Articles | Volume 20, issue 6
Hydrol. Earth Syst. Sci., 20, 2295–2307, 2016
Hydrol. Earth Syst. Sci., 20, 2295–2307, 2016

Research article 15 Jun 2016

Research article | 15 Jun 2016

Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

Matthew D. Berg1,a, Franco Marcantonio2, Mead A. Allison3,4, Jason McAlister5, Bradford P. Wilcox1, and William E. Fox1,5 Matthew D. Berg et al.
  • 1Department of Ecosystem Science and Management, Texas A&M University, College Station, Texas, USA
  • 2Department of Geology and Geophysics, Texas A&M University, College Station, Texas, USA
  • 3The Water Institute of the Gulf, Baton Rouge, Louisiana, USA
  • 4Tulane University, Department of Earth and Environmental Sciences, New Orleans, Louisiana, USA
  • 5Texas A&M AgriLife Blackland Research & Extension Center, Temple, Texas, USA
  • anow at: Save Water Co, Houston, Texas, USA

Abstract. Rangelands cover a large portion of the earth's land surface and are undergoing dramatic landscape changes. At the same time, these ecosystems face increasing expectations to meet growing water supply needs. To address major gaps in our understanding of rangeland hydrologic function, we investigated historical watershed-scale runoff and sediment yield in a dynamic landscape in central Texas, USA. We quantified the relationship between precipitation and runoff and analyzed reservoir sediment cores dated using cesium-137 and lead-210 radioisotopes. Local rainfall and streamflow showed no directional trend over a period of 85 years, resulting in a rainfall–runoff ratio that has been resilient to watershed changes. Reservoir sedimentation rates generally were higher before 1963, but have been much lower and very stable since that time. Our findings suggest that (1) rangeland water yields may be stable over long periods despite dramatic landscape changes while (2) these same landscape changes influence sediment yields that impact downstream reservoir storage. Relying on rangelands to meet water needs demands an understanding of how these dynamic landscapes function and a quantification of the physical processes at work.

Short summary
Rangelands, from grasslands to woodlands, cover much of the earth. These areas face great pressure to meet growing water needs. Data on large-scale dynamics that drive water planning remain rare. Our watershed-scale results challenge simplistic hydrological assumptions. Streamflow was resilient to dramatic landscape changes. These changes did shape sediment yield, affecting water storage. Understanding these processes is vital to projections of rangeland water resources in a changing world.