New tool provides gauge for freshwater health

A woman rowing a boat, pictured above, in the Greater Mekong region of Cambodia. (© Olivier Langrand)

The most cost-effective way to keep fresh water clean for human use? Nature itself.

Forests, rivers and wetlands filter out contaminants, store excess water, and in some cases even drive rainfall, so maintaining the health of those ecosystems — typically far upstream from population centers — is critical.

But every ecosystem is different. How to assess their health in a standardized and accessible way?

This is the problem Derek Vollmer and his team aim to solve with the Freshwater Health Index (FHI), an innovative new tool for gauging the state of what — to humans — are some of the most important ecosystems on the planet.

“I compare FHI to visiting your doctor for your annual checkup,” explained Vollmer, senior director of Conservation International’s Freshwater Science Program. “You don’t want to spend a lot of time there, you don’t want to spend a lot of money, but you need a comprehensive overview of your health.”

As a doctor might give a patient numbers for blood pressure and cholesterol, the FHI scores watersheds on a scale of 0-100 across three dimensions: a score for the “vitality” of the ecosystems; a score for whether people are getting the water services they need; and a score for the level of coordination among the people that govern the use of water. This trio of scores of course doesn’t tell you everything you need to know about freshwater health, but it’s a starting point.

“From there, you can decide what changes you want to make, and you can keep tabs on what’s going well,” Vollmer said. “In most freshwater ecosystems in the world, that [baseline] information doesn’t exist.”

The FHI framework was recently published in the journal Science of the Total Environment.

Testing the tool

The FHI has been tested in two locations: the Sekong, Sesan, and Srepok (“3S”) Basin of the Lower Mekong River in Laos, Vietnam and Cambodia; and the Dongjiang Basin of the Pearl River in China. (A basin includes all of the land that drains to a single body of water, with every drop of rain eventually making its way into the river.)

These two basins were chosen because they are emblematic of the rapid urbanization, declines in water quality and quantity, and climate change impacts affecting much of the Asia-Pacific region. They also serve an immense number of people: The Lower Mekong Basin directly supports the livelihoods of more than 60 million people, while the Dongjiang provides water for more than 40 million, including Hong Kong.

“There is a lot of demand to meet immediate human needs, but there is also potential for restoration upstream to help safeguard the resources,” Vollmer said.

To come up with the FHI scores, scientists bring decision-makers together to discuss the state of the watershed and to share available data on pollution levels, land cover changes and water flows.

“You can’t do FHI without speaking to people,” said Nick Souter, a co-author on the paper who managed the stakeholder process in the Lower Mekong. “We want to get as many relevant people involved as possible.”

In the Dongjiang, workshops prompted participants to go beyond the narrow perspective of “water security” as simply the volume of water available to a more comprehensive understanding of their river basin. Part of this came from bringing together representatives from both upstream and downstream the river and from sectors that don’t often collaborate, such as major private sector water users, NGOs, and municipal governments.

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The verdicts

How did the Dongjiang score? While the basin is meeting people’s water needs, the FHI found some warning signs. On the 0-100 scale, the Dongjiang earned 60 for ecosystem vitality, 82 for ecosystem services, and 56 for governance. Scientists found that changes to the river basin over the past few decades, including increased extraction of groundwater for the production of bottled water, channelization of the river, and growing industrialization are undermining the ecosystems supporting the river. Though ecosystem services — including water provisioning for drinking and agriculture — has not suffered much yet, Vollmer and his colleagues think that there might be a time lag between declining ecosystem vitality and declining services.

In other words, a low vitality score could be rather like high blood pressure: It doesn’t mean you’ll have a heart attack right now, but it’s a harbinger for the future.

The scores for the 3S Basin of the Lower Mekong fell across a similar spread: 66 for vitality, 79 for services, and 43 for governance. The major threat in this region is dam operation, which interrupts natural water flow and traps sediment in reservoirs instead of depositing it on agricultural lands. There are now 65 dams on these rivers, and the low governance score indicates a need for increased information sharing and transboundary cooperation across the three countries if the rivers are to continue to meet people’s needs.

Moving forward

In many countries, the biggest barrier to understanding freshwater health is data. While certain metrics such as nitrogen and phosphorous levels can only really be understood by taking water samples, other metrics such as stream connectivity and changes in water flow that can be derived from satellite imagery.

A new partnership between Conservation International and NASA aims to address this challenge. In the Lower Mekong, a hydrologic model that NASA developed has already helped the team understand some of the FHI indicators in places where there aren’t measurement instruments on the ground.

 Committed to improving the management of freshwater as a renewable but finite resource, Vollmer and his team now plan to take FHI beyond Asia-Pacific to test it in representative river basins in Africa and Latin America. After seeing how interested stakeholders in the Dongjiang were in using the FHI for future decision-making, they also plan to run sensitivity analyses to see how certain actions — building more dams, mining, converting forests to agriculture, or other scenarios — could affect the scores. This could help decision-makers who don’t always agree to work off of a common understanding of the consequences of their choices.

“People commented that the tool is nice, the reports are valuable, but it’s possibly even more valuable that we’re convening them from an objective and science-driven standpoint,” Vollmer said. “We don’t have an agenda of our own.”

Allie Goldstein is a researcher in Conservation International’s Moore Center for Science.

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