Aquifer Demarcation and Groundwater Resources Assessment in Lohagara Municipality, Narail, Bangladesh

Journal of Engineering Science 03(1), 2012 41-58 JES an International Journal AQUIFER DEMARCATION AND GROUNDWATER RESOURCES ASSESSMENT IN LOHAGARA MUNICIPALITY, NARAIL, BANGLADESH Sajal Kumar Adhikary1*, Tanmay Chaki2, Mizanur Rahman2 and Ashim Das Gupta3 1Department of Civil Engineering, Khulna University of Engineering & Technology, Khulna, Bangladesh 2Water Resources Planning Division, Institute of Water Modelling (IWM), Dhaka, Bangladesh 3Water Engineering and Management (WEM), Asian Institute of Technology (AIT), Bangkok, Thailand Received 01 September 2012; Accepted 18 October 2012 ABSTRACT This study presents the state-of-the-art methodology for investigating existing hydrogeological framework for delineating underlying aquifer system and existing groundwater (GW) resource assessment in Lohagara Municipality of Narail district in Bangladesh. Numerous hydrogeological, lithological, hydrological, meteorological and other relevant data and information in the study area have been collected. A number of hydrostratigraphic columnar sections representing the extent of aquifer system have been produced and yield properties of sediment formations are determined. The striplog distributions reveal that a productive aquifer exits beneath the study area with the alteration of fine sand aquifer, aquitard and aquiclude layers. The analysis also demonstrates that two major (upper and lower) aquifers are present within the depth from 61 m to 95 m and from 198 m to 216 m or beneath the study area. It is found that a prominent aquifer exists at 200 m to 235 m throughout the study area containing varying thickness of more or less 36 m below the aquiclude. However, estimated specific yield of aquifer materials varies from 0.07 to 0.20 indicating that the aquifer consists of fine to medium sand. The analysis of storage coefficient and hydrostratigraphic sections shows that the upper aquifer is semi-confined and lower aquifer is confined in nature. Based on the GW modelling results by an integrated MIKE-11 and MIKE-SHE platform, the study estimates that GW resources for shallow aquifer on May 01, 2003 for 6 m and 7 m depths are 7.48 million cubic meters (MCM) and 10.00 MCM, respectively, whereas on November 01, 2003, the resource is estimated as 11.29 MCM and 13.81 MCM for 6 m and 7 m depths, respectively. According to water balance studies, the GW recharge is found as 390 mm for the deeper aquifer in 2003 and the corresponding annual aquifer storage volume is estimated as 7.25 MCM, which mostly comes from the horizontal flow. Based on long-term simulation of GW model using potential water withdrawal options in future, the study concludes that the aquifer is sustainable for GW use in Lohagara Municipality of Narail district in Bangladesh. Keywords: Aquifer, Groundwater modelling, Hydrogeological framework, MIKE-11, MIKE-SHE, Recharge, Specific Yield. 1. INTRODUCTION Groundwater (GW) is usually considered as a source of potable water supply in the developing world because it is readily available in nature and naturally protected from the contamination. It is commonly used for irrigation and supplying water for meeting industrial and domestic requirements all over the world (Hoque et al., 2007). Like many other natural resources, GW resource is being abstracted at an increasing rate all over the world and thus, exploitation of this useful resource is an important issue in the field of modern hydrogeology (Balek, 1989; Butler, 2000; Elango and Sivakumar, 2005; Hoque et al., 2007). It is now widely recognized that sustainability of existing GW supply structure and supplementary use of surface water depends on the reliable assessment of available GW resources for the area under consideration. For this purpose, an integrated distributed hydrogeological model is often required. The model serves as a tool to simulate the recharge, flow and potential head of GW within the defined hydrogeological boundary (Anderson and Woessner, 1992; Sinha, 2005; Kumar, 2011). The numerical model helps in estimating the present available resources and subsequently helps in predicting the potential effect on GW changes under different options of water allocation scenarios (Anderson and Woessner, 1992; Sinha, 2005; El Yaouti et al., 2008). Therefore, numerous studies have been carried out in Bangladesh (MPO, 1987; SWMC, 1996; Nobi and Das Gupta, 1997; SWMC, 2000; Rahman and Roehrig, 2006; Hoque et al., 2007; Wahid et al., 2007; Yasmin, 2008; Adhikary et al., 2011) as well as in other countries of the Asia and other continents (Ala Eldin et al., 2000; Naik and Awasthi, 2003; Kazama et al., 2007; El Yaouti et al., 2008; Igboekwe et al., 2008; Chatterjee et al., 2009; Kushwaha et al., 2009; Praveena and Aris, 2010; Parveena et al., 2010; Rani and Chen, 2010; Raj, 2011; Singh et al., 2011) for the assessment of GW resources as well as * Corresponding author : [email protected] KUET @ JES, ISSN 2075-4914 / 03(1), 2012 42 Sajal Kumar Adhikary et. al. Aquifer Demarcation and Groundwater Resources Assessment in Lohagara................. hydrogeological investigations of the aquifers for appropriate utilization and management of this valuable resources. Underground aquifers are usually very convenient sources of water because they are naturally occurring underground reservoirs, which usually have an enormous storage capacity. However, it is often essential to understand the system dynamics within this aquifer system, when it is subjected to natural and artificial stresses prior to introducing appropriate water resources management practices (El Yaouti et al., 2008). Since many aquifers contain high quality waters, their application as suitable production source of drinking water and human consumption is obvious and they are used as a source of potable water source all over the world. As their storage capacity is quite large, they can provide a continuous supply of water, even in dry seasonal periods when rainfall is very less and/or nearly absent and surface water is rapidly depleted. GW is the principal source of drinking and irrigation water supplies in Bangladesh. About 97% of the population in Bangladesh used to rely on GW for drinking purposes while more than 70% of the total irrigated area is served with GW sources (Hasan et al., 2007; BGS and DPHE, 2001). In Bangladesh, GW occurs in the extensive alluvial aquifers at shallow depth (<10 mbgl) within widespread alluvial deposits (Shamsudduha et al., 2011; Michael and Voss, 2009; MPO, 1987) and meets most of the water demands for domestic, industrial supply and irrigation uses (Hasan et al., 2007; Hoque et al., 2007; Shamsudduha et al., 2008). More than 10 million shallow hand pumped wells, locally known as hand tube wells (HTWs), are used to provide drinking water to the almost entire rural areas and in urban areas of the country, where there is no piped water supply (Hasan et al., 2007). Development of the GW resource for irrigation and other uses is a vital component of the government’s agricultural strategy to achieve food self-sufficiency in Bangladesh (Wahid et al., 2007), which is also highlighted in the national water management plan of the country (WARPO, 2001). A lack of proper understanding of the GW system, in terms of resource utilization, is one of the major limitations to the effective management of GW resources in Bangladesh (Hoque et al., 2007). Thus, there is an urgent need to formulate a strategic plan for appropriate assessment and development of its GW resources for an aquifer system under consideration. Balek (1989) and Karanth (1987) reported that the component of GW study generally contains two major sub-components such as hydrogeological studies and GW modelling and assessment. Hydrogeological study has been carried out to understand the regional and local hydrogeological setting, hydrostratigraphical framework, delineation of the underlying aquifer system, status of groundwater level (GWL) fluctuations and groundwater quality (GWQ). The GW model is developed for understanding GW flow dynamics and assessment of existing GW resource at the present as well as future development scenarios. In the present study, the hydrogeological setting and available GWR in Lohagara Municipality under Narail district of Bangladesh have been studied. Although Lohagara Municipality is largely dependent on GW resources for domestic and irrigation purposes, currently there is no management plan in place and large scale uncontrolled GW exploitation is taking place.. Lack of appropriate understanding of the GW system in terms of resource utilization, is one of the major limitations to the effective management of this resource especially in the urban and peri-urban areas of Bangladesh (Hoque et al., 2007). Therefore, the major objectives of this present study are to investigate the existing hydrogeological framework and underlying aquifer characteristics as well as to quantify the available GW resources in relation to natural recharge and extraction options in Lohagara Municipality under Narail district of Bangladesh. 2. DESCRIPTION OF THE STUDY AREA 2.1 Location The study area, Lohagara Municipality, is located in Lohagara upazilla (sub-district) under Narail district of Bangladesh (Figure 1). The area is about 16.16 sq. km for the present case study. It is bounded by the Ganges River on the North, the River Padma on the East and the Western border upazillas on the west. The southern boundary of the study area is defined as the boundaries of the upazillas of Sharsha, Jhikargacha, Jessore Sadar, Narail Sadar, Lohagara, Kashiani and Muksudpur. 2.2 Climate The study area experiences a typical tropical monsoon climate, with hot wet summers from May to September and cool dry winters. The rainy season occurs approximately from May to October and almost 90% of the total annual rainfall occurs during this period. Both temperature and relative humidity remain high in this season. Mean daily temperature is fairly constant between months of April and September and show little variation across the region, being of the order of 280 C. From October, temperature begins to decline, and mean daily temperature reaches to a minimum of about 19 to 19.50 C in January.

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