1
Introduction
Due
to the equilibrium and kinetic fractionation of
stable hydrogen and oxygen
isotopes in water from different sources during the hydrological cycle
process, stable hydrogen and oxygen isotopes will exist in different
proportions in the natural water body, different isotopic composition
characteristics will be embodied (IAEA, 1983; Mook, 2000; Gat, 1996).
In
recent years, the stable isotope technique has been widely used in
tracer basin hydrological process and lake water volume change and
balance process; these tasks are difficult to achieve through
traditional hydrological methods (Liu et al., 2009; Cui et al., 2016) .
Evapotranspiration, an important part in the hydrological cycle process,
is the aspect most directly affected by climate change and is the main
water expenditure item. Terrestrial moisture produced by
evapotranspiration is called recycled moisture. Some researchers have
divided local water vapor sources into advection water vapor, surface
water evaporation and vegetation transpiration, and have used the
three-end-member linear mixing model to estimate the contribution rate
of each of these sources (Peng et al., 2011; Wang et al., 2016; Li et
al., 2016). But in arid areas with sparse vegetation or lakes with a
large water surface area,
the
effect of vegetation transpiration is mostly excluded since
it is considered that the
precipitating water vapor above the lake is mainly composed of the
advection water vapor and lake evaporation, and the contribution rate of
each source is estimated by using the linear mixing model with deuterium
excess parameter(Gat and Matsui, 1991; Gat et al, 1994; Xu et al., 2011;
Kong et al., 2013; Aemisegger et al., 2014). For a lake in a relatively
stable state, the ratio of evaporation to inflow can be determined by
using the method of stable isotopic mass equilibrium, and the
evaporation situation of external water inflow can also be determined
(Cui et al., 2016; Dinçer, 1968; Zuber, 1983; Gonfiantini, 1986; Gibson
and Edwards, 2002; Gibson et al., 2002; Liu et al., 2009).
The construction of reservoirs in the Basin under discussion here will
increase the total water area,
which
will lead to a change in the water and heat conditions between the land
and the water, and the transfer and exchange of water vapor and heat
between the earth and atmosphere. And local aerodynamic characteristics
will also be changed. All these changes will have a certain impact on
the local climate of the reservoir and its surrounding area (Straškraba
et al.,
1993).
The reservoir contributes water vapor to the atmosphere by evaporation,
and this process has an important impact on the regional climate. The
Xiying Reservoir is a typical reservoir in the Eastern Qilian Mountains
situated on the northeast edge of the Qinghai-Tibet Plateau and serves
as the main water supply for production and livelihood for the Wuwei and
the Minqing Oasis. The local atmospheric circulation system is diverse,
and the local hydrological cycle process is relatively unique. The
isotope technique has been widely used in Basin hydrology in recent
years; the influence of strong
evaporation background on water bodies such as lakes, reservoirs and
wetlands in arid areas has often been neglected in the relevant research
undertakings.
The Xiying Reservoir was selected as
the case to carry out an analytical research based on the stable isotope
technique to determine the effect of evaporation on the reservoir water
and the precipitation of the around reservoir. The research results can
provide reference and can be a source of accumulated raw data for the
lake water balance and hydrological cycle in this area. It also has the
potential to improve the level of local water resources management and
utilization.