Simulation of aquifer-peatland-river interactions under climate change

Abstract

Wetlands play an important role in preventing extreme low flows in rivers and groundwater level drawdowns during drought periods. This hydrological function could become increasingly important under a warmer climate. Links between peatlands, aquifers, and rivers remain inadequately understood. The objective of this study was to evaluate the hydrologic functions of the Lanoraie peatland complex in southern Quebec, Canada, under different climate conditions. This peatland complex has developed in the beds of former fluvial channels during the final stages of the last deglaciation. The peatland covers a surface area of ~76 km2 and feeds five rivers. Numerical simulations were performed using a steady-state groundwater flow model. Results show that the peatland contributes on average to 77% of the mean annual river base flow. The peatland receives 52% of its water from the aquifer. Reduced recharge scenarios (−20 and −50% of current conditions) were used as a surrogate of climate change. With these scenarios, the simulated mean head decreases by 0.6 and 1.6 m in the sand. The mean river base flow decreases by 16 and 41% with the two scenarios. These results strongly underline the importance of aquifer-peatland-river interactions at the regional scale. They also point to the necessity of considering the entire hydrosystem in conservation initiatives.

Long-term trends in groundwater recharge and discharge in a fractured bedrock aquifer – past and future conditions

“…This data set has been used in at least one additional case study in the Lanoraie region of southern Quebec (e.g. Bourgault et al 2014). It is important to underline the fact that the first weather station was installed around 1920 and the first station measuring snow on the ground was installed around 1965.…”

“…baseflow, spring flow, peatland-aquifer interactions) stemming from different future recharge scenarios (e.g. Scibek and Allen 2006;Jyrkama and Sykes 2007;Scibek et al 2007;Toews and Allen 2009;Sulis et al 2011;Bourgault et al 2014;Kurylyk et al 2014;Levison et al 2014a;Levison et al 2014b;Rivard et al 2014) or historical data sets (e.g. Chen et al 2004;Rivard et al 2009).…”

“…Reductions in recharge are usually considered the "worst-case scenario" from an ecohydrological standpoint (e.g. Bourgault et al 2014), since less recharge can induce declines in groundwater levels which can trigger drying of streams, springs and seeps. Holman et al (2012) note that the uncertainty of future conditions needs to be addressed by running a broad range of scenarios incorporating both climate and future socio-economic and land-use changes.…”

Quantification of peatland water storage capacity using the water table fluctuation method

“…Peatlands play important hydrologic functions by attenuating flooding by storing water during high precipitation events (Acreman and Holden, ), contributing to river base flows (Bourgault et al, ) and maintaining groundwater levels in superficial aquifers (McLaughlin et al . , ).…”

Quantifying peat hydrodynamic properties and their influence on water table depths in peatlands of southern Quebec (Canada)

“…Peatlands are water‐dependent ecosystems often connected to aquifers (Rossi, Ala‐aho, Ronkanen, & Klove, ) and rivers (Bourgault, Larocque, & Roy, ) and are characterized by an accumulation of organic matter that exceeds its decomposition. The connectivity of peatlands to aquifers and rivers, referred to as hydro‐connectivity, and their capacity to accumulate and store carbon depends on the water table depth (Ise, Dunn, Wofsy, & Moorcroft, ), which is strongly influenced by the physical properties of the peat (i.e., density (ρ dry ), peat composition and humification, hydraulic conductivity (K), and specific yield (S y ; Ise et al, ; Kelly et al, ).…”