KARAKTERISTIK HIDROKIMIA AIR TANAH BERDASARKAN SIFAT KIMIA (STUDI KASUS : KEPUTIH SURABAYA)

Abstract

Groundwater is one of the primary water sources utilized by the community to meet daily needs. However, its quality can be influenced by geological factors, mineral composition of rocks, and anthropogenic activities such as domestic waste, agricultural runoff, and seawater intrusion. Keputih Subdistrict, the largest area in Sukolilo District, still relies heavily on dug wells as a source of clean water. Groundwater conditions in this area vary significantly, ranging from clear to turbid, odorless to odorous, and in some cases, saline. This study aims to identify the hydrochemical characteristics of groundwater in Keputih based on cation (Na, K, Ca, Mg) and anion (Cl, HCO₃, SO₄) parameters. Laboratory analyses were conducted at PDAM Surya Sembada Surabaya. The test results were expressed as ion percentages (meq/L) and plotted on a Piper diagram using RockWorks17 software to determine the dominant ions and groundwater facies. The analysis revealed three dominant ions: calcium (Ca²⁺) cations in wells 3, 4, and 7; chloride (Cl⁻) anions in wells 1, 2, 3, and 7; and bicarbonate (HCO₃⁻) anions in wells 5 and 6. Based on the interpretation of the Piper diagram, the groundwater facies in the study area were classified into four types: CaCl, CaHCO₃, Ca(Mg)Cl, and Ca(Mg)HCO₃. These findings indicate that the groundwater quality in Keputih is influenced by surrounding environmental factors, including geological conditions, residential activities, and proximity to coastal areas.