Wetlands inform how climate extremes influence surface water expansion and contraction

Melanie K Vanderhoof,Michael G Mcmanus,Laurie C Alexander,Charles R Lane,Jay R Christensen

doi:10.5194/hess-22-1851-2018

Abstract

Effective monitoring and prediction of flood and drought events requires an improved understanding of how and why surface-water expansion and contraction in response to climate varies across space. This paper sought to (1) quantify how interannual patterns of surface-water expansion and contraction vary spatially across the Prairie Pothole Region (PPR) and adjacent Northern Prairie (NP) in the United States, and (2) explore how landscape characteristics influence the relationship between climate inputs and surface-water dynamics. Due to differences in glacial history, the PPR and NP show distinct patterns in regards to drainage development and wetland density, together providing a diversity of conditions to examine surface-water dynamics. We mapped surface-water extent across eleven Landsat path/rows representing the PPR and NP (images spanning 1985-2015). The PPR not only experienced a 2.6-fold increase of surface-water extent under median conditions relative to the NP, but also showed a 3.4-fold greater difference in surface-water extent between drought and deluge conditions. The relationship between surface-water extent and accumulated water availability (precipitation minus potential evapotranspiration) was quantified per watershed and statistically related to variables representing hydrology-related landscape characteristics (e.g., infiltration capacity, surface storage capacity, stream density). To investigate the influence stream-connectivity has on the rate at which surface water leaves a given location, we modeled stream-connected and stream-disconnected surface water separately. Stream-connected surface water showed a greater expansion with wetter climatic conditions in landscapes with greater total wetland area. Disconnected surface water showed a greater expansion with wetter climatic conditions in landscapes with higher wetland density, lower infiltration and less anthropogenic drainage. From these findings, we can expect that shifts in precipitation and evaporative demand will have uneven effects on surface-water quantity. Accurate predictions regarding the effect of climate change on surface-water quantity will require consideration of hydrology-related landscape characteristics including wetlands.

Highlights

Surface water dynamics have strong implications for ecosystem functioning and human land use including biogeochemical balances (Hoffmann et al, 2009), species distributionPublished by Copernicus Publications on behalf of the European Geosciences Union.M
The random forests were run with the Surface Water Climate Response (SWCR) as the dependent variable and landscape characteristics as independent variables
Random forest models are generally insensitive to collinearity among metrics; the inclusion of correlated variables can deflate variable importance as well as the overall variation explained by the model (Murphy et al, 2010)

Summary

Introduction

Vanderhoof et al.: Wetlands inform how climate extremes influence surface water expansion (Boschilia et al, 2008; Calhoun et al, 2017), hydrologic connectivity (Heiler et al, 1995; Pringle, 2001), and agricultural productivity (Mokrech et al, 2008; Gornall et al, 2010). Natural variability in surface water extent, makes gathering timely, accurate information, a challenge (Poff et al, 1997; Beeri and Phillips, 2007). The relative importance of hydrologic processes and flow paths across a landscape (e.g., surface storage, infiltration, evapotranspiration, runoff) can be expected to influence the timing, duration and extent of surface water for a given location (Euliss Jr. and Mushet, 1996; LaBaugh et al, 1998; van der Kamp et al, 1999)

Methods

Results

Discussion

Conclusion