The water in Otsego Lake is now the clearest it has been in the last 20 years, according to Biological Field Station director Dr. Willard Harman.

Back in September, field station officials said that for the second year in a row, indicators of better water quality have taken an upswing following almost two decades of decline.

But last week, field station personnel recorded a Secchi disk reading of 8.7 meters indicating a level of water clarity that had not been seen since the early 1980s.

To determine the water's clarity, or transparency, scientists like Harman employ a device called a Secchi disk, which has been in use for almost 100 years.

The Secchi disk is a white metal circle approximately 8 inches in diameter with a line attached. The disk is lowered into the water until it disappears from view. The line is measured to determine the depth or Secchi disk reading.

Last week's reading means the disk could be seen 28.5 feet below the surface.

Harman said the water is often the clearest under the ice because the algae that clouds it grows less during the winter months.

The average Secchi disk reading in 2003 was 3.4 meters - the highest since 1992.

The record high disk reading was 10 meters which was observed in both 1969 and 1982.

But since the mid-1980s, Harman said, pollution and the non-native alewife have been contributing factors in the declining water clarity.

Alewives, which were introduced to the lake, resulted in the demise of the Otsego bass and reductions in algae-grazing zooplankton.

The lowest disk reading - .8 meter or 2.8 feet - was in 1995.

Harman gives credit for the increased clarity to work to improve lakeside septic systems, best management practices instituted on agricultural land and the walleye stocked in Otsego Lake in recent years.

"We hope this trend continues, and feel that the clearer water can be attributed to the efforts of all the people and organizations that have worked to improve conditions over the last several years," Harman said.