The country’s largest hydroelectric complex is being managed hour by hour as officials try to preserve dwindling water reserves.

The water behind Ecuador’s Mazar dam has fallen so far that the operators of one of the country’s most important electricity reservoirs are conserving it whenever they can. That may mean temporarily stopping generation at Mazar itself to save water for the larger Paute hydroelectric complex downstream.

The reservoir’s rapid decline has become the most visible sign of Ecuador’s newest electricity crisis. Earlier this year, heavy rainfall helped fill mountain reservoirs. In recent weeks, a lack of water flowing into Mazar has forced the government to reduce demand from factories and seek power from other sources.

Mazar is more than an isolated power plant. Its stored water helps sustain generation farther down the Paute River, making the reservoir a central piece of the national power supply. The plant at Mazar has an installed generating capacity of 170 megawatts, but the value of its reservoir extends well beyond what its own turbines produce.

A reservoir under pressure

Mazar stood near 2,145 meters above sea level on September 7th. By October 11th, it had dropped to about 2,125 meters. A reading reported for 9 a.m. on October 18th put the reservoir at 2,122.99 meters, just 7.99 meters above the 2,115-meter threshold used for safe operation. That is a drop of roughly 22 meters in six weeks.

The decline has forced operators to make difficult choices. Between October 16th and 17th, Mazar stopped generating electricity for about 22 hours, allowing its water level to recover 64 centimeters to 2,123.76 meters by 9 a.m. Saturday. It was only a brief gain, and the reservoir remained dangerously close to the operating threshold.

That brief increase did not erase the larger problem: Ecuador is heading into the season when river flows in the Amazon basin normally weaken, and the dry period arrived early this year.

Hydroelectricity supplies much of Ecuador’s power in wetter periods. It also leaves the country vulnerable when reservoir inflows drop. The generating plants downstream from Mazar need water, and every day of high output draws from supplies that can take much longer to replace.

Factories carry the first burden

For now, the government has concentrated much of its rationing on industrial customers. Its three-day-a-week disconnection program is intended to preserve electricity for homes and other users while the reservoir remains under stress.

The dam was built to store water that can be released when the country needs electricity. But it has been losing that reserve much faster than the mountain rivers can replace it. Even shutting down Mazar’s turbines for nearly a day bought less than a meter of recovery.

Diesel-fired generation and electricity imports can reduce the amount of hydroelectric power needed on a given day, but neither changes how much rain has fallen in the mountains. Imports depend on availability and the transmission system, while thermal generation depends on fuel and working equipment.

The problem now reaches well beyond the dam. With less water available for the Paute complex, Ecuador is relying more heavily on thermal power, electricity imports and restrictions on industrial use. How long those measures last will depend in large part on whether sustained rain returns to the Paute watershed.