Conclusions
Based on a series of experiments on artificial sprinkling of tree
species, maximum values of specific moisture retention on the leaf
surface area were determined. The specific retention mass per 1
m2 of leaf surface was determined by the nature of
leaf surface area and, primarily, by venation type. Leaves with
pinnately-netted venation (elm, bird cherry tree) were observed to have
2–3 times higher retention values (180–200 g/m2) as compared to leaves
with pinnate venation (birch, aspen; 27–100 g/m2). Total retention mass
was determined by leaf surface area during rainfall as well as age and
stand height which is different for various tree species.
During the experiments, the leaf surface area was determined for the
”normal” leaf surface in a representative sample (statistical parameters
of the leaf area i. e. average, coefficients of variation and asymmetry
were determined for the sample). The number of leaves on the
experimental branch was determined manually. Statistical errors of total
area determination did not exceed 11%. Errors of determining the mass
of moisture retained were 4.3%.
The obtained values expressed in the characteristics of the layer of
precipitation retained by canopies were visualized on maps. Such maps
based on the methodology developed by the authors can be used to
calculate water balance elements of mixed forest areas, maximum rainfall
discharge from forest watershed. In addition, taking into account the
fact that rain precipitation retained by canopies is consumed only for
evaporation, this method of estimating the spatial distribution of
rainfall losses can be used to estimate monthly amounts of liquid
precipitation as corrections to daily rainfall values.
Based on the experiments on artificial branch sprinkling, the parameters
of dependency of the leaf surface area (LA, m2) on the maximum mass of
retained water (m, d) were established. On the basis of the dependencies
and the data on the leaf surface area of the estimated watersheds it is
possible to calculate the interception value during a rainfall as well
as evaporation losses from the canopy area distributed in space.
The precipitation observations made under coniferous canopies (by four
rain gauges) and in open areas (by one rain gauge) in the October of
2017 confirmed the calculated water retention values. According to the
data provided by field rain gauges M-99, it was found that the spruce
canopies (80 years, bonitet class II) intercept 2-4 mm of rainfall.
Meteorological observations need to be continued with the involvement of
rain recorders (pluviographs).
The method developed by the authors for estimating and mapping
irrecoverable rainfall losses by tree canopies can be used in modeling
the flood runoff of small rivers in the Ural forest zone. Taking into
account the value of irrecoverable precipitation losses from the stand
canopies allows us to increase considerably the accuracy of flood flow
calculations for small rivers using genetic methods.