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Hydrology

Variations in geological structures, geomorphology, rock types, and precipitation contribute to a wide variety of ground water conditions in different parts of the island. The primary aquifer systems in Dominica, Antigua, Barbuda, St. Kitts, and Nevis are as follows:

• Tertiary to Quaternary age limestone and Recent age beach sand

• Oligocene to Recent age mixed volcanic rocks with minor amounts of Recent age alluvium

• Pliocene to Pleistocene age clay and tuff

• Oligocene to Pleistocene mixed volcanic and sedimentary rocks

Access to existing and potential well sites is dependent upon geography, density of vegetation, and road networks. Other factors such as geothermal activity and landslides may impact ground water exploration. Lowland areas generally have improved roads and less dense vegetation than highland areas.

Surface Water Quality

The significant threat to Dominica’s water quality is turbidity. Documented studies have shown many of the upland areas are prone to landslides during the wet season from June to October.242 Such landslides allow considerable amounts of sediment to be introduced at the headwater of many streams in affected areas. Additionally, some rural communities deforest steep slopes for cultivation of crops, which further contributes to the sediment load in rivers.

Open dumping of solid and industrial wastes in rural communities (e.g., Marigot, Castle Bruce, La Plaine, etc.) also contributes to the pollution of streams. Rural communities have no central collection service for refuse. Streams provide easy outlets for household garbage. Industrial establishments such as rum distilleries, auto repair garages, and furniture manufacturers openly dump their effluents and by-products into adjacent streams.

The impact of pesticide use on water quality has not been determined. No formally mandated monitoring procedures to test for pesticides and fertilizers exist. Pesticides are used for the cultivation of bananas, citrus, coconuts, and other crops. In January, 1990, the Consortium for International Crop Protection (CICP) conducted limited sampling for selected pesticides (paraquat, glyphosphate, cabamates, organochlorides, and organophosphates) on selected rivers.243 Results of such sampling revealed no detectable pesticide residues. However, CICP investigators expressed concern over organochloride concentrations in wildlife.

A few small lakes exist in the Castle Bruce Basin (V). Small quantities of fresh water are available from Boeri Lake and Fresh Water Lake year-round. Both lakes are classified as open lakes (i.e., both lakes are fed by small streams and drain into streams). However, the government of Dominica diverts the drainage flow of both lakes, via a weir and pipeline, to feed the hydroelectric power stations at Laudat and Trafalgar Falls at the headwaters of the Roseau River. Boiling Lake, a very small geothermal lake measuring 67 meters (220 feet) in diameter, is the largest boiling lake in the world. Two small streams feed this boiling lake, which is situated inside a volcanic crater.

The Boiling Lake is situated in the Morne Trois Pitons National Park - Dominica's World Heritage site. It is a flooded fumarole 6.5 miles (10.5 km) east of Roseau, Dominica. It is filled with bubbling greyish-blue water that is usually enveloped in a cloud of vapour. The lake is approximately 200 ft (60 m) across.

The first recorded sighting of the lake was in 1870 by Mr. Watt and Dr. Nicholls, two Englishmen working in Dominica at that time. In 1875, Mr. H. Prestoe, a government botanist, and Dr. Nicholls were commissioned to investigate this natural phenomenon. They measured the water temperature and found it to range from 180 to 197 degrees Fahrenheit (82 to 91.5 degrees Celsius) along the edges, but could not measure the temperature at the centre where the lake is actively boiling. They recorded the depth to be greater than 195 ft (59 m).

Periodically, there have been fluctuations in the level and activity of the lake. It was all but empty in June 2006, however as of April 2008 the lake is full and boiling vigorously.

There is no road leading to the lake. In order to get there, people have to hike about 13 km, total of three hours one way.

On July 6th, 2007, Adventure film maker George Kourounis became the first person to ever cross the boiling lake from above, suspended by ropes over the most violently boiling section. This event was filmed for the TV series Angry Planet.