Quantification of the regional groundwater flux to a northern peatland complex, Schefferville, Quebec, Canada: results from a water budget and numerical simulations.

摘要

Peatlands are significant soil carbon and freshwater reservoirs at the global scale, and thus play a key role in the global carbon and water cycles. Peatland inception and development are intrinsically related to optimal environmental conditions, including an adequate hydro-morphological setting that promotes the occurrence of waterlogged soils and low topographic gradients. This thesis investigates the hydrology of 0.2 km2 northern peatland complex, located in the region of Schefferville, Quebec, Canada, in which a significant area has developed over a relatively steep topographic gradient. The objective of this thesis is to quantify and characterize the spatiotemporal flux of regional groundwater to the peatland local flow system in an attempt to evaluate the relative importance of this flux compared with other water inputs. A three-dimensional groundwater flow model, the finite-difference U.S. Geological Survey MODFLOW code, is used to simulate the peatland and characterize the groundwater flow system. The model is parameterized with data measured from June 17th to September 4th, 2009, including continuous meteorological measurements from an automatic weather station, 14 observation wells, and two 90° V-notch weirs gauging stream discharge. This study establishes that, over the measuring period, the regional groundwater influx accounted for 27% +/- 0.4% of the total water inputs, the remainder 73% +/- 0.4% consisting of precipitation (54% +/- 0.4%), surface water inflow (14% +/- 0.4%), and change in storage (5% +/- 0.4%). Consequently, it is the main conclusion of this work that regional groundwater inflows were, volumetrically, the second most important source of water to the peatland local flow system.