Overview

Another topic a hydrogeologist must be familiar with is how groundwater and surface water interact within rivers and drainage systems. This was briefly addressed in Chapter 5 under gaining and losing streams and in more detail under the discussion of water-level interpretations (Section 5.4). However, in this chapter, an extended treatment of this topic is presented, including concepts of channel geometry and groundwater exchange, the hyporheic zone, and stream health (Meyer 1997; Winter et al. 1998; Woessner 2000).

Traditionally, hydrogeologists considered groundwater/surface-water interaction in terms of water rights and streamflow reduction by evaluating distance-drawdown relationships and pumping wells adjacent to streams (Walton 1970; Sophocleous et al. 1995; Modica 1998; Winter et al. 1998). Flowing streams are complex systems with intricate interactions with living organisms (Hansen 1975; Grimm and Fisher 1984; Dahm et al. 1998), streamflow dynamics (Bencala and Walters 1983; Huggenberger et al. 1998), and groundwater discharge and recharge (Castro and Hornberger 1991). Additionally, streams are situated within a fluvial plain that may be meandering or braided and may have stratigraphically complex relationships, including rapid changes in grain size distributions, facies, and vegetation distribution (Anderson 1989; Mial 1996; Gross and Small 1998). There is a need to perform field work to better conceptualize groundwater/surface-water interaction within the fluvial plain and within channels (Woessner 2000).

Some of the reasons for having a basic understanding of groundwater/surface-water interactions are to better understand groundwater flow in fluvial plains for water-resource management, watershed assessment, watershed restoration, impacts to streamflows including water rights...