Developing Groundwater Variability Probes and Wireless Sensor Networks for Characterizing the Subsurface Low Flow Field

Abstract

Groundwater monitoring plays a key role in understanding solute transport processes, including pollutant fate and transport mechanisms, detection of leaks from groundwater storage containers, and development of early warning systems for flooding and bank stability. Furthermore, incorporating these monitoring fields into remote stations with wireless data transmittal has proven useful in real-time data analysis and field forecasting. A promising new technology called the groundwater variability probe (GVP) was developed, tested, and integrated into a wireless field station with inclusion of soil moisture probes and pressure transducers for monitoring hydraulic conditions within a pond bank. The GVP is capable of measuring real-time centimeter-scale velocity magnitude, flow direction, hydraulic conductivity, and dispersion coefficient measurements simultaneously. We found that the GVP can effectively measure seepage velocity in dispersion-dominated regimes from 26 to 460 cm ${\rm day}^{\mathrm {{-1}}}$ range and flow direction to within ±10°. The hydraulic conductivity was determined using Darcy's law. The GVP-derived velocity measurements were found to be within expected ranges of hydraulic conductivity. Dispersion coefficients of the plume were derived and found to be similar to values reported in the literature. A wireless sensor network was installed on a wet retention pond bank, allowing remote real-time access for monitoring changes in soil moisture, groundwater velocity, and stage fluctuations, providing insights into correlations with in-situ storm events.