Selling Dominica's Water: Is There Enough? A Rough Analysis

The other day I returned a call from a fellow who wants to sell Dominica's fresh water - 37B gallons per year, to be exact. That is about 114,000 acre-feet per year (140 MCM).

Dominica is a rugged, volcanic island nation in the Caribbean Sea. Its area is about 754 square km (290 square miles) with a population of about 73,000. It is known for its great natural beauty.

The water he wants to sell is not desalted water - it's all fresh water, from streams (365!) and aquifers (my contact said it was 'runoff'). The water will be shipped out in supertankers or bags to whomever wants to purchase it. By my calculation, 37B gallons would fill 440 average supertankers (assuming a capacity 2 million barrels or 84M gallons per tanker). So that's about 10 supertankers per week headed for wherever needs it.

My contact said it would help the world's water crisis. I pointed out that although 37B gallons is a lot of water, it's literally a drop in the bucket on a global scale. But it certainly could relieve short-term problems, such as coastal cities undergoing dry times. 

And, oh yeah - he mentioned about $3B in annual profits.

He said that China and Venezuela are also interested in the island's water, which has apparently piqued the curiosity of the U.S. Department of State.

So does Dominica have enough water? It is one of the wettest islands in the Caribbean. Here's the rainfall and temperature plot from the World Travel Guide for the capital, Roseau, located on the drier southwest coast of the island: 

If you add the rainfall numbers up you get over 2000 mm (2 meters or almost 80 inches) of rain per year.

I don't know the water budget of the island, but the Wikipedia entry says that the wetter, east side of the island gets as much as 500 cm (almost 200 inches) of annual rainfall, with mountain slopes receiving 900 cm (almost 360 inches!). The drier west side gets about 180 cm (70 inches).

So let's do some back-of-the-envelope calculations. Let's assume that the average annual rainfall over the entire island is (500 cm+ 180 cm)/2  = 340 cm = 3.4 m.

Distribute that amount over 754 square kilometers (754,000,000 square meters) and you have 2.6 B cubic meters (rounded).

So, since over the long term, P = ET + R (precipitation = evapotranspiration + runoff) we can calculate the long-term average runoff if we know the ET. I will assume that on average, 2/3 of the P is ET and 1/3 is R (global continental averages from G. Hornberger et al., 1998, Elements of Physical Hydrology, Chapters 1 and 2 - not great approximations for a tropical island). That means that the average annual runoff is about 1.1 meters per year, or about 0.9B cubic meters. In other units the average annual runoff is about 900,000,000 cubic meters or about 730,000 acre-feet or about 238B gallons!

So my friend wants to take about 16% of the total runoff for export. Is that going to be a problem?

The answer: I don't know for sure. Dominica does have a heckuva lot of fresh water, but don't forget that the island's environment and the near-shore marine ecosystem are adjusted to this amount. So what happens when you remove 16% of this fresh water each year? That's the question that must be asnwered before this project proceeds.

Keep in mind that my figures are very crude and I'm using a steady-state budget to evaluate an inherently transient situation. I'm just trying to illustrate a point: there is a lot of fresh water on Dominica but we still need to be concerned about withdrawing some of that water. Adverse effects could result not only on the land-based ecosystems but also near-shore marine ones. 

"What is done in the dark will appear in the light." -- Caribbean proverb

Comments

[Jan]

Privatization of water has been a huge problem for other countries...the poor are always the ones that suffer. Some countries don't even allow their own people to use the water...they have to buy it! Some wont even allow the people to collect their rainfall. Big problems and greed is always at the base of it. If large corporations are involved, you can be sure someone is getting hurt.

[Colin]

1. Rainfall is a natural resource. It costs nothing to produce and falls freely onto everybody's land. Why should individuals or companies, local or foreign, be allowed to profit from the sale of Dominican water? If water is sold to other countries, then Dominica - the Government of Dominica - should be the only entity permitted to collect revenue from its sale, for the benefit of the island and all its inhabitants. I would urge our recently re-elected government to pass legislation to this effect.
2. Has an environmental impact assessment been conducted? I doubt. As your article correctly points out, the removal of 37bn gallons or more annually MUST have an effect on ecosystems which have evolved in these conditions, whether it be the farmland or flora and fauna downstream from collection point or the marine habitat offshore. Another article I read today on dominicacentral.com suggests that 300bn gallons will be exported! Removal of all this fresh cool water might even affect the system of ocean currents, thus the weather patterns. We often seem too eager these days to interfere with the very environment that sustains us. The motivation? What else - profit and greed!

[Jeff L. Stott]

If they are going to take the water right before it reaches the ocean then it should not have an effect on land based ecosystems. Simply because the land based ecosystems have used all the water they need by the time the water reaches the ocean.

The amount of water being shipped elsewhere is such a small percentage that there really should not be a huge effect on the near shore ecosystems either. There might be a slight increase in salinity but not enough to change anything significantly.

[PAUL F MILLER]

The writer/author brings up very valid points for consideration, though caught in the contemporary web of immediacy I suspect we take the money first and ask and answer the questions later, if at all.

[David Zetland]

Yeah -- near shore marine problems for sure. The other problem (perhaps) is getting enough streams consolidated into one "pipe" for export. Better than towing icebergs, tho...