Johnson Adewunmi, a soil and water engineering professor at the Federal University of Agriculture, Abeokuta, led a team that conducted a dam study in Nigeria’s north-western region in 2004. He speaks with DAUD OLATUNJI of the Punch Newspaper on how Nigeria can best control the country’s devastating flooding.
Does Nigeria have enough dams?
Nigeria does not have enough dams. We are talking about dams either for irrigation purposes or for irrigation for over 200 million people.
Currently, how many dams does Nigeria have and where are they located?
The review study in Nigeria dams and reservoirs and safety assessment of 20 large and medium dams, 18 of which form the headworks of some of the Public Irrigation Sector Schemes, and the other two dams are the NEPA Dams of Kainji and Jebba on the Niger River. The list of the dams is spread over the five zones of the review and includes: in the North West, we have Bakolori in Zamfara State; Goronyo in Sokoto State; Jibiya in Kastina State; Tugan Kawo Swashi in Niger State; and Kubli and Zobe in Kastina State.
In the North East, we have Tiga, Ruwan Kanya, Hadejia Barrage, Challawa Gorge, Central, Cham, Dadin Kowa, and Kiri in Kano State. In the South East, we have Obudu; in the South West, we have Oyan in Ogun State. There are NEPA Dams in Kainji and Jebba, which are partly in Kwara and Niger states.
What is the current status of the dams?
Many of the dams are over 20 years old and under-utilised. The dams are not being monitored and very little information exists about their status.
These dams were 22 in number at the time this study was conducted for the Food and Agricultural Organisation of the United Nations. Specifically, the dams are 17 in number. In 2004, when the study was carried out, I was the team leader that studied the north-western part of Nigeria. There are 17 dams in total. Five more dams have been created between that period and now, and they are still counting. Recently, the Federal University of Agriculture, Abeokuta, just finished constructing a dam for the university community both for irrigation and water supply.
Are they put to use sufficiently? What uses can the dams be deployed for?
No, they are not. Primarily, the dams can be used for the generation of electricity for large dams like Jebba in Kwara, Shiroro in Niger and Tiga in Kano State.
Likewise, they can be used for water supply either in urban areas or rural villages by constructing earth dams. Thirdly, they can be used for recreation facilities and fourthly for irrigation purposes.
Can dam construction reduce flooding in Nigeria?
Yes, it can reduce flooding by about 75 per cent. In the event of excessive rainfall, the dam will overflow. In order not to damage the dam, an emergency spillway was created during construction, in addition to releasing more of the excess water from the main dam sluice gate. For example, when the Ogun River, which is dammed and called Oyan Dam, is excessively flooded as a result of unanticipated rainfall, releasing the excess water damages properties at the downstream end of the dam —Lagos State for those people that built their houses along the river path. The other example is the dam built within the Cameroonian territory. Whenever there is excess rainfall, the dam reservoir is released to protect the dam, and the consequence is the downstream effect on the River Benue axis. This is currently a yearly occurrence.
How does the release of water from the Lagbo Dam in Cameroon cause flooding in Nigeria?
Whenever there is excess rainfall, it exceeds the dam’s design capacity and the emergency spillway constructed for the dam cannot handle the excess water from the reservoir. The main stream gate of the reservoir is open to protect the dam structure and people living downstream of the dam. The consequence is the flooding of the downstream waterways. Whoever settles along the downstream area, either for settlement or for agricultural practice ends up losing their farm produce or their houses, as the case may be.
How can this be checked?
This can usually be checked by controlling water downstream of the dam in terms of designing a sufficient capacity canal that can take care of the excess water and, in addition to that, advising people living in the downstream area to relocate. Usually, during the reconnaissance survey (that is, preliminary studies feasibility study) before the dam is designed and constructed, villages downstream of the dam and, in some cases, upstream are warned to relocate to safer areas in case of future occurrence of the dam overflow. In most cases, the government usually settles these inhabitants in terms of allocating them to a new site and providing them with monetary compensation.
Talking about irrigation, what is the strength of Nigeria?
The Federal Republic of Nigeria lies between latitudes 40 10’ and 130 50’ North and longitudes 20 15’ and 140 45’ East, occupying an area of approximately 923,770 km2. During the year 2000, a study revealed that the total irrigable areas were 605,238 ha in both public and private sectors, while during the year 2004, the irrigable areas slightly increased to 624,408 ha in both public and private sectors, an increase of 19,170 ha. Going by this figure and considering the slow adoption of irrigated agriculture in the 21st century, Nigeria has a large expanse of land to practise irrigated agriculture but it is yet to fully cultivate even up to 50 per cent of the available land for irrigation. To put it mildly, less than 35 per cent of Nigeria’s irrigable land is under irrigation cultivation. Nigeria has enough strength and capacity in terms of land available and human resources.
Does Nigeria still need to continue with the known ways adopted by farmers for irrigation?
The answer is a capital “No.” Nigerian farmers do not need to continue the old traditional way of practising irrigation. The world has since moved from surface irrigation, which was what our farmers were already used to doing. The majority of our River Basin Development Authorities are practising surface irrigation, which depends on a lot of water before any farmer can break even. This surface irrigation requires a large volume of water. Presently, the world has shifted from surface irrigation to sprinkler, drip, or macro-drip irrigation methods. This type of irrigation requires technical skills to be efficient and consume less water. We need our extension agencies in the River Basins and the Ministry of Agriculture to teach our farmers these new techniques. Our surface water is being depleted every day as a result of climate change, as is our groundwater through boreholes here and there. Our farmers (or any big-time farmer) need to find an efficient new irrigation method that consumes less water.
From your experience, do farmers in the South need irrigation as their counterparts in the North?
Yes, farmers in the southern part of Nigeria need irrigation as much as their counterparts in the northern part of Nigeria. Previously, and even now, the majority of our dams were concentrated in the north. I will say more than 70 per cent of Nigeria’s dams are located in the North. This was possible because of our climate and weather at that time. In the northern part of Nigeria, they usually experience the maximum amount of rain in a year within four to five months of the year. In some cases, not up to five months. During this period, farmers in the north require more water for their crops to survive than in the southern part. In the south, we usually experience rainfall for between 9 and 10 months in a year. Most vegetation is almost green in the south throughout the year. Because of the effect of climate change, the period of our rain both in the north and south has changed considerably. Therefore, what the South needs at this time of climate change is what we call the supplemental irrigation method. This will require farming throughout the year, including in the north. We cannot predict accurately the time of rainfall again.
Irrigation and climate change: is there a link? What should farmers learn about climate change?
The changes in the pattern of rainfall within the last 15 years or so indicate that the time farmers used to plant or harvest is no longer feasible. The new climate regime will have to be studied seriously and communicated to the farmers in both the northern and southern parts of the country. Flooding has occurred in places where it has never occurred before as a result of the effects of climate change. Serious flooding in the north? Can you imagine that? This is where supplemental irrigation will have to be introduced to the farmers. For example, if you were planting your crop and the rain suddenly stopped, to be able to farm all year round, what we refer to as supplementary irrigation, has to be adopted so that the crop planted will die off. This normally leads to a lack of agricultural products and, consequently, drought or famine.
Some farmers still use their old knowledge to study climate change. What is your advice?
The university’s relationship with the town should be strengthened. This is where the extension arm of the university will have to meet the farmers for improved agricultural practices.
Floods have ravaged everywhere and there seems to be no end to this. How best can this volume of water be turned into an asset for farmers and others?
There is something we call “water harvesting techniques.” This involves designing or developing a shallow area or depression within your farm. This technique requires the excess water, known as flooding, to be intercepted (harvested) and stored in this depression as a mini reservoir. This water, captured during the rainy season, will be used during the dry period. Also, it can be used intermittently when there is a period of water scarcity on the farm. This will save the farmers from losing substantial farm produce.