1.10 Namibia

Since the beginning of 1992, extensive efforts have been invested in the further practical testing of the integrative model described in part 4.2 within the scope of technical cooperation between GTZ and the Department of Water Affairs (DWA) in Namibia. In the interest of pertinent progress, project-relevant dowsing data is being checked and verified as systematically as possible according to two different measurement techniques (VLF, SF). The VLF long-wave measurements are being conducted with the set of equipment known as "WADI." An expanded version (variable transmitter with receiver) of the SF short-wave method was made available by the Munich-based group of researchers in cooperation with the GTZ following encouraging experience in the Sinai (part 1.9). The project proved successful, and the authorities in Namibia asked GTZ to extend Schröter's assignment to beyond the previously agreed year 1992. At the time of printing, prospecting is still under way, so that no final report is yet available. However, in addition to ample information on results to date, three interim reports [23–25] are at hand which justify preliminary reporting within the framework of the intended phenomenon profiles. Final evaluation of the results, however, will be contingent upon the forthcoming final report from the DWA, which will include the geotechnical measurements and their correlation with the dowsing data.

The prospecting was done in regions where conventional methods have proved difficult and extensively disappointing. As regards the geological set-up in the subject areas, the water is confined to fissured zones of the crystalline solid rock. Covered by 60 to 120 meters of unconsolidated rock (sand, gravel), those zones begin at relatively large depths. The bushy terrain makes it extremely difficult to find superficial features with which to pinpoint the borehole locations. Nevertheless, the first hole Schröter had arranged to be drilled in the village of Tsumis was successful, yielding 80 l/min at a depth of 150 m.

An initial prospecting series was conducted in the areas surrounding Kamanjab, which was characterized by granite and gneiss. Of the 28 boreholes with an average depth of 74 m drilled there in 1987, as many as 25 were completely dry, and the remaining 3 yielded only very small amounts of water. Schröter located three new drilling points at which boreholes were sunk to about 80 m: they yielded 170, 35 and roughly 15 l/min, respectively. Considering the circumstances involved, the first result was quite good. A verticality check of the other two boreholes showed that they ran at an inclination and may not have properly intercepted the fissured zone (see below). All 3 locations were surveyed with the aid of the WADI unit, and the results showed striking coincidence between Schröter's points and salient maxima in the real part of the measuring curves.

Fig. 3. Examples of VLF data obtained with the TWADIU-instrument at sites with fissured bedrock in Namibia: in an area near Namutoni Schrter indicated the presence of two intersecting water-carrying subsoil structures. He determined a survey line which covered the two structures; his dowsing-reaction points are labeled A and B. The TWADIU-profile measured at a later time exhibits prominent maxima in the real part of the data. F signifies the influence of a fence.

Fig. 4. Similar data obtained at the well site where the drilling point was initially displaced by 1.6 m with respect to SchrterUs point C, resulting in a low yield. A second strictly vertical drilling at the precise point C turned out to be successful (see text). Obviously, VLF data does not suffice to guarantee a successful drilling. However, dowsing reaction points and locations of maxima in VLF data do not always coincide as well as is the case in the examples shown here.

Between 1968 and 1990, some 17 deep wells were sunk in the vicinity of Kalkfeld. Only one of them proved useful, while the others were all either totally dry or extremely weak. Consequently, the town remained without a safe supply of water. Within half a day, Schröter located two promising drilling points and suggested a depth of 140 m for each. The first hole immediately yielded a spectacular 250 l/min, thus solving the community's most urgent problem. The second well produced only about 15 l/min, but a subsequent verticality check showed a 1.5 deviation from perpendicular, which can be of significance, as explained below.

In Grünau, the drilling team sunk a hole 1.6 m away from the point indicated by Schröter. The resultant yield at the final depth of 120 m amounted to only 10 l/min. A subsequent verticality check indicated again a deviation of about 2 degrees, meaning that the well face was actually shifted by several meters away from the target point. Since Schröter had assumed very narrow zones of fissuring, this time a new well was sunk at exactly the originally indicated point 1.6 m away from the first hole. Of course, more appropriate measures were taken to guarantee vertical drilling. The results justified the work, i.e., the new yield was high enough to warrant completion of a service well (although the final numerical results of the pumping test are not yet available).

This test is most significant in that it provides experimental verification of two frequently articulated suppositions: water-bearing fissure zones can be (1) very narrow and (2) located with surprising accuracy by dowsing. Moreover, the result proves that it is not at all an excuse when Schröter attributes poor results to the non-verticality of a drilled well.

Those remarkable findings led to measures aimed at making all further wells in that area as vertical as possible. In Owambo, Kokoland and West Hereroland, where the ground water situation is by no means better than in the areas discussed above, 17 new boreholes were drilled according to the modified and improved method. Even though some of them had to reach as deep as 200 m, all were successful. The project experience gained with the type-WADI long-wave measuring instrument is especially noteworthy. As already mentioned, numerous signal patterns that could be interpreted as indicative of good prospects were obtained in the latter-mentioned prospecting area. As widely known and accepted among experts, such patterns can be quite helpful. On the other hand, such measurements normally would not suffice as a sole indicator of suitable drilling points. Notably the most productive well near Owambo, with more than 3000 l/min — did not betray its presence via a conspicuous VLF signal. If those responsible had relied more on the WADI readings, they might not have even drilled that well. Consequently, it would most probably be worthwhile using the latest technology to look for other types of physical signals at that particular location.