INFLUENCE OF EL NINO SOUTHERN OSCILLATION ON HISTORICAL STREAMFLOW IN THE REEDY RIVER BASIN, SOUTH CAROLINA.

The El Niño Southern Oscillation (ENSO) influences the climate across the world differently. Identifying the ENSO influence on water availability at a regional scale is essential to enable efficient water resources management to safeguard access to adequate quantities of water for sustaining livelihoods and allow socio-economic development of populations. While previous research has been conducted to analyze these patterns at large-scale (e.g., global, continental), regional patterns may not follow this general hypothesis, requiring regional scale studies to provide actionable information to water resources managers. This study investigates the historical influence of ENSO on monthly average streamflow in the Reedy River basin in South Carolina, aiming to answer the following question: What patterns are shared between the streamflow magnitude and the phases and intensity of ENSO? To answer this question, we analyzed monthly average streamflow data recorded between 2007 and 2024 at four United States Geological Survey (USGS) river gauges along Reedy River. We investigated the presence of seasonal trends, as well as the correlation between streamflow magnitude and the intensity of the El Niño or La Niña period. The results show a positive trend for streamflow in the winter and spring months, while no significant trend was observed for the other seasons. When comparing El Niño periods, higher monthly streamflow occurred during moderate to strong El Niño, and during shifting periods from a moderate El Niño to a strong La Niña. Finaly, higher streamflow variability was found during El Niño periods. Understanding the connection between the ENSO and streamflow from historical data provide guidance on how water availability may be impacted in the future when analyzing seasonal forecasts and enable early water management actions to mitigate potential impacts.