LONDON/ LUSAKA, March 11 (Reuters) - China Nonferrous Metal Mining Corp's Chambishi Copper Smelter in Zambia has cut one-fifth of its production due to power shortages in the country, two sources with knowledge of the matter told Reuters.

The plant, which produces about 250,000 metric tons of copper per year, is one of the biggest processing facilities in Africa's second-largest copper producer.

Zambia generates about 87% of its electricity from hydropower, and lower water levels due to its current drought, the worst in two decades, have curbed power generation, the managing director of state-owned power utility Zesco said.

Zesco said last week it would start rationing electricity supplies from March 11. However, the sources said that Chambishi had already reduced capacity as of last week.

CNMC did not immediately respond to emailed questions on the matter. The company is now considering plans to install diesel generators at the plant to help alleviate the impact of power shortages, according to the sources.

The power shortage comes amid a gradual decline in Zambia's copper production due to lack of new investment at some operations, including Konkola Copper Mines and Mopani Copper Mines.

Output of the metal slumped to about 698,000 tons in 2023 from 763,000 tons the prior year, according to data from the Zambia Chamber of Mines.

Some of Zambia's smaller producers may also be affected by the power shortages, though its still too early to calculate the overall impact on production, the sources said.

The utility plans to meet mining companies on March 14 to discuss ways it could "claw back" about 250 megawatts or 20-25% of supplies, managing director Victor Mapani told journalists in Lusaka last week.

The Zambezi River Authority (ZRA) has reduced its allocation of water for electricity generation to Zambia and Zimbabwe to 16 billion cubic litres currently from 30 billion in 2023 and 40 billion in 2022, Mapani said. (Reporting by Julian Luk and Chris Mfula; Additional reporting by Felix Njini; Editing by Jan Harvey)