Groundwater Quality and Irrigation Suitability in Carbonate Aquifers of Semi-Arid Regions: A Case Study from the Dammam Aquifer, Southern Iraq

Groundwater serves as the primary source of freshwater in arid and semi-arid rural regions due to low precipitation, limited surface water, and growing socio-economic activities. Understanding the hydrogeochemical processes that influence groundwater quality is essential for effective management and long-term sustainability. This study evaluates the hydrogeochemical characteristics of groundwater within the Dammam Formation in the Samawa region of southern Iraq based on data from 30 wells. Laboratory analyses include measuring pH, EC, TDS, total hardness (TH), major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺), and anions (SO₄²⁻, Cl⁻, NO₃⁻, HCO₃⁻). Groundwater suitability for human consumption was assessed using the Groundwater Quality Index (GWQI) according to World Health Organization (WHO) standards. In contrast, irrigation suitability was evaluated using sodium percentage (%Na), sodium adsorption ratio (SAR), permeability index (PI), magnesium hazard (MH), and Wilcox and USSL classification charts. GWQI results showed that 6.67% of samples were "excellent," 6.67% were "good," 66.67% were "poor," 6.67% were "very poor," and 13.33% were "unfit for drinking." Piper diagram analysis indicated 87% of samples in the Ca-Cl field and 13% in the Ca-Mg-Cl field. Wilcox's results revealed 70% of samples were unsuitable for irrigation and 30% of uncertain use. PI results showed 93.33% in class II, suitable for irrigation, and 63.33% with no magnesium hazard. The study recommends desalination with monitoring of sodium, chloride, and sulfate to improve groundwater quality.