아프리카 탄자니아에 우물짓기 사업 이렇게 진행되고 있습니다.

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아프리카에 우물을 짓는다는 생각, 처음에는 막연하기만 했지만 이제 본격적으로 진행이 되고 있습니다.
한편으로는 과연 일을 맡은 측에서 성실하게 해 줄 것인지 걱정도 많았고,
또 보낸 돈이 제대로 사용되는지 알수도 없는 노릇이기도 해서 마음에 근심도 있었지만,
신앙 있는 분들이 기도하면서 진행하고 있어서 이제는 많이 마음이 놓입니다.
 
아래는 필드 조사 장면이구요...
그리고 필드 조사 결과 내용도 첨부로 올려 드립니다.
 
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
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아래는 필드 조사 관련 내용입니다.
(일일히 번역 못 해 드림을 죄송하게 생각합니다.) 
 

HYDROGEOLOGIOCAL / GEOPHYSICAL SURVEY  REPORT ON BOREHOLE SITING AT MAHAKA VILLAGE

MANYONI DISTRICT SINGIDA REGION

BY

M. CHALI

WATER RESOURCES DIVISION

P.O. BOX 412

DODOMA

             NOVEMBER, 2010

1.0         INTRODUCTION

Dr. Yohana S. Masinga Arch Bishop of Philadelphia Gospel Assembly Dodoma commissioned the Authour of this report to study/investigate the groundwater potential of Mahaka village in a bid to locate borehole drilling site (s) so as to establish a water supply source for the village.  The water is  intended to solve water shortage  for the village.

The main task of the investigations team being to asses the potential of  the villages groundwater resources recommend drill sites for the new borehole, comment on the aspects of  depths to potential aquifers with  reasonable yields and quality.  The investigation was approached as a multi step exercise that comprised of:-

I.          Inventory of geological, borehole drilling and other hydrogeological data.  Study of geological and Topo guide maps to check for geological structures extent of catchment area and select sites for further investigations.

II.            Fieldwork verification of the sites selected from guide maps, reconnaissance to check for hydrogeological conditions, magnetic survey to locate possible geological structures relevant to groundwater occurrence and resistivity survey to investigate subsurface conditions.

III.           Interpretation of Geophysical data, correlation, analysis and eval‎uation of all information gathered both in field and from guide maps, interpretation preparation of findings and recommendations.

2.0         LOCATION

Mahaka village is located about 50 km South West of Chikuyu village.  Geographically Mahaka village appears within the following meridians 06.12701^o S and 035.05803^oE.

3.0         PRESENT WATER SOURCES

At present the Mahaka villagers are depending only on one shallow well fitted with hand pump with the yield not  sufficient to meet the demand of the  village population.  It is because of the  above reason that Arch Bishop of Philadelphia Gospel Assembly opted to find the new source to augment the supply .

4.0        PHYSIOGRAPHY AND DRAINAGE PATTERN

           4.1        Physiography

Mahaka village is placed on the northerly sloping land of Bahi swamp and  South West of Kilimatinde Escarpment.  High grounds – Nyambaru hills and Kilimatinde Escarpment influencing areas morphology are placed Westwards and strike NE – SW.

The study area is generally a plain land that gently slopes Westwards.  The altitude of the study area range between 840 m and 845 m above mean sea level (amsl).

Situated in the semi-arid zone, the area experiences less precipitation than evapotranspiration a climatic condition that does not sustain perennial streams or natural surface water bodies.  As such Mahaka village is characterized by a few drainage gullies and ephemeral streams.

4.2         Drainage pattern

All notable streams flow in a NE – SW direction.  However, the drainage of the study

area fall under the Bahi swampy drainage system.

5.0        GEOLOGY AND HYDROGEOLOGY

             5.1        Geology

The pre-Cambrian rocks exclusively cover the area with low grade metamorphic rock (gneiss and schist) dominating.  These rock type can rarely be observed on hill tops and on gulley bottom  to the West.  The surface geology of the study area is made up of grayish sandy clay soils.

The clays, cover extensively the study area.  At valley bottom sandy clays and mbuga clays are formed after excessive weathering clay based minerals.

5.2         Hydrogeology

One  borehole was drilled within the village  to the  West of the village near the Escarpment some years back.  This borehole was vandalized and no datas were available.

As afore said, only one shallow well fitted with  hand pump was constructed in the village.

5.3         Groundwater flow and recharge means

Groundwater flow and recharge in the basement system strictly obeys the structure and the topographical set up.  That means, groundwater flows are controlled by drainage devides.  Groundwater quantity is therefore a factor of rainfall intensity, extent of catchment area and related secondary permeability.

 As a rule, groundwater flows along a porous formational media from high gradient to low gradient areas.

6.0         GEOPHYSICAL SURVEYS

Subsurface conditions were studied by the  magnetic and resistivity methods via the Line-Tie and Vertical Electrical Sounding (VES) modes of geophysics science.

6.1         Magnetic Method

Ø  Aim

This was engaged to detect your intrusive rocks and or disturbed portions of the bedrocks through measuring magnetic intensity variations of the bedrock.

Ø  Field Measurement

Measurements were dome by executing the Tie-line mode.  Profiles were oriented to cross possible structures of magnetic low zones as detailed on the structural map.  In this case, the nearest magnetic low zones trend about S – N and so the profiles were oriented in E – W.

Reading in nT were recorded at 5 m interval between consecutive stations and variations noted upon plotting results in nT against distance in metres.  Notable negative anomalies were subjected to Geo-electric method (survey) follow up

Two (2) magnetic profile lines were recorded across the study area and five (5) notable anomalies were picked along profiling.  There were later subjected to VES  probing.

6.2         Geo-electric (Resistivity) Method

Ø  Aim

To study subsurface conditions through Vertical Electrical Soundings (VES) mode.  This method is able to delineate subsurface conductive geo-formational strata hence establish than number, interprete their true resistivities and thickness thus deduce for aquifer possibilities depth of occurrence and  possible depth to stable bedrock.

Five (5) VES were recorded at anomalous stations along the two (2) profiles.  The interpreted resistivity at each station is as follows in Table I.

Table I Interpreted resistivity results

VES 1 P 1

Depth range (m)	Layer Resistivity   (Ohms-m)	Depicted geology	GPS Location
0.0         -  0.596 0.596   -  0.911 0.911   -  12.6 12.6     -  23.5 Over 23.5	4.44 35.2 5.89 0.638 333	Top clay sandy Weathered Sands and gravels Sandy clay Clay Highly weath./fract. rock	S 06.1264o E 035.05636o

VES 2 P 1

Depth range (m)	Layer Resistivity   (Ohms-m)	Depicted geology	GPS Location
0.0        -  0.219 0.219   -  4.3 4.3       -  8.35 8.35     -  15.4 Over 15.4	4950 36.2 20.3 1.68 7.25	Top hard sands Sands & gravels Decomposed rock Clay Highly decomposed rock?sand clay?	S 06.12532o E 035.05442o

VES 3 P 1

Depth range (m)	Layer Resistivity   (Ohms-m)	Depicted geology	GPS Location
0.0      -  0.736 0.736 -  5.1 5.1     -  19.7 19.7   -  36.4 Over 36.4	18.3 13.9 2.23 0.9 900	Sandy clay Highly decomposed rock Clayey sands Clay Fractured  rock	S 06.12570o E 035.05336o

 VES 1 P 2

Depth range (m)	Layer Resistivity   (Ohms-m)	Depicted geology	GPS Location
0.0       -  1.02 1.02     -   1.15 1.15     -   19.4 19.4     -   63.8 Over 63.8	2025 652 12 34.1 364	Top hard sands Fractured rock Highly fractured rock Highly decomposed rock Highly fractured rock	S 06.12589 E 035.05636o

VES RV - 1

Depth range (m)	Layer Resistivity   (Ohms-m)	Depicted geology	GPS Location
0.0       -  0.194 0.194   -  3.6 3.6       -  17.6 17.6     -  91.3 Over 91.3	5889 18.4 2.86 6.57 189	Top hard sands Sands & gravels Clay Sand clay Highly weath./fract. rock	S 06.12701o E 035.05803o

7.0         DISCUSSION OF RESISTIVITY DATA

7.1         Magnetic data

The two (2) magnetic profiles recorded at a very strategic locations were responsive in terms of low magnitude disturbance of the bedrock.  Positive magnetic anomalies were however picked that could depict a geological phenomenon of a hard rock.  While negative magnetic anomalies recorded over the profiles are attributed to fracturing of the country rock.

7.2         Resistivity data

At all stations, resistivity probing suggest a medium to a deeply disturbed bedrock.  Weathering has gone as deep as  between 15.4 m to 91.26m.  From there fracturing of the bedrock starts.  Degree of weathering varies from excessive to slight weathering as probing is advance.  

Quantities of groundwater are expected in the weathered/fractured rock mantle.   The  layer depicting the bedrock has resistivity values ranging from 7.25 to 900 Ohm-m.  This tells of a bedrock that has suffered deep disturbances (fracturing) of varying intensities.  Disturbances of the  bedrock create further secondary permeability conditions hence added aquifer conditions.

8.0         CONCLUSIONS

From all the aforesaid, the following can be deduced in relation to groundwater occurrence within the study area.

(i)         The areas overburden and weathered/fractured column can enable reasonable groundwater infiltration and percolation to make aquifer zones below the ground.

(ii)        The western placed high grounds are the major local recharge sources of the study area.  From the somehow wide catchment of the area reliable groundwater recharge is of a regional nature, mainly from the south west.

(iii)       Groundwater is expected to occur under semi-artesian conditions.  This is because aquifers of the area are likely to exist under semi – confinement where porous formations posing as potential aquifers.

9.0         SELECTION OF DRILLING SITES

Drilling sites have been selected based on their exposure to recharge conditions, qualitative data on likeliness to groundwater  occurrence and related quality.  In this case VES 1P2  is recommended as first drilling site and VES 2P1 as an alternative.

10.0      RECOMMENDATIONS

(i)           VES 1P2 is recommended for drilling to a maximum depth of 100m.

(ii)        In case of technical problem during drilling VES 2P1 should be taken as alternative and be drilled to a maximum depth of 100 m.

(iii)       Drilling must obey the exploratory cum-production drilling approach where drilling is commenced by a pilot hole then it is reamed to a desired production diameter.  This approach is also cost conscious.

(iv)       Water strike zones be carefully noted and individual performance and quality observed.

(v)        Lithological samples be retrieved at 2 m intervals and get securely kept in a site box ready for logging.

(vi)       The borehole must be cased to the bottom with inflow zones sections getting screened.

(vii)      The development exercise get stopped only when water is clear and free from sand fines.

(viii)     Pumping test phase be of at least 12 hrs.  During the constant discharge test, water samples be collected for laboratory analysis.

(ix)       All activities should be under supervision of a Hydrogeology expert.  This is to design the casings/screens installation plan and establish other hydrogeological parameters.

NOTE:           The Driller is advised to have sufficient pieces of steel working casings to overcome collapsing.

11.0      GUIDE

Ndugu Abraham Saimon the Village Executive Officer and Ndugu Adam Mswaga know the drilling sites.  A wooden peg has been driven in to temporary mark it  but the client is advised to dig in concrete beacon to permanently mark it.  The sites are also coded into GPS locations.

MAHAKA PROFILE-2.xls

MAHAKA PROFILE-3.xls

MAHAKA PROFILE-4.xls

MAHAKA PROFILE.xls

REPORT MAHAKA - MANYONI.doc

[TAK9.COM]

이거 문서가 살짝 밀려서 올라가네요. 어떻게 수정할지 모르겠어요. 원본 파일을 첨부하니 혹시 아프리카 우물 짓는 일에 관심이 있으신 분들은 원본을 보세요. ^^

[Conan]

이힝.. 넥시 좋아요. ㅜ_ㅜ

[pingpong★s†ar]

탁구닷컴에서 하시는건가요? 좋은 일 하심에 박수를 보냅니다:)

[ARIA]

잘 되시길 빕니다.

[나무살기]

고맙습니다..^^

[맑은물]

정말 좋은 일 하시는군요..^^

[트릴리온]

좋은 일 하시네요^^ 넥시의 번창을 기원합니다(__)

[수평희망]

감동적이군요 ^^

[chanho1]

싱기다 마뇨니에서 하시는 군요.. 물이 많이 부족한 곳인데 정말 좋은 일 하시는거 같아서 참 보기 좋습니다.. 괜한 참견 같습니다만 누굴 통해서 하시든 항상 꼼꼼하게 챙겨보셔야 할겁니다.. 그 곳이 좀 그렇지요..

[TAK9.COM]

찬호님은 그쪽 지역을 좀 아시나요? 궁금하네요.

[chanho1]

두바이에 있을 때 일 때문에 몇 번 탄자니아를 다녀온 적이 있습니다.. 무완자에 가던 중 마뇨니는 한 번 들려 본 적이 있습니다..^^