Introduction

Enugu State is located in the south-east of Nigeria. It was wounded in 1991 on the basis of Anambra state and included such cities as Udi, Agani, Nsukka, Oji-River, Awgu, and Enugu. This state has borders with Benue state, Ebonyi state, Abia and Imo state, Anambra state, and Kogi state.

“Enugu” means “the top of the hill”. This city was the first city occupied by Europeans in 1909. This group, headed by Albert Kitson, have found coal deposits in the Udi Ridge. This discovery attracted the attention of Frederick Lugard, the Governor of Nigeria in 1914. Shortly thereafter, they organized first shipments of coal to England. As the result of the development of this industry, new big cities appeared, and they have been supported by a good railway system. In 1917, Enugu became a town that was strategically important for Britain.

Big companies, like United Africa Company and British Bank of West Africa, moved to the new city. This city was also quite important for British government regarding the influence on the whole Nigeria. This period of Nigerian history can be observed now in Georgian buildings and special roads made for white people. Today this area is reserved by the government.

Nigerian government consists of two levels, which are the local government and the state government. Enugu is a mostly agrarian state. However, 18.8% of its population works in trading, and 12.9% are service workers. Trading is mostly concentrated in urban areas. A small amount of people works in manufacturing sphere. There are a few markets with divisions in this state, for example, Electricity Supply and Ogbete Market. The Oji River power station supplies electricity to various regions of Eastern Nigeria. It is located in Enugu state, as well as Igbo of southeastern Nigeria. In 2006, 3,267,836 people lived here, and in 2012, its population grew by other 600,000.

The temperature in Enugu varies from 60 to 80 degrees Fahrenheit through the year, which is a quite friendly climate for everyone who likes spending time outdoors. This city is located 732 feet above the sea level, and it has good fertile lands, which is another feature that makes this place useful for agrarians. During the rainy seasons, the soil gets enough water, and the warm temperature allows farmers to grow crops all year round.

The Hottest temperature in Enugu state was 87.16°F during February which is the hottest month of the year, and the lowest recorded temperature was 60°F, in November. The highest rainfall was 2.18 cubic inches, in July.

Various regions of the country have their own peculiarities regarding relief and altitude, which causes significant differences among climate zones. The climate of semi-arid zones may considerably change every year, and even with seasons. According to Workneh (1987), rainfalls in these regions are irregular, unreliable, and small.

The position of the Inter Tropic Convergence Zone (ITCZ) determines the whole rainfall cycle in tropical regions of Africa, and in Nigeria in particular (Griffiths, 1971). Differences in rainfall patterns are also determined by seasonal changes and differences in elevation. Yilma et al. (1994) note that entire Nigeria is characterized by variations in rainfall patterns. In some regions, rainfalls occur during the whole year, while other regions receive only seasonal rainfalls. Thus, these regions often need good irrigational systems. Rainfalls in different regions demonstrate temporal variability, which has an impact on water supplies, environment, agrarian production, urban planting, transportation, etc. All these things are of key importance for the country and its people. Such variability is the main cause of floods and droughts. In regions with high year-to-year variability, people suffer from natural disasters more often. Obviously, damage from droughts and floods cannot be avoided, but Nicholls (1980) notes that forewarning is quite useful under such conditions. The whole economy of Nigeria depends on rain cycles, and the whole country often faces floods. Natural disasters constantly worsen the quality of the water, food security, and energy supplies. These factors are the main obstacle on the way to a productive development and reduction of poverty.

Studies of physical features of rainfalls, as well as statistics on rainfalls in Nigeria, formed a basis for prediction of natural disasters related to rainfalls. Rainfall forecasts are very important for the agriculture sector, and so for the whole economy of Nigeria. Meteorologists use stochastic methods, particularly methods of series, to model certain hydrologic events. Utilization, as well as other associated problems, can be solved only with access to the information on rainfalls, including data on distribution, variability, frequency, and quantity. Correct estimation of variability creates a strong basis for risk management and decision-making, as well as for the proper use of water sources. In this study, we used Box-Jenkins methodology in order to build AIRMA model. This allows us to analyze data from Nigerian Meteorological Agency and assess patterns of rainfall in Enugu state.

Climate and Weather

Weather and climate are not constant things, they change with time all over the earth. Weather characterizes the atmosphere during short periods of time, and climate is the behavior of the atmosphere during longer periods. Variability is the basic characteristic of climate. Studying fluctuations of climate, we can investigate how these fluctuations happened in the past, and also understand what effects they will cause in the future. Rainfalls are results of condensation of water in the atmosphere, just like snow and frozen rain. Water is extremely important for all kinds of life on earth, as well as for agricultural production. According to Yilma et al. (1994), Nigeria always balances between two extreme conditions: droughts and floods.

Rainfall Characteristics

Rainfalls vary by such characteristics as seasons, latitude, distance from the sea, topography, and elevation. Being located north of the equator, Nigeria is in the humid tropical climate zone, which is characterized by wet and hot conditions, formed under the influence of inter-tropical convergence zone, which is located south and north of the equator.

Generally, Nigeria experiences a decrease in rainfalls, though coastal regions face the opposite process. The duration of rainfalls changed from 50-360 days per year during 1993-2003 to 30-280 during 2003-2013. This tendency destabilized the ecological situation in this region, and affected vegetation, especially in northern areas. Changes in rainfall patterns are followed by increased erosion and coastal flooding in the coastal, east and north regions of Nigeria.

There are high temperatures in Nigeria all year round. Given that temperatures don’t change considerably, rainfalls are the most important factor of season differentiation. Climatic changes in the country depend on the movement of ITCZ, and they are determined by two huge air masses: the Tropical continental (Tc), and the Tropical marine (Tm). The first one is dusty and dry, and it comes from the Sahara Desert. The latter one comes from the Atlantic Ocean, and it’s wet.

Thus, Nigeria can be divided into a few climatic zones:

  1. the middle-belt, hot and wet tropical zone;
  2. the humid sub-equatorial zone;
  3. the moderated sub-temperate zone;
  4. the hot tropical continental zone.

Effects of Rainfall

Extreme events associated with rainfalls cause a significant negative impact on infrastructure, ecology, and agriculture. Socioeconomic activities like water supply, agriculture, healthcare, and power generating depend on rainfall patterns. This is a reason why Nigerian economy is completely dependent on rainfalls, and they have an impact even on the national currency.

Drought.Droughts are hazards of nature. Effects of draughts vary in different regions, which makes draughts a difficult phenomenon to understand. If there was no rain during six days in Bali, it is considered draught. Meanwhile, in Libya, it won’t be a draught, since this country receives less than 180 mm of rainfalls per year.

Flood.According to Osti et al. (2008), floods are most common natural disasters in both developing and developed countries. East Africa experienced a number of massive floods during the period from 2000 to 2008. Ethiopia suffered from these episodes most of all, since geographical features of this country make it quite vulnerable to floods. These disasters caused a significant damage to infrastructure, health system, livelihoods, and services in Ethiopia (FDPPA, 2007). Usually, floods occur here from June to September, during the rainy season.

In Enugu, the flood issue is as important as in other regions of Nigeria. Floods are especially dangerous for people who live in lowlands. Flood disasters cause damage to the cost of living, environmental resources, and livelihoods in Enugu. Since Enugu state consists of river basins, valleys, hills and mountains with steep slopes, this region constantly suffers from soil erosions caused by floods.

Soil Erosion. Soil erosion is a movement of soil. It is mostly caused by rainfalls that strike the ground. It’s a significant danger for farmers, since their high-quality fertile soil can be washed out with every rainfall. Other negative effects of erosion include washing out roads and weakening of bridges. Vegetation helps decrease amounts of eroded soil, but the rate of eroded soil increases. This means that soil erodes faster than it is produced. This fact caused a significant loss of crop production. Along with erosion of fertile soil, layers of infertile soil were moved on croplands that were fertile.

Aim and Objectives of the Study

This study considers rainfall patterns in Enugu state based on researches of the past fifteen years. It also analyzes data from Nigerian Meteorological Agency.

Significance of the Study

Knowledge of rainfall patterns is very important, because it can be used in solving subsurface water problems and improving the management of water resources. Given that countries like Nigeria are dependent on the agricultural sphere, the information on water requirements in various regions, availability of water and other seasonal features of climate is extremely important for the productive development of the economy, and agricultural sector in particular. Under conditions of climate change, we have to implement new strategies aimed to decrease social and economic damage from natural disasters. The correct assessment of past rain cycles helps better understand risks and develop new mitigation systems. Therefore, weather forecasting and rainfall forecasting, in particular, are very important for all regions of Nigeria and for the entire country.

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