Hydrological functions of a peatland in a Boreal Plains catchment

Abstract

Streamflow response in Boreal Plains catchments depends on hydrological connectivity between forested uplands, lakes, and peatlands, and their hydrogeomorphic setting. Expected future drying of the Boreal Plains ecozone is expected to reduce hydrological connectivity of landscape units. To better understand run-off generation during dry periods, we determined whether peatland and groundwater connectivity can dampen expected future water deficits in forests and lakes. We studied Pine Fen Creek catchment in the Boreal Plains ecozone of central Saskatchewan, Canada, which has a large, valley-bottom, terminally positioned peatland, two lakes, and forested uplands. A shorter intensive study permitted a more detailed partitioning of water inputs and outputs within the catchment during the low flow period, and an assessment of a 10-year data set provided insight into the function of the peatland over a range of climate conditions. Using a water balance approach, we learned that two key processes regulate flow of Pine Fen Creek. The cumulative impact of landscape unit hydrological connectivity and the peatland's hydrological functional state were needed to understand catchment response. There was evidence of a run-off threshold which, when crossed, changed the peatland's hydrological function from transmission to run-off generation. Results also suggest the peatland should behave more often as a transmitter of groundwater than as a generator of run-off under a drier climate future, owing to a reduced water supply.

Hydrological Function of a Mountain Fen at Low Elevation Under Dry Conditions

“…Fen hydrological function was assessed using the Spence () method, with modification, at a daily time step. This method has been employed elsewhere to assess when wetlands are predominantly storing, transmitting, and contributing (Goodbrand et al, ; Spence et al, ). The storage function predominated when the fen outflow rate was lower than the absolute value of daily ΔS.…”

“…Poor flow regulation occurs because frozen ground restricts water infiltration (Hayashi, Goeller, Quinton, & Wright, ), limits water storage capacity (Roulet & Woo, ), and lowers soil hydraulic conductivity (Guan, Westbrook, & Spence, ). Fens though can strongly regulate runoff when thawed (Quinton & Carey, ; Wells, Ketcheson, & Price, ), particularly when the water table is low (Goodbrand et al, ; Spence, Guan, & Phillips, ). Water tables of mountain fens are highly dynamic (Karran, Westbrook, & Bedard‐Haughn, ; Millar, Cooper, & Ronayne, ).…”

“…Precipitation events can trigger the water storage function in periods of high evapotranspiration demand (Spence & Woo, 2006). Fens often exhibit runoff threshold behaviour where crossing a threshold triggers a sudden change in hydrological function from transmission to storage or contribution (Goodbrand, Westbrook, & van der Kamp, 2018). Internal and external factors govern transition between runoff states (Spence, 2010), including soil and plant characteristics, antecedent conditions, rainfall rate and volume, and incoming surface and subsurface runoff (Waddington et al, 2015).…”

Seasonal ground ice impacts on spring ecohydrological conditions in a western boreal plains peatland

“…However, during the spring (e.g.,March-June), water losses from peatlands can be enhanced by the presence of thick seasonal ground ice (SGI) due to a reduction in storage capacity, which increases surface run-off (Price & Fitzgibbon, 1987;Woo & Winter, 1993). SGI can also persist well into the growing season (Brown, Petrone, Mendoza, & Devito, 2010;Goodbrand, Westbrook, & van der Kamp, 2018;Thompson & Waddington, 2013), which extends its potential ecohydrological impacts. SGI differs from permafrost because it melts within a year of its formation, generally occurring soon after ground surface temperatures are ≤0 C. The warmer peatland surface underlying cooler air creates a temperature gradient resulting in a transfer of energy from the ground via conduction (Hayashi, Goeller, Quinton, & Wright, 2007) and radiation (Hayashi, 2013;Oke, 1987), leading to the freezing of water within the peat pore spaces.…”

Drivers, pressures, and state responses to inform long-term oil sands wetland monitoring program objectives

“…Studies that were determined to be out of scope included, for example, observational studies that characterized wetland hydrology but did not include tests of independent and dependent variables (e.g. Ketcheson et al 2017;Goodbrand et al 2019;Elmes and Price 2019). Overall, however, this finding suggests the need for explicit metrics of, and research on, surface water diversions and groundwater and surface water withdrawals and releases.…”