Divergence and flow direction as indicators of subsurface heterogeneity and stage-dependent storage in alluvial floodplains

Abstract

Assuming homogeneity in alluvial aquifers is convenient, but limits our ability to accurately predict stream‐aquifer interactions. Research is needed on (i) identifying the presence of focused, as opposed to diffuse, groundwater discharge/recharge to streams and (ii) the magnitude and role of large‐scale bank and transient storage in alluvial floodplains relative to changes in stream stage. The objective of this research was to document and quantify the effect of stage‐dependent aquifer heterogeneity and bank storage relative to changes in stream stage using groundwater flow divergence and direction. Monitoring was performed in alluvial floodplains adjacent to the Barren Fork Creek and Honey Creek in northeastern Oklahoma. Based on results from subsurface electrical resistivity mapping, observation wells were installed in high and low electrical resistivity subsoils. Water levels in the wells were recorded real time using pressure transducers (August to October 2009). Divergence was used to quantify heterogeneity (i.e. variation in hydraulic conductivity, porosity, and/or aquifer thickness), and flow direction was used to assess the potential for large‐scale (100 m) bank or transient storage. Areas of localized heterogeneity appeared to act as divergence zones allowing stream water to quickly enter the groundwater system, or as flow convergence zones draining a large groundwater area. Maximum divergence or convergence occurred with maximum rates of change in flow rates or stream stage. Flow directions in the groundwater changed considerably between base and high flows, suggesting that the floodplains acted as large‐scale bank storage zones, rapidly storing and releasing water during passage of a storm hydrograph. During storm events at both sites, the average groundwater direction changed by at least 90° from the average groundwater direction during baseflow. Aquifer heterogeneity in floodplains yields hyporheic flows that are more responsive and spatially and temporally complex than would be expected compared to more common assumptions of homogeneity. Copyright © 2012 John Wiley & Sons, Ltd.

Continental hydrosystem modelling: the concept of nested stream–aquifer interfaces

“…Along with the sediment heterogeneities, the geomorphological structures of the alluvial plain can also create preferential pathways, which can have a significant impact on stream-aquifer exchanges (Conant, 2004;Fleckenstein et al, 2006;Poole et al, 2002Poole et al, , 2008Storey et al, 2003;van Balen et al, 2008;Weng et al, 2003;Woessner, 2000). Overall, the preferential flow paths lead to a spatially and temporally complex piezometric head distribution in the alluvial plain, especially during transitional event as floods (Bendjoudi et al, 2002;Heeren et al, 2014;Koch et al, 2011;Wondzell and Swanson, 1999;Wroblicky et al, 1998), when bank storage occurs (Whiting and Pomeranets, 1997).…”

Climate, water use, and land surface transformation in an irrigation intensive watershed—Streamflow responses from 1950 through 2010

“…The Cimarron Terrace and Alluvial aquifer is used for irrigation in the Cimarron-Skeleton watershed and lower portion of the Cimarron-Eagle Chief watershed and consists of quaternary and tertiary-aged river alluvium and terrace deposits of varying thickness (Bingham and Bergman, 1980). The deposits on the river's southwestern side are thin and are poor for irrigation, however, the deposits on the northeastern side of the river are considered one of the best alluvial aquifers in the state (Ryder, 1996), with fast exchange between surface and groundwater (Heeren et al, 2013). As a result, this alluvial-aquifer dominated watershed has been turned into a very productive agricultural region with substantial groundwater withdrawal to support row crop production.…”

The hydraulic conductivity structure of gravel-dominated vadose zones within alluvial floodplains

“…The data acquisition and inversion utilized a proprietary Oklahoma State University method (HF, OSU Office of Intellectual Property, 2004;Halihan et al, 2005) to acquire apparent resistivity data and convert them to a model resistivity profile. The HF method has been utilized successfully within a number of applications published in the peer-reviewed literature (Halihan et al, 2005;Ong et al, 2010;Heeren et al, 2010Heeren et al, , 2011Keppel et al, 2011;Halihan et al, 2011Halihan et al, , 2012Halihan et al, , 2013Christenson et al, 2012;Heeren et al, 2014). The method has even been used and accepted by government agencies, such as the Department of Defense and U.S. EPA.…”

“…Research interest in this vadose zone heterogeneity heightened with the discovery of a PFP originating within the gravel subsoil that was capable of transporting dissolved P long distances without sorption (Fuchs et al, 2009;Heeren et al, 2010;. Of interest in this research was estimating the properties of the unsaturated zone of alluvial floodplains to better understand ephemeral preferential flow paths when the unsaturated zone becomes inundated with water such as during storm events (Heeren et al, , 2014. This was significant because the streams in the region have been shown to be sensitive to nutrient oversupply (e.g., Popova et al, 2006), and because land application of poultry litter from regional poultry production is a significant source of nonpoint P to waterways (Haggard et al, 2003;Storm et al, 2010).…”