<p>Springs in tropical volcanic regions are vital resources for drinking water, irrigation, and sustaining local communities. However, rapid land use changes and intensified anthropogenic activities have contributed to the degradation of spring water quality. This study analyzed 13 physicochemical parameters in 30 spring samples from the southern slopes of Mt. Merapi, Indonesia, during the dry and rainy seasons to characterize seasonal hydrogeochemical dynamics, evaluate spring water quality, and assess associated health risks. The Water Quality Index (WQI) and Irrigation Water Quality Index (IWQI) were applied to determine suitability for drinking and irrigation, alongside a non-carcinogenic risk assessment based on nitrate (NO₃⁻) and fluoride (F⁻) ingestion. The results indicated that the groundwater facies were dominated by Ca–Mg–HCO₃ and mixed Ca–Na–HCO₃ types. Most springs had good to excellent WQI, confirming drinking suitability, whereas those influenced by agriculture and urban activities showed lower quality. The IWQI assessments similarly indicated generally good water quality, with low salinity and sodicity hazards, supporting the suitability of the water for irrigation. Statistical analysis revealed that seasonal variations did not significantly affect the hydrogeochemical composition or overall groundwater quality. Furthermore, NO₃⁻ and F⁻ contamination was closely linked to surface runoff and infiltration from agricultural and domestic wastewater. The Total Hazard Index (THI) of NO₃⁻ and F⁻ indicated that infants are more vulnerable to non-carcinogenic health effects than children and adults. These findings emphasize the link between spring water quality and human health, providing evidence for sustainable groundwater management in volcanic regions.</p>