Detection and potential early warning of catastrophic flow events with regional seismic networks.

Early warning is a critical potential tool for mitigating the impacts of large mass wasting and flood events, a major hazard in the Himalaya. We used data from a dense seismic network in Uttarakhand, India, to detect and track a fatal rockslide to mass flow to flood cascade and examine the potential for regional networks to provide early warning for extreme flow events. Detection limits of the 7 February 2021 event depend on the nature of the active process and on the anthropogenic and environmental seismic noise levels at each station. With the existing network, a seismic monitoring system could have detected all event phases from up to 100 kilometers and provided downstream warnings within minutes of event initiation.

Source identification and management of perennial contaminated groundwater seepage in the highly industrial watershed, south India.

Perennial contaminated groundwater seepage is threatening the downstream ecosystem of the Kazipally Pharmaceutical industrial area located in South India. The sources of seepage are unknown for the last three decades that challenging the regulatory authorities and industries. In general, water quality monitoring and geophysical techniques are applied to identify the sources. However, these techniques may lead to ambiguous results and fail to identify the seepage sources, especially when the area is urbanized/paved, and groundwater is already contaminated with other leakage sources that have similar chemical compounds. In the present study, a novel and multidisciplinary approach were adopted that includes satellite-based Land Surface Temperature (LST) observations, field-based Electrical Resistivity Tomography (ERT), continuous Soil Electrical Conductivity (SEC) and Volumetric Soil Moisture (VSM%) measurements along with groundwater levels monitoring to identify the sources and to control the seepage. The integrated results identified that the locations with the Standard Thermal Anomaly (STA) in the range of -0.5 to -1 °C, VSM% >50%, SEC > 1.5 mS/cm, bulk resistivity < 12 Ω m with shallow groundwater levels < 3 m below ground level (bgl) are potentially contaminated perennial seepage sources. Impermeable sheet piles have been installed across the groundwater flow direction to control the seepage up to 1.5 m bgl, where groundwater frequently intercepts land surface. The quantity of dry season groundwater seepage has been declined by 79.2% after these interventions, which in turn minimized the treatment cost of 1,96,283 USD/year and improved the downstream ecosystem.