Paper ID: 177
SALINE WATER INTRUSION TREND IN PATENGA COASTAL AREA
S. K. Palit1 , I. Alam2*
1 Professor, Department of Civil Engineering, Chittagong University of Engineering & Technology,
ABSTRACT Port city Chittagong is the second largest commercial hub in Bangladesh but dwellers are not equally getting civic facility everywhere. CWASA supplies water through distribution route to the inhabitants after proper treatment of surface and ground raw water. Among 41 wards in Chattogram, no. 40 and 41 under Patenga Thana are not yet connected to the pipe supply water of CWASA. So residents of these two wards solely depend on Shallow & Deep tube well water. Being a coastal area, people living here very often suffer from lack of drinking and domestic water. So, their daily livelihood is hampered. From various studies on many coastal regions of Bangladesh, it has been found that ground water quality degrades due to excessive salinity and is becoming unusable for domestic and industrial purposes. So groundwater salinity condition in the coastal areas should be examine. This study attempts to determine the salinity level of ground water for the coastal area of Patenga thana and to generate salinity Map of Patenga indicating the change in salinity level from the sea-shore. The study area includes different locations under ward no 40 and 41: Muslimabad, Kathgor, Fulsoripara , Nazirpara, Chowdhury Para, Maizpara, Dail Para and Dhompara and will be extended up to ward no 39 Patenga. Random sampling was conducted using GIS coordinate and questionnaire for the owners of 169 shallow tube wells and 11 deep tube wells. According to questionnaire survey, participants opined that the shallow and deep tube well water is becoming contaminated gradually due to saline water and these wells are turn into unusable. So the crisis of wholesome water interferes the livelihood continuously along with different types of waterborne diseases. On-site test of pH, TDS, EC and Salinity has been examined in order to identify the scenario of ground water quality considering all circumstances and limitations. The study revealed that maximum salinity level found in shallow tube well 1368, 1346 and 1164 ppm and minimum 1074, 1133 and 728 ppm respectively which exceeds the acceptable limit of 250- 600ppm as per WHO and Bangladesh standard and showed a clear variation in the intensity of salinity from place to place. Some parts of the Muslimabad Residential area nearby the sea-shore and Kathgor is excessively salinity prone. According to depth 30 to 260 feet water is found salty and the groundwater quality is unsuitable enough for drinking, domestic and agriculture as well. Soil test report of ring road and sea-beach road clearly indicate up to 40m soil is medium dense silty sand and most favorable for sea water migration towards inland. So salinity is a hazard in all sorts of activities of that ward and may an alarming threat for surrounding ward as shown in developed map. Alternate water supply technique like rainwater harvesting, groundwater research, supply water connection of CWASA and central treatment plant, RO device in household stage, and awareness raisings among stake holders have been suggested in this study ensure sustainable water management to meet the SDG. Keywords: Groundwater; Salinity; Coast; GIS.
INTRODUCTION Coastal areas are densely populated and often the most developed stretches of land in many parts of the world. It is estimated that 50 percent of the world’s population lives within 100km of a coastline (BBS, 2009) and expectations are that this figure will grow in the next half century. Water has an important role for human life and livelihood. Unfortunately water in the term of quality and quantity is getting worse over the time. The issues related to water quality and quantity has been increasing all
1 over the world, including saline water pollution. Therefore, problems related to saline water pollution (as seawater intrusion) have become a crucial issue for the communities (Obikoya and Bennel, 2010). Saltwater intrusion is the induced flow of seawater into freshwater aquifers primarily caused by groundwater development near the coast. Where groundwater is being pumped from aquifers that are in hydraulic connection with the sea, induced gradients may cause the migration of salt water from the sea towards a well, making the freshwater well unusable. Bangladesh has 47,201 Square kilometer coastal area which is one third of the country and accommodates 28 percent of countries population (MoWR, 2006 and Islam 2004). The coastline area lies in the alluvial plains of Bangladesh between 89.0ºE and 92.20ºE in the northern and northeastern part of the Bay of Bengal. According to coastal zone policy (CZPo, 2005) of the government of Bangladesh 19 districts out of 64 are in coastal zone covering a total of 147 Upazillas of the country. Out of these 19 districts, only 12 districts meet the sea or lower estuary directly. Patenga is located in the South- East zone under Bandar Upazilla of Chittagong district (www.banglapedia.com/Bangladesh_ coastal_ areas). Salinity in drinking water is a common problem here. Furthermore UNDP globally forming SDG goal after MDG. The goal SDG six (6) sub clause (https://sustainabledevelopment.un.org ) targets by 2030, achieve universal and equitable access to safe and affordable drinking water for all. Maximum people live in Patenga is low income, poor, fisherman & farmer. They have not so much ability to buy wholesome water for their daily needs. People solely rely on ground water- Tube well water, Surface water, Bottle supply water. There is a question about the sources of drinking & domestic water potability & suitability. Few of small scale study were done in this area but yet to not a clear idea extent to get. At present in Patenga mega and medium infrastructure like 18 km Ring Road, Karnaphuli Tunnel, Flyover, various residential and industries development works are going on. Due to global warming, sea-level rise, rapid pace of urbanization, huge abstraction of ground water coastal belt aquifers are highly in vulnerable condition of saline water migration. So it is necessary to examine the level and extent of salinity of ground water of shallow tube well of Patenga coastal area to draw an actual contamination scenario of that area. From the preceding article and above discussion, it has been decided to take up a study area where salinity intrusion may arise several problems. Ward no 40 Muslimabad is closely near to the sea shore which is in Patenga Thana and no CWASA supply water is there. The following objectives have been selected for the present investigation: i. To inspect the study area salinity interference through questionnaire survey. ii. To evaluate the present level of ground water salinity concentration on existing shallow tube well water. iii. To identify the salinity contamination suspects location towards inland. iv. To predict the future scenario associated with salinity ingression and its potential impact on livelihood. (Under Process)
METHODOLOGY Study Area and Sample Locations Patenga Thana (Chittagong metropolitan) area 22.34 sq km, located in between 22°13' and 22°18' north latitudes and in between 91°46' and 91°50' east longitudes is shown in Fig. 1. It is bounded by Bandar thana on the North, Anowara thana on the South, Karnafuli thana and Karnafuli river on the East, Bay of Bengal on the West and consisting of ward no 39(part), 40 and 41. Coastal areas are very often treat as a tourist place and economic zone. The study has investigate & measure the salinity concentration level of existing shallow tube well water sample collected randomly of different depth as well as short number of deep tube well. Secondary data has generated to validity of the research works. The study was start from December 2018.
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[Fig.1]: Map of Patenga Thana, Chittagong. (BBS, 2009).
Experimental Design A general works flow of the investigation has been shown in Fig. 2
Site Selection
Physical investigation of the study area
Questionnaire survey Co-ordinate data
Sample & Data collection Water Sample – Shallow Tube well
Soil information EC (μS/cm) Field / Laboratory tests (Salinity)
TDS (ppm) Data Processing & Analysis
pH Application of Arc GIS 10.4
Conclusions & Recommendation
[Fig.2]: Flow diagram of the present investigation
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Field Sample, Coordinate data collection and Onsite test experiment Water sample has been collected randomly from different locations of the existing shallow tube well to get the variety of depth as shown in table 1 .Geographic coordinate system has taken at each sample location using Garmin etrex 30x GPS device. A total number of 169 shallow tube well and 11 deep tube well sample has been taken randomly from this said locations using GIS coordinate and questionnaire to owners of the tube well. as shown in Fig.3 Existing soil test report of ring road to be collect from the study area to know about the soil information. CON30 was used to measure Conductivity, Total Dissolved Solids, Salinity and Hanna potable pH was used to measure hydrogen ion activity of water. Standard procedure and precaution was maintained during onsite test of the collected sample parameter.
[Fig.3]: Red Marks are Shown GW Sample Location using GIS Coordinate System by Arc GIS 10.4
Table 1: Overall Sample Collection area, Tube well type and depth ranges Sl Total Area Depth Range- Shallow Electric Hand Ward Deep no Number type tube no Tube of well Well Sample 1 78 Muslimabad 30,35,40,50,55,70,80,90100,110, 74 4 40 1 120,130,150,160 2 45 Kathgor , Maizpara & 35,40,45,50,55,60,70,80,90,100, 43 2 40 ChowdhuryPara(Partly) 110,120,140,160, 170 , 3 41 Maizpara & 35,40,45,50,55,60,70,80,90,100, 38 3 41 7 ChowdhuryPara(Partly) 110,120,140,160, 210 , Nazirpara 164 nos 4 5 New Moring & CEPZ 100,120,150,160,170 5 ---- 39 3
RESULTS & DISCUSSIONS Examined ground water quality parameter pH, TDS, EC and Salinity of collected STW samples from different location along ward 40, 41 & 39 are summarized in Table- 2. The interviewed result is included on Table 3 and Table 4.
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Table 2: Ground Water Parameter Concentration Range after Test Zone-1: Muslimabad Zone-2,Kathgor & Adjacent Zone-3,CEPZ & Adjacent Type Area Ward-40 Ward-40 & 41 Ward -39 1 – 78 79 - 165 166 - 170 West Side of Beach Road East Side of Beach Road Both side of Main Road Level Concentration Concentration Concentration Parameter Max Min Mean Max Min Mean Max Min Mean pH 7.70 6.30 6.95 8.50 7.10 7.81 8.9 7.4 7.86 Shallow 8.10 8.10 7.30 7.30 6.0 NA Deep TDS 1039 840 959.27 1048 562 903.91 910 858 883.80 Shallow (ppm) 567 881 145 938 368 NA Deep EC 2066 1671 1919.60 2074 1119 1787.59 1897 1747 1798.40 Shallow (µS/cm) 1553 1827 244 1872 727 NA Deep Salinity 1346 1074 1246.68 1368 728 1152.05 1164 1133 1159.80 Shallow (ppm) 912 1170 179 1216 478 NA Deep Shallow Tube well 78 nos 86 5 169 nos 30 feet – 260 feet Deep Tube 1 7 3 11 nos well 450 - 1000 feet
Table 3: Different sources of water used in daily purposes Purpose DTW STW Pond PSF RWH BW Aid Water Quality Compliance
Drinking 0 50% 0 0 20% 30% 0 Poor Cooking 0 40% 20% 0 10% 30% 0 Fare Using Washing/ 0 80% 10% 0 0 10% 0 Poor Water Not in Cleaning satisfactory Irrigation 0 50% 50% 0 NA 0 0 Poor condition *DTW-Deep tube well, * STW-Shallow Tube Well, *RWH-Rainwater Harvesting,*BW-Bottle Water
Table 4: Opinion Regarding Salinity Influence Questions Category % Opinion 1.What are the main problem in the locality Salinity 100 2. How has the salinity been changed in the locality in the last Moderately 60 20 years? High Level 40 3.What are the main problem to plant/grow vegetables & Salinity 70 Crops Lack of Availability of irrigation 30 water due to quality 4.What is the main source of water for rice/vegetable Ground Water 60 cultivation Shallow Surface Water 40 5.What is the most common disease that affected you or your Diarrhea 20 family members in the mentioned seasons in last 5 years Dysentery 10 Skin diseases & Hair problem 15 Fever 20 High Blood Pressure 30
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Salinity In every case water salinity level exceeds the acceptable limit 250 - 600ppm as per WHO and Bangladesh Standard (https://jhpn.biomedcentral.com) which shown in Fig 4. A salinity map is developed using Arc GIS software is shown in Fig 5 which red color clearly indicates that the wards are salinity pron.
1500 Max Max 1350 Mean Mean Max 1200 Min Mean Min
) 1050
900
Min
range (ppm range
750
600 600ppm
Salinity
450
300 250ppm 150
0 Muslimabad - 40 Kathgor amd Adjacent 40 & 41 CEPZ and New mooring-39 Sample Locations
[Fig.4]: Variation in Salinity range in different location in Patenga Thana
[Fig.5]: Salinity Map Generated by Arc GIS 10.4
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CONCLUSIONS Ground salinity is a global problem. Bangladesh is no out of that. Through questionnaire, people opined existing shallow and deep tube well water turn into brackish and well has becoming unusable. So, livelihood regularly interferes due to crisis of wholesome water with extent of different kind of waterborne diseases. The study shown that maximum salinity level found in shallow tube well 1368, 1346 and 1164 ppm and minimum 1074, 1133 and 728 ppm respectively which exceeds the permissible limit of 250- 600ppm as per WHO and Bangladesh standard. Although pH and TDS value in maximum place within permissible range 6.5-8.5 and 500-1000ppm respectively. On the other hand 95% EC value exceeds the standard range of 1200µS/cm. Soil test report of ring road and sea-beach road clearly indicate up to 40m soil is medium dense silty sand and most favorable for sea water migration towards inland. A clear variation in the intensity of salinity of the study area from place to place and contaminated the suit water aquifer. Some parts of the Muslimabad Residential area nearby the sea-shore and Kathgor is excessively salinity prone. It has been found that the groundwater quality of the salinity prone area is unsuitable enough for drinking, domestic and agriculture as well. According to depth 30 to 260 feet water is salty. So salinity is a hazard in all sorts of activities of that ward and may an alarming threat for surrounding ward. An Alternate water supply technique like Rainwater harvesting, CWASA supply water connection, Groundwater research, Central water treatment plant, RO device apply in household stage, and awareness raisings among stake holders are suggested in this study to ensure sustainable water management to meet the SDG.
ACKNOWLEDGEMENTS We are happy and grateful to Head of the Department of Disaster and Environmental Engineering (DEE) CUET for providing all kinds of possible helps and support both in technical editorial aspects of the study. We also disburse thanks to CDA, Manager Jamuna oil Company, Chief Engineer CEPZ, Engineer Spectra Construction Company, Confidence Cement Ready-mix Plant and Councilor ward 40 for cordial assistance during field investigations.In fine, I’m heartily full thanks to all of my well-wishers in home and abroad.
REFERENCES Area of Aberwyngregyn. MSc Thesis. School of Ocean Sciences, University of Wales. Bangor. BBS (Bangladesh Bureau of Statistics), World Bank, and World Food Programme. 2009. Updating Poverty Maps of Bangladesh. CZPo, 2005. Coastal Zone Policy, Ministry of Water Resources, Government of the People’s Republic of Bangladesh, Dhaka MoWR (2006), Coastal Development Strategy, Water Resources Planning Organizations, Ministry of Water Resources, Government of People’s Republic of Bangladesh, Obikoya IB and Bennel JD. 2010. Geophysical Investigation of The Fresh-Saline Water Interface in Coastal (www.banglapedia.com/Bangladesh_ coastal_ areas). (https://sustainabledevelopment.un.org › sdg6) (https://jhpn.biomedcentral.com)
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