This is the last of four on-the-scene reports
MIRAFLORES LOCKS, Panama - The pelicans hovering near the Pacific Ocean entry to the Panama Canal know that ships mean dinner time.
As the Panamax vessel Mayfair rose through the locks late last year, some 26 million gallons of fresh water rushed through the gates into the ocean behind it. The flood of fresh water mixed with the brackish ocean, upsetting the salinity and confusing the fish so that they became easy pickings for the ungainly birds.
The Mayfair, which paid a $113,491 toll to move its cargo of shipping containers 50 miles across the Panamanian isthmus, then passed through the 164-square-mile man-made Lake Gatun, where dredging goes on 24 hours a day. During its descent from the lake, another 26 million gallons of fresh water poured into the Atlantic.
It is a good thing the canal slices through a rain forest, because every ship that makes the crossing uses 52 million gallons of fresh water.
Multiply that by 30 to 40 crossings a day - roughly 13,000 a year - and it is obvious that this toll way requires lots and lots of water.
It is estimated that the lake needs a daily inflow of 1.6 billion gallons to service the canal and provide drinking water for Panama. As the United States prepares to hand over the canal to the Panamanians at noon on Dec. 31, that water supply is at risk. One only has to do the math.
* The populations of Panama City and Colon, which are located at either end of the canal and get their water supply from Lake Gatun, are growing dramatically. About half of Panama's 2.7 million population lives within 30 minutes of the watershed.
* Panama is losing an estimated 59,000 acres of rain forest every year - about 1,000 acres of that in the canal watershed - to logging, mining and slash-and-burn farming. It is estimated that Panama has lost two-thirds of its rain forest since the 1950s.
* Panama receives an average of between 70 and 140 inches of rain a year, depending on the region. This fills the canal with water, but also with silt, requiring $150 million worth of dredging each year. And despite constant dredging, an estimated 1 percent of the canal's water volume is being lost each year to sedimentation.
* Panama's clay soils are highly susceptible to sliding and erosion, especially during Panama's nine-month rainy season, which brings torrential downpours. And much of the watershed is steep mountainside. Research shows that the average annual soil loss is about 2.4 tons per acre. On cleared land, the soil loss can be as high as 11 tons per acre each year.
* The possibility of global warming is becoming a concern. …