A Monitoring Tool for Analyzing Sediment Dynamics Using Water Turbidity Sensor Data

Watershed management interventions to maintain the quality of surface waters used for drinking water supply provide significant benefits to health. A common water resource issue that needs addressing to ensure clean drinking water is the presence and excessive amount of turbidity in a waterbody. This is an important issue in the watersheds of the New York City (NYC) water supply system, which happens to be one of the world’s largest unfiltered water supplies. In order to sustainably maintain the water quality standards, the NYC Department of Environmental Protection has implemented watershed protection and sediment mitigation projects informed by various sediment dynamics studies to reduce and control excessive turbidity. As part of these studies, the United States Geological Survey has been monitoring the stream discharge and sediment transport in many of the NYC water supply watersheds since 2011 using a network of turbidity sensors. The latter provides massive volumes of high-frequency, real-time streamflow (Q) and turbidity (C) data. There are many uses and analysis methods for these data. Our research employs these data to visualize hysteretic behavior of the C-Q relation during individual storm events, which gives insights into the temporal sediment dynamics of a watershed. The research focuses specifically on developing a new monitoring tool to 1) process the high-frequency streamflow and turbidity data, 2) automate the detection and delineation of streamflow and turbidity events, and 3) visualize the suspended sediment hysteresis patterns. The tool has been applied to the sensor data from the Stony Clove Basin, a watershed with higher turbidity measurements than other tributaries that comprise the NYC water supply system. The results will help inform the watershed managers of the sediment dynamics and assist them in designing and assessing the effectiveness of mitigation strategies. This monitoring tool can be utilized for other studies that also investigate the water quality dynamics at the event scale.