From precipitation to groundwater baseflow in a native prairie ecosystem: a regional study of the Konza LTER in the Flint Hills of Kansas, USA

Abstract

Abstract. Methods are developed to study hydrologic interactions across the surficial/groundwater interface in a native prairie ecosystem. Surficial ecohydrologic processes are simulated with the USDA's EPIC model using daily climate data from the Kansas Weather Data Library, vegetation and soil data from the USDA, and current land-use management practices. Results show that mean annual precipitation (from 1985-2005) is partitioned into 13 % runoff regionally and 14 % locally over the Konza LTER, lateral flow through soil is 1 % regionally and 2 % locally, groundwater recharge is 11 % regionally and 9 % locally, and evapotranspiration accounts for the remaining 75 %. The spatial distribution of recharge was used in a regional Modflow groundwater model that was calibrated to existing groundwater observations and field measurements gathered for this study, giving a hydraulic conductivity in the Flint Hills region of 1-2 m day −1 with a local zone (identified here) of 0.05-0.1 m day −1 . The resistance was set to fixed representative values during model calibration of hydraulic conductivity, and simple log-log relations correlate the enhanced recharge beneath ephemeral upland streams and baseflow in perennial lowland streams to the unknown resistance of the streambeds. Enhanced recharge due to stream transmission loss (the difference between terrestrial runoff and streamflow) represents a small fraction of streamflow in the ephemeral upland and the resistance of this streambed is 100 000 day. Long-term baseflow in the local Kings Creek watershed (2 % of the groundwater Correspondence to: D. R. Steward (steward@ksu.edu) recharge over the watershed) is met when the resistance of the lowland streambed is 1000 day. The coupled framework developed here to study surficial ecohydrological processes using EPIC and groundwater hydrogeological processes using Modflow provides a baseline hydrologic assessment and a computational platform for future investigations to examine the impacts of climate change, vegetative cover, soils, and management practices on hydrologic forcings.

Targeting perennial vegetation in agricultural landscapes for enhancing ecosystem services

“…Additionally, perennial vegetation can improve soil structure and hydraulic properties by increasing the number and size of macropores [51][52][53] , building organic matter 53,54 and improving soil porosity 55,56 . Combined, these changes in plant water fluxes and soil properties contribute to greater soil water storage capacity 57 , higher infiltration rates 58 and reduced runoff 59 . Perennial grasses 60,61 , trees 62 and tree-grass mixtures 63 have also been shown to more effectively trap and retain sediment compared with annual crops.…”

Aquifer configuration and geostructural links control the groundwater quality in thin-bedded carbonate–siliciclastic alternations of the Hainich CZE, central Germany

“…As caprock sinkholes are arranged in lineaments (Fig. 2a) parallel to regionally known fault orientations, it is very likely that they are coupled to the penetration of surface-subsurface water at fracture zones (compare to Smart and Hobbs, 1986;Worthington, 1999;Klimchouk, 2005) that promote preferential recharge (Smart and Hobbs, 1986;Suschka, 2007). Although dissolution of soluble rocks is limited within the target aquifers of this study, it is reasonable that collapse structures are accompanied by enhanced rock fracturing and permeability.…”

“…This is supported by higher concentrations in Na + , K + , NO − 3 , Cl − and TOC in the deeper site of H3 compared to the shallower well of this site, related to agriculture and fertilizing (Matthess, 1994;Kunkel et al, 2004). Crossformational descending flow in shattered or fractured rocks is assumed to take place in fracture zones (Worthington, 1999;Goldscheider and Drew, 2007), tracked by lineaments of caprock sinkholes (Mempel, 1939;Hoppe, 1962;Smart and Hobbs, 1986;Jordan and Weder, 1995). (4) ratios) and low concentrations in K + , Na + , and NO − 3 that points to a non-surface import of sulfate (chloride) groundwater due to dissolution of evaporite rocks (Edmunds and Smedley, 2000).…”

“…Confined diffuse flow is considered laminar and takes place in interparticle pores and fractures of dense limestones with low primary porosity (Smart and Hobbs, 1986). This results in the well oxygenated moTK-1 and moM-1 groundwaters and a significant oxygen consumption/deficiency (coupled to the mobility of Fe 2+ and Mn 2+ ions and the low mobility of NO − 3 and SO − 4 ions) in the moM-2 to moM-9 groundwater, resulting in completely different milieu conditions for the biogeochemical processes and for the life in the subsurface as well.…”

“…Suk and Lee, 1999;Moore et al, 2009) often lack a comprehensive analysis of the structural buildup and composition of the entire compartments, whereas the important "biogeoreactor" of the overburden soils is vastly neglected. Studies that include land use and soil groups (Pronk et al, 2009;Steward et al, 2011;Allocca et al, 2014) typically leave groundwater chemistry out of their focus. In this study, we follow a holistic approach for reconstructing the pristine groundwater quality in the aquifers of the Hainich Critical Zone Exploratory (Hainich CZE) in central Germany.…”