland large-scale businesses, and, consequently the Gross
\[3\]
Domestic Product (GDP) of Nigeria. However, studied
weather elements, inflow of reservoir and their patterns
in Kainji dam of Niger State, Nigeria, where rainfall,
temperature, evaporation and inflow parameters were
considered, neglecting the effect of outflow on energy discharged. But in the case of this research, rainfall, temperature, evaporation, inflow and outflow were considered,
though they have an element of similarity but in different
locations.
Energy is one of the commodities in which the provi-

Energy is one of the commodities in which the provision of goods and services depends. Its availability and
consumption rate are economic index for measuring the
\[8\]
development of any community . In Nigeria, there is a
limitation to power supply from the national grid which
has adversely affected the economic and social development of the populace. This really necessitates the need
for decentralized power source as a viable alternative to
which hydro power schemes readily fit in. Major rivers
and dam development provide an enviable energy potential for the exploitation of hydro energy in Nigeria. The
problem of electricity generation in the country is on the
increase on a daily basis as both urban and rural dwellers
need electricity. Jebba dam is one of the major producers

of electricity in Nigeria though not enough to meet the
demand of the growing population; this is why the need
for the assessment of the water resources in some areas
becomes so important in order to meet internal and external demands. Ever increasing demand for electricity
has intensified the quest for generation per kw and for
an increase in production. The dam, river discharge and
turbines alone will not improve productivity if significant
deterioration of natural condition occurs. It is in the light
of this that this study is justified.
\[9\]
revealed that Africa and other developing countries

of this that this study is justified.
\[9\]
revealed that Africa and other developing countries
will incessantly have severe effects of climate change and
\[10\]
water resources. showed that Africa, especially Nigeria and other sub-Saharan countries will be knocked by
climate change phenomenon due to their high values of
climatic parameters. Generally, the effects of greenhouse
gases will affect solar intensity, rainfall, temperature, humidity, pressure and other variables of climate, thereby influencing reservoir discharge and electric power supply in
\[3\]
Jebba Reservoir . This study explores the effects of various climatic variables of rainfall, temperature, evaporation
and the inflow-outflow reservoir data to understand their
relationships in order to manage Jebba dam hydro-electric
power project in Nigeria. Therefore, this research focuses
on the impact of climate variability on reservoir-based hydro-power-generation of Jebba dam, Niger State, Nigeria.

2. Methodology

Data for reservoir inflow, reservoir outflow and amount
of power generated as well as climatic variables of rainfall, evaporation and temperature for the period of thirty
years (1988-2018) were obtained from Mainstream Energy Solution Limited, Hydro-Power Plant, Jebba. The annual mean variable was computed using simple statistics.
The amount of power generated during the rainy and dry
seasons within the last thirty-one years was analyzed by
getting the grand total seasonal mean of power generation within the study period. Man-Kendall analysis was adopted to understand the monotonic trend of rainfall,
evaporation, temperature and reservoir flow patterns and
displayed on the graph. The interactions of rainfall, evaporation and temperature patterns on the reservoir inflow
and outflow were determined using the Pearson Moment
Correlation Co-efficient in the environment of the Statistical Package for Social Scientist (SPSS).
\[Image: Im0\]

Figure 1. Niger State in Nigeria

(33.00^{0}\\mathrm{C})

The result in Figure 3 showed the trend in rainfall in
the study area which fluctuated over the years and the pattern showed gradual steady increase between 1988-1991
(79.99 mm, 93.92 mm, 94.24 mm and 121.90 mm respectively) and decreases between 1992-1994 (86.54 mm,
82.93 mm and 81.37 mm respectively). However, amount
of rainfall received in Jebba reservoir dropped drastically
in 2009 (77.81 mm). The amount of rainfall received in
Jebba reservoir was fluctuated throughout the study period. Thus, Figure 4 showed that the temperature of the
study area was on a steady increase between 1991 and
2005 with little fluctuations in some years and decreased
0
sharply in 2016 (33.00 C) with a sharp increase in 2010
0
having 36.00 C which could result from climate change.
It was shown in Figure 5 that the evaporation in the

36.00^{0}\\mathrm{C}

3. Results

study area for the time frame moderately fluctuated and
gradually increased and dropped significantly to an average of 16.16 M3/Sec in 2011. Also, the average evaporation for 2004 was 10 mm while the amount of power generated in 2004 was one of the highest with 328.33 MWH
recorded. High rate of evaporation was capable of reducing the amount of water in the reservoir, thereby resulting
to shortage in power generation. Figure 6 displayed the
inflow pattern in negative trends having different degrees
of fluctuations between 1990 and 2015, rise in 1998, 1999
and 2010 (1436.42 M3/Sec, 1581.08 M3/Sec and 1641.08
M3/Sec respectively) and a steady increase in 2016, 2017
and 2018 (1556.0042 M3/Sec, 1556.4242 M3/Sec, and
1635.7542 M3/Sec respectively).
The Figure 7 indicated the outflow pattern showing

The Figure 7 indicated the outflow pattern showing
negative trends in varying degrees of fluctuation between
1990 and 2015, rise in 1998, 1999 and 2010 at the rate of
1421.75 M3/Sec, 1581.58 M3/Sec and 1641.16 M3/Sec,
had stable increase in 2016, 2017 and 2018 at the rate of
1535.00 M3/Sec, 1558.83 M3/Sec, and 1632.00 M3/Sec
respectively.

Figure 3. Trends of Rainfall in Jebba Dam from 1988-
2018

Figure 4. Trend of Temperature in Jebba HEP Station
from 1988-2018

* * *

Figure 6. Trend of Reservoir inflow in Jebba HEP station
from 1988-2018

There were trends and fluctuations in the amount of
power generation in the study area. Figure 8 showed
the trend and variations in the amount of power generated in both dry and wet seasons. The lowest amount of
electricity was generated in wet and dry seasons in 1993
(182.00 mwh and 158.24 mwh) while the highest amount
of electricity was generated during the wet season in 2016
(352.26 mwh) and 1999 (352.26 mwh) in the dry season.
But the highest annual mean amount of the electricity generated was in 2016 with the average mean of 689.12 mwh
for both dry and wet seasons (352.26 mwh and 336.86
mwh).
The correlations between various climatic variables,

The correlations between various climatic variables,
reservoir inflow, reservoir outflow and power generation
were carried out at 0.05 level of significant. Table 1 indicated that the correlation between rainfall amount and
power generation was 0.370. This showed a moderate positive correlation significance between rainfall and power
generation which revealed that an increase in rainfall
could result in an increase in the amount of power generated and vice versa. The Table 1 still showed the value of
0.178 correlation between temperature and the quantity
of power discharged. This showed a weak positive significant relationship between temperature and quantity of
power discharged. This revealed that temperature does not
really affect power generation in the study area.
Furthermore, as still the Table 1 showed the correlation

reservoir inflow and quantity of discharged power were
correlated at 0.875. This showed a strong significant positive relationship. It revealed that a change in reservoir
inflow will surely affect the amount of power generated.
The Table 1 showed that reservoir outflow and power generated had correlation of 0.878. This also showed strong
significant positive relationship, indicating that change in
reservoir outflow would significantly affect the amount of
power generated.

Figure 8. Variations in amount of Power Generated in the
Wet and Dry seasons

ated in both dry and wet seasons. The lowest amount of
Table 1. Correlations between Various Climatic Variables,
electricity was generated in wet and dry seasons in 1993
Reservoir Inflow, Reservoir Outflow and Power Genera-
(182.00 mwh and 158.24 mwh) while the highest amount
tion
of electricity was generated during the wet season in 2016

| VARIABLES | PEARSON PRODUCT MOMENT |
| --- | --- |
| Power Generated Correlation(R) |  |
| Rainfall | 0.370 |
| Temperature | 0.178 |
| Evaporation | -0.268 |
| Inflow | 0.875 |
| Outflow | 0.878 |

The study has demonstrated that the trend of each variable (climatic and reservoir variables) for the period under
study is subjected to fluctuation, which could be as a re-
\[11\]
sult of climate change over the years. Similarly, studied
the impacts of climate change on the water resources of
Jebba hydropower reservoir. The study shows some no-

4. Discussion

\*Significant at 0.05 level table changes in the climate of Jebba hydropower station.
It reveals that in the past few years, rainfall and relative
humidity have exhibited negative trends in the area. This
indicates that climatic parameters have the tendency to influence reservoir characteristics. In the study the evaporation loss shows negative trends resulting from low relative
humidity. According to the result, there exist is a positive
impact of climate variables on reservoir water discharge.

Thus, statistical analysis for the amount of power generation reveals that there is increased electricity generation during dry season than the wet season, though the two
seasons exhibit fluctuations at different levels. This could
be as a result of the high surface flows toward dry season
\[3\]
period. This is in tandem with the findings of and other
scholars who show that months/period with higher inflow
is expected to have a high amount of power generation.
The study shows that since more inflow is being received
towards months of dry season it is expected that more
electricity will be generated in this period. Nevertheless,
the amount of power generated in September and October
is high and can be compared to the amount generated in
the dry season months. While the month of July marks the
period with the lowest amount of power generation with
the lowest average mean in the study area.
Moreover, the result of the Pearson Correlation Co-ef-

Moreover, the result of the Pearson Correlation Co-efficient revealed that rainfall, reservoir inflow and outflow
have a significant relationship with the amount of power-generated than other parameters. This means that, a
drop in the amount of rainfall or inflow will definitely
affect the amount of power-generation, which will con-
\[12\]
sequently affect the outflow. In the same vein, studied
various parameters that influence reservoir discharge in
Jebba hydropower. These elements include peak inflow,
storage balance, evaporation, minimum inflow, average
outflow, peak outflow, average inflow, reservoir level,
discharge and minimum outflow. The results of the cumulative contributions show that December has the highest
elements contributing to the explanations of electricity
generation. Generally, months of high runoff are known to
have lower numbers of elements contributing to electricity generation. This suggests that reservoir management
\[13\]
in dry period is more challenging. Considerably, investigated the impacts of decadal precipitation variations
on reservoir inflow, flood releases and pool elevation in
Fortcobb reservoir, at Central Oklahoma. The study shows
that watershed runoff, reservoir inflow and flood releases
are highly sensitive to decadal precipitation variations.
Yet, the only reservoir operation that appears to be impacted by decadal precipitation variations is the frequency
\[14\]
of flood release activities . So, it is known that high reservoir inflows during wet periods leads to an increase in

flooding that affects power generation.

5. Conclusions

Assessing the impact of climate variability on reservoir-based hydro-power generation in Jebba dam, Niger
State, Nigeria has revealed the extent at which climate
variables could influence hydro electricity generation.
The interactions of rainfall, temperature and evaporation
have shown that they are key factors to reservoir inflow
and outflow of water resources. The finding establishes
that the Jebba reservoir does have inflow in all seasons,
resulting from constant upstream flow from Kainji Reservoir which sometimes brings about flooding. The inflow
and outflow of reservoir which are determined by climatic
variables of rainfall, temperature and evaporation have
the capacity to influence electric power generation. The
study unveiled the trend and fluctuation of electricity
alongside the trends of climatic variables showing that
hydro electric power generation is a phenomenon of the
climate. The practice of climate change as a contemporary
global phenomenon which has strong influence on power
generation should be given adequate attention in order to
survive in the Nigerian hydroelectric sector. The Nigerian
government should review the current water resources and
drainage basin management framework that will consider
the present stage of development. Some of non-hydrological factors such as maintenance and spare parts problems,
inadequate funds, human resources, and policy issues
should be considered to avoid system collapse as in the
case of the faulted sixth turbine. Therefore, ability of the
government to improve the reservoir water capacity considering the current climate reality will accelerate electricity output during period of water scarcity.

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