『Abstract
The interconnections between groundwater and river systems
remain poorly understood in many catchments throughout the world,
and yet they are fundamental to effectively managing the quantity
and quality of water resources. Many of the techniques traditionally
employed by hydrogeologists and hydrologists rely on characterising
the groundwater flow systems, topography, geology/aquifer systems,
climate and/or the rainfall-runoff processes within a river basin.
These studies can provide useful process characterisations that
are fundamental to developing a physical understanding of hydrological
processes within a specified region. However, in many instances
the findings are descriptive and the results are difficult to
up-scale to the larger sub-catchment/catchment scale at which
water is managed and allocated. Moreover, they many have significant
time and cost requirements. An alternative approach is to collate
a range of hydrometric data, that for many catchments may already
available, and to then analyse data patterns and infer processes
from the data without being overly concerned about the details
of the physical processes driving the system taking a top-down
approach. In this paper the river reaches in the semi-arid Namoi
River catchment in Australia were characterised according to three
levels of information; namely; (1) presence of aquifer-river hydraulic
connection; (2) dominant direction of flux; and (3) the potential
for groundwater extraction to impact on river flows. The methods
used to characterise the river reaches included an analysis of:
(1) groundwater and river channel base elevations using a GIS/database;
(2) stream hydrograph data; (3) flow duration data; (4) vertical
aquifer connectivity at nested piezometer sites; and (5) paired
river and groundwater hydrographs. The data patterns seen in the
stream gauging station derived data for gaining, losing and variably
gaining-losing river reaches were described together with the
general processes that operate in these systems. Subsequently,
a map was prepared for the Namoi River catchment river reaches
indicating aquifer-river connectivity and dominant direction of
flux. The potential for groundwater extraction to impact on river
flows was also assessed and found to be a significant issue for
the connected aquifer-river systems.
Keywords: Top-down; Groundwater; Aquifer; River; Surface water;
Interactions』
Introduction
Groundwater-river water interaction: basic principles
Classification of river reaches
Case study area
Methods to classify groundwater-river interactions
Flow duration data
Hydrograph analysis
Results and discussion
Hydraulic connection - Level 1
River-aquifer direction of flux - Level 2
Connected-gaining reach
Connected variably gaining-losing reach
Connected-losing reach
Disconnected-losing reach
Map of aquifer-river reach connectivity and dominant flux
Potential for groundwater extraction impacts on river - Level
3
Conclusions
Acknowledgements
References