HOW CONNECTED SHOULD A STREAM BE TO ITS CATCHMENT? ASSESSING STREAM-GROUNDWATER INTERACTIONS AND HYPORHEIC EXCHANGE IN STREAM ECOSYSTEM RESTORATION

Open Access
Author:
Gregg, Susan Elizabeth
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 20, 2010
Committee Members:
  • Michael N Gooseff, Thorsten Wagener, Thesis Advisor
  • Mike Gooseff, Thesis Advisor
  • Thorsten Wagener, Thesis Advisor
Keywords:
  • stream restoration
  • groundwater/surface water interaction
  • transient storage modeling
Abstract:
Stream classification systems used today, particularly when applied to stream restoration, do not take into account stream-groundwater interactions, hyporheic flows, or landscape characteristics. They generally ignore hydrological connectivity of a stream to its catchment by focusing on channel morphology. Thus resulting restoration approaches do not necessarily promote proper hydrologic function of a reach. Stream-groundwater interaction is important to stream ecosystem function and hyporheic exchange, in particular, has a significant influence on stream water quality. Therefore, it is proposed that stream restoration techniques need to address the subsurface interactions with streams, as much as the morphology of the channel. The goal of this research is to determine which of the commonly used restoration practices is superior at enhancing the stream-groundwater interactions of the stream. Two main types of restoration efforts were explored using tracer studies and a two-storage zone transient storage model. The first type, which focused on reconnecting the floodplain (RTF), was expected to have a more positive effect on hyporheic exchange than restoration approaches that make use of in-stream structures (ISS) alone. However, both methods were found to produce no significant differences when compared with the unrestored reaches. This was not found to be an entirely robust conclusion and other methods are discussed which may lead to one.