Flow regimes and alternate stable states in a non-perennial river
Abstract
Non-perennial rivers and streams are widespread and support both aquatic ecosystems and society. Historically, most non-perennial stream research has focused on relatively small, undisturbed catchments, and the drivers of transitions between flowing and dry conditions in larger rivers remain understudied. Here, we investigate the historical patterns and drivers of stream intermittency in a large (7th order) reach of the Arkansas River near Larned, KS, USA using streamflow, groundwater level, stream stage, meteorological, and water use data integrated in a time-series modeling approach. We found two distinct hydrologic regimes at this location: a wet regime characterized by near-continuous flow, and a dry regime characterized by near-continuous no-flow conditions. Multiple lines of evidence indicate that these two regimes reflect alternate stable states caused by groundwater pumping and ecohydrological feedbacks that interact to stabilize the stream-aquifer system in either a wet or dry regime. Regime shifts occur when alluvial aquifer water levels fall below (or rise above) the streambed elevation for wet to dry (or dry to wet) transitions. Due to stabilizing feedbacks, regime shifts require long-term (annual and longer) anomalies in the climatic water balance, for example when prolonged precipitation deficits have caused alluvial aquifer levels to fall and the stream to transition from wet to dry. Agricultural pumping in the underlying High Plains aquifer also contributes to long-term declines in alluvial aquifer levels and stream intermittency, which acts as an additional stabilizing feedback of dry regimes. Overall, there is a complex interplay between top-down (climatic) and bottom-up (pumping) controls on intermittency in this large river, and stability-inducing feedbacks mean that it may be difficult to reverse shifts between wet and dry regimes once they occur.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H45P1362Z