Water discharges which in result of water abstraction are lower than Q
min, min
and equal and higher
than 0.5*Q
min, min
can be considered to belong to “POOR” hydrological class(as provided by them
condition for living organisms will significantly differ from
the widest living environment with high
biological quality observed in natural period) and water discharges below 0.5*Q
min, min
or equal to”0”
(when river dries)
can be considered to belong to “BAD” hydrological class(as
provided by them
condition for living organisms will be very bad and have significant deviation from
living environment
observed in natural period). In this case Q
min, min
will be a border between MODERATE and POOR
statuses and 0.5*Q
min,min
between POOR and BAD statuses and also will play role of
“Critically Low
Ecosystem Flow”.
Biological quality indicators as the main characterizing element of ecological
status depend from
quality and quantity of water in the water body. Depending on geography, geology, relief, climatic
conditions and etc. ecological status differ from water body to water body. Therefore by use of
hydrological classification system for each hydrological status class can be assessed corresponding
ecological status and based on that one can assess if character of future change of ecological status is
related to natural or antropogenic impact
Relationship between the hydrological and ecological status can be established by use of hydrological
and biological monitoring data collected in natural period of observation.
As is noted above HIGH hydrological status provides water environment that correspond to
wide living
environment with high biological quality observed in natural period which according to EU WFD is
characterised with “HIGH ” ecological status. Therefore required for this hydrological condition will be
provided by all water discharges corresponding to “HIGH” hydrological quality status of the Hydrological
Classification System(water discharges equal and higher than Q
max,min
identified as a “High Ecosystem
Flow”).
Next stage will be to check if for water discharges below Q
max,min
and equal and higher than Q
mean
any
changes in biological quality elements or ecological status take place. If no changes then ecological
status can be kept as HIGH if there are some changes then it is necessary to check if biological quality
elements meet requirements of GOOD or lower ecological status classes according to EUWFD . Similar
rule can be applied for classifying of ecological status corresponding to water discharges between Q
mean
and Q
min,min
(to check if ecological quality elements correspond to MODERATE or higher or lower
ecological status) and then for discharges between Q
min,min
and 0.5*Q
min,min
(for POOR or higher or
lower ecological status) and also finally for water discharges smaller than 0.5*Q
min,min
(for
BAD or
higher status)
The ecological classification can be carried by use of biological monitoring data corresponding to
different water discharges in the natural period. If there is no such data the new bio monitoring needs
to be carried to assess ecological status corresponding to different water discharges. In this case one
needs to conduct monitoring in areas with low level of antropogenic impact.
Established relationship between the hydrological and ecological statuses may help to assess
any future
change of ecological status by human impact.
Based on above approach relation of hydrological and ecological status classes can be identified by use
of below table.
96
Table 4. Relation between the hydrological and ecological status classes
N
Daily water
discharge
(m
3
/s)
Hydrol
ogical
status
Biological quality indicators
Ecological
status
provided by
hydrological
condition
1 ≥High Ecosystem
flow
(Q
max,min
)
HIGH
If biological quality elements are as in natural
period
HIGH
2 ≥Mean
Ecosystem Flow
(Q
mean
)
GOOD If biological quality elements are as in natural period
HIGH
If as result of reduction of area of living environment
biological quality elements slightly differ compared to
natural condition
GOOD
3 ≥Low Ecosystem
Flow (Q
min,min
)
MODE
RATE
If as result of reduction of area of living environment
biological quality elements don’t differ compared to
natural condition
HIGH or GOOD
If as result of reduction of area of living environment
biological quality elements
differ compared to
natural condition moderately
MODERATE
4 ≥Critically Low
Ecosystem Flow
(0.5*Q
min
)
POOR If as result of reduction of area of living environment
biological quality elements don’t differ significantly
compared to natural condition
MODERATE or
higher
If as result of reduction of area of living environment
biological quality elements differ significantly
compared to natural condition
POOR
5 ≤ Critically Low
Ecosystem Flow
(0.5*Q
min
)
,
BAD
If as result of reduction of area of living environment
biological quality elements don’t differ very
significantly compared to natural condition
POOR or
higher
If as result of reduction of area of living environment
biological quality elements differ very significantly
compared to natural condition
Bad
If river water body is located in protected area (National Park, Natural Reserve or is considered as a
strategic water body and environment protection organizations decide to prevent any decoration of its
ecosystem according to identified in EU WFD “HIGH ” ecological status then required for this least
hydrological condition will be provided by water discharges corresponding to “HIGH” hydrological
quality status of the Hydrological Classification System. In this case all water discharges
should be equal
and higher than Q
max,min
identified as a “High Ecosystem Flow”.
According to EU WFD currently all EU Member countries are required to provide “”GOOD” ecological
status of all river water bodies at their territories. In this case required hydrological status should be
GOOD or HIGHER to provide needed quality of biological elements to meet GOOD ecological status
requirements.
As it is not easy to provide “GOOD” ecological status for all water bodies in short period of time
therefore stepwise approach can be applied to water bodies which have “MODERATE” or lower classes
to improve corresponding them status of hydrological quality elements according to steps described
97