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Is Liwonde the appropriate position of a barrage on the Shire River?

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Introduction

The question ‘Is Liwonde the appropriate position of a barrage on the Shire River?’ seeks to answer questions on the challenges our country is facing, especially those of persistent power outages and perennial floods, particularly in the Lower Shire districts of Chikwawa and Nsanje.

Lower Shire floods

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From my understanding, Liwonde must have been chosen as the position of Kamuzu Barrage to take advantage of the existing bridge to mount the brackets of the facility— with the aim of regulating the flow of water downstream, where we have our hydro-electric power plants.

In the rainy season, when Lake Malawi and the Shire River have too much water, the barrage is opened to avoid flooding upstream [of the barrage], thereby letting out huge quantities of water— and more water downstream causes massive flooding of the Shire Valley.

Power outages as viewed by Escom

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Electricity Supply Corporation of Malawi (Escom) Public Relations Officer, George Mituka— in the Weekend Nation of December 5 2015, on the Opinion and Analysis page— attributes massive load-shedding to low water levels in Lake Malawi and the Shire River.

Mituka goes on to say that, as of November 24 2015, water flow, as measured at Kamuzu Barrage, measured 128 cubic metres per second (cumecs). This is against a total requirement of 284 cumes for Nkula Hydro Electric power plant, 258 for Tedzani and 268 for Kapichira power plants.

Possible solutions

If we complain about low water levels in our lake, I believe the heavens laugh at us by reminding us that most of the water that wrecked havoc to our brothers and sisters in the Lower Shire came from Lake Malawi through the barrage at Liwonde.

They might go on to say our donors and cooperating partners are on the brink of being tired of helping us, in terms of mitigating the impact of floods by, among other things, re-constructing damaged infrastructure.

So, what could be our long term solution to the challenges of power outages and floods? How can the ordinary woman in the village go to the maize mill anytime of the day and be assured that she will find the mill running?

To begin with, we could kill two birds with one stone by constructing a barrage at the outlet of Lake Malawi; that is, where the Shire River starts to drain water from the lake.

My suggestion is borne out of experience. Sometime in the 1980s, I worked as Assistant Dye – House Engineer at David Whitehead and Sons Limited, now Mapeto— and we used to install and maintain water, air and steam pipes.

Among other things I learned that if the size of a pipe has shrunk in diameter and one needs to fix a control valve, they fix the pipe the moment the valve’s size has decreased. If one installs the valve further away, the pipe might burst or leak because pressure increases with reduced diameter.

Likewise, Lake Malawi and Shire River can be equated to a pipe; one whose size has shrunk from, for example, several kilometres to a few metres in diameter. That is why the water in the Shire River flows faster than in the lake.

Consequently, if one fixes a barrage a few kilometres from Lake Malawi, the barrage will either cause flooding upstream or downstream when closed or opened.

The merits of fixing the barrage at the outlet of the lake are that the Lake cannot flood when the barrage is closed. It will only swell to a few metres, which is not dangerous.

If we raised the water level of the lake by, for example, one metre, we would conserve 29 billion cubic metres of water in the lake, which is a significant quantity considering that the lake is roughly 29,000 square kilometres.

If we allowed the water to flow at the operating capacity of Nkula Hydro-electric Power plant, which is 284 cumecs, we would use this water, assuming evaporation is at zero, and all the rivers that drain into the Lake have stopped, for a period of three years, two months and 26 days— with the water flowing out of the lake day and night.

But, thanks to the forces of nature, we get rains every year to replenish the lake whose water we have to use wisely.

Let me also touch on the Salima – Lilongwe Water Project. Many quarters have raised concerns over the project, mainly on its effect on power generation. I also subscribe to these concerns.

According to authorities, the project has a capacity to pump 50 million cubic metres of water per day. This, in a way, means Malawi will have created another outlet of the lake, apart from the Shire River and natural water evaporation from the surface of the Lake.

But that is food for thought.

In conclusion, I would like to say that constructing a barrage at the outset of Shire River will enable Malawi to store as much water as possible in Lake Malawi during the rainy season, making the Salima–Lilongwe Water Project equally viable.

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