GROUNDWATER CHARACTERIZATION FOR SUSTAINABLE USAGES IN SOUTHWEST AND NORTHWEST BANGLADESH ON GIS AND WATER QUALITY INDEX (PhD Thesis- Running)

1.      INTRODUCTION

Groundwater is the most important source of domestic, industrial and agricultural water supply in the world. It is estimated that approximately one third of the world’s population use groundwater for drinking purpose (Nickson et al. 2005). It is found in aquifers that have the capacity of both storing and transmitting water, in significant quantities (Todd 1980). Generally, groundwater quality depends on the quality of recharged water, atmospheric precipitation, inland surface water and subsurface geochemical processes (Twarakavi and Kaluarachchi 2006; Kumar et al. 2014). In coastal regions groundwater quality patterns are complex, because of the input from different water sources including precipitation, seawater, ascending deep groundwater and anthropogenic sources (Steinich et al. 1998). Problems in coastal areas are typically connected to contamination of fresh water resources by saline water and include well field salinization, crop damage, and surface water quality deterioration (Karro et al. 2004).

Bangladesh lies in the northeastern part of South Asia, has 710 km coastal line and the coastal area covers about 32% of the country (Policy, C. Z. 2005). Although, coastal aquifers serve as major sources of freshwater supply, the groundwater in coastal region is relatively vulnerable to contamination by seawater intrusion, which makes groundwater unsuitable (Kim et al. 2006; Jorgensen et al. 2008). Natural processes and anthropogenic activities like; over extraction, urbanization and agricultural activities are the main reason for seawater intrusion and water quality deterioration in coastal aquifers (Mondal et al. 2011; Selvam et al. 2013). Nowadays, almost 53% of the coastal areas of Bangladesh are affected by salinity (Hoque et al. 2003; Woobaidullah et al. 2006). Salinity becomes a major problem in south-western coastal region of Bangladesh, where irrigation water quality is affected by high levels of salinity (Shammi et al. 2016), which is a source of irrigation salinity and it mainly results from rises in the groundwater table due to excessive irrigation and the lack of adequate drainage for leaching and removal of salts (Corwin et al. 2007). The total area under irrigation in Bangladesh is 5,049,785 ha and 78.9% of this area is covered by groundwater sources including 3,197,184 ha with 1,304,973 shallow tubewells and 785,680 ha with 31,302 deep tubewells (DPHE and JICA 2010). However, most crop lands in the coastal areas of Bangladesh remain fallow in the dry season because surface water resources are saline and unsuitable for irrigation, while groundwater is not intensively utilized because of the fear of seawater intrusion into aquifers (Mondal et al. 2008). Seawater intrusion is a major threat in the coastal aquifers of Bangladesh, especially in southwestern region (Bahar and Reza 2010; Islam et al. 2015, 2016; Islam and Bhuiyan 2016). The over dependence on groundwater for drinking, agricultural and industrial sector and different climatic and natural phenomenon causes coastal groundwater contamination (Srinivas et al. 2015).

Geochemical studies of groundwater provide a better understanding of water quality and possible changes (Kumar et al. 2014). However, the coastal groundwater system is fragile and its evaluation will help in the proper planning and sustainable management (Sefie et al. 2015). Therefore detailed investigations regarding the groundwater hydrogeochemistry and water quality in shallow aquifer is imperative. So the present study aims to investigate the groundwater, to determine its utility and find out the major geochemical process in study area. It also intended to delineate the spatial distribution of hydrogeochemical constituents for proper understanding and future management perspective.

Urban agglomerates in the Lower Bengal Delta, Bangladesh are characterized by high population density (Ahmad, 2005; Ahmed, 2011), a poorly maintained and dilapidated built environment (Ahmad, 2005), an ineffective natural drainage system (SDP, 2011), drainage congestion, and limited and restricted aquifer recharge (Brammer, 2010; Adri and Islam, 2012; Brammer, 2014; Rakib et al., 2019). Obviously, the scarce resource in such deltaic urban centres is fresh water, and its availability is delimited because of high population density, where overexploitation is imminent (Erban et al., 2014; Schmidt, 2015). The surface water repositories in these regions are also locations of contaminated and induced salinization (Nobi and Gupta, 1997; Rahman and Bhattacharya, 2006). The situation exacerbates due to accelerated urbanization (Burgess et al., 2010; Abedin et al., 2013; Barbosa et al., 2016; Hoque et al., 2016; Islam et al., 2017) as well. Moreover, the Bengal delta is environmentally more stressed as compared to other mega-deltas such as that of the Mekong and Amazon (Brammer, 2014; Szabo et al., 2016).

Khulna (southwest coastal) region of Bangladesh is designated as one of the most stressed locations globally under the realm of rapid changes in the climatic pattern (Mondal et al., 2013; Auerbach et al., 2015; Chatterjee, 2015; Shahid et al., 2016). The Khulna City Corporation (KCC) is located at the core of the Lower Bengal delta and its urbanization has taken place at the cost of natural wetlands, including ponds and lakes (Khan et al., 2016). The KCC accommodates a staggering 1.5 million people within an area of about 46 km2 (ADB, 2010; Mondal et al., 2013) and the city is the third most populated urban agglomerate of Bangladesh (Mondal et al., 2013; Khan et al., 2016). It is under intense stress for potable water because of both in-situ and ex-situ stressors such as urbanization, climate change, and regional and upstream interventions on the hydrological regime (Khan et al., 2016). Demands for potable water in KCC are maintained mainly through groundwater extraction but is not suitable for most domestic purposes (Adhikary et al., 2012; Datta and Ghosh, 2015). The surface water bodies such as ponds and lakes are shrinking and these water-repositories are becoming hubs of urban waste. Khulna Water Supply and Sewerage Authority (KWASA) is supplying piped groundwater to only 23% of the urban population (ADB, 2011a; ADB, 2011b). Under such situations, it is essential to search for additional sources of quality potable water for KCC residents.

Knowledge on geochemical attributes of water from surface and sub-surface sources and their mutual geochemical interactions is essential in assessing suitable geochemical options for water security in coastal regions.

Quality aspects of groundwater in Khulna City Corporation (KCC) have been studied by Bahar and Reza (2010) and Adhikary et al. (2012) among others. Nevertheless, exploring options for potable water through geochemical exploration of multiple water sources in one of the most environmentally stressed city like Khulna and others in this region is lacking.

It is estimated that approximately one-third of the world’s population use groundwater for drinking (Nickson et al. 2005). Fresh groundwater is an important resource because of its potable, agricultural and industrial use. The ever increasing population density in coastal zones (Finkl, 1994; Vandenbohede et al., 2009) and the demand for potable freshwater globally (UNEP, 1999; Nickson et al., 2005) renders coastal groundwater supplies to ceaseless depletion worldwide (Barlow, 2003). Generally the coastal aquifers are shallower and fragile and are susceptible to contamination and pollution (Chidambaram et al., 2009). The major threat to coastal aquifers is saltwater intrusion, sometimes induced because of over exploitation, due to their proximity to the sea (Nadler et al., 1981; Morell et al., 1996; Sukhija et al., 1996) and also there are many aquifers deposited in palaeo-saline environment, mostly in deltas. The variability in hydrochemistry of coastal aquifers is thus complex due to presence of conflicting processes in the geoenvironment (Morell et al., 1996).

Urban conglomerates in southwestern coastal Bangladesh are characterized by high population density (Ahmad, 2005, 2011), poorly maintained and dilapidated built environment (Ahmad, 2005), restricted and ineffective natural drainage system (SDP, 2011), water logging but limited recharge due to concrete envelope (Adri and Islam, 2012; Brammer, 2010). The aquifers in such locations are also susceptible to contamination and induced saltwater intrusion (Nobi and Gupta, 1997; Rahman and Bhattacharya, 2006). A number of generalized studies on groundwater of the southwestern coastal Bangladesh as a whole and also on specific issues may be found elsewhere (Nobi and Gupta, 1997; Yokota et al., 2002; Rahman and Bhatacharya, 2006; Bahar and Reza, 2010; Burgess et al., 2010; Haque et al., 2010; Islam et al., 2011; Rahman et al., 2011; Adhikary et al., 2012; Ghosh et al., 2012; Khanom and Salehin, 2012; Rahman et al., 2012; Harun and Kabir, 2013). However understanding hydrochemistry is essential in coastal aquifer management ( Datta and Ghosh, 2015). The present work would investigate the hydro-chemical nature of solute load of aquifers in urban conglomerates situated in the southwestern coastal Bangladesh.

2.      BACKGROUND OF THE STUDY

Ground water is one of the earth’s most important resources for human life. The water quality depends upon the geological environment, natural movement, recovery and utilization. Geochemical processes have an influence on the prevalence of anthropogenic and natural contaminants in coastal environments (Toda et al 2002). It is estimated that approximately one third of the world’s population use groundwater for drinking purposes (Nickson et al 2005). Similarly in Southwest Bangladesh the total water supplied to a growing mass of about 30 million is groundwater and to some extent surface water. Urbanization, industrialization, unplanned land use, lack of people awareness etc. worsen the quality of groundwater (eg. Laluraj et al 2005). Moreover this region comprises Khulna, Satkhira and Bagerhat is always vulnerable to sea-water intrusion due to coastal proximity. On the other hand, according to DPHE except the hilly districts arsenic has been identified in the ground water of 61 districts. This area falls within the western part of Faridpur Trough of Bengal Foredeep (Alam 1990) which is filled with Tertiary and Quaternary sand and clay rich sediments with few coarse sand beds (Roy et al. 2005). Hydrochemistry of groundwater is important to assess the ground water quality for understanding the suitability for various purposes like domestic, irrigation, industrial etc. No extended studies in ground water had so far been carried out in this area, some localized analyses were done but literature on hydrochemical characterization of ground water is scarce.

3.      LITERATURE REVIEW

The review of literature is one of the important parts to carry out the research on the field of hydrochemical characterization of ground water. Number of researches has so far been done in this country and abroad. According to the research title the present work mainly focuses on the hydrogeochemical characteristics of ground water in southwest Bangladesh. Quality based research work is available but more research should be carried out to get a clear picture. Some important published papers relevant are discussed here in brief.

Literature on generalized hydrochemical studies on surface- and groundwater of the south-western coastal (the Lower Bengal Delta) and other part of Bangladesh may be found elsewhere (Nobi and Gupta, 1997; Yokota et al., 2002; Rahman and Bhattacharya, 2006; Anwar et al., 2008;  Burgess et al., 2010; Haque et al., 2010; Islam et al., 2011; Rahman et al., 2011; Ghosh et al., 2012; Khanom and Salehin, 2012; Harun and Kabir, 2013; Rahman et al., 2014a; Datta and Ghosh, 2015; Akter et al., 2016; Islam et al. 2016a, b; Ayers et al., 2017; Mostafa et al., 2017; Tanvir et al., 2017; Datta et al., 2018, Islam et al., 2018; Roy et al., 2018; Md. Bodrud-Doza et al. 2019; Saha et al., 2019; Datta et al.,2020; Molla Rahman et al. 2021, Shaibur, M. R. 2022, Rahman M. M. 2023, Moumita et al., 2023 and elsewhere).

Besides, different geochemical processes in groundwater governing the chemical characteristics of groundwater, is well documented in many parts of the world by many authors i.e., Iren et al. (1997), Beatriz Helena et al. (2000), Panagopoulos et al., (2004), Laluraj et al. (2005), Montety et al. (2008), Jalali (2008), Adepelumi et al. (2009),  Manjusree et al. (2009), Srinivasamoorthy et al. 2011, 2013) Thilagavathi et al. (2012), Sivasubramanian et al. (2013), Nagaraju et al. (2014), Kumar et al. (2015), , Balaji et al. (2016), Halder et al. (2023) etc.

4. OBJECTIVES OF THE RESEARCH

4.1 General Objectives

The present research is proposed to find out temporal and spatial characteristics of hydrochemical parameters of the ground water in urban cities Southwest Bangladesh, which is essential to find out security of groundwater as a resource in the study area.

4.2 Specific Objectives

1. To develop physicochemical database of groundwater in the study area.

2. To investigate physicochemical database of ground water in the study area.

3. Provide support and services to water security issues of the region. 

• Supervision