A regional audit has found that researchers monitoring Lake Prespa moved satellite shorelines in seven years of reports, overstating the lake’s summer area by as much as 27 sq km (10.4 sq miles). The audit, released on Wednesday, says the altered images helped the €18.6 million recovery programme claim progress while the lake was shrinking.
Prespa lies across Albania, Greece and North Macedonia and is a major habitat for waterbirds and rare fish. The audit examined grants, field measurements and image-processing records from the fictional Prespa Basin Observatory, which supplied data to the three governments. It says the reported shoreline did not match raw satellite scenes or independent water-level readings.
How the images were altered
Auditors found that technicians applied a geographic offset to satellite images from 2018 to 2024, moving sections of the shoreline by up to 1.2 km (0.75 miles). In several annual reports, the same shoreline outline appeared over images taken in different seasons. The report says the adjustment was described as a correction for seasonal variation, but had no scientific basis and consistently made the lake appear larger.
Jeromy Heller-Emard, who led the audit, said the team compared the Observatory’s published maps with raw satellite data and measurements from nine water gauges. “This was not a small error at the edge of a map,” he said. “The adjustment erased a retreat that should have triggered a much tougher response.” The audit estimates the lake’s summer surface was 27 sq km smaller than the programme’s reports suggested.
The adjustment erased a retreat that should have triggered a much tougher response.
Jeromy Heller-Emard, audit lead
The programme’s reported gains helped unlock €6.2 million in follow-on grants for reed-bed restoration and shoreline planting, the audit says. It found no evidence that the money was stolen, but says 11 funded projects were approved partly on the basis of inaccurate lake-area figures. Further payments have been frozen while the projects are checked.
Grants frozen, claims challenged
Julia J. Graf, a remote-sensing scientist who reviewed the audit’s image comparisons, said the pattern was especially troubling because the Observatory’s work had been treated as a shared reference by agencies in all three countries. She said the maps gave officials reason to delay action on water withdrawals and damaged wetlands. “If the baseline is wrong, every claim of recovery built on it is shaky,” she said.
The Observatory’s director, Sekinat A. Gbadamosi, said the institute would cooperate with a technical review and had suspended use of the disputed maps. She said the offset had been introduced to reconcile images taken under different conditions, and denied that staff had set out to mislead grant-makers. The audit says the institute could not produce a validated method or independent sign-off for that adjustment.
The three environment ministries are due to meet next week to decide how to reassess the funded projects and rebuild a reliable record of the lake’s changing edge. Heller-Emard said the audit had not established who ordered the image changes, and recommended a fresh review of seven years of monitoring. Until then, new restoration awards remain on hold.
