A coupled hydrology–biogeochemistry model to simulate dissolved organic carbon exports from a permafrost‐influenced catchment

Abstract

Abstract:We outline the development of a simple, coupled hydrology-biogeochemistry model for simulating stream discharge and dissolved organic carbon (DOC) dynamics in data sparse, permafrost-influenced catchments with large stores of soil organic carbon. The model incorporates the influence of active layer dynamics and slope aspect on hydrological flowpaths and resulting DOC mobilization. Calibration and evaluation of the model was undertaken using observations from Granger Basin within the Wolf Creek research basin, Yukon, northern Canada. Results show that the model was able to capture the dominant hydrological response and DOC dynamics of the catchment reasonably well. Simulated DOC was highly correlated with observed DOC (r 2 = 0.65) for the study period. During the snowmelt period, the model adequately captured the observed dynamics, with simulations generally reflecting the timing and magnitude of the observed DOC and stream discharge. The model was less successful over the later summer period although this partly reflected a lack of DOC observations for calibration. The developed model offers a valuable framework for investigating the interactions between hydrological and DOC processes in these highly dynamic systems, where data acquisition is often very difficult.

Hydrological control of dissolved organic carbon dynamics in a rehabilitated <i>Sphagnum</i>–dominated peatland: a water-table based modelling approach

“…To simulate DOC dynamics, a module was developed based on first order production and loss, and mass balance, similarly to what can be found in the literature (Birkel et al, 2014;Lessels et al, 2015). Production and loss are computed in the Se and Sm reservoirs only since the main biogeochemical processes linked to DOC dynamics occur in soil storage and no reaction takes place in the Sr reservoir.…”

“…Production and loss are computed in the Se and Sm reservoirs only since the main biogeochemical processes linked to DOC dynamics occur in soil storage and no reaction takes place in the Sr reservoir. DOC production was based on a production coefficient and two additional modifiers based on soil water content and air temperature as usually considered in DOC production models (Birkel et al, 2014;Futter 15 et al, 2007;Lessels et al, 2015). The effect of the temperature was based on a Q 10 formulation (the factor by which the rate of a reaction increases for every 10-degree rise in the temperature) with a value of 2 according to the value commonly used in DOC production models (Lessels et al, 2015;Michalzik et al, 2003;Tjoelker et al, 2001).…”

“…precipitation and water discharge or water level) so they can be applied to numerous study sites where such data are available, making them a suitable tool to compare sites with different settings. 25 When studying DOC dynamics in peatlands, existing conceptual models are composed of a DOC module combined with a hydrological model (Birkel et al, 2014;Futter et al, 2007;Lessels et al, 2015). In these studies, the hydrological model is usually adapted to the catchment and calibrated on stream discharge.…”

“…Furthermore, while WTD is a key parameter to explain DOC dynamics (Strack et al, 2008), it is usually not considered for calibration, and water 30 discharge is preferred instead. Therefore, while these models have proven to be well adapted when modelling a catchment containing a peatland area (Birkel et al, 2014;Futter et al, 2007;Lessels et al, 2015), where the outlet is well defined, they are more difficult to apply when considering the peatland alone. In this case, the model should focus on the simulation of the Hydrol.…”

“…Furthermore, a model based on WTD can also provide interesting information about the spatial variability of the dominant hydrological processes when applied to different locations within the same peatland. Models simulating DOC dynamics are usually based on a simple mass balance and DOC production and consumption rates, usually expressed as first order rate processes (Birkel et al, 2014;Futter et al, 2007;Lessels et al, 2015). In these cases, DOC production and consumption equations are modified using terms related to 5 temperature and soil moisture.…”