| Home | Français | ||
|---|---|---|
HYDROLOGY
Discharge is the first factor that controls water chemistry, mainly through dilution. Discharge is also closely related to the transport of suspended sediment in rivers. Without continuous discharge measurement, fluxes (transport) of sediment and chemicals in rivers cannot be calculated. A plot of discharge through time is called a hydrograph. The shape of the hydrograph is linked to river size, river regime, and the effects of lakes or groundwater.Long-term monthly discharges characterize the regime of a river. Some examples are given in Figure 3.
- tropical with maximum linked to rainfall pattern (Senegal)
- mountain snow melt and rainfall (Tigris)
- late monsoon rainfall (Chao Phrya)
- oceanic type linked to evapotranspiration pattern (Loire)
- equatorial with two maxima linked to rainfall pattern (Ogooue)
- complex regime from glacier melt to oceanic type (Rhine)
- lowland snow melt (Lena)
- early monsoon type (Godavari).
Regularity of the hydrograph is linked to river size, river regime, and the effects of lake or groundwater. In a complex regime such as the Rhine, peak flow may occur at different seasons. Simple regimes such as snow melt (Pechora) or monsoon rain (Blue Nile), are more regular. The influence of lakes is shown in the Finnish example.
The water chemistry in areas of sedimentary rocks depends on carbonate and/or evaporite deposits. Where these are absent (most of Africa and South America), waters are very dilute. Outcrops of carbonate rock (in Western Europe, South China, Eastern Mississippi Valley) produce hard waters. Generally, pre-alpine mountain ranges have been exposed to weathering for long periods of time and, globally, their surface waters have less TDS than for rivers on newer alpine rocks which have been more recently exposed and where folded carbonates and evaporites may be abundant. (Tectonics)
Home | Français
GEMS/WATER
URL of this page: http://www.cciw.ca/atlas-gwq/hydrology-e.html
Last updated: 2002-02-04
