Dislodged by weeks of heavy rain in their natural habitat, the plants had at one point blocked up to 2km of the Rio Grande river.

Water hyacinths have clogged the river for a week. (Photo: Asheffield/Flickr)

 

Armed with machetes and cutting equipment, and in a bid to prevent flooding in and around the Philippine city of Cotabato on Mindanao island, hundreds of troops and civilians cleared tonnes of water hyacinth from the Rio Grande river on June 18-19.

The innocuous-looking plants are the prime culprits of recent flooding in and around this city of 400,000, according to local officials. Water hyacinth are a free-floating perennial aquatic plant native to tropical and sub-tropical South America. They have been widely introduced as an ornamental plant throughout North America, Asia, Australia and Africa because of their beautiful purple blossoms.

“This is the worst I have ever seen it,” said Cotabato Archbishop Orlando Quevedo, who chairs the Presidential Task Force on the Mindanao River Basin. “This happened two years ago, but never like this.”

Dislodged by weeks of heavy rain in their natural habitat, the plants had at one point blocked up to 2km of the river, the longest in Mindanao and the second largest in the Philippines, he said.

As of 20 June, some 25,000 families in the city had been affected. Of these 8,000 were staying in temporary shelters, mostly schools, with some 17,000 remaining at home, local authorities said.

Heavy rain in eastern Mindanao in recent weeks caused the river to burst its banks, leaving parts of 33 of Cotabato City’s 37 low-lying villages inundated.

Thousands of children were forced out of school, the UN Children’s Fund (UNICEF) reported, as water levels in some parts of the city rose to 0.7 metre.

Meanwhile, in nearby Maguindanao and North Cotabato provinces, the government of the Autonomous Region in Muslim Mindanao (ARMM) reported another 30,000 families affected, many of whom remained in their homes, unwilling to abandon their possessions: In one house, some family members were perched on a table watching TV as knee-deep water swirled below them.

 

Thousands of people have been affected. (Photo credit: David Swanson)

Dislodged

According to officials, the river level began rising when about eight hectares of water hyacinth were dislodged from Liguasan Marsh – an extensive 288,000-hectare swamp region in central Mindanao – following weeks of heavy rain and the emergency release of water from the NAPOCOR (National Power Corporation) dam upstream from the marsh.

Moving downstream, the plants – about 3 metres in length with their dangling roots and soil in tow – converged, blocking bridges and spillways, and preventing the flow of water in the normally 5-metre-deep river.

Natural silting of the river, combined with sand deposited by the fresh downstream torrents, was making matters worse, officials say.

“This is an ongoing problem and one we will need to again address as part of our regular maintenance efforts once the flooding subsides,” Quevedo said.

 

Appeal for volunteers

However, it was the removal of thousands of the water lilies that remained the biggest immediate concern for the authorities, prompting an urgent appeal for volunteers by the Philippine army on June 18-19.

“This is alarming and we need every available human and material resource to contain it,” Brig Gen Rey Ardo, commander of the Army’s 6th Infantry Division, told reporters. “Let’s work, whether or not outside help, or no help, comes along. This is the time to save our own skin through bayanihan [community cooperation].”

Even though about seven hectares of water lilies have been removed, the danger of more of them making their way downstream and causing further flooding remains.

“There are still another 20,000 hectares of water hyacinths in the marsh area. If the rains continue, I’m afraid they’re going to start moving downstream,” Quevedo warned, adding that some the plants were already on the move.

According to the Philippine National Disaster Risk Reduction and Management Council (NDRRMC) on 19 June, flooding since the end of May has affected 120,038 families or more than 611,000 individuals in nine of Mindanao’s 26 provinces.

At least five people have been reported dead.

 

This article was first published in IRIN.