Asking poor households how much they would be willing to pay to protect a river in Thailand can help put a tangible price-tag on the river’s benefits — from clean water to flood control — and realistically assess the costs of overexploitation and degradation.

Over the past few weeks, Thailand has been preparing for its biggest event of the year — a water festival, Loi Krathong, which begins on 27 October.

The week-long festivities will include the annual ritual of launching krathongs — small rafts, traditionally made from sections of banana tree trunk — down Thailand’s waterways to pay respect to Khongkha, or Ganga, the river goddess, and ask for her protection during the coming year.

On the banks of the Ping River in the northern hills of Chiang Mai province, tens of thousands of locals and visitors are expected to gather to launch krathongs. And for good reason — nicknamed the ‘lifeline of Chiang Mai’, the Ping traditionally provided vital water for washing, bathing, irrigating, food and transport. Today it still underpins the livelihoods of thousands of Thais who live on its banks.

But just how much is this lifeline worth? Once a broad, clear and gentle river full of fish and bathers, it is now a turbid, polluted and silted waterway that speeds by, with few fish and even fewer swimmers — the result of half a century of overexploitation and degradation brought on by rising populations, tourism, deforestation and waste.

Many farmers downstream no longer have enough water for their crops in the dry season. And flash flooding — a rare phenomenon fifty years ago — is now an annual event, with sometimes fatal consequences, most notably in 2005 when flooding in the region affected more than 100,000 families.

It’s an all too-familiar story. Across the world, rivers are drying up and water quality is deteriorating.

The problem, as highlighted in a previous post on this blog, is that if the benefits, or ‘environmental services’ that rivers provide — from clean water to flood control — are not properly or accurately valued in tangible, concrete financial terms, they are easily overexploited and degraded.

Of course, putting a price-tag on a river’s services is hard — but not impossible. One option is to calculate how much money people would be willing to pay to both restore the river and implement strategies to mitigate further degradation — and use this as a proxy measure.

In Chiang Mai, residents happily pay homage to Ganga to reap the benefits of her river. But would they also be willing to pay their hard-earned cash? Last year, I tried to find out just how much Chiang Mai locals thought the Ping River was worth.

I surveyed 347 households in Chiang Mai, asking how much they would be willing to pay to conserve the Ping and reduce the effects of environmental degradation — in particular, to restore parts of the river, increase awareness to halt waste disposal into the river, control gravel mining, promote afforestation upstream and control the use of chemicals to combat pollution.

The average sum of money that the surveyed households were willing to pay for this was US$2.3 (72.67 Thai Baht) per month, or 0.56 per cent of the average monthly income. By extrapolating this figure across a full year and across all households in the district — officially estimated at 117,925 — I calculated that residents in Chiang Mai would be willing to pay an impressive US$3.4 million per year to protect their river (although, as a hypothetical question, people may have been overly optimistic — if it came to actually putting hands in pockets, the price-tag could end up lower).

This kind of concrete valuation provides a sharp reminder that the benefits we reap from rivers are by no means ‘free’. It shouldn’t necessarily be used to make people actually pay out. But it should prompt governments to take environmental protection seriously and paint a tangible picture of the costs involved if they do nothing. It should also give them the impetus and justification they need to design and invest in sound environmental policies that protect their natural resources and mitigate degradation.

In Chiang Mai, until that happens people will continue to pay for their river’s services in the way they know best — this week it’ll be millions of krathongs, not dollars, that are thrown at the mighty Ping.