1.7 Cape Verde Islands (Fogo)

One of the Cape Verde Islands in the Atlantic Ocean west of Senegal, Fogo has been investigated and intensively examined since 1979 for water resource development, first by the Bundesanstalt für Geowissenschaften and Rohstoffe (BGR, Germany), as well as by the Kreditanstalt für Wiederaufbau (KFW) [16, 17], and finally by GTZ and partners [18]. The island extends over an area of some 25 km in diameter and consists mainly of a volcano (last eruption in 1951) rising to 2829 m above sea level; the island has 40,000 inhabitants living on the steep slopes and on the coastal zone. The mean annual precipitation varies from 1100 mm in the northern part to less than 300 mm in the southern part of the island. In the last decade, a strong decline in precipitation could be noticed.

Without supplementary artificial irrigation, agriculture can only be practiced during the 4 months of the rainy season when surface water is available. At other times, people get their water from three springs which have a total yield of 20 l/sec and lie at sea level. Besides that, there are some other small springs and wells of less significance. On account of the difficult geological conditions, traditional dug wells are generally not possible. In the higher lying regions of the island the supply situation is absolutely unsatisfactory for private and agricultural needs; because of economic considerations, the required large water quantities cannot be pumped up to all the prospective users.

The availability of all-year productive springs proves the existence of permanent ground water; however, there are only seven springs on higher sites whose total yield does not exceed 70 l/min. The ground water recharge is estimated to be relatively high and is estimated to be several times the yield of the known springs. Permeable volcanic ashes and scoriae, as well as the bottom of the volcano crater which lacks of an outlet, promote significant infiltration. It may be supposed that the major part of the ground water (more than 90%) flows through a subterranean channel system and predominantly emerges undetected below sea level.

The underground consists of a complex layer structure of basalt, scoriae, volcanic breccia, tuffaceous rock and ashes, varying abruptly in order and locality. For that reason, one has to take into consideration significant anisotropies in the ground water body, as well as frequent occurrence of galleries. Due to the uncertain ground water situation, an investigation program involving 50–300 m deep boreholes was proposed. The rocks are considered to be more or less impermeable and one assumes that dry boreholes are not only possible, but probable.

Because of the strongly varying rock formations geophysical measurements were not conducted to site drilling spots — they would not have provided supplementary useful information for the area. Accordingly, the proposed final drilling points were dictated by considering topographic-morphologic features and appropriate access possibilities.

In the scope of GTZ activities, Schröter was requested at the end of 1988 to undertake dowsing investigations on Fogo. He located seven drilling sites on the highlands (about 1000 m above sea level), where useful yields of several liter/sec were expected at depths of 45, 70, 80, 90, 130, 150 and 250 m below the ground level of the respective site. Particularly remarkable is the fact that he located shallow fracture zones at seven other sites on the highlands: there, the possibility for dug wells was given which could be built without excessive effort and would deliver (predicted) mean yields of 30 l/min in depths between 8 and 25 m.

More than 10 years after the beginning of the original investigations, the first exploration drillings were carried out, though only at sites conventionally determined. At a location some 500 m above sea level, the first drilling was conducted to a depth of 150 m without finding a single sign of ground water. With this, the early hypothesis supposing that a ground water surface lies in a large front not too deep below ground level had to be abandoned. Consequently, no further drillings were carried out on the higher lying slopes. Instead, the next drilling was carried out at a spot 100 m above sea level on the shore and struck a rich fresh water lens at a depth of 100 m, quite close to sea level. With this, a fourth spring was provided to solve the problem for the coastal zone, but the shortage in the higher lying regions still remains.

After concluding of the still ongoing investigation by the KFW/BGR group, GTZ plans to drill some of the dug wells proposed by Schröter on the higher lying sites. Although results are not yet available, the existing quite interesting situation which evolved until 1990 is well documented and partly mentioned here. If only a fraction of the dowsing predictions could be verified in this extremely difficult area, it would contribute towards a better understanding of the unconventional water detection technique.

1.8 Kenya

In Kenya's Lamu District, a thinly populated area of 100 sq km, a settlement program has been put into effect for some future 10,000 inhabitants. For this reason, a new water supply system had to be provided with high priority. One of the main problems consisted in the well-known circumstance that a ground water horizon can be reached by means of usual dug wells, but the water exhibits generally a high content of salt and, thus, does not satisfy the needs. Near the neighboring village Witu, however, there were four old wells with depths of 13 and 28 m, of which two could still deliver fresh water. At the beginning of 1990, GTZ tried to implement also the unconventional method to locate appropriate sites for dug wells. The prospecting based on dowsing was quite specific, as Schröter predicted the presence of fresh water in shallow layers in spite of the risk of sea water intrusion.

At once, provisional test drillings of limited scale were undertaken by means of hand drills at several of the points specified by Schröter. The overburden was only a few meters thick with underlying coral-calcareous deposits. Relatively close to the surface saline water was found between 5 and 10 m, which was of no help. Nevertheless, Schröter insisted that the fracture zone he had sensed by means of his dowsing reaction was not yet reached and that fresh water could only be found below the encountered salt water table. As this prediction seemed to be unlikely from a hydrogeological point of view, one first hesitated to continue with further drilling. Finally, it was decided to deepen seven of the boreholes. It turned out that Schröter¹s unbelievable prediction was indeed correct: a thin clay layer underlay the saline water stratum and immediately beneath, the expected fresh and good drinking water showed up at depths between 12 and 15 m. At several other points located by means of the dowsing technique, hard rock was reached which could not be pierced by the simple hand drill employed. In these cases, one must wait for the results until more suitable technical measures can be implemented into the project.

An appropriate construction and development of the already successful boreholes could lead to useful fresh water wells by correctly sealing off salt water inflow from the upper layers. This situation is interesting and informative as it is impossible or very difficult to make quick and reliable predictions of small fresh water resources situated below an extended thicker salt water stratum without exploration drillings. The continuation of the project will reveal the significance of the dowsing technique within this kind of soil formation.

1.9 Sinai

In most parts of the country, Egypt suffers from an ongoing water scarcity. This applies especially to the Sinai peninsula, whose desert character is even known to non-experts. Within the scope of a cooperation between Egyptian authorities and GTZ, especially focusing on rural areas in central and north Sinai, called RDNS (Rural Development North-Sinai) and SHF (Self Help Fund El Arish), the usefulness of the dowsing technique could once more be demonstrated. A high degree of drought characterizes this project area; precipitation is generally less than 30 mm/yr, of which the major part evaporates. Accordingly, the regeneration rate of ground water is exceedingly low. Only in the northern coastal zone, are some what higher quantities recorded, e.g. about 100 mm/yr in El Arish. In central Sinai folded rock formations and flat regions with Tertiary, shallow weathered karst can be found. Under certain conditions, it may be possible that limited amounts of water accumulate at moderate depth.

In the past, numerous attempts have been undertaken to find both deep and shallow lying aquifers. More recently, renewed efforts were made by Israeli authorities (during the occupation from 1967 to 1982), and three projects were implemented after 1985, initiated by UNICEF, EC (European Market Community) and a cooperation with Japan, especially in order to investigate deep aquifers (down to 1000 m). Achieved success was moderate and did not match expectations. For example, 87 drillings were executed up to 500 m within the EC project, but only 8 of these resulted in the finding of water. It should be added, that the extraction from a great depth is both less economic and not very advisable since the water found there is mostly of fossil origin, that means it hardly regenerates.

In central Sinai, there are only a few production wells and the additional use of tank-trucks is necessary to ensure a minimum water supply for the scattered population. Hitherto, investigations for the detection of supposed shallow and very small subterranean water bearing structures remained practically without success. Therefore, the Egyptian authorities welcomed the GTZ proposal to try the dowsing technique in this most intricate area.

Under the control of experts from the Desert Institute of Cairo, Schröter determined within a few days 15 drilling points in 8 different areas, separated some 150 km from each other. Besides the exact location, he also predicted the supposed drilling depth and the expected yield. The suggested depths ranged from 8 to 60 m, with an average of 25 m, whereas the indicated yields varied between 15 and 60 l/min.

Meanwhile, 12 of the 15 sites have been explored. In view of the difficult conditions the provisionally available results are very impressive and had not been expected at all: right away, in 10 cases the attained yield amounted to 30 l/min, without exceeding the predicted drilling depth. It might be hoped that the ongoing well construction increases the initial yield numbers. Only two holes were dry; for given reasons, it has yet to be checked whether exceedingly large quantities of bentonite, used in conjunction with the applied drilling method, might have clogged the small water influx from narrow weathered fissures.

In any case, the available results have been classified as highly positive so that the Egyptian authorities requested the GTZ dowser for a survey of two other arid areas elsewhere in the country where conventional water prospecting programs had produced so many series of expensive and unsuccessful dry drillings that their continuation was at stake. The results due to dowsing are not yet available.

TABLE 4 Site Rate (m3/day) Depth Remark th exp th exp 1 Quseima 50 > 50 30 25 2 Quseima 50 > 50 5-15 5 3 Quseima 75 - 60 ? displaced 1 m 4 Bir Buraid 30 50 17 7 5 Bir Guriad 40 35 17 14 displaced 5m 6 Bir Guraid 50 45 25 21 displaced 1m 7 Bir Guraid 60 50 30 20 8 El Tamad 100 25 17 7 (a) 9 Kuntilla 50 30 not drilled 10 Naqab 75 35 ? displaced 1m (b) 11 Naqab 30 18 not drilled 12 Ghofga 75 40 35 19 (b) 13 Ghofga 25 27 25 17 14 Ghabiya 25 - 18 bentonite (c) 15 Natila 25 20 18 < 18

Table 4. New wells in Central Sinai Desert. The data stated includes delivery capacities in cubic meters per day and well depths in meters, once according to the dowserUs prognosis (th) and once according to preliminary results of drilling (exp). All wells still have to be conditioned and washed out, which should yield even higher delivery capacities Q particularly for the well in El Tamad (a). Since some of the wells were not drilled at the designated points, a number of very narrow water-bearing fissures may have been missed. One borehole near Naqab (b) has not yet been completed, because the rock proved extremely hard. In some cases, especially in Ghabiya (c), so much bentonite was poured into the boreholes that small influxes at the entrance into the hole may have been plugged off.

For further investigations of the dowsing phenomenon, which yet remains to be understood, the following observation from the prospecting in central Sinai is very important: some of the drilling points determined initially and solely by the dowsing technique could be verified thereafter by a simple technical measuring procedure. Operating a receiver working in the lower UKW band, anomalies of the field strength appeared, which were quite sharply localized (to less than about 1 m) and harmonized very well with the points, respective lines, formerly pinpointed by means of the dowsing technique. It must also be made clear, though, that the investigated fracture zones appeared as being so weak and narrowly confined that their purely technical localization is still totally impractical without combination with dowsing. By the way, this finding must be viewed as another indication for the validity of the statement that dowsing reactions are not only occurring merely by chance, but are linked with a deeper origin, which may also relate to the electromagnetic sensitivity of biological organisms (part 3.3).

Finally, it remains to be added that the localization of successful wells could not be explained by resorting to known effects. Most of the wells lie in a flat area where no anomalies due to vegetation or topography can be spotted. If such subtle indications had been available here, indigenous local experts would surely have recognized and exploited them long ago (see part 3.1).