Landslides: How rainfall dried up Panama's drinking water

May 17, 2011
Heavy rains cause landslides on the steep slopes of the Panama Canal watershed, releasing large quantities of sediment into rivers and streams. Credit: Robert Stallard

To understand the long-term effects of a prolonged tropical storm in the Panama Canal watershed, Robert Stallard, staff scientist at the Smithsonian Tropical Research Institute and research hydrologist at the U.S. Geological Survey, and Armando Ubeda, the LightHawk Mesoamerica program manager, organized four flights over the watershed to create a digital map of landslide scars.

Two feet of heavy rain inundated the watershed between Dec. 7 and 10, 2010. tore down steep slopes, choking rivers with sediment and overwhelming Panama City's . Flooding closed the Panama Canal for the first time since 1935. Despite the deluge, the influx of sediments in the water forced authorities to shut down the plant, leaving a million residents of central Panama without for nearly a month.

LightHawk, a conservation organization based in the U.S., donates flights for research and conservation efforts. Retired United Airlines captain David Cole flew the Cessna 206 aircraft, and the four flights yielded images of 191 square miles (495 square kilometers) of watershed. Stallard observed numerous new landslide scars left behind by the December storm, supporting his prediction that landslides supplied much of the suspended sediment that disrupted Panama's water supply.

The new watershed erosion map will allow Stallard and collaborators from the Panama Canal Authority to calculate the landslide risk of future storms and direct strategies to minimize the effect on Panama's water supply.

Tropical hydrologists agree that river-borne sediment originates from surface erosion or from deep erosion from landslides. In 1985, Stallard predicted that "deep erosion, not shallow surface erosion, is the primary process controlling the chemistry and sediment levels in many tropical rivers that pass through mountainous areas." Few studies have been conducted to test this prediction.

Deforestation of steep slopes is the primary factor determining the number of landslides. Six decades of aerial photographs analyzed by USGS researchers in similar landscapes in Puerto Rico showed that landslide frequency doubles outside protected nature preserves, and that roads and infrastructure make landslides eight times more likely. Although landslides happen in natural forests, the objective is to limit their impact through appropriate land-use practices.

"With development, landslide intensity increases dramatically," said Stallard. "In its history, the Panama Canal watershed has experienced huge floods. It's still hard to say whether future floods will be accompanied by disastrous landslides like those produced by Hurricane Mitch in Central America." In 1998, Hurricane Mitch swept across Honduras, Guatemala, Nicaragua and El Salvador causing more than 10,000 deaths and incalculable economic damage. Panama's proximity to the equator puts the country outside the usual hurricane zone, but prolonged tropical storms may occur.

Erosion control is possible. Partnering with the Panama Canal Authority and Panama's Environmental Authority, the Smithsonian is conducting a 700 hectare experiment in the canal watershed funded by the HSBC Climate Partnership to compare the effects of land-use choices, such as cattle ranching or reforestation with native tree species on water supply, carbon storage and biodiversity. Stallard hopes that this research will provide new information about which land uses provide a steady supply of clean water for the Canal.

With the first rains in May, the eight-month wet season begins anew in central Panama. Drinking water flows freely, the rivers are clear and the Panama Canal is open for business. But bare slopes of past landslides continue to create secondary erosion, which will dislodge sediments from the steep, rainy and rugged Panama Canal watershed in 2011. The long-term effects of the 2010 storm may continue as renewed interruptions in the water supply in 2011.

Explore further: Smithsonian identifies invasive crab species in Panama Canal expansion area

Related Stories

Panama butterfly migrations linked to El Nino, climate change

October 5, 2009

A high-speed chase across the Panama Canal in a Boston Whaler may sound like the beginning of another James Bond film—but the protagonist of this story brandishes a butterfly net and studies the effects of climate change ...

Two new frog species discovered in Panama's fungal war zone

May 26, 2010

Trying to stay ahead of a deadly disease that has wiped out more than 100 species, scientists at the Smithsonian Tropical Research Institute continue to discover new frog species in Panama: Pristimantis educatoris, from Omar ...

Recommended for you

History shows more big wildfires likely as climate warms

October 5, 2015

The history of wildfires over the past 2,000 years in a northern Colorado mountain range indicates that large fires will continue to increase as a result of a warming climate, according to new study led by a University of ...

Predictable ecosystems may be more fragile

October 7, 2015

When it comes to using our natural resources, human beings want to know what we're going to get. We expect clean water every time we turn on the tap; beaches free of algae and bacteria; and robust harvests of crops, fish ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) May 18, 2011
How rainfall dried up Panama's drinking water . . .

Is an attention grabbing title, but it is unclear how four flights over the watershed to create a digital map of landslide scars will provide useful information.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.