Engineer Babagana Zanna was the Managing Director of the Chad Basin Development Authority (CBDA) from 1988 to 1995. He was also a senior officer at the Authority when the original idea of the Alau Dam in Borno State was conceptualised. The dam recently had an issue that led to a serious flood which submerged more than half of Maiduguri, the state capital, with devastating impact on lives, public and private buildings. In this exclusive interview, Engr. Zanna said the integrity of the Alau Dam, when it was constructed was not in doubt.
What will you say about the incident at the Alau Dam, as someone who is from Borno State, who knows the terrain and the concept of the dam?
The unfortunate incident due to the overflow of the Alau Dam is something that had happened earlier in 1994. I think it’s a similar cause that resulted in the breach of the dyke. And I want to at this point, make it clear, that it is not the actual dam per se that was destroyed. Dams have levees/dykes to provide additional protection in the event of rising water levels. If these levees are not strong enough, they can fail instead of the dam itself. This is what occurred in 1994.
In 1994, we were monitoring the dam almost daily. There’s a maximum water level that must not be exceeded, the spillway should be opened before reaching that point. The spillway is a gate that releases water in large quantities down the river channel thus reducing pressure on the dam. 1994 was a very wet year, and I alerted the then military administrator of Borno State at the time that the dam was reaching its peak and we needed to open the spillway gate. He suggested we visit the dam and its surrounding area to access the situation, so we toured the accessible parts of the Alau area on a Thursday. It rained all day and we were drenched. During the visit, I informed him about the danger of people farming along the levees, the levees were compacted earthwork at that time, and small canals made by farmers weakened them. These are the spots that would break when water pressure increase. Unfortunately, the breach occurred exactly where I had cautioned them.
Eventually the dam was reconstructed with concrete material, which has stood for the last 30 years.
Was there collateral damage in 1994?
Maiduguri was flooded, but not like the flood of September 9th, 2024. This time around, from google map and the videos I have seen, I think almost 70 per cent of the city has been inundated. The city of Maiduguri is located on a flat area of land, so it’s very easy for the flood waters to spread easily and widely. The second point is, in the 60s, the local authority built many small and large concrete drains to channel storm water in to the Ngadda River which flows through the city. These drains were designed to carry rainwater and storm runoff into the river. At that time, the river channel was well-defined, with little silt build up nor illegal structures obstructing it. However, when the recent flood occurred, the force of the water was so great that it was flowing back up through the drains, impacting streets and homes.
So, it had been blocked by siltation somewhere?
No, not completely. The rains washed away some of the debris at the beginning of the rainy season. It’s the water from the flood that is now moving back up the channels.
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Assuming those channels in the town that feed into the river were okay, would the flood have happened?
Yes, because the city is flat, the flood water would still have spread to many areas. You cannot create barriers to fully stop the backflow. For example, Dubai is a very well planned and relatively new city, yet when it experiences even a small amount of rainfall, cars and other areas become submerged because the water has nowhere to go. The flat topography and lack of sufficient drainage systems contribute to the flooding.
There is this fear that what happened in Alau is likely to happen in other places. What is your take on this?
I hope not. What’s interesting is that, I worked briefly in Kano, where the late Audu Bako, constructed dams. There was a strong focus on monitoring the rivers, particularly in the rainy season. There were hydro metrological stations and river gauges in place. Every day, someone was responsible for measuring the water level; which provided a good indication of the water volume flowing downstream.
If the river level was high, they would consider opening the gates to release water, and toward the end of the season, they would close the gates to capture the remaining inflow, potentially filling the dam. It’s important to ensure that the dam isn’t near full at the start of the rainy season. That way, there’s enough capacity to safely store the tail end of the inflow. There is a maximum water level for rivers, and once that limit is reached, flooding is likely, though it can be managed. By placing sandbags and temporary barriers at vulnerable points, the risk of flooding in those areas can be reduced. It’s possible to predict which sections are most prone to flooding and construct levees in advance. However, this can be quite costly. The necessary resources and equipment must be readily available. So, in the absence of dedicated flood control systems, permanent structures should be built to provide long-term protection.
There is this debate; who owns Alau Dam?
This dark area on the downloaded map (showed to us) represents the water body. It’s from the river where the Alau dam is located, commonly referred to as Gambole. The river used to flow through Maiduguri, winding its way through the city and exiting toward Jere. Historically, this region has been a rice-growing area, as paddy rice requires substantial water. The river floods the surrounding plains, creating the ideal conditions for rice cultivation.
The Ngadda River flows for only five to six months each year, and once the rainy season ends, it completely dries up. To prevent water shortages for any large-scale irrigation project, it’s essential to store the river’s water. This makes constructing a dam necessary for effective water storage.
When the river basins were established in 1973, most of the investment of the CBDA was in New Marte area, near the Lake Chad. The CBDA looked at other feasible locations for irrigation projects, but ultimately the Jere Rice Bowl Scheme was identified in the Jere area. It was proposed that the water from Alau dam be transferred to Jere rice project via a canal, and to position the canal behind the University of Maiduguri to the catchment.
And then the canal will go to the Jere area for the irrigation?
Yes. And the advantage of that is, there is less loss of water than through the natural river channel. As time passed, before the project could take off, Maiduguri’s population was increasing rapidly and consequently there was a higher demand for water.
Maiduguri has been relying on ground water for its source of water. Over the years, the yield (output) from the boreholes has decreased and the demand for water in Maiduguri has increased steeply. It became necessary to look for an alternative source of water supply. The Borno State government requested to use the Alau Dam for Maiduguri water supply. The request was approved by the federal government and the Jere Irrigation Project was suspended.
Were the canals for the irrigation built already?
No. When this decision was taken, the construction of the dam had been approved. The state government secured a loan from the World Bank to put the treatment plant in place.
But was it the federal government that completed the dam?
Yes, I was in CBDA, when it was completed. The arrangement was that the Borno State government will pay CBDA for the supply of raw (untreated) water, while they will levy consumers an appropriate rate for the treated water.
CBDA built the dam with funding from the defunct NAL Merchant Bank.
There’s also this allegation that the dam has been having problems over the years. How true is that?
When the dam was being constructed between 1984 and around 1990, those were extremely dry years. During that time, the river had completely dried up, leading to criticism of the CBDA for building a dam on a dry river. This prompted us to explore ways to supplement the Ngadda River in case drought conditions continued. Here on the map (shown to Weekend Trust), you can see the Ngadda River, and also the Yedzaram River, which both flow into the Sambisa swamp.
You mean between Ngadda and Yedzaram?
Yes, this is the Sambisa area. We’re currently unaware of the situation there, but we constructed a water control system that connects water from the two rivers through a canal with a gate control mechanism. During drought years, the Yedzaram River supplies water to the Ngadda River, ensuring that the Alau Dam receives adequate inflow. Conversely, in extremely wet years, the Ngadda gate will be closed, allowing excess water to flow through the Yedzaram into Lake Chad. The dam was designed by an Italian consulting firm called ALTS, which utilised hydro-meteorological data sourced from the archives of the Borno State Ministry of Agriculture and the Water Board. Some of this data included records from the defunct Northern Region.
They used records of the 60s to arrive at the final design?
Yes, because you have to have record of how much water flows through the river over the years and conduct soil tests to be able to select the best suitable location for the dam site.
And all these were done?
Yes.
But were they the ones who constructed the Alau Dam?
No, they were not.
Was it an indigenous company that constructed the dam?
No, it was a semi-indigenous company; Edok-Eta Mandilas, a Greek company. Later on, Edok-Eta Mandilas pulled out and they changed the name to Nigerian Dynamic. The staff were expatriates, though they had a lot of Nigerian engineers working with them.
But there were reports that a certain contractor from Bauchi turned down the contract because the design was compromised.
I do not know about that. Alhaji Yelwaji Saleh was one of the first engineers from the North, and I think he worked briefly with Alhaji Sali Iliasu, of Diyam Consultants based in Kano. Then he established his construction from Mansa Construction Ltd and they were road contractors from my knowledge.
He had nothing to do with the dam?
No he did not. I believe there’s been a lot of discussion about various names being associated with the Alau Dam. However, the contract wasn’t awarded by the Chad Basin Authority; it was granted by the federal government during a Federal Executive Council meeting when General Muhammadu Buhari was the military Head of State.
Some people would say, assuming the original master plan was respected, for instance, with respect to the canal maybe we wouldn’t be having these issues. Would that be correct?
No, there is no need for the canal because the Jere bowl irrigation project had been suspended/cancelled. The main challenge is monitoring and dam operations i.e regulating the dam reservoir.
Maybe they should have been using it for large scale irrigation?
There are no irrigation infrastructures around many of the dams in the country.
Can we link the lack of monitoring to the over 16 years of Boko Haram, where it was difficult for experts to access the gates around Sambisa?
I do not know. However, the Chad Basin engineers have not been able to visit and monitor the controls. You see the three rivers (showing on the map), Elbe, Yedzaram, Ngadda. This is the Mandara Mountains. The run off from the rainfall flows to the swampy area in Sambisa. The water is absorbed by a swamp before flowing out to the rivers Ngadda and Yedserem. So for quite a long time, nobody could go there to inspect the area. I’m not saying that it’s the sole reason, but it would help if you could divert some water with the control gates.
From our findings, a lot of money had been allocated for maintenance of the Alau Dam, but here we are with a lot of problems. What do you think happened?
I cannot really comment on something that I don’t have the background on. The key thing here, and I keep emphasising, is importance of monitoring, and if the water level is very high, alarm must be raised. Every action taken must be to reduce the potential damage a flood can cause.
People are taking the blame to the Borno State government because the Secretary to the State Government (SSG) was at the Alau Dam before the spillage and he assured citizens that nothing would happen. Do you have anything to say on this?
No. Well, he’s right, and he’s also not quite right. There was nothing wrong with the dam and dyke when he visited. However, the dyke was overflowing even though the three spillway gates were also opened sometime earlier, which was an indication that the water level was still rising.
After the interview by the SSG took place, there was heavy rainfall for the next three days and it rained heavily all over the catchment. It is very possible a fresh flash flood reached the dam, which breached the dyke, then the massive volume of water and its velocity caused flooding in Maiduguri. The main dam remained undamaged, so it’s important for people to understand that it wasn’t the dam that burst; it was the dyke that failed. The dam itself is intact.
Do you think that commercialising this dam and others around the country will help?
Commercialising as how?
There was a time the federal government said they wanted to commercialise the dams, so maybe large farmers and companies can go and leverage the water resources there.
I don’t believe that approach will be effective. We need to recognise that these services aren’t free. Currently, raw water isn’t being charged for, but if we implement rates for it, the revenue generated could be used for monitoring, servicing, and maintaining the dam.
I think if we have strong adherence to the rule of law and by granting autonomy to water resources agencies, while compensating them appropriately, we can see better outcomes.
For example, when Margaret Thatcher became Prime Minister in the UK, she privatised the water supply agencies. Now they are facing a crisis and considering renationalisation due to high water supply charges and citizen complaints. Meanwhile, those managing the privatised companies are consistently declaring profits and paying substantial sums to directors and shareholders. This has raised questions among citizens about whether these agencies are serving the public or their own interests.
In Nigeria, there’s a belief that water should be provided to citizens for free. However, I don’t think that’s feasible. Producing clean, potable water is costly, and our government lacks the resources to supply it for free, especially considering our large population.
What do you think government should do to save all the dams that we have in the states?
Let me speak on the Alau Dam. Let me just say that Maiduguri is now going to have problems with clean supply of water.
The monitoring of all the dams in the country should be intensified. Where there is risk of flooding, the spillways should be professionally managed. The federal government should ensure proper operations of the dams to minimise risk. The Alau Dam must be rehabilitated as soon as possible. It will not be too expensive because the main dam is not damaged. Going forward, the water supply from the dam may not be adequate for the growing city of Maiduguri.
In my opinion, the options are limited. I recommend that an additional dam be built on the Yedseram to meet up with demand.
You mean government should build another dam?
Yes.
But we have more than enough that are not being maintained…
We are talking about a city that has four million people. You can’t relocate them, right?
Building another dam with its own treatment place with supply from the Yedseram will compliment Alau water supply to Maiduguri.
But a lay man would say this is an engineer, prescribing another dam when we cannot take care of Alau Dam…
No. I think I’ve been saying it over and over. These flash floods are happening everywhere now because of climate change. Everywhere, you have excess rain and when you have excess rain, it flows downstream and floods the low lands. Very wet years that cause severe floods are rare. It took 30 years from the last major flood for another one to occur. With modern technology we make accurate predictions about the weather. We could make adequate provision in the event of these extreme climate changes. We must improve the flood protection structure and be on the alert at all times.
Presently a lot of the dams are underutilised…Are you not worried?
I understand that some may disagree with me on this because many Nigerians are weary and times are extremely tough, but water is crucial for drinking, sanitation, agriculture, and nearly every aspect of life. It simply cannot be compared to resources like oil and others. If we invest in water supply projects, we need to generate revenue to sustain those investments over the long term. I would not recommend taking foreign loans to fund water resource development projects.
You left the Chad Basin Development Authority over 30 years ago. What have you been doing since then?
I was Director General of the National Directorate of Employment (NDE), I retired and set up a consultancy firm generally on water, civil engineering and of course, trying to take the much-needed rest.
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