Chapter 6 - Modeling short-term trends of ground water chemistry of a compound-barrier-spit aquifer, Alappuzha (district), Kerala, in the southwestern seaboard of India

Abstract

Groundwater (GW), one of the most important natural resources on the earth, is utilized for domestic, irrigation, and industrial purposes. Consequent on the rapid growth of population, urbanization, industrialization, and other developmental activities, GW resources have been threatened by steady depletion and quality degradation due to improper or inadequate pretreatment of wastewater before its release to the natural system. Here we report, results of hydro-chemical modeling (using Geostatistical tools, such as IDW and first degree trend and weighted overlay analysis), of GW parameters (viz., pH, TH, EC, Ca2+, Mg2+, Cl− and NO3−) of 36 dug wells or DW (for 2011) and 60 dug wells (24 more added for 2018)—monitored by the Central Ground Water Board (CGWB), Govt. of India, in the Alappuzha Dist. (AD, av. elevation=1.0m amsl; area=1414km2) of Kerala, India. The AD, in the southwestern seaboard of India, is sandwiched between the brackish Vembanad Kayal (one of the two Ramsar sites in Kerala) to the east, Kuttanad polder to the south and Lakshadweep Sea to the west. The Geostatistical-modeling-enabled visualization and scrutiny of sweet water challenges AD is exposed to in the summer (premonsoon season). In addition, results of modeling of chemical variables of GW of AD, brings to fore, the impact of rising water demand in this population dense, water-scarce region (<562m3 annual per capita), sitting on a compound-barrier-spit of Holocene age in this low coastal plain district of Kerala. Alongside, we need to reckon the consequences of global sea-level rise (@1.00mm/year). Furthermore, the results of this study give a grim forecast that AD is unfavorably predisposed to “unimaginable” drinking water challenges in the decade of 2020s and beyond, due to the twin causes of landward migration of seawater-freshwater interface driven by steadily rising withdrawal from the aquifers on the one hand and anthropogenic pollution of shallow coastal aquifer, driven by nonexistent adequate wastewater treatment facilities in the population centers and in the adjoining regions beyond the eastern shore of Vembanad Kayal. Moreover, this analysis unveiled modulation of areal spread of “suitable GW” between data years of 2011 and 2018.