A comparison of fibre‐optic distributed temperature sensing to traditional methods of evaluating groundwater inflow to streams

Abstract

Abstract:There are several methods for determining the spatial distribution and magnitude of groundwater inputs to streams. We compared the results of conventional methods [dye dilution gauging, acoustic Doppler velocimeter (ADV) differential gauging, and geochemical end-member mixing] to distributed temperature sensing (DTS) using a fibre-optic cable installed along 900 m of Ninemile Creek in Syracuse, New York, USA, during low-flow conditions (discharge of 1Ð4 m 3 s 1 ). With the exception of differential gauging, all methods identified a focused, contaminated groundwater inflow and produced similar groundwater discharge estimates for that point, with a mean of 66Ð8 l s 1 between all methods although the precision of these estimates varied. ADV discharge measurement accuracy was reduced by non-ideal conditions and failed to identify, much less quantify, the modest groundwater input, which was only 5% of total stream flow. These results indicate ambient tracers, such as heat and geochemical mixing, can yield spatially and quantitatively refined estimates of relatively modest groundwater inflow even in large rivers. DTS heat tracing, in particular, provided the finest spatial characterization of groundwater inflow, and may be more universally applicable than geochemical methods, for which a distinct and consistent groundwater end member may be more difficult to identify.

Detecting groundwater discharge dynamics from point-to-catchment scale in a lowland stream: combining hydraulic and tracer methods

“…However, DTS and VTP measurements showed that the spatial distribution of groundwater discharge in this section is not homogeneous (Fig. 4), similarly to the DTS observations of Lowry et al (2007), Briggs et al (2011) and the VTP-based flux estimations of Schmidt et al (2007) and Anibas et al (2011). The large spatial variability in groundwater discharge is most likely due to heterogeneity in streambed hydraulic conductivity (Kalbus et al, 2006;Sebok et al, 2014), which was also suggested by the streambed composition with interchanging sand, gravel and clusters of macrophyte growth.…”

“…Thus, the detection and quantification of groundwatersurface water dynamics present a challenge, particularly in lowland streams. In these streams the diffuse groundwater discharge along the stream channel reduces the sensitivity of thermal methods (Lowry et al, 2007;Krause et al, 2012), as well as tracer methods (Gonzales et al, 2009), and can cause low net increase in stream flow which also limits the available methods for detecting groundwater discharge (Briggs et al, 2011). At the same time due to the presence of focused, significant discharge zones (Lowry et al, 2007;Matheswaran et al, 2012) the spatial variability of groundwater discharge can be large (Krause et al, 2012).…”

“…At the reach scale more integrated measures, such as differential flow gauging (McCallum et al, 2012;Briggs et al, 2011), have been applied to quantify net differences in stream discharge caused by groundwater recharge and discharge. The use of this method, however, is limited by the measurement uncertainty which prevents it from being applied for detecting small changes in groundwater discharge (Briggs et al, 2011).…”

“…The use of this method, however, is limited by the measurement uncertainty which prevents it from being applied for detecting small changes in groundwater discharge (Briggs et al, 2011). However, recent advances of acoustic Doppler current profiler (ADCP) instruments for stream discharge measurements open up new possibilities for a more detailed detection of net groundwater discharge with short measurement periods and with a high precision (Mueller and Wagner, 2009).…”

“…Hence, more recently point-to-reach-scale groundwater-surface water interactions have been studied by applying multiple methods covering different spatial scales such as groundwater head gradients and DTS (Krause et al, 2012); differential flow gauging, chemical tracers and DTS (Briggs et al, 2011); or chemical tracers and differential flow gauging (McCallum et al, 2012). However, either the studies did not detect small-scale spatial variability in groundwater discharge (Briggs et al, 2011;McCallum et al, 2012) or did not quantify discharge fluxes at the identified discharge zones (Krause et al, 2012). Furthermore, to our knowledge no study has so far combined point-to-reach-scale DTS, VTPs and differential gauging with catchment-scale tracer-based hydrograph separations.…”