New Vision of the Role of Land Reclamation Systems in Nature Protection and Water Management - Wetlands and Water Framework Directive: Protection, Management and Climate Change - page 91

soil retention:

￿

soil loosening;
increasing humus content;
liming;
proper agro-technical measures;
proper crop rotation

— green fields the year round;

landscape retention:

￿

complex spatial set of arable lands, meadows, pastures, forests, streams and
ponds;
cluster and lane thickets;
counter-erosion measures;
large area of wetlands.

Having in mind that the potential of small retention may be estimated at several
billion m 3 and the combined capacity of 10 largest retention reservoirs in Poland is
1.7 billion m 3 , one has to notice that applied notions have reversed meaning — the

potential of “ small retention ” is much larger than that of “ large retention ” but the

former is more dif cult to control. In the above set of elements composing the so-

called small retention surprisingly many fall within the scope of reclamation. Data
presented in Table 6.1 show that periodically there is a huge retention reserve. Its
size is such that elevation of ground water table in peat soil by 10 cm is equivalent
to an increment of several hundred m 3 of water per ha. Data presented in Table 6.2 .
evidence potential retentive role of reclamation systems.
The author of the above simulation attributed great importance to soil retention.
Water lifting in the network of detailed reclamation ditches in grasslands and

—

practically not used ow from drainage networks are also of

great importance. Though the simulation is of a theoretical character, it shows a
potential of the so-called small retention. Below, there is another simulation of the
same author pertaining to a real catchment of an area of 9.2 km 2 (Fig. 6.1 , Table 6.3 ).

— regulating the out fl

Table 6.2 Potential possibilities of increasing catchment retentiveness through reclamation
measures — an example of the upper Narew River catchment (Kowalewski 2003 )
Potential measure Existing status, mln m 3 Target status, mln m 3

Water lifting in streams and rivers 1.89 3.14

Water lifting in reclamation canals 0.16 0.26

Regulating the out ow from the

valley reclamation objects

fl 0.75 2.72

Water lifting in the network of
detailed reclamation ditches in grasslands

20.84 41.69

Regulating the out ow from drainage

networks in arable lands

fl 20.89 41.79

Small water reservoirs 15.84 31.69

Soil retention 12.76 51.40

Total 73.12 172.70