What would have been the impacts of wetlands on low flow support and high flow attenuation under steady state land cover conditions?

Abstract

Located at the interface between terrestrial ecosystems and water resources such as water courses and shallow water tables, wetlands are a pivotal part of the drainage network of a watershed.Consequently, they affect the routing of overland and subsurface flows through modification of hydrological processes, namely increased evapotranspiration, water storage and groundwater recharge (Bullock and Acreman, 2003). These interactions have led researchers and land planners to attribute some hydrological services to wetlands, such as low flow support and high flow attenuation. As defined by Roche (1986), low flows refer to the lowest annual flow of a water course at a given point in space.To characterize low flows, various hydrological indicators have been defined, taking into account the return period: 2-year minimum flow over 7 days, 10-year minimum flow over 7 days, 5-year minimum flow over 30 days, etc. On the other hand, high flows are defined as the peak flow within a specific return period, typically 2-, 20-or 100-year maximum flows.In the last century, anthropic activities such as agricultural and urban development have induced major land cover changes; affecting the hydrological regime of watersheds (St-Hilaire et al., 2015;Salvadore et al., 2015;Savary et al., 2009;DeFries and Eshleman, 2004). Agricultural impacts on hydrological processes are mostly associated with artificial drainage, which alters the water volume and timing of runoff (e.g.: Muma et al., 2016;Blann et al., 2009). For example, in the Redwood basin, a Midwestern United States agricultural basin, the total area of soybean (associated with the installation of extensive subsurface drainage tiles) increased from 15% to 40% between 1971 and 2002, and this led to an increase in mean annual flows from 2.3 m 3 /s to 6.0 m 3 /s (Foufoula-Georgiou et al., 2015). Similarly, Muma et al. (2016) showed that subsurface drainage increased base and total flows, and decreased peak flows of an intensively farmed 2.4 km 2 watershed (90% in cropland with 30% of the watershed area tile-drained). As for the impacts of urban development on hydrology, characterized by increasing impervious surfaces, they range from affecting water supply by limiting infiltration, to changes in water demand in response to an increased population (DeFries and Eshleman, 2004;Diem et al., 2018). In the Atlanta metropolitan area, impervious cover of the Big Creek and Suwanee Creek watersheds increased from 8 to 17% and from 9 to 21% respectively, between 1992 and 2011, inducing an increase in the annual stream flow of 26% (Diem et al., 2018).Anthropic activities have also led to the draining of wetlands and modification of the land cover within their drainage area (Zedler and Kercher, 2005;Brinson and Malvarez, 2002). At the global scale, wetland losses estimations are up to 87% and the yearly rate of these losses accelerated between -0.68 to -0.69% in the 1970s to between -0.85 to -1.60% in the 2000s, depending on the region (Davidson, 2014; Ramsar Convention on Wetland, 2018). In all li...

Critical Zone Response Times and Water Age Relationships Under Variable Catchment Wetness States: Insights Using a Tracer‐Aided Ecohydrological Model

“…This suggests that blue water movement, including flow attenuation provided by wetlands (e.g., Blanchette et al. (2019)) and low topographic relief (Figure 1a) will have increasing importance in moderating the temporal variability of water storage in the catchment. Spatial variability of precipitation during re‐wetting periods may also drive some spatial differences in soil moisture sensitivity to wetness (Maneta et al., 2018); however, the dominance of ET water use in the catchment (∼90% of precipitation) likely limits the importance of precipitation‐induced spatial variability.…”

Surface Depression and Wetland Water Storage Improves Major River Basin Hydrologic Predictions

“…To explain how surface depressions affect downstream waters, the degree of attenuation in high flow events has been the most widely acknowledged indicator ( Blanchette et al, 2019 ; Huang et al, 2011 ; Shook & Pomeroy, 2011 ; Wilcox et al, 2011 ), although maintenance of baseflow is another important consideration (e.g., Evenson, Golden, et al, 2018 ). While peak flow attenuation helps prioritize land management alternatives via “what-if” scenarios focused on the abundance and spatial distribution of surface depressions (e.g., Ameli & Creed, 2019 ; Evenson, Golden, et al, 2018 ), we suggest that it cannot be a universal indicator for quantifying cumulative depression-effects.…”

“…First, the effect of surface depressions on peak flows is best understood in small-to meso-scale relatively unregulated watersheds (e.g., Blanchette et al, 2019;Nasab et al, 2017). In these systems, surface depressions typically demonstrate collinearity with peak flow conditions: As volumetric depression storage increases, peak flows exhibit greater attenuation (Figure 6a; also see Babbar-Sebens et al, 2013).…”

“…With the improved process-level understanding of how surface depressions affect watershed hydrology and increased opportunities for quantifying their water storage capacities through recent geospatial data developments ( Jan et al, 2018 ; Jones et al, 2019 ), the interdisciplinary hydro-geoscience community has recently started including surface depression storage in spatially explicit models with varying levels of spatial heterogeneity, physical interactions, and connectivity (e.g., Ameli & Creed, 2017 ; Blanchette et al, 2019 ; Evenson, Golden, et al, 2018 ; Evenson, Jones, et al, 2018 ; Fossey & Rousseau, 2016 ; Golden et al, 2019 ; Nasab & Chu, 2020 ). However, these model applications have been limited to small or meso-watershed scales, with drainage areas ranging from a few hectares to several thousand square kilometers.…”

Application of a High‐Resolution Distributed Hydrological Model on a U.S.‐Canada Transboundary Basin: Simulation of the Multiyear Mean AnnualHydrograph and 2011 Flood of theRichelieu River Basin

“…Since the early 1980s, the hydrological model HYDROTEL (Fortin et al, 1995(Fortin et al, , 2001Turcotte et al, 2007) has been developed by a group of researchers at the "Institut National de Recherche Scientifique" (INRS) in Quebec City, Canada. It has been applied on several watersheds-especially over the Quebec province-to study, among other things, the impacts of hydrological model structure in climate change impact assessment studies (Chen et al, 2011;Poulin et al, 2011;Velazquez et al, 2013), the simulation of the effects of wetlands on watershed hydrology under current and future climate and land cover conditions (e.g., Blanchette et al, 2019;Fossey et al, 2015Fossey et al, , 2016Fossey & Rousseau, 2016a, 2016b, the simulation of snow water equivalent (SWE; Oreiller et al, 2014), and the assessment of future trends in low flows (Foulon et al, 2018). Since many years, HYDROTEL is the main hydrological model used operationally at the Direction de l'Expertise Hydrique (Québec's Water Expertise Direction) for short-term flow forecasting (Turcotte et al, 2004) and for simulating the impacts of climate change on river flows as part of the Hydroclimatic Atlas of Southern Quebec (DEH, 2018a).…”