1.2 Philippines

According to an agreement between Germany and the Philippines a special energy program had to be set up, which involved the equipment of Verde Island with small solar power systems. In accordance with the desire of the population, GTZ first tried, as a measure to improve the confidence in technical aid programs, to ameliorate the catastrophic water supply. As no comprehensive and financial planning was foreseen for such a small additional action, the GTZ expert Schröter was requested to establish all-season potable water wells in some villages as soon as possible and at a most economical level—feasible only by means of the effective dowsing method.

Verde Island extends over some 17 sq km and, because of its volcanic origin, is only inhabited by about 8000 persons who live in the flat coastal zone. The existence of 7 boreholes could be ascertained after a survey, but only two of them were very deep (about 70 m) and could provide potable water; the one borehole had a former yield of 40 l/minute; by now, however, both wells were out of order. Furthermore, there were 47 dug wells of which 14 could not be used on account of a high salinity; the remaining wells either fell dry in the period from January to May, or exhibited significant deterioration due to salt water intrusion. During that critical season, drinking water had often to be brought by ship to the island.

Modestly extensive geological and hydrogeological information, as well as some data on the existing wells were available from local and national authorities [12]. They indicated a mean precipitation of about 1600 mm/yr, which quickly drains away from the slopes of the 350 m high central mountain range towards the sea. Surface water like perennial rivers or lakes is not present throughout the year. The volcanic underground lies under a surface layer with thickness of typically a few meters and of a strongly varying formation (porphyry, limestone, sandstone, tuff and diverse conglomerates). The underground is considered as being relatively impermeable with respect to the infiltration of water. Ground water occurs especially in permeable fractures and weathered zones. These consist partly in locally limited fracture zones and partly in greater aggregations often containing sulfur, loose rock and different sediments; a continuous water influx is considered to be weak in these zones.

Thus, one can find most different conditions in close proximity on this island. In summary, peculiar problems arise for water prospecting because of the limited water storage capacity of the underground, the poor permeability, the lack of extended aquifers and the intrusion of salt water from the sea. For the areas lying next to the shore line, the same observations are valid as have been amply described in the Sri Lanka project. The totally different yields and qualities of wells existing on Verde island support these conjectures.

Of the six communities on Verde Island, only San Andres had no water shortage all round the year due to several productive dug wells. Hydro-geological causes could not be found to explain this fortunate situation. More recently, however, it turned out that the good wells had been sited by a local dowser, namely the previous mayor of the place who is still alive. Though this person, after the successful sitings, was still living there, the apparent talent has not been exploited by the neighboring villagers; the reasons remain unknown. Incidentally, of the two deep wells described above, the one having the better yield has also been located by means of the dowsing technique, applied by a foreign clergyman.

In four villages, Schröter found a total of 11 positions for dug wells which ought be equipped with hand pumps. He determined the sites for 10 of the 11 wells on the 10-200 m wide inhabited shore area where he claimed to have found shallow fractured zones by means of the dowsing technique. To support his expectation on hydrogeological grounds, it could be argued that fresh water might be present at these shallow positions: water running down from the mountain along the subterranean fracture zone might exert enough pressure to impede salt water infiltration from the sea. It is quite noteworthy that these sites were sometimes less than 100 m away from existing but unusable (salty) wells.

In 9 of 11 cases, the expected fresh water could be found, although the sites lay only between 20 and 50 m away from the sea and the well bottom was below the sea level. In one instance, a layer of 4 m thick hard rock had to be pierced before water was indeed found in a layer of loose rock at a depth of 5 m below ground level. One of the two dry dug wells was situated at some 1000 m from the sea and remained waterless even up to a depth of 10 m.

At one of the 9 successful wells, Schröter sensed several underground water courses streaming down from the mountain slopes, allegedly exploitable at a depth of about 7.5 m; this prediction, though treated with skepticism, was put down to protocol. In order to attain a maximum water yield the well should be dug at the intersection of the outlined streamlets. After Schröter had left, the well was dug and water was indeed found at a depth of 7.2 m. Unfortunately, it turned out to be too mineralized. The responsible program leader then decided to take the prognostic details established by Schröter more seriously and pumped out the well to check for the possible existence of different inflows. To his surprise, four of these small streamlets could be clearly identified and were separated from each other. One of them was mineralized and could be sealed off by simple means. The remaining 80% of the influx (6 l/min) was potable water. This precise and conventionally unbelievable prognosis will be considered later on again, because it is contrary to what can be expected on the basis of conventional prospecting, and because such a situation is well suited for appropriate scientific test purposes.

Additionally, Schröter localized the sites for another three deep boreholes further away from the coast. The first 24 m deep well provided excellent fresh water; at first, the two other wells produced good water too, but it became slightly saline after completion of the well construction, probably on account of the use of inadequate sea sand as filter material.

On request of the local project management another dowser, a clergyman of German origin, was appointed in 1990 to locate 30 new wells in order to improve the future water supply. Later on, Schröter checked the sites by means of his method and made a detailed prediction referring to the expected depths and yields, as well as to the salinity risk (see the corresponding discussion in part 3). If these locations are drilled later on, the value of the indications of both dowsers could be well checked. The provincial government, impressed by the success of the GTZ procedures, thereafter appointed other dowsers for new successful water investigations.

To conclude, it may be said that decisive indications for appropriate well points cannot be obtained in this area without excessive input of measuring techniques. Useful vegetation indications are lacking. As has been repeatedly mentioned, geo-electrical procedures are not very helpful for a safe identification of small streamlets in inhomogenous underground. Larger fracture formations are certainly detectable, but those show an increased risk for multiple salt infiltration. The successfully dug wells were all fed by small and very narrowly localized streamlets; if these wells had been displaced by only one or two meters, fresh water (from the direction of the mountains) would not have been found. Numerous unproductive dug wells of former times testify that such small fluxes are not very often available and may be hardly found by accident or by intelligent guessing.