Response of a fractured bedrock aquifer to recharge from heavy rainfall events

Abstract

The response of a fractured bedrock aquifer in a temperate region (Gulf Islands, British Columbia) to heavy rainfall events is characterized. Of the 14 provincial observation wells with hourly groundwater level data, wells with shallow water levels showed pronounced responses to heavy rain events, a lag less than 12 hours, and a strong correlation to all rain events. Rises in groundwater level at Well 125 appear to be better related to all rain events than exclusively heavy rain during summer, and decrease as the rainfall intensity increases. Thermal infrared images and δ 18 O and δ 2 H composition for precipitation and seepage indicate an increase in seepage in the late fall and winter.Solution of the Green-Ampt equation for rainfall events of varying magnitude suggest that an increase in winter rainfall intensity leads to more surface ponding and overland flow. The projected occurrence of more heavy rain events in the future may result in lower net recharge.

Global Isotope Hydrogeology―Review

“…Assessing annual recharge rates is important for estimating the extent to which groundwater pumping impacts groundwater storage and discharge (Theis, , ). Yet understanding recharge rates at shorter (i.e., seasonal) timescales is also important in order to (i) forecast changes to annual recharge rates under changing seasonal climate conditions (e.g., Ajami et al, ; Earman et al, ; Earman & Dettinger, ; Meixner et al, ; Niraula et al, ), (ii) develop more sophisticated conceptual models detailing hydrological processes and conditions conducive to groundwater replenishment (e.g., Alsaaran, ; Dripps, ; Dripps & Bradbury, ; Flerchinger et al, ; Gat & Tzur, ; Gates, Edmunds, Ma, et al, ; Hammarlund & Edwards, ; Liefert et al, ; Nasta et al, ; Pavlovskii et al, ; Rathay et al, ; Wilson & Guan, ; Zhang et al, ), (iii) interpret paleoclimate conditions from fossil groundwater and speleothem isotopic records (e.g., Bar‐Matthews et al, ; Benson & Klieforth, ; Denniston et al, ; Fairchild et al, ; Johnson, Hu, et al, ; Johnson, Ingram, et al, ; Jones et al, ; Simpson et al, ; Treble et al, ), and (iv) understand the ways that plants obtain water, and the relationships among vegetation, runoff, and recharge (e.g., Grossiord et al, ; Guswa & Spence, ; Kim & Jackson, ; Vico et al, ).…”

Spatial Prediction of Groundwater Potentiality in Large Semi-Arid and Karstic Mountainous Region Using Machine Learning Models

“…An additional complication arises because mountainous regions are frequently fractured (e.g., the Atlas Mountains) and contain a discontinuous aquifer (e.g., a karstic aquifer). The groundwater potential in mountainous aquifers is governed by several parameters (i.e., lithology, geomorphology, topography, secondary porosity, geological structures, fracture density, permeability, drainage pattern and density, groundwater recharge, piezometric level, slope, land use/cover and climatic conditions, and their interrelationships) [7].…”

The effect of sample size on different machine learning models for groundwater potential mapping in mountain bedrock aquifers

“…They are discrete, exhibit anisotropy, have small pathways, and are less common (Coleman et al, 2015). The occurrence and movement of groundwater in fractured bedrock aquifers in a given area is very complicated and governed by many factors, such as lithology, landforms, topography, secondary porosity, geological structures, fracture density, aperture and connectivity, drainage pattern, groundwater recharge, groundwater table distribution, slope, land cover, climatic conditions, and their interrelationships (Levison et al, 2012;Rathay et al, 2018). In general, there is insufficient data regarding groundwater in fractured bedrock aquifers in mountainous environments worldwide due to a lack of piezometric wells in these high-elevation settings (Voeckler and Allen, 2012).…”