『Abstract
Predicting groundwater supply for an entire watershed in mountainous
terrain required an approach that considered a wide range in data
availability between valley bottom and headwater areas, large
change in elevation, and steep topography. The methodology utilized
the MIKE-SHE numerical code to simulate overland flow, actual
evapotranspiration and recharge for data-rich areas, and a simpler,
seasonal water budget for data-limited areas. Recharge estimates
were combined to form spatially variable recharge boundary conditions
for a larger-scale groundwater flow model of the entire mountainous
watershed. Research focused on the BX Creek watershed, located
in the north Okanagan Basin in British Columbia, one of Canada's
fastest growing and most water-limited regions. Groundwater recharge
was found to vary from 0 to 20 mm/yr at lower elevations, and
from 20 to 50 mm/yr at higher elevations. Simulation of the whole
flow system illustrated that 58％ of the groundwater flux from
upland areas occurs through a relatively narrow alluvial fan aquifer
that extends to the valley bottom, and the remaining recharge
is nearly equally divided between groundwater flow through the
mountain block (20％) and direct recharge (22％). Geochemical data
from domestic water wells within the watershed suggest that water
in the alluvial aquifer and bedrock are generally similar (i.e.,
common origin); however, stable isotope data indicate that groundwater
in the alluvial aquifer may be derived from snowmelt recharge
at a different time and elevation than snowmelt recharge to the
bedrock. The combination of modelling results and complimentary
geochemical and isotopic analyses of surface water and groundwater,
provide an adequate first-order approximation of groundwater flow
in the watershed.
Keywords: Recharge; Modelling; Semi-arid; Stable isotopes; MIKE-SHE;
Mountainous terrain』
Introduction
Study area: BX Creek watershed, Okanagan Basin
Methodology
Valley bottom recharge model
Upland water budget
Watershed-scale flow model
Surface water and groundwater sampling
Results and discussion
Direct valley bottom recharge
Upland area water budget
Groundwater flow at the watershed scale
Water sources for valley bottom aquifers
Isotopic and geochemical signatures of waters
Conclusions
Acknowledgements
References