Chapter 6 Existing Well Inventory Survey
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Chapter 6 Existing Well Inventory Survey Chapter 6 Existing Well Inventory Survey CHAPTER 6 EXISTING WELL INVENTORY SURVEY 6.1 INTRODUCTION 6.1.1 BACKGROUND OF THE SURVEY The objectives of the existing well inventory survey are to provide the hydrogeological information related to the existing wells, it is mainly tube well, and to analyse the hydrogeological conditions of the study area. The inventory survey consists of location survey, well structure investigation, on site hydrogeological measurement, on site water quality measurement and interview survey. The survey was carried out during the period of September to December 2004. 6.1.2 OUTLINE OF THE SURVEY A total of 640 wells for the survey were selected from the 1,399 wells, which has fundamental data collected from DDCA (Drilling and Dam Construction Agency), Regional Water Engineer office and District Water Engineer office. A list of identified existing wells, consisting 229 well in Coast Region and 1170 wells on Dar es Salaam is presented in Data Book. Among 640 selected wells for the survey, a total of 500 wells were measured. Rest of 140 wells were not able to measure due to owner’s particular circumstances, unclear location and abandonment. The number of wells collected, surveyed and measured in each district is shown in Table 6.1. Table 6.1 Number of Wells Surveyed District, Number of Existing Wells Region Municipal Collected Data Surveyed Measured Bagamoyo 37 37 35 Coast Kibaha 68 68 42 Kisarawe 92 92 63 Mkuranga 32 32 28 Sub-total, Coast Region 229 229 168 Ilala 545 143 97 Dar es Salaam Kinondoni 280 140 129 Temeke 346 128 106 Sub-total, Dar es Salaam 1,171 411 332 Total 1,400 640 500 6.2 SURVEY ITEMS AND METHODOLOGIES The list of the wells measure is annexed as the following section. The survey was carried out in accordance with the following survey items. The survey was conducted through visiting the wells and interviewing owners and users. 1) Location Survey There are databases or the records of the existing wells established by the institutions concerned. However, no data recorded regarding the location (coordinate) and elevation. For the hydrogeological analysis, especially using GIS system, the location data are the essential. The survey team have visited the all the wells selected and measured the location (Longitude, Latitude) and ground elevation above sea level (masl) by GPS and altimeter. 2) Well structure investigation The structure of the well, regarding borehole and pipes were investigated by collecting the well completion data from DDCA, and field measurement for verification. The obtained data will be utilized for the examination of preliminary of the water supply facility. The data collected and measured are as follows. 6 - 1 Chapter 6 Existing Well Inventory Survey • Drilled depth (m) • Diameter of borehole (inches) • Diameter of casing pipe (inches) • Top of screen pipe (m) • Bottom of screen length (m) • Pump type 3) On site hydrogeological measurements Simplified pumping test were carried out by submersible pump installed or the provided pump (33 liter/min., 70m Head) in case of hand pump well. The items measured by the test are as follows. • Static Water Level, SWL (m) • Dynamic Water Level, DWL (m) • Pumping rate (liter/min) 4) On site water quality measurements During the simplified pumping test, water sample are collected and measured following parameters of water quality by handy instruments. • Electric Conductivity (mg/liter) • pH • Water Temperature 5) Interview survey The survey team have visited the wells and interviewed owners and users for the following items. • Name of Owner • Well Identification No. • Drilled Year of Well • Number of People and Families using the well • Purpose of the Well (Domestic Water, Livestock Water or the Irrigation) • Consumption amount for each purpose • Estimated extracting amount (m3/day) of the water • Pump operation hours The conceptualistic structure and water level measured at each well are shown in Figure 6.1. The collected data obtained by field measurement and completion report of the wells were compiled, and established the well inventory and database system. Motor Pumped Well Hand Pumped Well Ground Level 1) GL Elevation, above sea level (m) 2) Static Water Level (m, from GL Elevation) 3) Diameter of Borehole (inches) 4) Diameter of casing pipe (inches) P 5) Top of screen pipe (m, from GL Elevation) 6) Bottom of screen pipe (m, from GL Elevatio 7) Drilled depth ((m, from GL Elevation) Figure 6.1 Schematic Diagrams of the Existing Wells 6 - 2 Chapter 6 Existing Well Inventory Survey 6.3 SURVEY RESULTS AND FINDINGS The locations of the surveyed 500 existing wells are shown in Figure 6.2. The survey results regarding the location and hydrogeological measurement are summarized in Table 6.2 for Coast Region and Table 6.3 for Dar es Salaam. The survey results regarding the well structure, water quality and water use are summarized in Table 6.4 for Coast Region and Table 6.5 for Dar es Salaam. The distribution of wells is highly densest in the central part of Dar es Salaam especially in Ilala Municipal, while it is very scattering in Coast Region. Although the distribution of the wells are corresponding the distribution of the population, the number of the wells in Bagamoyo District is very small especially where Precambrian formation are distributed. This distribution suggested that the distribution of wells are corresponding not only population but also difficulty of groundwater development. 6.3.1 OPERATIONAL CONDITION The condition of the well operation was analyzed by comparing the number of drilled wells, abandoned well, depleted wells, malfunctioned or stolen wells and operating well. The abandoned well is the dry well in regard to depleted well is the well dried up after the certain period of operation. The wells which is not operating due to malfunctioned and stolen the equipment such submersible pump, is identified as malfunctioned or stolen wells. The operating well is the well in use at present. The Figure 6.3 shows the ratio of the operating condition of the wells by districts. 100% 0 1 2220 1 140 Abandoned 90% 8 21 25 Depleted 33 14 120 80% 26 9 1 70% 100 60% 4 4 80 50% 17 11 10 40% 107 102 60 Malfunction/Stolen 73 30% 17 Number of Wells Utilization Ratio of Wells of Ratio Utilization 40 20% Operating 22 13 9 20 10% 35 42 62 28 132 129 106 0% 0 a yo o Ilala m rang Kibaha u ga Temeke a Kisarawe Kinondoni B Muk Abandoned District Depleted Malfunction/Stolen Operating Figure 6.3 Operational Conditions of the Existing Wells The operation rates are high in Dar es Salaam, these are 68% to 81% of the total number of drilled well. On the other hand, the rates in Coast region are generally low, it is lowest in 25% of Bagamoyo, and is highest in 60% in Mkuranga. This is because of high abandoned rates in Cost Region especially in three districts of Bagamoyo, Kibaha and Kisarawe. These are 23% in Bagamoyo, 33% in Kibaha, and 42% in Kisarawe. The abandoned rates in Dar es Salaam are 6 - 3 Chapter 6 Existing Well Inventory Survey [J4 775/04 µ [J5 772/04 Bagamoyo [ Kinondoni J6 773/04 [ Kibaha [J7 774/04 IlalaIlala J2 771/04 Temeke [ J3 699/04 [J8 770/04 [ [J9 768/04 Kisarawe Mkulanga J10 769/0 Legend [ District_Boundary [ JICA_Test_Well Existing_Well 010 20406080100 Kilometers FIGURE 6.2 LOCATION OF EXISTING WELLS AND TEST WELLS THE STUDY ON WATER SUPPLY IMPROVEMENT IN COAST & DAR ES SALAAM JICA 6 - 4 Chapter 6 Existing Well Inventory Survey Table 6.2 Results of Existing Well Survey in Coast Region, Location and Hydrogeology (1/4) No. Latitude LongitudeGL Depth Water Level (mbgl) Yield Sc Cond BH/No DistrictArea/Village Owner Coast Dist. Deg. Min. Deg. Min. (masl) (mbgl) SWL DWE DD (l/min) (l/min/m) (µS/cm) 1 1 152/99 Bagamoyo Lower Ruvu UNDP 6 33.80 38 55.90 105 47.0 21.50 43.76 22.26 150.00 6.74 786 2 2 356/99 Bagamoyo Chasimba DAWASA 6 35.15 38 50.57 95 50.0 30.00 31.50 1.50 41.67 27.78 1520 3 3 168/99 Bagamoyo B.moyo Sec Bagamoyo Sec 6 27.32 38 55.60 80 30.0 19.00 21.20 2.20 120.00 54.55 1163 4 4 146/99 Bagamoyo Zinga Farm Hon. D. Yona 6 33.53 39 0.40 7 95.0 29.80 31.06 1.26 188.50 149.60 970 B.moyo Sec Bagamoyo 5 5 247/99 Bagamoyo 6 27.43 38 55.57 75 30.0 17.22 21.52 4.30 7.92 132.00 125 School Sec. 6 6 498/2000 Bagamoyo Nyamatanga M/s Msuya 6 35.77 39 3.59 95 51.0 42.00 44.00 2.00 15.60 7.80 231 7 7 383/2001 Bagamoyo Mapinga M/s Njovu 6 35.53 39 4.20 110 75.0 42.06 51.30 9.24 220.00 23.81 133 8 8 323/2001 Bagamoyo Mapinga M/s Msuya 6 35.70 39 4.80 100 61.0 43.27 50.63 7.36 130.67 17.75 1230 9 9 324/2001 Bagamoyo Mapinga M/s DAWASA 6 35.50 39 3.58 85 37.0 16 23.15 7.15 377.00 52.73 231 M/s Chuo cha 10 10 231/2001 Bagamoyo Mbegani 6 28.5 38 58.14 58 34.0 11.60 30.80 19.20 35.00 1.82 170 Uvuvi M/s Chuo cha 11 11 88/2001 Bagamoyo Mbegani 6 28.36 38 57.69 55 25.0 dry dry dry dry dry dry Uvuvi M/s Chuo cha 12 12 114/2001 Bagamoyo Mbegani 6 28.36 38 57.62 14 28.0 7.60 15.20 7.60 78.00 10.26 670 Uvuvi II M/s Village 13 13 169/2001 Bagamoyo Kiwangwa 6 22.40 38 38.55 245 15.0 1.70 8.79 7.09 52.83 7.45 139 Comm M/s Kiwangwa 14 14 163/2001 Bagamoyo Kiwangwa 6 23.25 38 34.15 250 40.0 dry dry dry dry dry dry Vill 15 15 392/2002 Bagamoyo Mapinga M/s T.