Post-seismic turbidity response in the Goksu Stream after the 2023 Kahramanmaras earthquakes

Abstract The Kahramanmaras earthquakes (Mw 7.7 and Mw 7.6) significantly affected the turbidity levels of the Goksu Stream, an essential drinking water source for the city of Gaziantep. Understanding the impacts of such natural disasters is critical for ensuring water security and sustainability. This study investigates the effects of seismic activity and precipitation on turbidity variations in the Goksu Stream, utilizing satellite imagery from the PlanetScope mission, orthophotos captured by drones and aircraft, and in situ turbidity measurements provided by Gaziantep Water and Sewerage Administration (GASKI). The Normalized Difference Turbidity Index (NDTI), a technique commonly used to monitor turbidity via remote sensing, was calculated to assess spatial turbidity variations. Results indicated that NDTI closely reflects ground-based turbidity measurements during the wet season, from March to May. After the Kahramanmaras earthquakes, turbidity levels on average rose from 5.15 Nephelometric Turbidity Units (NTU) to 23 NTU. In particular, turbidity spiked from 1.32 NTU to over 2000 NTU immediately after the February 6, 2023 earthquakes, clearly reflecting the stream’s rapid response to seismic activity. Moreover, unlike snow events, both seismic shaking and rainfall events were found to significantly contribute to turbidity spikes. These findings highlight the necessity of continuous monitoring of turbidity in streams after natural disasters, particularly in regions with scarce water resources.