Located along the great Ruaha River between the borders of Iringa and Dodoma regions of Tanzania, Mtera hydro power plant is the largest dam in the country.
Its down-stream dam also supplies other hydro plants, Kidatu and Kihansi, and its reservoir is the largest man-made lake in Tanzania.
Since its construction was completed in 1988, the giant power plant has been producing 80MW electricity that feeds 14.3% of the nation's power grid system, and for long has been among the back-bone of the nation's electricity need.
The plant is run by Tanzania National Electric Supply Company (Tanesco), the country's main power utility firm.
However, the year 2011 doesn't look good in the calendar of Tanesco's power generation endeavours, as the water flow of Ruaha River, which Mtera hydro power plant depends on, remains insufficient.
The flow is very low compared to other years, and with the situation not expected to improve any time soon, there are fears that largest dam in the country could be closed.
According to Julius Chomolla, a principal operations engineer at Tanesco, Mtera dam's full water supply level is 698.5m, and the minimum is 690m.
But as last week, the level was 690.94m, which means the plant had only 0.94 cubic meters left before it reaches the minimum level. He says the two hydro electric plants available at Mtera dam consume a total of 47,000 cubic meters of water per second each.
"2011 is going to be the most catastrophic year comparing to others, as we are in March, and the water isn't still coming in," says Engineer Chomolla.
But the clock is ticking, and we are now at the end of March, heading to April. These are the two months when the experts in the hydro power generation expect to get adequate rain. But on the contrary, so far there hasn't been any adequate rain in March and the metrological people have already cautioned Tanesco, saying very little rain is expected even in April.
"From the trend we have registered between 2005 and 2010, March is usually the pick rain season, and a time we get the maximum average inflow to the dams," the engineer explains. "But this year, things aren't good and in 2012 the average rain might even go further down below the minimum supply level."
Year 2006 was a dry season in Tanzania. That was also the only time when water supply level in the dam had reached 688.78m, and the plant was forced to close down its machines.
The same situation seems likely this year if the weather trend continues the same until April. Since rain is not expected in May, June and July, the engineer fears the same hard times of 2006 could be back.
Following the continuous power interruptions and rationing of electricity in the country, there has been speculation that siltation could be one of the reasons for the reduced water level in the dam.
However, the principal maintenance engineer of the power plant, Stephen Kitt Mpfubusa, says siltation isn't a problem at all. "The reservoir is quite clear. In fact, the designers who constructed it have indicated it would take a hundred years before siltation could occur and we have still 80 years to go," he says. "The dam is just a victim of climate change."
The scary situation of rain shortage doesn't only risk the existence of the country's largest dam, but will also affect the remaining smaller dams.
Engineer Chomolla says if the dam that caters for Mtera dries, the Kidatu and Kihansi power plants will be affected as well. "If Mtera is in a mess, Kidatu and Kihansi will also be, and closing the two means shutting 240MW of the country's electric supply."
Kihansi hydro power plant, as it is called, doesn't have any reservoir or storage like the Mtera plant. If there is no running water coming from the river Kihansi, the plant can't operate.
Mr Willie Mwaruvanda, a basin water officer, says the river flow situation is below average due to three consecutive years of drought, which have affected supply in the Great Ruaha, the most used water source in the area, and with a lot of water use conflicts around it.
Great and little Ruaha rivers that flow their water into Mtera dam and Kihansi are among those exposed to high usage of water by the villagers living in the area for agriculture and livestock keeping. Water flow is therefore very much affected when there is no rain. "They take their cattle to the water sources, and it is a limited amount of water that has to be used also for electricity generation. But yet the pastoralists and farmers fight for it too," says Mr Mwaruvanda.
He says the villagers have been taking their cattle deep into the dam, and also use the water for fishing too. In addition, some of them are even farming on the shores of the dam, thereby contributing to its siltation.
Rice farming is popular in Mtera district, but it is a kind of agriculture that consumes a lot of water. "Investors in the area, especially, use drains to channel water to their farms and those drains consume a lot of water. We now want to ask the ministry of Natural Resources and Tourism to declare Mtera dam a conserved area so as to protect it," Mwaruvanda adds.
Mr George Samuel, the Director of Mbarali District, where most of the water sources of Great Ruaha river are allocated, has also confirmed that the number of pastoralists around Ruaha River have kept on increasing from time to time, and the impact is paralysing the Mtera ecosystem, with the result that there soon won't be enough water left at the dam for power generation.
Due to the pressure on the river and the impact felt in 2006, there has been an effort by the government to relocate the pastoralists to other areas, including some parts of Mbeya, Iringa, Lindi, Rukwa, Ruvuma and Coast regions.
However, so far these efforts have not been very effective as the pastoralists kept on coming back to the Great Ruaha areas, either by through connivance or corruption.
"There were reports about underground efforts by some politicians who encouraged the pastoralists to come back during the elections to vote for them. There were also cases of pastoralists bribing local leaders to allow them feed their cattle there," says Mr Samuel.
He says some pastoralists had even managed to force their way into Ihefu conserved area from time to time, despite ongoing legal action been taken against them by the authorities.
"Last year eleven pastoralists forced their way into the area, and we opened a case against them, which is still pending in court," he noted.
However, the district Director dismisses the fear of water shortage in Ruaha River, and even Mtera hydro power plant.
"We already have formed a team to work on the issue; why should there be no water at the hydro plant, while there is water at the main source?" Mr. Samuel queried.
But according to Mwaruvanda, the fear of water shortage at the power plant is not far-fetched. He says one of the tributaries supplying Mtera from the Rufiji Basin was once blocked, apparently due to encroachment of the ecosystem, and they had to go ahead and unblocked it.
So a repeat of a similar situation cannot be ruled out, hence the need to step up conservation efforts along the river catchment areas.
"We are trying to involve the people of this area in conserving the water, and so far we are getting high participation at the source areas like Kilombero, Rufiji and Ruwegu," Mwaruvanda noted.
Meanwhile, the Mtera hydro power plant is currently operating under an emergency plan. The plant can only produce 52MW of electricity, given the amount of water that is remaining there.
The current output is 28MW less than its full capacity, and there is no likelihood of the water inflow increasing any soon. By this time last year, the average water level had been reached, but this time there is no such hope.