Temporal and spatial patterns of wetland extent influence variability of surface water connectivity in the Prairie Pothole Region, United States

Abstract

Context Quantifying variability in landscape-scale surface water connectivity can help improve our understanding of the multiple effects of wetlands on downstream waterways. Objectives We examined how wetland merging and the coalescence of wetlands with streams varied both spatially (among ecoregions) and interannually (from drought to deluge) across parts of the Prairie Pothole Region. Methods Wetland extent was derived over a time series (1990-2011) using Landsat imagery. Changes in landscape-scale connectivity, generated by the physical coalescence of wetlands with other surface water features, were quantified by fusing static wetland and stream datasets with Landsat-derived wetland extent maps, and related to multiple wetness indices. The usage of Landsat allows for decadal-scale analysis, but limits the types of surface water connections that can be detected.Results Wetland extent correlated positively with the merging of wetlands and wetlands with streams. Wetness conditions, as defined by drought indices and runoff, were positively correlated with wetland extent, but less consistently correlated with measures of surface water connectivity. The degree of wetlandwetland merging was found to depend less on total wetland area or density, and more on climate conditions, as well as the threshold for how wetland/upland was defined. In contrast, the merging of wetlands with streams was positively correlated with stream density, and inversely related to wetland density. Conclusions Characterizing the degree of surface water connectivity within the Prairie Pothole Region in North America requires consideration of (1) climate-driven variation in wetness conditions and (2) within-region variation in wetland and stream spatial arrangements.

Wetlands inform how climate extremes influence surface water expansion and contraction

“…Landscapes with a tendency to accumulate surface water are relatively common across the globe and include former glacial landscapes including the Prairie Pothole Region (PPR) (Sass and Creed, 2008;Shaw et al, 2012), parts of China (Yao et al, 2007) and Russia (Stokes et al, 2007), and permafrost regions (Smith et al, 2007), as well as low-gradient landscapes including the Argentine Pampas (Kuppel et al, 2015), the Pantanal in Brazil (Hamilton et al, 2002), and the Orinoco Llanos in Columbia and Venezuela (Hamilton et al, 2004). Although such landscapes have previously been shown to experience surface water expansion in response to increased precipitation (Huang et al, 2011;Kuppel et al, 2015;Vanderhoof et al, 2016) or melting ice (Stokes et al, 2007;Yao et al, 2007), we are unaware of studies that have explicitly compared surface water expansion and contraction between landscapes of differing surface water expansion potential.…”

“…Water level data at Devils Lake, North Dakota, for example, have been collected as far back as 1867 and provide a regional indicator of hydrological conditions (LaBaugh et al, 1998;Wiche, 1996). Efforts have been expanded to map interannual changes in surface water extent across the PPR at a landscape scale using remotely sensed imagery (Kahara et al, 2009;Niemuth et al, 2010;Vanderhoof et al, 2016). However, while substantial interannual variation in water level has been documented across the PPR (Huang et al, 2011;, and primarily attributed to interannual variation in temperature and precipitation (Johnson et al, 2005;Zhang et al, 2009), such surface water patterns have to date been minimally characterized for the remainder of the NP.…”

Patterns and drivers for wetland connections in the Prairie Pothole Region, United States

“…Previous work in the PPR documented variability in wetland-to-wetland and wetland-to-stream connectivity as surface water merges in low relief areas and/or wetlands fill and spill (Leibowitz and Vining 2003;Kahara et al 2009;Shaw et al 2013;Vanderhoof et al 2016), and sought to predict connectivity based on storage capacity and spill point elevation (Huang et al 2011b), temporal changes in surface-water extent (Rover et al 2011), and wetland vegetation and water chemistry (Cook and Hauer 2007). This study sought to move from the prediction of connections for individual wetlands to explaining variability in the abundance of such surface-water connections on a landscape scale.…”

“…Substantial variation in surface-water extent in response to climate is well-documented within the region (Beeri and Phillips 2007;Zhang et al 2009;Niemuth et al 2010;Huang et al 2011a;Liu and Schwartz 2011). Changes to surface waters can result in variable wetland-to-wetland (Winter and Rosenberry 1998;Kahara et al 2009) and wetlandto-stream connectivity (Leibowitz and Vining 2003;Sass and Creed 2008;Vanderhoof et al 2016). Minimal research, however has sought to explain the abundance of wetlands that show variable surfacewater connections, or understand at a landscapescale how these wetlands consolidate and become connected to streams.…”

“…Vanderhoof et al (2016) quantified and examined temporal variability from drought to deluge, in surface-water connections between wetlands and streams in the PPR. In this study we eliminated the temporal aspect and instead investigated spatial landscape patterns related to the abundance of variable surface-water connections, exploring specifically, (1) the spatial mechanism and wetland cluster size through which wetlands merge with streams in wet years, (2) patterns in distance metrics for variably connected wetlands in relation to streams, and (3) landscape variables influencing the spatial abundance of these variably connected wetlands.…”