17 Water Problems in Urban Areas
407
structures of the riverbeds and banks, covering and transferring the trough (change
of course), mechanical pollution and numerous places of sewage discharge.
In small urban catchments, a linear delivery to riverbeds of water, dissolved
substances and sediment is dominant, which determines the high dynamics of runoff
and fluvial transport. Extensive supply areas can reach a watershed and locally even
exceed it. There are numerous sources of supply of clastic and dissolved matter of
an aerial, point and linear nature [35]. In the latter case, the most important role is
played by roads where a significant mass of matter is accumulated, mainly traffic
pollution of anthropogenic and natural origin. This material in the periods of occurrence of surface runoff with great ease is activated and transported on the surface
of roads and a system of rain drains. In a short time, it is introduced to the riverbed
[37, 38, 73, 93]. Below the city centers, as a result of increased accumulation of
discharged clastic matter, river beds are often silted and shallow, and, in the situation
of excessive concentration of nutrients, they are intensively overgrown. As a result of
this process, the cross-sectional areas and the bottoms of the valleys are significantly
reduced. This, in turn, contributes to more frequent overflows [35, 124].
Storm sewers provide water with a high concentration of suspended and dissolved
matter to urban watercourses [55, 125]. Their high concentrations have been documented in the winter season in the Silnica basin (Kielce). During the mid-winter
thawings, the concentration of suspended matter found in water flowing out of the
storm sewer (1377 mg/dm
3 ) was almost 100 times higher than it was at the same time
in the river bed (14 mg/dm
3 ) [35]. The concentration of dissolved material reached
then even higher values, i.e. at the outlet of the storm sewer—a dozen thousand or
so mg/dm
3 , and in the river—over 3 thousand mg/dm
3 . It is a hydrochemical effect
of the delivery of mainly communication pollutants, which are associated with the
use of different salts (NH 4 Cl, CaCl 2 , MgCl 2 ) for winter road maintenance [126].
Urban areas against a background of neighboring areas are the “salt islands” [35].
Excessive salinisation of urban areas is reflected not only in fluvial transport but
also affects environmental pollution. It has a negative impact on fauna and flora
[127] and hydrotechnical constructions. For example, in Sokołówka (Łód´ z) during a
sudden thaw in January 2013, the concentration of chlorides reached 3750 mg/dm
3
[38]. A measurable and troublesome effect of excessive concentration of chlorides
in water in urbanized areas is the decay and corrosion of hydrotechnical structures.
In many small urban streams, the ecological capacity, which is also affected by the
nitrogen, phosphorus, phenolics, detergents and oil derivatives, is in danger [35, 38,
128, 129]. Within administrative borders of cities, sections of watercourses being
relatively similar or far from natural conditions extend up to 70% of the total length
of streams [63].
17.4 The Use of Water
There are 166 cities in Poland, within which there are 314 lakes and 31 artificial water
reservoirs (in whole or in part) with an area larger than 1 ha. Most lakes are in the
407
structures of the riverbeds and banks, covering and transferring the trough (change
of course), mechanical pollution and numerous places of sewage discharge.
In small urban catchments, a linear delivery to riverbeds of water, dissolved
substances and sediment is dominant, which determines the high dynamics of runoff
and fluvial transport. Extensive supply areas can reach a watershed and locally even
exceed it. There are numerous sources of supply of clastic and dissolved matter of
an aerial, point and linear nature [35]. In the latter case, the most important role is
played by roads where a significant mass of matter is accumulated, mainly traffic
pollution of anthropogenic and natural origin. This material in the periods of occurrence of surface runoff with great ease is activated and transported on the surface
of roads and a system of rain drains. In a short time, it is introduced to the riverbed
[37, 38, 73, 93]. Below the city centers, as a result of increased accumulation of
discharged clastic matter, river beds are often silted and shallow, and, in the situation
of excessive concentration of nutrients, they are intensively overgrown. As a result of
this process, the cross-sectional areas and the bottoms of the valleys are significantly
reduced. This, in turn, contributes to more frequent overflows [35, 124].
Storm sewers provide water with a high concentration of suspended and dissolved
matter to urban watercourses [55, 125]. Their high concentrations have been documented in the winter season in the Silnica basin (Kielce). During the mid-winter
thawings, the concentration of suspended matter found in water flowing out of the
storm sewer (1377 mg/dm
3 ) was almost 100 times higher than it was at the same time
in the river bed (14 mg/dm
3 ) [35]. The concentration of dissolved material reached
then even higher values, i.e. at the outlet of the storm sewer—a dozen thousand or
so mg/dm
3 , and in the river—over 3 thousand mg/dm
3 . It is a hydrochemical effect
of the delivery of mainly communication pollutants, which are associated with the
use of different salts (NH 4 Cl, CaCl 2 , MgCl 2 ) for winter road maintenance [126].
Urban areas against a background of neighboring areas are the “salt islands” [35].
Excessive salinisation of urban areas is reflected not only in fluvial transport but
also affects environmental pollution. It has a negative impact on fauna and flora
[127] and hydrotechnical constructions. For example, in Sokołówka (Łód´ z) during a
sudden thaw in January 2013, the concentration of chlorides reached 3750 mg/dm
3
[38]. A measurable and troublesome effect of excessive concentration of chlorides
in water in urbanized areas is the decay and corrosion of hydrotechnical structures.
In many small urban streams, the ecological capacity, which is also affected by the
nitrogen, phosphorus, phenolics, detergents and oil derivatives, is in danger [35, 38,
128, 129]. Within administrative borders of cities, sections of watercourses being
relatively similar or far from natural conditions extend up to 70% of the total length
of streams [63].
17.4 The Use of Water
There are 166 cities in Poland, within which there are 314 lakes and 31 artificial water
reservoirs (in whole or in part) with an area larger than 1 ha. Most lakes are in the