Spring-fed sources constitute a major component of rural and peri-urban drinking water supply in mountainous regions, yet their seasonal reliability remains poorly quantified. This study evaluates the seasonal and inter-annual variability of spring discharge and its implications for water supply sustainability in a sub-Himalayan region. Spring yield (Lpm) was monitored at 50 representative springs distributed across five blocks during pre-monsoon and post-monsoon periods for two consecutive years (2021 and 2022). Seasonal variability was assessed using box-plot analysis to examine changes in discharge distribution, while statistical significance between pre- and post-monsoon yields was evaluated using paired t-tests at a 95% confidence level. Results indicate a consistent and statistically significant increase in spring discharge following the monsoon across all locations in 2021 (p < 0.01) and in four out of five locations in 2022, with mean post-monsoon yields increasing by 27–95% in 2021 and 25–105% in 2022. Box plots reveal a pronounced upward shift in median discharge and a reduction in low-flow occurrences during the post-monsoon period, confirming effective monsoon recharge. Despite seasonal recovery, several locations exhibit persistently low pre-monsoon yields, indicating continued vulnerability to water scarcity. The findings demonstrate that spring-fed water supply systems are strongly controlled by monsoon recharge and remain seasonally constrained. These results highlight the need for recharge augmentation, storage provision, and springshed management to ensure a reliable year-round drinking water supply under increasing climatic variability.