Simulation of baseflow accounting for the effect of bank storage and its implication in baseflow separation

Andersen

et al. 2013

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).

Section: Methods Comparisonmentioning

confidence: 99%

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

Unland

Andersen

et al. 2013

“…The quickflow component will include event water but can also include older water displaced from soils and the unsaturated zone, groundwater mobilised by hydraulic loading due to recharge on the floodplains or groundwater displaced from perched aquifers (Sklash and Farvolden, 1979;Rice and Hornberger, 1998;Anderson and Burt, 1980;Wittenberg and Sivapalan, 1999;Kirchner, 2009;Hrachowitz et al, 2011;Zabaleta and Antiguedad, 2013). In gaining river systems, baseflow will include inputs from regional groundwater but may also include interflow, the return of water from bank storage, or draining of pools on the floodplain (Chen et al, 2006;McCallum et al, 2010;Hrachowitz et al, 2011), and these components may change in importance at different times of the hydrological cycle or during wet or dry years (Aubert et al, 2012). The potential presence of multiple sources of water contributing to both the baseflow and quickflow components complicates our understanding of groundwater-surface water interaction.…”

Section: Cartwright Et Al: Contrasts Between Estimates Of Baseflowmentioning

confidence: 99%

Contrasts between estimates of baseflow help discern multiple sources of water contributing to rivers

Gilfedder

Hofmann

2014

Abstract. This study compares baseflow estimates using chemical mass balance, local minimum methods, and recursive digital filters in the upper reaches of the Barwon River, southeast Australia. During the early stages of highdischarge events, the chemical mass balance overestimates groundwater inflows, probably due to flushing of saline water from wetlands and marshes, soils, or the unsaturated zone. Overall, however, estimates of baseflow from the local minimum and recursive digital filters are higher than those based on chemical mass balance using Cl calculated from continuous electrical conductivity measurements. Between 2001 and 2011, the baseflow contribution to the upper Barwon River calculated using chemical mass balance is between 12 and 25 % of the annual discharge with a net baseflow contribution of 16 % of total discharge. Recursive digital filters predict higher baseflow contributions of 19 to 52 % of discharge annually with a net baseflow contribution between 2001 and 2011 of 35 % of total discharge. These estimates are similar to those from the local minimum method (16 to 45 % of annual discharge and 26 % of total discharge). These differences most probably reflect how the different techniques characterise baseflow. The local minimum and recursive digital filters probably aggregate much of the water from delayed sources as baseflow. However, as many delayed transient water stores (such as bank return flow, floodplain storage, or interflow) are likely to be geochemically similar to surface runoff, chemical mass balance calculations aggregate them with the surface runoff component. The difference between the estimates is greatest following periods of high discharge in winter, implying that these transient stores of water feed the river for several weeks to months at that time. Cl vs. discharge variations during individual flow events also demonstrate that inflows of high-salinity older water occurs on the rising limbs of hydrographs followed by inflows of low-salinity water from the transient stores as discharge falls. The joint use of complementary techniques allows a better understanding of the different components of water that contribute to river flow, which is important for the management and protection of water resources.

“…In addition, bank waters may represent a source of nutrients or contaminants derived from the river that are gradually released following diminishing of the flood peak. The volume and duration of bank storage for a given river stretch will depend on the flood peak height and the flood duration (Cooper and Rorabaugh, 1963), as well as the hydraulic conductivity of the alluvial aquifer and the hydraulic gradient between the aquifer and river (Cartwright et al, 2014;Chen et al, 2006;McCallum et al, 2010). Whiting and Pomeranets (1997) showed that deeply incised narrow rivers with wider floodplains and coarse alluvial material have greater bank storage potential.…”

Section: Introductionmentioning

confidence: 99%

“…Whiting and Pomeranets (1997) showed that deeply incised narrow rivers with wider floodplains and coarse alluvial material have greater bank storage potential. The potential for significant storage beneath the streambed was identified by Chen and Chen (2003), while Chen et al (2006) showed that bank storage will return more rapidly Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

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

Unland

Cendón

et al. 2014

Abstract. Bank exchange processes within 50 m of the Tambo River, southeast Australia, have been investigated through the combined use of 3 H and 14 C. Groundwater residence times increase towards the Tambo River, which suggests the absence of significant bank storage. Major ion concentrations and δ 2 H and δ 18 O values of bank water also indicate that bank infiltration does not significantly impact groundwater chemistry under baseflow and post-flood conditions, suggesting that the gaining nature of the river may be driving the return of bank storage water back into the Tambo River within days of peak flood conditions. The covariance between 3 H and 14 C indicates the leakage and mixing between old (∼ 17 200 years) groundwater from a semiconfined aquifer and younger groundwater (< 100 years) near the river, where confining layers are less prevalent. It is likely that the upward infiltration of deeper groundwater from the semi-confined aquifer during flooding limits bank infiltration. Furthermore, the more saline deeper groundwater likely controls the geochemistry of water in the river bank, minimising the chemical impact that bank infiltration has in this setting. These processes, coupled with the strongly gaining nature of the Tambo River are likely to be the factors reducing the chemical impact of bank storage in this setting. This study illustrates the complex nature of river groundwater interactions and the potential downfall in assuming simple or idealised conditions when conducting hydrogeological studies.