Generation of complex karstic conduit networks with a hydrochemical model

Abstract

In this paper, we present a hydrochemical model that can be used to generate plausible karstic conduit networks that honor what is known about geology, hydrology, and topography of a karst system. To make the model applicable to a range of natural karst systems, we introduce a flexible and physically realistic flow boundary condition along the land surface. Moreover, whereas comparable existing speleogenesis models use an explicit reactive‐transport scheme, we propose an implicit reactive‐transport scheme to permit a coarser spatial discretization of the conduit cells. An application to a real karst system illustrates that the model can generate a realistic karstic network that reproduces observed hydrologic behavior in terms of current spring flow rates, regional hydraulic head field as well as average groundwater residence times. Our model provides a useful tool to generate ensembles of possible karstic conduit networks that may be used within a stochastic framework to analyze flow and transport prediction uncertainty associated with a lack of knowledge about network geometry.

A Complicated Karst Spring System: Identified by Karst Springs Using Water Level, Hydrogeochemical, and Isotopic Data in Jinan, China

“…Karst aquifers crop out in approximately 12% of the global land surface and offer water resource for almost 25% of the world population [1][2][3][4]. In the past several decades, karst systems have been widely studied in aspects of the conceptual model [5][6][7], recharge sources [8][9][10], flow types [11,12], hydrogeochemical processes [13][14][15][16][17][18][19][20][21], hydrodynamics [22][23][24], responses to climate changes [25][26][27], and numerical modeling [28][29][30]. However, the heterogeneity and anisotropy of karst conduits and fractures created by uneven groundwater flow give rise to the complex hydrogeological conditions and make it difficult to understand and characterize the karst system [4,31,32].…”

Disaggregating Landscape‐Scale Nitrogen Attenuation Along Hydrological Flow Paths

“…However, while land use patterns are correlated with N concentration within and across springsheds, there is a possibility that land use patterns are secondary to the geological drivers that circumscribe the possible land use in a given area. Larger‐scale assessments are needed to evaluate the relationship between land use and physiographic characteristics such as soil types, vadose zone thickness, and density of sinkholes and karst conduits (de Rooij & Graham, ; Yang et al, ).…”

What Makes a First‐Magnitude Spring?: Global Sensitivity Analysis of a Speleogenesis Model to Gain Insight into Karst Network and Spring Genesis

“…where Q is conduit volumetric flux rate [L 3 T 21 ], c is the calcium concentration [ML 23 ], s the spatial coordinate in the direction parallel to the conduit [L], q a sink term [L 2 T 21 ], r the conduit radius, and R the dissolution rate [ML 22 T 21 ]. Based on previous speleogenesis modeling, the reaction rate in our model switches from first-order to higher-order kinetics when the calcium concentration exceeds a certain value (Dreybrodt, 1990;Dreybrodt et al, 2010;Gabrov sek & Dreybrodt, 2010;Kaufmann, 2003aKaufmann, , 2003bKaufmann, , 2009Kaufmann et al, 2010):…”