1. Introduction
The activities of urbanization, reclamation of the land and higher agricultural production have increased due to the incredible increase of human population (Sawant & Shete, 2016). These activities have makes a higher demand for groundwater resources and it is increasing in higher to higher day by day (Al Tanjil, Ahmed, Akter, Biswas, & Policy, 2019). Therefore, it has become a new challenge for the supplying of safe groundwater according to the demand of the population (Ahmed, Hasan, Khan, & Hasan, 2019; Biswas et al., 2017). The authors (Hasan et al., 2016; Mahmood & Environment, 2012) have indicated that the groundwater has flowed north to south in Bangladesh. This is happened because most of the rivers are connected in the north with the Bay of Bengal (Monir, Khan, Hossain, & Hossain, 2011; Monir, Khan, Quamruzzaman, Kabir, & Hossain, 2012) and elevation of these coastal areas is lower from the north to south (Sarker, Van Camp, Islam, Ahmed, & Walraevens, 2018). The coastal area is connected with 19 districts of Bangladesh. Such flow of groundwater and elevation, salinity intrusion has been considered the main cause of potential water resources (Mahmuduzzaman, Ahmed, Nuruzzaman, & Ahmed, 2014). The coastal regions is found higher sandy layers so irrigation activities have been considered a higher concern because of groundwater reported by Rahman, Rahman, and Majumder (2012). For this, the safe water zone is found in the higher depth of lithological distribution (Mahmood & Environment, 2012). In the arid period (March to August), the water demand became acute in every year in Bangladesh because the water static table goes to low down (Mahmood & Environment, 2012). Some authors (Rahman et al., 2012; Shammi et al., 2016; Shammi et al., 2017) have investigated that this higher increased stress of water demand has been emphasized the inhabitants collect water resources from the higher depth of lithological layers. Moreover, the safe water-bearing zone or saturated zone have been found in higher depth along the coastal district’s areas of Bangladesh (Hasan et al., 2016).
The step-down test is considered as short pocess and moderately simple and cheaper than the other pumping tests because of this processes are regulated the highest rate of flow water in a well (Ophey et al., 2019). The proportion of abstraction on step-down test from the water level of the well is increased in different numbers of steps (minimum 3 times ) (Abdalla & Moubark, 2018). Well-performance tests have been conducted to estimate the losses of energy in the aquifer and the pumping well which is developed during the extraction of groundwater. The procedures of pumping well consist of increasing discharge rates (Q) at a stepwise. Until the drawdown stabilized, it is measures every test temporary changes in water levels at every step (Kruseman, De Ridder, & Verweij, 1970). Moreover, some researchers (Gahala, 2015; Louwyck, Vandenbohede, & Lebbe, 2010) studied that the analytical process of step-drawdown test assists to identify the quantify aquifer mechanisms which evaluate the rate of flow into the well laminar/turbulent. The discharge rate (Q) and time are proportional to the resistance of formation on the water-bearing zone. The well (non-linear) loss has considered as the parameter of difference between the immediately head of inside and the outside casing during pumping of an aquifer (F. J. P. b. J. S. Driscoll, St Paul, Minnesota, 1986). Jacob method (Jacob, 1947) has been applied for determining the pumping rate, step down tests and the specific pumping rate of an aquifer which has been considered as very easy and low expensive for calculation (Abdalla & Moubark, 2018). According to Jacob’s method, F. J. S. P. Driscoll, Minn (1986) has used the term of aquifer loss in laminar and turbulent term of well loss. Bierschenk (1963) also represented Jacob’s method in a graphical interpretation for the determination of well loss and aquifer whereas Logan (1964) and Gabrysch (1968) have proposed the transmissivity estimation method from the loss coefficient of the aquifer. This transmissivity estimation method has been evaluated by various graphical interpretations from the coefficient on well loss. Singh (2002) has been applied this method for the determination of transmissivity (T), stepdown, specific recharge depends on Jacob method (Jacob, 1947). The single-well step-drawdown test and its performance of well criteria (coefficient of well loss, the efficiency of well) provides the estimation of highest yield (optimal pumping propotion) under varying conditions of the water-level (Guttman, Negev, & Rubin, 2017).
The lithology of subsurface deposits, saturation of (aquifer) thickness, groundwater depth, hydraulic properties of the aquifer is controlled the hydrogeologic characteristics and potential of grundwater resouces in a area. In the previous study (M. T. Ahmed et al., 2019), it has investigated the distribution of groundwater quality and its valuation on Shagordari but there is no indicator of lithological distribution and aquifer characteristics. Another study (M. Ahmed et al., 2019) has indicated only the hydrogeological condition of Jessore but there is no evaluation pumping rate or well performance according to hydrochemistry. Moreover, several authors (Jahan et al., 2007; Tanvir Rahman, Rahman, Majumder, & Technology, 2012) have also identified the depositional environment of the aquifer by using the gamma-ray well log data. However, there is no identification of well of recharge. As the water level has been being decreased day by day so static water level and the recharge rate condition of the water should be needed to water resources safety. Moreover, it has evaluated by the authors (Abdalla & Moubark, 2018; Louwyck et al., 2010) that step drawdown (aquifer) pumping and performance tests have been considered as the main process to determine the sufficient and accurate assumption of groundwater resources in any aquifer.
Therefore, this study evaluated the performance of well criteria, steps drawdown and pumping tests of the investigation area. Hence, the main objectives of this investigation area have indicated that the identification of the safe zone according to various pumping rates, step down test and estimation of well performance with its aquifer characterization by the estimation of well loss and well efficiency, the specific capacity of well and an optimal pumping rate of various water-level conditions. This study also evaluated the lithologic characteristics of the aquifer, water-bearing zone from the logging data and levels of aquifer zone.