Groundwater and surface water data of Ganga Delta
Description
The present study attempts to characterize the strontium signatures and exchanges between surface water and multi-depth groundwater in and around the tropical, Himalayan Ganga River mega-delta. This work is an amalgamation of previously published datasets and newly collected data from surface and groundwater reservoirs which are predicted as potential strontium sources. Rainwater, seawater, river water, estuarine water and groundwater are considered as the different reservoirs within the delta where continuous cycling between the surface and subsurface waters is clearly observable. Strontium concentration data along with other solute geochemistry such as calcium, magnesium and salinity are reviewed from various previous literatures. Additionally, groundwater is sampled and analysed in two distinctly different parts of the delta. The first cluster of groundwater stations is distributed methodically in Nadia District, located inland in the northern part of the delta. The second set of groundwater stations is placed in 5 locations on the Bakkhali Island of Sundarbans, situated at the southern end. In total 13 observation wells, categorized into four depth ranges ̶ D1 (14 to 25 m bgl), D2 (30 to 50 m bgl), D3 (115 m bgl), and D4 (333 m bgl) and 2 monitoring wells were installed. D1 and D2 wells are installed in each of the five locations. D3 has two wells at locations B and D while D4 has only one well for observation at location A. This aids in a spatial understanding of the study area. For a similar reason, the assimilated groundwater data is geographically classified into Eastern and Western Bengal Basin whereas hydrostratigraphically, following our previous continuing study by Chakraborty et al., 2022 it is categorized under Type-I, Type-II and Type-III aquifers. Depth-wise variation is furthermore scrutinized to identify varying surface, shallow surface and deeper subsurface processes prevailing in both inland and coastal aquifers. Again, data variability from coastal reservoirs to further inland areas is used to demarcate a spatial change in the dominant hydrogeochemical process controlling water geochemistry and strontium evolution in the delta.