Using Remotely Sensed Imagery to Document How Land Use Drives Turbidity of Playa Waters in Texas

Scott Starr,Kevin Mulligan,Lucia Barbato,Lucas Heintzman,Nancy Mcintyre

doi:10.3390/rs8030192

Abstract

Sedimentation (primarily from human land use) is a major threat to runoff-fed wetlands of the Great Plains of North America (playas), but it is unknown how many playas are turbid, how prevalence of turbidity has changed over time, and how turbidity is related to surrounding land use. We used remotely sensed imagery to assess sedimentation in the waters of over 7700 playa basins in Texas on four dates during a 29-year span: 25 July 1986 (a regionally wet time), 3 May 2014 (during drought), 4 June 2014 (after the drought was broken), and 25 July 2015 (one year post-drought). Even on the wettest date examined, 64% of playa basins did not hold water. Turbidity varied over time, was already present in over half of the basins examined in 1986, and prevalence of turbidity was not simply proportional to overall wet playa abundance. There was an increase in total and irrigated cropland in our focal region and a statistically significant association between sedimentation and land use within 100 m of a playa: clear playas were associated with more urban development and pasture/grassland, and turbid playas were surrounded mostly by cropland.

Highlights

There were 7921 playa basins within the area covered by Landsat 5 (1986 image) and 8372 basins within the area covered by Landsat 8 (2014 and 2015 images) (Table 1)
Runoff-fed wetlands of the Great Plains of North America that are regionally important in supporting biodiversity
Sedimentation is a major threat to playas and their associated biota because infill decreases the volume of water that can be stored, even to the point of causing the basin to be entirely filled with earth, and creates turbid water

Summary

Introduction

Runoff-fed (i.e., depressional) wetlands are inherently susceptible to sedimentation and are vulnerable when their watersheds experience accelerated rates of erosion due to anthropogenic activities such as land-cover change [3,4]. Playas are depressional wetlands of the tablelands of the central and southern Great Plains of North America that are foci for biodiversity [5,6]. The playa network of the Great Plains of North America is akin to other depressional wetland complexes around the world ( in arid and semi-arid regions) that are experiencing land-cover change, including the prairie potholes of the northern Great Plains, vernal pools of the northeastern U.S, and wetlands of Spain, India, Brazil, southern Africa, and central Asia [7,8,9,10,11,12]

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