INSIGHT: How saving water can increase power supply

Dar es Salaam. On March 16, when inaugurating the construction of Kinyerezi II (240 megawatts) dual power plant in Dar es Salaam, President John Magufuli cautioned the minister for Energy and Minerals, Prof Sospeter Mhongo, and Tanzania Electric Company Limited (Tanesco) managing director Felchesmi Mramba to look for ways to preserve rain water so that hydropower generating plants won’t be affected by prolonged drought.

His concern came following a water report on hydropower generation stations to be low, thus causing power woes despite the long rainy season the country had experienced over the years.

It is now the rainy season and Tanesco is put on test.

Kidatu Dam

Last week Tanesco officials and Morogoro Regional Commissioner, Dr  Stephen Kebwe, who was accompanied by his security and safety committee at regional and district levels, visited  Kidatu Hydro Electric Dam, whose water level had increased to the extent of threatening the dam infrastructure.

This has just come six months after Tanesco was forced to shut down three of its four electric producing machines at Kidatu Power Plant due to an alarming  fall in the water level in October last year.

The then Kidatu Plant manager, Mr Justus Mtolera, said dam’s water level fell to 441.88 cubic metres, while the plant required amount was 450 cubic metres above sea level.

Usually, the dam requires 17 cubic metre-difference from the maximum of 450 cubic metres and the minimum of 433 cubic metres for production. Below that it is a threat.

Speaking during a one-day visit to the dam, Mr Mramba said following the overflowing of water at Kidatu Dam, they decided to discharge water into the river.

He, however, noted that the decision was made after thorough consultation with both government and Tanesco experts to avoid destruction if the main pipe burst. It was also an opportunity to save dam water.

He said the dam’s maximum capacity was to store 450 cubic metres above sea level, but as of Tuesday last week the water had reached 450.5 cubic metres. According to him, for safety reasons excess water has to be released.

“As you can see, the water level is very high leading them to force their way up to the gate…if we continue blocking them they might burst to the rock and flow in an amount that we cannot control.

“If water flow in uncontrolled manner may affect thousands of residents in the nearest villages together with their crops but most importantly damage infrastructure of the dam which might cost us billion of shillings to repair,” he said.

According to Mr Mramba the ongoing rainfall is the main reason to the increase of water in different hydropower plants. He further  said that the discharge of water would depend on the increase of water inflow in order not to affect the required level.

For his part, Dr Kebwe said more than 4,500 Mkamba and Nyange villagers could be affected if the water reached an uncontrolled level. He directed he village leaders to ensure their people were well informed of  Tanesco’s preventive measures.

“Morogoro is one of the 10 regions the Tanzania Meteorological Agency (TMA) has warned of experience rainfall above average that although it is a blessing to farmers, challenges like this one are inevitable,” said Dr Kebwe.

Golden opportunities

Tanesco describes various ways that it can use to save water at its various hydropower dams for future use giving hope for reliable power supply this year. First, water at Kidatu Dam has increased despite the fact that Mtera Dam remained closed for more than two weeks.

Thus, allowing the two rivers - Lukosi and Iyovi - that have for many years been supplying little water, they have now become the main sources of water for Kidatu Dam.

Mtera, the largest dam in Tanzania, has also reached 697.14 cubic metres, just one cubic metre to reach its maximum level of 698 cubic metres.

Second, according to Mr Mramba, despite the increase in water level in various hydroelectric dams, for future use power generation continue to be emphasised using natural gas from its various completed gas plants, including Kinyerezi I.

He said more than 700 megawatts of electricity at the National Grid was coming from gas generating plants and the remaining megawatts depending on demand would be produced by hydropower plants.  “For example, this year, the highest demand of electricity was 1,441 megawatts, of which nearly half of it was produced from natural gas because we want to be keeping water from one rainy season to another,” added Mr Mramba.

Third, allowing water to be discharged in controlled manner in dams saves it.

Expounding on this, Kidatu Plant acting manager Manfred Mbyallu said, for example, the opening of the spillway gate at Kidatu would help Tanesco control the amount of the water to be discharged, thus save water in the future.

He said the impact of leaving water to find its own way out was difficult to measure the amount of overflowing water and that posed a risk to the dam level. “We will open the spillway gate depending on the inflow…this is to protect the water level and River Ruaha users,” he said.

Bright year

For many years Tanzania has been experiencing not only frequent power shortages, but also high tariffs. But, with the ongoing rain, the completion and maintenance of different power stations, Tanesco is keen on producing reliable power. According to the Tanesco director, this year Tanzanians will experience the most reliable power in history.

While this is assured, early this month the Energy and Water Regulatory Authority (Ewura) announced the reduction of electricity tariffs to household consumers. Current prices have gone down between Sh2 to Sh6 (1.5 per cent and 2.4 per cent), depending on the category of consumers.

According to Ewura, there are five electricity consumer groups, namely D1 - the lowest consumers using up to 75 units, T1 - above 75 units, T2 -  medium industries using more than 7,500 units and T3 - those connected to medium and high voltage and buying electricity in bulk.

 According to Ewura, the Sh100 per unit for small consumers (D1) has remained unchanged, while medium consumers (T1) are now paying Sh292 down from Sh298 per unit.

Others prices are Sh195 from Sh200 for medium industries, Sh157 from Sh159 for large industries (connected to medium voltage) and Sh152 from Sh156 per unit for those connected to high voltage and buying electricity in bulk. Consumers are also not paying Sh5, 000 that was mandatory, when applying for power supply.

A new proposal for power system reduction

In August, Ewura will also review a new proposal of power cost reduction, when the Mtwara gas pipeline will be handled over to the government. Tanesco proposed a 9-per cent electricity tariff reduction plan come 2017 driven by huge gas discoveries. Early this month, Ewura suspended the reduction proposal until a proper cost-analysis study of investments in gas infrastructure is done.

Ewura director general Felix Ngamlagosi was quoted saying that Tanesco’s tariff reduction plan was based on a calculation of interim gas prices, but they overlooked other matrixes such as investment on gas infrastructure.

He said the completion of the major natural gas pipeline from Mtwara that would be used to generate low cost power from the Kinyerezi plants was only one aspect of the matter. But he promised, hope for more tariff reduction was there.