Investigating the spatio-temporal variability in groundwater and surface water interactions: a multi-technique approach

Abstract

Abstract. The interaction between groundwater and surface water along the Tambo and Nicholson rivers, southeast Australia, was investigated using 222 Rn, Cl, differential flow gauging, head gradients, electrical conductivity (EC) and temperature profiles. Head gradients, temperature profiles, Cl concentrations and 222 Rn activities all indicate higher groundwater fluxes to the Tambo River in areas of increased topographic variation where the potential to form large groundwater-surface water gradients is greater. Groundwater discharge to the Tambo River calculated by Cl mass balance was significantly lower (1.48 × 10 4 to 1.41 × 10 3 m 3 day −1 ) than discharge estimated by 222 Rn mass balance (5.35 × 10 5 to 9.56 × 10 3 m 3 day −1 ) and differential flow gauging (5.41 × 10 5 to 6.30 × 10 3 m 3 day −1 ) due to bank return waters. While groundwater sampling from the bank of the Tambo River was intended to account for changes in groundwater chemistry associated with bank infiltration, variations in bank infiltration between sample sites remain unaccounted for, limiting the use of Cl as an effective tracer. Groundwater discharge to both the Tambo and Nicholson rivers was the highest under high-flow conditions in the days to weeks following significant rainfall, indicating that the rivers are well connected to a groundwater system that is responsive to rainfall. Groundwater constituted the lowest proportion of river discharge during times of increased rainfall that followed dry periods, while groundwater constituted the highest proportion of river discharge under baseflow conditions (21.4 % of the Tambo in April 2010 and 18.9 % of the Nicholson in September 2010).

Characteristics and controls of variability in soil moisture and groundwater in a headwater catchment

“…Lana-Renault et al (2014) found in a Mediterranean catchment that patterns of near-surface saturation and transient water tables were affected not only by topography, but also by soil properties and previous agricultural land use. The riparian zone facilitates mixing between soil water and groundwater, and tracers, temperature, electrical conductivity, flow gauging and head differences may all be used to quantify the interactions (Unland et al, 2013). Using modelling and tracer data, Binley et al (2013) found that in a 200 m river reach the upper section was connected to regional groundwater, but lower section inflows were from local lateral and down-river flow paths.…”

Linking Spatial Patterns of Groundwater Table Dynamics and Streamflow Generation Processes in a Small Developed Catchment

“…Nevertheless, following the line of arguments, groundwater flow directions pointed out the same as Ksat values and the results of the incremental stream gauging already showed: effluent conditions in the stream section between piezometers 32-35 and influent conditions at the catchment's outlet (piezometers [1][2][3][4][5][6][21][22]. The simultaneous occurrence of influent and effluent conditions in different sections of the Vollnkirchener Bach combined with high spatial variability was in line with references [4,72] who likewise observed temporal and spatial variability in the groundwater-surface water exchange fluxes.…”

“…Stream gauging has to be conducted under baseflow conditions allowing the net groundwater discharge or recharge to be calculated [4,11]. Incremental streamflow is measured on 24 April 2013 at low flow conditions via salt dilution measurements from the outlet of the Vollnkirchener Bach to the upstream boundary in 200 m steps, resulting in 12 sampling points ( Table 2).…”

“…While multi-method approaches have historically been less common, they can overcome the large uncertainties that are attributed to single method applications and provide additional and more robust information for example in groundwater-surface water interactions [3][4][5] to obtain unequivocal results [6]. Moreover, by combining methods in different compartments of the hydrological cycle or different scales within the catchment (plot-, reach-scale) long time series are not necessarily needed to understand catchment reaction or the contribution of runoff components during varying saturation conditions (floods or low flow) in small and meso-scale catchments [7][8][9][10].…”

Residence times and mixing of water in river banks: implications for recharge and groundwater–surface water exchange

“…Recognising that bank storage waters may contribute to rivers over long time frames is important for estimating groundwater discharge by chemical mass balance. If the bank storage waters are chemically similar to surface water rather than regional groundwater, using the composition of regional groundwater as an endmember will result in underestimation of the groundwater flux (Cartwright et al, 2014;McCallum et al, 2010;Unland et al, 2013).…”