6 Natural and Anthropogenic Lakes of River Valleys
97
Direct methods
Comparison of the size of expenditure side the balance equation of the basin (evaporation and outflow), the dominance of which would indicate evaporation or flooddominated lake type. The absence of clear dominance of one of the components may
mean that it belongs to a transition type.
Determination of the lake type, based on the water residence time in the lake,
regardless of how it is calculated. Lakes with a long residence time are evaporationdominated reservoirs, whereas fast flushing is characteristic of flood-dominated
lakes. The group of transitional lakes requires the determination of the limits of
the range of variability.
Indirect methods
– Method of recharge. In the case of direct supplying of floodplain lake basin with
potamic waters, one deals with the flow type. When potamic recharge takes place
through a basin of another lake or a system of such lakes (cascade), one deals
with transitional lakes, while if the recharge with river waters is episodic or does
not occur, then these are evaporation-dominated lakes.
– Location of the lake basin. The flow type includes the lakes located in the modern
meandering belt or within the lower floodplain terrace. Transitional lakes occur
within the floodplain higher terraces, whereas the waters under the edge of the
terraces are usually evaporation-dominated reservoirs.
– Bathymetric parameters. For example, the ratio of the lake surface to its maximum
depth, or the ratio of the shoreline development to the mean depth. The high
value of the first quotient is usually characteristic for evaporation-dominated
lakes, whereas the low value for flood-dominated lakes. The remaining lakes
constitute an intermediate class. Determination of the range of variability should
be established individually for different river valleys. In the case of the ratio
of the coefficient of shoreline expansion and the average lake depth, the values
>1 are characteristic for flood-dominated type, about 1 transitional type and <1
evaporation-dominated type.
– Linking the origin of the floodplain lake with the way it is supplied. Oxbow and
avulsion lakes in the vast majority belong to the group of flood-dominated lakes.
The anastomotic lakes are most often transitional lakes, while the inter-levee lakes
are evaporation-dominated lakes.
Division by water hydrochemistry
The quality parameters of the floodplain lake waters result from the period of their
functioning cycle (potamophase, limnophase, flooding). During the potamophase,
the parent rivers transform the quality of the lake waters in a short period of time
as a result of intensive exchange. During overbed flows of the parent river, multiple
mixing of waters in the basin takes place. Dynamic supply of allochthonous river
waters determines the ionic composition of lake waters often for many months, and
hydrochemical processes of catchments of the lakes are of little importance. In the
period of limnophase, the physical and chemical parameters of the waters of the
97
Direct methods
Comparison of the size of expenditure side the balance equation of the basin (evaporation and outflow), the dominance of which would indicate evaporation or flooddominated lake type. The absence of clear dominance of one of the components may
mean that it belongs to a transition type.
Determination of the lake type, based on the water residence time in the lake,
regardless of how it is calculated. Lakes with a long residence time are evaporationdominated reservoirs, whereas fast flushing is characteristic of flood-dominated
lakes. The group of transitional lakes requires the determination of the limits of
the range of variability.
Indirect methods
– Method of recharge. In the case of direct supplying of floodplain lake basin with
potamic waters, one deals with the flow type. When potamic recharge takes place
through a basin of another lake or a system of such lakes (cascade), one deals
with transitional lakes, while if the recharge with river waters is episodic or does
not occur, then these are evaporation-dominated lakes.
– Location of the lake basin. The flow type includes the lakes located in the modern
meandering belt or within the lower floodplain terrace. Transitional lakes occur
within the floodplain higher terraces, whereas the waters under the edge of the
terraces are usually evaporation-dominated reservoirs.
– Bathymetric parameters. For example, the ratio of the lake surface to its maximum
depth, or the ratio of the shoreline development to the mean depth. The high
value of the first quotient is usually characteristic for evaporation-dominated
lakes, whereas the low value for flood-dominated lakes. The remaining lakes
constitute an intermediate class. Determination of the range of variability should
be established individually for different river valleys. In the case of the ratio
of the coefficient of shoreline expansion and the average lake depth, the values
>1 are characteristic for flood-dominated type, about 1 transitional type and <1
evaporation-dominated type.
– Linking the origin of the floodplain lake with the way it is supplied. Oxbow and
avulsion lakes in the vast majority belong to the group of flood-dominated lakes.
The anastomotic lakes are most often transitional lakes, while the inter-levee lakes
are evaporation-dominated lakes.
Division by water hydrochemistry
The quality parameters of the floodplain lake waters result from the period of their
functioning cycle (potamophase, limnophase, flooding). During the potamophase,
the parent rivers transform the quality of the lake waters in a short period of time
as a result of intensive exchange. During overbed flows of the parent river, multiple
mixing of waters in the basin takes place. Dynamic supply of allochthonous river
waters determines the ionic composition of lake waters often for many months, and
hydrochemical processes of catchments of the lakes are of little importance. In the
period of limnophase, the physical and chemical parameters of the waters of the