1.3 Dominican Republic

In the south-west of the Dominican Republic, an inhospitable arid area extends over some 1000 sq km and until now has been only marginally usable. The institutions of the country developed a model which includes ground water investigation as part of a "project for a rational use of the dry forest." In this way, continued destruction and exploitation by charcoal-burners and goat breeders would come to an end, regeneration of the natural vegetation would become possible while allowing the inhabitants of the island a moderate utilization. For that purpose, both drinking water and irrigating water for young vegetation is necessary.

The project area is situated about 100 km west of Santo Domingo and borders the Caribbean Sea. The very hilly region lies at a mean height of 120 m above sea level and slopes gently to the sea and to the interior. The annual precipitation is generally below 500 mm/yr. The surface layer is rarely thicker than 10 cm and mostly dry, in some areas slightly salty. At numerous places, the rock formation is exposed without any cover. Geological maps do not give any information about this area. In the more densely populated and better investigated areas flysch zones and clay underground with karstified calcareous sandstone intercalations are indicated.

In a joint investigation by the local national water authority and GTZ experts it became apparent after a survey of the area, comprising geo-electrical investigations and smaller-scale ground exploration, that no useful aquifers were available and that the ground water potential was insufficient for irrigation. Deliverable ground water might only—if at all—be found in very limited quantities in small fissures [13]. It is therefore necessary to localize the junction of faults on one hand, and the mostly deep lying fractured limestone banks on the other hand. In the western part of the project area, near Canao and not far from San Antonio, three 300 m deep boreholes are known, all of which were dry.

As a last resort, Schröter was requested to inspect the area referred to. By means of the dowsing technique he tried to locate faults in one part of the area. Very soon he thought he had found one of them and indicated 5 drilling points in 5 km intervals, not far from Galindo. In each case, he predicted not only the precise sites but also the approximate obtainable yield and the required drilling depth. The first borehole should have been drilled to a depth of 50 m. After having pierced through a thick layer of clay, strong artesian water was surprisingly found at a depth of 48 m. Unfortunately, it was a hot mineral spring with a water temperature of 35 degrees which, due to its high sulfate content, was not appropriate for irrigation purposes. However, electrical conductivity measurements as a function of depth showed a prominent decrease in sulfur content below 40 m, so that possible fresh water might have been also present, but local conditions did not allow a further investigation.

One of the four other drilling points next to Galindo should have been drilled to 70 m. Once more, water was found at 68 m which rose to a depth of 30 m in the borehole. The immediately measured water conductivity showed that it might have been good drinking water quality. The upper layers, however, had revealed the presence of significant amounts of clay; this resulted in a gradual plugging of the borehole which eventually ran dry. The local limited technical facilities were not adequate to solve this problem of mere borehole maintenance and development. Likewise, the next borehole became clogged too, so that the project had to be abandoned for the time being. Unfortunately, the drilling of the two remaining locations was also postponed.

Nevertheless, three borehole drillings had been performed in such an undoubtedly difficult area and in each case unexpectedly large water quantities had been encountered. On account of the available hydro-geologically relevant data and according to the opinion of specialists, it must be viewed as practically impossible to locate such sites by accident or by means of usual classical techniques.