Interactions Between Drying and the Hyporheic Zone of a Desert Stream

Abstract

Global warming models predict that increased temperatures will be accompanied by changes in precipitation and runoff in many parts of North America (Schlesinger and Mitchell, 1985), and subsequent reduction and/or loss of streamflow may occur, particularly during summer months, in many parts of North America (e.g., Manabe et al., 1981; Gleick, 1987; Riebsame, 1988). Thus, many permanent streams in mesic environments may become intermittent, and temporary streams characteristic of more xeric regions may become increasingly intermittent or ephemeral. The development of intermittent conditions in streams causes major structural and functional changes (Boulton and Suter, 1986; Williams, 1987) and therefore must be considered in order to understand ecological patterns and processes in these ecosystems. Many arid-land streams are characterized by spatial and temporal discontinuities in flow and therefore provide a good opportunity to study the effects of intermittency on ecosystem structure and functioning. Current information on trends associated with drying can be extrapolated to predict future patterns as intermittency becomes more common in arid-land streams. Further, desert streams can be used as models for considering future trends in more mesic systems due to global warming (Grimm and Fisher, Chapter 10, this volume).