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Publications > Zlotnick and others, 2010.

Mechanisms controlling variability of lake salinity in dune environments in semi-arid climate — Nebraska Sand Hills

V.A. Zlotnik (vzlotnik1@unl.edu)
Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA

J.T. Ong (jbong@bigred.unl.edu)
Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA

J.B. Swinehart (jswinehart1@unl.edu)
School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE, USA

S.C. Fritz (sfritz2@unl.edu)
Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA

J.D. Lenters (jlenters2@unl.edu)
School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE, USA

J.U. Schmieder (schmiederjens@web.de)
Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA

J.W. Lane, Jr. (jwlane@usgs.gov)
Office of Groundwater, Branch of Geophysics, U.S. Geological Survey, Storrs, CT, USA

T. Halihan (todd.halihan@okstate.edu)
School of Geology, Oklahoma State University, Stillwater, OK, USA

Abstract

Shallow endorheic saline lakes are common in semi-arid environments in North America, Africa, Asia, and Australia. These lakes receive minimal surface runoff and are supported by groundwater seepage. A combination of hydrologic and geologic factors (regional groundwater flow, evaporation, precipitation, lake size, groundwater recharge, and geologic setting) may preclude seepage out of these lakes, even in the presence of ambient regional flow. Solutes from groundwater are captured by these lakes and become enriched over time by evaporation. The importance of understanding lake dynamics in these arid and semi-arid systems is increasing with societal concerns, including water availability and quality, the use of aquatic ecosystems by waterfowl and other biota, and dangers of dust emissions associated with lake desiccation. We consider the salinity of shallow lakes as a useful indicator of hydroclimatic factors operating at centennial and millennial scales. The Nebraska Sand Hills cover 58 000 km2 of the central Great Plains and are the largest dunefield in the Western Hemisphere. The grass-stabilized dunes attain heights up to 130 m and have been modified by soil development and erosion. In an area <7000 km2, there are ~400 lakes with surface areas >4 ha and depths <1 m. Annual lake evaporation exceeds precipitation by 600 mm, according to some estimates. The salinity of natural lakes in the Nebraska Sand Hills ranges from fresh (~0.3 g L-1) to hypersaline (>100 g L-1), with pH values as high as ~10. We assess the mechanisms that control lake salinity in a group of lakes with different subsurface flow regimes. Our methods combine aquifer coring, electromagnetic and electrical resistivity tomography geophysics, hydraulic testing, lakebed dating using 14C and optically stimulated luminescence, energy and water balance analysis, and salt crust and dust collection. Our theory and results show that terrain and water-table topography, lithology, and climate control the lake-aquifer solute exchanges. This study also brings attention to an underappreciated mechanism in the area, namely eolian deflation, which has not been quantified previously. An interaction of hydraulic and eolian mechanisms controls lake salinity, which may strongly depend on the sequence of arid and pluvial episodes.

Final copy as submitted to the American Geophysical Union for publication as: Zlotnick, V., Ong, J., Swinehart, J., Fritz, S., Lenters, J., Smieder, J., Halihan, T., and Lane, J.W., Jr., 2010, Mechanisms controlling variability of lake salinity in dune environments in semi-arid climate — Nebraska Sand Hills [abs.], in 2010 Fall Meeting, San Francisco, California, 13-17 December 2010, proceedings: American Geophysical Union, Washington, D.C., abstract H41C-1092.