9. Discussion and conclusion
The ongoing increase of air temperatures, changes in precipitation and
permafrost degradation affect the hydrological cycle via seasonal
redistribution of water balance elements, changes in soil wetness and
ALT, intensification of ground and surface water runoff exchange
(Makarieva, 2019a; Rawlins et al., 2010; Shiklomanov & Lammers, 2013;
Tananaev et al., 2016; Walvoord & Kurylyk, 2016).
However, the research is complicated by the lack of observed data and
the inaccessibility of the study area of the most of the Arctic (Bennett
et al., 2015). In the conditions of insufficient information, typical
for the high-altitude mountain permafrost regions, the main tool for
studying the processes is the method of mathematical modeling. The
Arctic places increased demands on hydrological models. The vast
majority of hydrological models, well-established in areas with a
temperate climate, cannot be used in the permafrost zone. The main
requirements are the physical validity of models to natural processes,
their versatility in terms of use, both in different landscapes and
spatial and temporal scales, and most importantly, the ability to assess
the parameters of the model based on the measured properties of
landscapes.
Stationary observations in small research catchments are the main source
of information on the physical mechanisms of runoff formation and
changes of hydrological cycle. But such observations are often expensive
to maintain (especially in hard-to-reach regions), require large number
of specialists, and are difficult to perform without additional support
from the state or other interested stakeholders. In these conditions,
the information for improving the models can also be integrated from
short-term studies at certain landscapes and watersheds. The concept of
such studies was proposed by Vinogradov (1988), he called it
“nonstationary research watersheds and plots”. The idea was further
developed by Vinogradova and Vinogradov (2014) and Gartsman and Shamov
(2015) who called this approach “mobile watershed”. According to this
approach, one or several indicative watersheds or plots are selected in
the study area. The research visits are short-term (approximately from
2-3 weeks to 2 months) and last for several years. The observations are
vaster and less detailed.
Conducting short-term intensive observations on specially selected
representative watersheds, despite their fragmentation, allow
formulating a general idea of the conditions of runoff formation and
hydrological phenomena of the territory in question, and most
importantly, approximate quantitative assessment of the parameters of
mathematical models of hydrological processes (Vinogradov &
Vinogradova, 2014). However, not having in their basis the tasks of
model development and parametrization, or refining existing methods for
calculating the flow characteristics, such observations lose most of
their value and do not justify the investment.
The three-years extensive observations at the Suntar-Khayata Station can
be regarded as the good example of such approach. Among the others
expeditions to remote regions we may mention historical studies at the
Putorano Plateau in 1988-1990 (Reports…, 1988-1990), recent
studies at Chukotka (Tregubov et al., 2020) and the Lena River delta
(Tarbeeva et al., 2020). We emphasize the need for open access to the
detailed hydrometeorological data of such research sites which can
provide the opportunity for multi-criteria assessment of hydrological
models in different conditions of permafrost zone (e.g. Fang et al.,
2018; Makarieva 2017, 2018a; Rasouli et al., 2019).
In this research, based on the observation data at the high altitude
Suntar-Khayata Station (the Indigirka river upper reaches) under the
program of the International Geophysical Year in 1957-1959, the
parameters of the hydrological model Hydrograph were developed, which
describe the runoff formation processes in the high mountain goltsy
landscape of the Suntar river basin. Variable states of snow cover and
heat dynamics in ground profile in the goltsy zone were simulated, as
well as runoff formation process and its changes in recent time
throughout the whole catchment of the Suntar river. Modeling results are
considered acceptable.
Model calculations have allowed evaluation of long-term average annual
values of water balance for different landscapes, their contribution to
runoff formation in the mountain river outlet. It is established that
the runoff formation occurs mainly in the high-altitude region of goltsy
and tundra (about 70%).
The model reproduced observed trend values and change point of
streamflow during the study period supporting the hypothesis that the
increase of liquid precipitation in autumn due to climate warming could
be the main factor of streamflow changes in the autumn-winter period in
this permafrost region.
Currently, in the mountain regions of the Yana, Indigirka and Kolyma
rivers basins no hydrological research stations are left to perform a
comprehensive study of runoff formation processes. Therefore,
development and verification of methods for hydrological processes
modeling which may successfully utilize short-term, extremely scarce
data, become more of great current interest. The presented study has
demonstrated that the Hydrograph model and its further development may
become a foundation for solving scientific and practical issues in the
research region.