Geography Reference
In-Depth Information
(a) Longitudinal Profile of
River
(b) Vertical Profile of
Reservoir
(c) Two-dimensional Profile
of Groundwater
Variable
Distance
Variable
Contours
Distance
Modified from Meybeck and Helmer, 1992.
Figure 2. Sampling strategies for exploring spatial variations of water quality in (a)
river, (b) reservoir and (c) groundwater aquifer.
Table 2. Scale of temporal water quality variability and causing factors
Scale of Temporal Variability
Causing Factor
water mixing, fluctuations in
inputs, etc., mostly linked to meteorological
conditions and water body size (e.g.
variations during river floods)
Minute-to-minute to day-to-day
variability
biological cycles, light/dark cycles etc. (e.g.
O2 , nutrients, pH), and to cycles in
pollution inputs (e.g. domestic wastes).
Dual variability (24-hour
variations)
climatic factors (river regime, lake
overturn, etc.) and to pollution sources (e.g.
industrial wastewaters, run-off from
agricultural land).
Days-to-months variability
seasonal hydrological and
biological cycles
mostly in connection with climatic
factors
Year-to-year trends
human influences
After Bartram and Ballance, 1996.
Most hydrogeologic applications of spatial interpolation involve quantities
that vary in space but the methods may also apply to quantities that vary in
time (Kitanidis, 1999).
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