56
Z. Michalczyk and J. Sposób
value of biological discharge from exploitable resources, we obtain the amount of
exploitable resources of Poland for irreclaimable use equalling 7 km
3 ·year
−1 . The
value can be increased to 9–10 km
3 ·year
−1 after regulating discharges of Polish
rivers, i.e. after an increase in reservoir and soil retention.
4.4 Water Resources Balance and Use
The amount of water in the natural environment changes in a seasonal and annual
scale. Performing its balance requires the determination of the time and areas for
which the value of water inflow and outflow is assessed. The water balance equation
components may be expressed as a mean depth of water over the basin or water body
(mm), as a volume of water (m
3 ), or in the form of discharge (m
3 ·s
−1 ) [22]. Therefore,
it is possible to present components of water circulation for different areas and time
intervals. It is the most efficient, due to the unambiguously determined water runoff
area, to prepare water balances for catchments. Balances for other areas are also based
on calculations performed in catchments within the analysed area. Basic information
on water resources of the area is included in normal water balance, prepared based
on data from the multi-annual period in which precipitation is balanced by outflow
and evapotranspiration. In the case of presentation of parameters for shorter periods,
they should consider the change in retention in the balancing period, described as the
difference between the amount of resources at the end and beginning of balancing.
In an average year, atmospheric precipitation supplies approximately 190 km
3 of
water to the territory of Poland, and approximately 7 km
3 inflows from the neighbouring countries. In the years 1901–2000, mean precipitation in the territory of
Poland was 628 mm, and outflow 175.2 mm [7]. Approximately 450 mm corresponds to evapotranspiration, i.e. field evaporation. In a year with average humidity,
the amount of precipitation in the territory of the country varies from approximately
500 mm in the lowland belt to more than 1000 mm in the mountains, which directly
affects the amount of regional water resources. In an average year [23], mean river
outflow is dominated by water supply from groundwater resources (95 mm, 55%).
The remaining part is accounted for by surface runoff (76 mm, 45%). The percent
contribution of both components varies in a regional scale. The mountain areas
surface runoff is prevalent, and on uplands – groundwater outflow.
Satisfying municipal, industrial, and agricultural water needs of the population
and economy of Poland occurs from groundwater and surface water resources. They
develop from atmospheric precipitation, within particular regions and places of
occurrence of water which in water management should be treated jointly. A separate
calculation of surface water and groundwater resources is only justified in valleys of
large transit rivers, i.e. in situations when flowing water resources development in
different precipitation regions. Water intake for economic purposes is only possible
in the case of relevant values of its discharge occurring in river channels or in rock
pores and fissures, with the maintenance of biological flow.
Z. Michalczyk and J. Sposób
value of biological discharge from exploitable resources, we obtain the amount of
exploitable resources of Poland for irreclaimable use equalling 7 km
3 ·year
−1 . The
value can be increased to 9–10 km
3 ·year
−1 after regulating discharges of Polish
rivers, i.e. after an increase in reservoir and soil retention.
4.4 Water Resources Balance and Use
The amount of water in the natural environment changes in a seasonal and annual
scale. Performing its balance requires the determination of the time and areas for
which the value of water inflow and outflow is assessed. The water balance equation
components may be expressed as a mean depth of water over the basin or water body
(mm), as a volume of water (m
3 ), or in the form of discharge (m
3 ·s
−1 ) [22]. Therefore,
it is possible to present components of water circulation for different areas and time
intervals. It is the most efficient, due to the unambiguously determined water runoff
area, to prepare water balances for catchments. Balances for other areas are also based
on calculations performed in catchments within the analysed area. Basic information
on water resources of the area is included in normal water balance, prepared based
on data from the multi-annual period in which precipitation is balanced by outflow
and evapotranspiration. In the case of presentation of parameters for shorter periods,
they should consider the change in retention in the balancing period, described as the
difference between the amount of resources at the end and beginning of balancing.
In an average year, atmospheric precipitation supplies approximately 190 km
3 of
water to the territory of Poland, and approximately 7 km
3 inflows from the neighbouring countries. In the years 1901–2000, mean precipitation in the territory of
Poland was 628 mm, and outflow 175.2 mm [7]. Approximately 450 mm corresponds to evapotranspiration, i.e. field evaporation. In a year with average humidity,
the amount of precipitation in the territory of the country varies from approximately
500 mm in the lowland belt to more than 1000 mm in the mountains, which directly
affects the amount of regional water resources. In an average year [23], mean river
outflow is dominated by water supply from groundwater resources (95 mm, 55%).
The remaining part is accounted for by surface runoff (76 mm, 45%). The percent
contribution of both components varies in a regional scale. The mountain areas
surface runoff is prevalent, and on uplands – groundwater outflow.
Satisfying municipal, industrial, and agricultural water needs of the population
and economy of Poland occurs from groundwater and surface water resources. They
develop from atmospheric precipitation, within particular regions and places of
occurrence of water which in water management should be treated jointly. A separate
calculation of surface water and groundwater resources is only justified in valleys of
large transit rivers, i.e. in situations when flowing water resources development in
different precipitation regions. Water intake for economic purposes is only possible
in the case of relevant values of its discharge occurring in river channels or in rock
pores and fissures, with the maintenance of biological flow.