Geology topics

Ian Cartwright

Publications and source records attributed to Ian Cartwright.

3 recordsLinked to original sources

USGS2021

Temporal and spatial variations in river specific conductivity: Implications for understanding sources of river water and hydrograph separations

Specific conductivity (SC) is commonly used to estimate the proportion of baseflow (i.e., waters from within catchments such as groundwater, interflow, or bank return flows) contributing to rivers. Reach-scale SC comparisons are also useful for identifying where multiple water stores contribute to baseflow. Daily SC values of adjacent gauges in Australian (the Barwon, Glenelg, and Campaspe Rivers) and North American (the Upper Colorado River) catchments are commonly not well correlated (R 2 = 0.32 to 0.82). Smoothed inter-gauge SC values averaged over 7 to 45 days are better correlated and define a series of hysteresis loops. The variable SC patterns between adjacent gauges probably reflect varying proportions of groundwater, bank return waters, interflow, and soil water contributing to baseflow. In some rivers using SC values to compare baseflow along river reaches on sub-annual timescales may be not be feasible.

Journal of Hydrology↗

USGS2016

Using diurnal temperature signals to infer vertical groundwater-surface water exchange

Heat is a powerful tracer to quantify fluid exchange between surface water and groundwater. Temperature time series can be used to estimate pore water fluid flux, and techniques can be employed to extend these estimates to produce detailed plan-view flux maps. Key advantages of heat tracing include cost-effective sensors and ease of data collection and interpretation, without the need for expensive and time-consuming laboratory analyses or induced tracers. While the collection of temperature data in saturated sediments is relatively straightforward, several factors influence the reliability of flux estimates that are based on time series analysis (diurnal signals) of recorded temperatures. Sensor resolution and deployment are particularly important in obtaining robust flux estimates in upwelling conditions. Also, processing temperature time series data involves a sequence of complex steps, including filtering temperature signals, selection of appropriate thermal parameters, and selection of the optimal analytical solution for modeling. This review provides a synthesis of heat tracing using diurnal temperature oscillations, including details on optimal sensor selection and deployment, data processing, model parameterization, and an overview of computing tools available. Recent advances in diurnal temperature methods also provide the opportunity to determine local saturated thermal diffusivity, which can improve the accuracy of fluid flux modeling and sensor spacing, which is related to streambed scour and deposition. These parameters can also be used to determine the reliability of flux estimates from the use of heat as a tracer.

Groundwater↗

USGS2016

Improved vertical streambed flux estimation using multiple diurnal temperature methods in series

Analytical solutions that use diurnal temperature signals to estimate vertical fluxes between groundwater and surface water based on either amplitude ratios ( A r ) or phase shifts (Δ ϕ ) produce results that rarely agree. Analytical solutions that simultaneously utilize A r and Δ ϕ within a single solution have more recently been derived, decreasing uncertainty in flux estimates in some applications. Benefits of combined ( A r Δ ϕ ) methods also include that thermal diffusivity and sensor spacing can be calculated. However, poor identification of either A r or Δ ϕ from raw temperature signals can lead to erratic parameter estimates from A r Δ ϕ methods. An add-on program for VFLUX 2 is presented to address this issue. Using thermal diffusivity selected from an A r Δ ϕ method during a reliable time period, fluxes are recalculated using an A r method. This approach maximizes the benefits of the A r and A r Δ ϕ methods. Additionally, sensor spacing calculations can be used to identify periods with unreliable flux estimates, or to assess streambed scour. Using synthetic and field examples, the use of these solutions in series was particularly useful for gaining conditions where fluxes exceeded 1 m/d.

Groundwater↗