Estimating the Hyporheic Depth Beneath a Pool-Riffle Bedform Using the Rankine Body Analytical Method

Abstract

The hyporheic zone connects groundwater and surface water allowing active exchange of water and solute, and thus plays a vital role in many hydrological and ecological processes. Many sophisticated high-dimensional models have been developed to study the hyporheic zone, but they require extensive site information and may involve significant time and effort to set up. This emphasizes the need for a preliminary characterization. This paper proposes an analytical model based on the Rankine body method to estimate the maximum hyporheic depth using minimal site information. The hydraulic conductivity of the alluvium is not needed, and for thick alluvium it is not necessary to know the location of any underlying impervious layer. Applied to an idealized pool-riffle sequence, the proposed method is able to calculate the maximum hyporheic depth to within 20% of those from a two-dimensional (2D) reference numerical model for a wide range of conditions. Comparable results are also achieved with other independent studies for hyporheic zone under various bedforms, surface flows, and alluvium conditions. The proposed method provides a quick estimate of the hyporheic depth, which would be useful in the design of a field data collection program and/or a numerical modeling study.