An evaluation of analytical stream to groundwater exchange models: a comparison of gross exchanges based on different spatial flow distribution assumptions

Abstract

Abstract. In this paper, a new method for estimating gross gains and losses between streams and groundwater is developed and evaluated against two existing approaches. These three stream to groundwater exchange (SGE) estimation methods are distinct in their assumptions on the spatial distribution of the inflowing and outflowing fluxes along the stream. The two existing methods assume that the fluxes are independent and in a specific sequence, while the third and newly derived method assumes that both fluxes occur simultaneously and uniformly throughout the stream. The analytic expressions in connection to the underlying assumptions are investigated through numerical stream simulations to evaluate the individual and mutual dynamics of the SGE estimation methods and to understand the causes for the differences in performance. The results show that the three methods produce significantly different results and that the mean absolute normalized error can have up to an order of magnitude difference between the methods. These differences between the SGE methods are entirely due to the assumptions of the SGE spatial dynamics of the methods, and the performance for a particular approach strongly decreases if its assumptions are not fulfilled. The assessment of the three methods through numerical simulations, representing a variety of SGE dynamics, shows that the method introduced, considering simultaneous stream gains and losses, presents overall the highest performance according to the simulations. As the existing methods provide the minimum and maximum realistic values of SGE within a stream reach, all three methods could be used in conjunction for a full range of estimates. These SGE methods can also be used in conjunction with other endmember mixing models to acquire even more hydrologic information as both require the same type of input data.

Spatiotemporal processes that contribute to hydrologic exchange between hillslopes, valley bottoms, and streams

“…The discharge lost ( Q lost ) in each reach was calculated as the product of the percent of tracer mass lost by the average discharge in the reach. Using an average discharge assumes concurrent gain and loss within a reach [ Payn et al ., ; Exner‐Kittridge et al ., ].…”

The Hydrological Open Air Laboratory (HOAL) in Petzenkirchen: a hypotheses driven observatory

“…centrations and flow were measured for five locations along the stream. This allowed the estimation of stream bank fluxes (Exner-Kittridge et al, 2014). An infrared camera was used to identify hotspots of groundwater recharge into the stream.…”

“…-Background: on-line detection of enzymatic beta-D-Glucurondiase (GLUC) activity has been suggested as a potential surrogate for microbiological faecal pollution monitoring with a capacity for near-real-time applications in the context of water safety management (Farnleitner et al, 2001(Farnleitner et al, , 2002. Such measurements will also allow shedding of light on microbial transport processes at the catchment scale.…”