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, <[email protected]> *2 Student, Department of DEE, Chittagong University of Engineering & Technology,Chittagong <[email protected]> *Corresponding Author 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. 2 [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 3 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.