Американский Научный Журнал DYNAMICS OF RIVERS FLOW UNDER THE IMPACT OF FOREST HARVESTING IN CHANGING CLIMATE

ABSTRACT This paper is devoted to the study of the dynamics of river flow under the influence of large-scale forest felling in a changing climate. Region of study is Sayan Mountains in South Siberia. Forests of Sayan Mountains have been logging extensively over the past seventy years. As a result, forest area has been reduced and forest age structure and composition have changed. These changes are reflected in the water balance structure and hydrological regimes of region. The dynamics of river runoff of the region studied was analyzed spatially and temporally, the flow trends were analyzed taking into account Climate Change and forestry activities at the catchment areas. The obtained results showed that at the regional level the influence of climatic changes on runoff of medium and small rivers is less pronounced than forest harvesting and the trajectory of subsequent reforestation. Скачать в формате PDF
16 American Scientific Journal № ( 20 ) / 201 8
НАУКИ ОБ ОКРУЖАЮЩЕЙ СРЕДЕ
D Y N A M I C S O F R I V E R S F L O W U N D E R T H E I M P A C T O F F O R E S T
H A R V E S T I N G I N C H A N G I N G C L I M A T E

Burenina Tamara,
Candidate of Biological Sciences, docent
Fedotova Elena,
Candidate of Biological Sciences
Sukachev Institute of Forest SB RAS, Federal Research Center «Krasnoyarsk Science Center SB RAS»
Akademgorodok 50/28, Krasnoyarsk, 660036, Russia

ABSTRACT
This paper is devoted to the study of the dynamics of river flow under the influence of large -scale forest
felling in a changing climate. Region of study is Sayan Mountains in South Siberia. Forests of Sayan Mountains
have been logging extensively over the past seventy years. As a result, forest area has been reduced and forest age
structure and composition have changed. These changes are reflected in the water balance structure and hydrolog-
ical regimes of re gion. The dynamics of river runoff of the region studied was analyzed spatially and temporally,
the flow trends were analyzed taking into account Climate Change and forestry activities at the catchment areas.
The obtained results showed that at the regiona l level the influence of climatic changes on runoff of medium and
small rivers is less pronounced than forest harvesting and the trajectory of subsequent reforestation.
Keywords: hydrology regime, Sayan Mountains, Siberia, dynamics of river flow, climate c hange, forest
felling

Introduction
Forest ecosystems are a major control of moisture
circulation in watersheds. Boreal forests have been long
recognized to influence global moisture circulation
considerably. Therefore, it is logical to expect that fur-
ther large -scale forest cover disturbances, such as cata-
strophic fires, large -scale insect outbreaks and forest
logging, will affect the processes of water r esource de-
velopment and hydrological regime in any river basin.
Of all human activities, forest logging and post -
logging regeneration have the greatest influence on wa-
ter budget and total runoff at watersheds [2, 8, 12, 13] .
Reported first -year increases i n water yield following
forest clearance in the humid tropics, for instance,
range from 110 to 825 mm, depending on local rainfall
[7]. A dated, but still valid review of almost 100 paired
catchment experiments throughout the world [2] indi-
cated that all o f those involving removal of forest cover
resulted in higher stream flow totals. A number of stud-
ies [22, 25, 26] showed that logging -caused conversion
of forestlands to grasslands only leads to local flood in-
creases and is not among the key controls of la rge -scale
high water. The authors of present paper were tasked to
assess the impact the large -scale forest felling on river
runoff under Climate Change.

Methods and study areas
To identify regional hydrological regime charac-
teristics, we analyzed spatial and temporal dynamics of
water yield for thirty river basins found in Sayan Moun-
tains (Fig.1). To do this analysis, we used runoff data
available for rivers of West and East Sayan and The
Minusinsk hollow , as well as precipitation and air tem-
perature measu rements from the weather stations
within the areas of interest [9, 14, 15, 27, 28]. The du-
ration of water yield observation was based upon when
selecting rivers. For the rivers chosen, the observation
period ranged twenty to sixty years and covered a wide
variety of hydro -climatic situations.
Numerical methods were used for hydrological
calculations [11, 23]. The statistical parameters neces-
sary for the analysis were obtained after smoothing
time series by the method of moving average. To build
linear tren d and to analyze variability of hydro -climatic
parameters, we used the methodology by Shelutko’s
[19]. The least -squares method was used to identify and
analyze the trends.

American Scientific Journal № (20 ) / 201 8 17
Figure 1. Location of hydrological stations

We analyzed the changes of the forest area in the
river basins with the help of forest inventory data [29].
For each 5 -year period, we summed the area of river
catchment subject to clearcutting.
To extrapolate the hydrological obser vation re-
sults obtained on the river catchments, we use Landsat
images obtained for different years since 1974 and a
digital elevation model (DEM). Assessment of the dy-
namics of the logging sites in the study area involved
the use of the 1974, 1976, 1989, 1991, 1999, 2001, and
2010 Landsat images. As the study area is a mountain
area, the images were topographically normalized us-
ing C -factor method [16].

To classify the 1974, 1976, 1989, and 1991 im-
ages, learning samples were created for logging sites of
various ages. The classification was done. The classifi-
cation accuracy was evaluated using an error matrix
[17]. The classification appeared to be av. 91% accurate
for all images.

The results
Assuming that the end of the 1990s was a turning
point in the t rend of climate change in the region, we
analyzed the temperature and precipitation data sepa-
rately for the observation period up to 2000 and to the
first decade of the third millennium (Table 1). The re-
sults of the analysis of air temperature dynamics at rep-
resentative weather stations showed that in the region
study air temperature increases from the 30s of the last
century to 2000 and the maximum values of linear trend
coefficients are typical for the cold period of the year.
Since 2001, for all represen tative weather stations, the
average annual air temperature has been decreasing.
The coefficients of linear air temperature trends
for periods up to 2000 and after differ not only in sign,
but have significant differences quantitatively. This is

18 American Scientific Journal № ( 20 ) / 201 8
due to th e fact that the average values of air tempera-
tures and precipitation for different averaging periods
vary considerably depending on the choice of the length
of the time interval and its beginning [24]. Neverthe-
less, even for a short series of observations, it is possi-
ble to identify emerging trends in climate change.

Table 1. Coefficients of linear trends in air temperature and precipitation according to the data of repre-
sentative weather stations
Weather stations Coefficients of linear trends
annual XI -IV V-X annual XI -IV V-X
Air temperature, C°
1940 -2000 2001 -2012
Krasnoyarsk 0.039 0.058 0.020 -0.007 0.042 -0.055
Solyanka 0.023 0.046 0.001 -0.142 -0.198 -0.085
Minusinsk 0.036 0.069 0.005 -0.152 -0.243 -0.062
Olenya Rechka 0.026 0.049 0.005 -0.085 -0.106 -0.064
Sum of precipitation, mm
1966 -2000 2001 -2012
Krasnoyarsk -0.801 0.083 -0.884 -0.395 2.738 -3.133
Solyanka 1.624 0.699 0.925 1.449 0.746 0.703
Minusinsk 0.185 0.263 -0.077 -11.906 -3.122 -8.784
Ermakovskoe -1.721 -0.837 -1.089 - - -
Grigor'evka -0.913 0.430 -1.343 - - -
1947 -2000 2001 -2012
Ermakovskoe -0.760 -0.482 -0.276 - - -
Grigor'evka -1.728 -0.744 -0.984 - - -
Olenya Rechka -3.644 -1.900 -1.744 0.398 -1.880 2.278
Comparison of precipitation trends for different
periods at the weather stations Ermakovskoe,
Grigor'evka and Olenya Rechka, which are representa-
tive for the Western Sayan ridge and its foothills, shows
that the trends are character ized by a single direction of
the process - precipitation reduction, but the indicators
for 1966 -2000 and the years 1947 -2000 are different
(Table 1). As we mentioned above the value of the trend
of climatic parameters depends on the duration of a se-
ries o f observations. The rate of decrease in precipita-
tion over the period 1966 -2000 twice as high as in
1947 -2000 the annual precipitation trends for the Mi-
nusinsk depression and offshoots of the East Sayan
have a positive sign, but there has been no significa nt
increase in precipitation from 1966 to 2000.
In order to determine the closeness of correlation
between climatic and river flow trends at the regional
level, we analyzed the runoff trends of the rivers under
study for different observation periods (Tabl e 2).

Table 2. Indicators of river flow trends
River - hydrological station Years of ob-
servations Basin area, km ² Average long
term runoff, mm
Coefficients of
linear flow trends
Western Sayan
Amyl - Verkhny Amyl 1958 -2002 537 557,3 -1,56
Aradanka - Aradan 1965 -2002 217 700,5 -3,55
Zolotaya - Ust -Zolotaya 1968 -1994 382 149,2 -0,12
Kebezh - Grigorjevka 1948 -2002 1000 554,7 1,23
Kop - Cherepanovka 1950 -2002 959 501 -2,78
Migna - Migna 1965 -1994 190 177,5 -1,35
Oya - Ermakovskoe 1946 -2002 2540 414,4 -0,67
Us - Ust -Zolotaya 1951 -2002 6110 333,9 -0,05
Us - Aradan 1968 -2002 1260 780,5 -4,44
Shadat - Ust -Shadat 1958 -2002 1680 856,7 1,96
Eastern Sayan
Kazyr - Tajaty 1963 -1994 11900 794 -1,91
Mana - Koy 1961 -2002 3520 502,7 1,48
Mana -Man skiy 1936 -2002 9260 344,9 0,42
Mimia (Mina) - Mina 1959 -2002 841 436,8 2,81
Shush - Idzha 1946 -2002 531 230,1 0,09
Sisim - Berezovka 1962 -2002 2810 388,7 -2,09
Syda -Beloyarsk 1927 -1986 3260 258,6 -1,48
Rybnaya - Vershin o- Rybnoye 1945 -1994 110 156,6 0,51

American Scientific Journal № (20 ) / 201 8 19
Slizneva -Sliznevo 1975 -2002 104 221,2 -1,24
Minusinsk depression
Birya - Lebyazhye 1956 -1994 238 23,1 0, 00
Coma - Black Coma 1965 -2002 504 92,2 -0,27
Minus a - Minusinsk 1954 -2002 221 35,8 -0,53
Orlovka - Novopokrovka 1946 -1994 107 62,4 0,43

Analysis of river flow dynamics has shown that
for most of rivers the trend of annual runoff changes
coincides with the precipitation trends: the coefficients
of linear trends of flow at these rivers vary from -0.05
to -4.44. For the seven rivers, the posi tive river flow
trend is marked. The highest values of positive coeffi-
cients of linear trends are characteristic for river basins,
in wich large -scale logging were conducted in the mid-
dle of the twentieth century. These are river basins,
Rybnaya, Mana, Mim ia in the Eastern Sayan and the
basins of the rivers Kebezh and Shadat in the Western
Sayan.
For the Mana River, a positive trend of runoff was
recorded for the entire observation period, beginning in
the mid -thirties of the 20th century, but it was most p ro-
nounced from the mid -sixties to the early nineties (Fig.
2). The average decade runoff for 1986 -1995 increased
by 40 mm compared with the average runoff in 1967 -
1976. Based on the analysis of forest inventory data and
space images [5] in the central part of basin of Mana at
the territory of the Maganskiy leshoz by 1950 up to 30
thousand hectares of forests were cut down, by 1977 the
area of felling was 25 thousand hectares and the sec-
ondary forests occupied 15 thousand ha. By 1989, the
area of felling was markedly reduced (up to 10 thou-
sand hectares), but in total with the secondary forests
this area reached 40 thousand hectares. This indicates
that for almost 40 years the formation of runoff in this
part of the basin of Mana was associated with logging
and subsequent after cutting reforestation.
Similar trends in runoff dynamics appear on the
rivers Kebezh and Shadat, but a more significant in-
crease in the coefficients of linear trends occurs from
the 60s of the last century to the mid -1990s. For thirty
years, the runoff on the Shadat River has increased by
almost 100 mm.
The analysis of the forest inventory data at the
river basins of Western Sayan show that in this region
the forests were cut down at great areas since the mid -
1950s until the end of the 60 s of the 20th century. By
1975, the main massifs of

Figure 2. The trend of the Mana River flow by moving 10 -year averages

accessible forests had been harvested. According
to remote sensing data the total area of felled areas at
the Kebezh and Taigish river basins increases from
1989 to 1999 due to forest harvesting in the high moun-
tain taiga zone. This is also confirmed by the analysis
of the age structure of secondary forests. The youngest
forest stands are characteristic of the high mountain
taiga zone, 40 -50 years old stands predominate in the
chern taiga - middle mountain zone [3].

Discussion
The impact on water resources is a manifestation
of climate change. However, the forecast of this impact
is the most difficult, one can only judge in general terms
how managed water systems and natural watercourses
can respond to a particular climate warmi ng scenario.
This is due to the fact that the impact on water resources
is determined by many differently directed processes,
and their complex impact is difficult to predict. In many
countries, the impact of global climate change on hy-
drological situation s was assessed, but the findings are
contradictory due to the differences in the forecasting
methods, the different scenarios of climate change, and
the different directions of the processes affecting water
resources [1, 6, 21]. Given the important role of cli-
matic factors in the formation of river runoff in the re-
gion under study, we`d like to identify the effect of
global climate change on regional and local features of

20 American Scientific Journal № ( 20 ) / 201 8
the hydrological regime of the area. The authors of
some studies [4, 18] maintain the idea of climatic
changes in the Altai -Sayan mountain region based a
general tendency for Global Warming
There are few publications on the dynamics of the
modern climate for the Sayan Mountains. According to
studies of the dynamics of climatic parameters, d uring
the period from 1950 to 2000 [10] in West Sayan there
is a positive trend of air temperatures in all seasons, but
the most intense in winter and during transitional peri-
ods. A comparative analysis of the radiation tempera-
ture trends in the mountain t aiga of the Sayan Moun-
tains and the dynamics of the monthly average temper-
atures of the Ermakovskoe weather station for the
period 1999 -2010 [20] showed that this period was
characterized by a decrease in the average annual air
temperature.
The results of our studies on the dynamics of the
temperature regime folly agree with the data given in
the above studies. According our data the warming of
the climate in the Sayan Mountains was mainly mani-
fested in the temperature regime during the winter pe-
riod. We di d not reveal correlation between the temper-
ature trends and the change in river flow. A compara-
tive analysis of precipitation trends and river runoff has
shown that in the whole region, the decrease in precip-
itation is reflected in the runoff, especially i n the high-
lands. For several rivers, as noted above, the runoff in-
creased, despite the general trend of decreasing precip-
itation.
In order to trace the impact of forest harvesting on
the runoff and to exclude the influence of precipitation,
we carried out a comparative analysis of the runoff co-
efficient dynamics (the ratio of runoff to precipitation)
with the dynamics of logging areas for every the five -
year period. According to the results, the maximum val-
ues of the runoff coefficient on the river Kebezh d uring
the periods 1954 -59 and 1969 -1973 coincide with the
increase of cut down areas. A similar situation can be
traced for the period from 1984 to 1993 (Fig. 3).

Thus, based on the results of our investigation, we
can state that the trends of the hydrolo gical regime of
the study region depends not only on climatic changes,
but also largely determined by forest management at
river
Figure 3. The change in the flow coefficient and the area

of felling of 1 -5-year -old age in the basin of the
river Kebezh

watersheds. Felling of forests and the nature of
subsequent reforestation successions affect the change
in the structure of the water balance. Comparison of the
dynamics of the area at watersheds Mana, Kebezh and
Shadat rivers affected by the felling of mature forests
with the flow trends of these rivers shows that the forest
harvesting leads to reduce of evaporation in the catch-
ment area and increase runoff.
Despite the considerable variability of the r unoff
from year to year, the trends of the run -off coefficients
of these rivers vary insignificantly, indicating a relative
stability of the water reserves of these rivers. This, in
our opinion, is associated with the cumulative effect of
anthropogenic tra nsformation of forest vegetation in
the catchment areas, i.e. new felling, forestation of old
felling, and the creation of forest plantations.
Conclusions
Studies have shown that the revealed trends in the
annual runoff of the studied rivers differ in sign and in
magnitude. At whole, the general of the area’s humidi-
fication determines hydrological regime, it is con-
firmed by the negative trend of annual runof f of the
most of rivers studied. While the positive trend of flow
under the general trend of decreasing precipitation is
caused by a decrease of evaporation in the catchment
area, which depends on anthropogenic transformation
of forest vegetation after cut ting. For the mountain
taiga of the Western and Eastern Sayan, the forest har-
vesting leads to a change in the water balance of the
territories with a redistribution of its expenditure side
in the direction of reducing the total evaporation and
increasing t he runoff. Under anthropogenic press the
role of global climate change in the change in river run-
off is less pronounced for medium and small rivers, the
effect of felling and subsequent reforestation dynamics
is more significant. Therefore, with large -scal e felling
and large forest fires, the disturbance of forest vegeta-
tion can become the main factor determining the condi-
tions for the formation of the runoff.

American Scientific Journal № (20 ) / 201 8 21
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