共查询到20条相似文献,搜索用时 15 毫秒
1.
L. M. Sorokovikova G. I. Popovskaya I. V. Tomberg N. V. Bashenkhaeva 《Water Resources》2009,36(4):443-452
Specific features of the concentration dynamics of biogenic substances, organic C, and phytoplankton in the lower reaches of the Selenga and its delta branch are identified. The quantitative and qualitative changes in these components are demonstrated for the conditions of extremely low water abundance. High correlation was shown to exist between variations of the concentrations of nitrate N, mineral P, and phytoplankton biomass. 相似文献
2.
Long-term variability of nitrate and nitrite nitrogen runoff in the Amur River near Khabarovsk 总被引:1,自引:0,他引:1
The long-term dynamics of the runoff of mineral oxidized forms of nitrogen in the Amur River near Khabarovsk City is discussed. An increase in nitrate nitrogen runoff by a factor of 2.1 is recorded as compared to the period of 1981–2000. It is shown that the Sungari River is now responsible for the formation of the anthropogenic component of the runoff of mineral nitrogen forms. 相似文献
3.
Analyses of trends and causes for variations in runoff and sediment load of the Yellow River 总被引:4,自引:1,他引:3
Due to the impacts of globe climate change and human activities, dramatic variations in runoff and sediment load were observed for the Yellow River. Analyses of nearly 65 years' data measured at main hydrologic-stations on the Yellow River from 1950 to 2014 indicated that, except for the Tangnaihai station in the head region, sharp downward trends existed in both the annual runoff and annual sedi-ment load according to the Mann–Kendal trend test;and their abrupt changes occurred in 1986 and in 1980, respectively, according to the rank sum test. Factors affecting the changes in the runoff and sediment load were very complicated. Results indicated that the reducing precipitation and the increasing water consumption were the main causes for the runoff decline, while the impoundment of the Longyangxia Reservoir and its combined operation with the Liujiaxia Reservoir exerted a direct bearing on the abrupt change in the annual runoff. In addition to the sediment load decrease associated with the runoff reduction, the reduced storm intensity, the conducted soil erosion control, and the constructed dam buildings all played an important role in the trends and abrupt changes of sediment load decline. 相似文献
4.
Averaged many-year measurement data on the concentrations of mineral forms of biogenic elements are analyzed, and their total concentrations in the rivers of Selenga, Chikoi, Khilok, Uda, Dzhida, and Temnik are evaluated. The monthly variations of the concentrations of major biogenic substances are characterized, and their ratios within a year are determined. Characteristics of river water runoff and biogenic substance concentrations are used to evaluate their within-year discharge by rivers. Characteristic variations in the ratios between the total and mineral forms of biogenic elements discharged by rivers have been revealed. It is established that the share of mineral components in the total input into the Selenga delta Ntot and Ptot are 82 and 22%, respectively. 相似文献
5.
N. L. Frolova P. A. Belyakova V. Yu. Grigor’ev A. A. Sazonov L. V. Zotov 《Water Resources》2017,44(3):359-371
Many-year variations of river runoff in the Selenga basin are analyzed along with precipitation, potential evapotranspiration, and basin water storages. Data of ground-based (1932–2015) and satellite observations, as well as the analysis of literature data suggest the presence of within-century cycles in the series of annual and minimum runoff. Compared with 1934–1975, the Selenga Basin shows a general tendency toward a decrease in the maximum (by 5–35%) and mean annual (up to 15%) runoff at an increase in the minimum runoff (by 30%), a decrease in the mean annual precipitation (by 12%), and an increase in potential evapotranspiration by 4% against the background of a decrease in evaporation because of lesser soil moisture content and an increase in moisture losses for infiltration because of permafrost degradation. The observed changes in water balance may have unfavorable environmental effects. 相似文献
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8.
A. G. Tlatov 《Geomagnetism and Aeronomy》2013,53(8):953-956
Relative variations in the number of sunspots and sunspot groups in activity cycles have been analyzed based on data from the Kislovodsk Mountain Astronomical Station and international indices. The following regularities have been established: (1) The relative fraction of small sunspots decreases linearly and that of large sunspots increase with increasing activity cycle amplitude. (2) The variation in the average number of sunspots in one group has a trend, and this number decreased from ~12 in cycle 19 to ~7.5 in cycle 24. (3) The ratio of the sunspot index (Ri) to the sunspot group number index (G gr) varies with a period of about 100 years. (4) An analysis of the sunspot group number index (G gr) from 1610 indicates that the Gnevyshev-Ohl rule reverses at the minimums of secular activity cycles. (5) Ratio of the total area to area of Ssp/Sum nuclei has long-term variation with a period approximately 8 cycles. Minimum ratio falls on 16–17 cycles of activity. (6) It has been indicated that the magnetic field intensity and sunspot area in the current cycle are related to the amplitude of the next activity cycle. 相似文献
9.
Ye. I. Polyakova T. S. Klyuvitkina E. A. Novichkova H. A. Bauch H. Kassens 《Water Resources》2009,36(3):273-283
The spatial and temporal changes in the Lena River runoff over the last 9 thousand years are reconstructed through studying the freshwater microfossils in sediment cores obtained from the Laptev Sea inner shelf immediately adjacent to the Lena delta and subject to the freshening effect of river water inflowing the sea through the main arms of the delta (the Trofimovskaya, Bykovskaya, and Tumatskaya arms), the sediments having been thoroughly AMS 14C dated. The freshwater species of diatoms (predominantly the river ones) and green algae that enter the shelf with river water served as indicators of river runoff. The reconstruction of paleosalinity of the sea surface water in the regions under study is based on the relationships (established earlier) between the distribution of freshwater diatoms in the surface layers of sediments in the Arctic seas and the gradients of water salinity in summer. Data on variations in the composition of aquatic microfossil associations in sediments and the reconstructed paleosalinity in the regions of the eastern and western paleovalleys of the Lena River are used to determine the main paleohydrologic events that controlled the variations in the Lena runoff into the shelf zone of the Laptev Sea during the Holocene. 相似文献
10.
Spatial and temporal variations in hydro-climatic variables and runoff in response to climate change in the Luanhe River basin,China 总被引:3,自引:3,他引:0
Weiguang Wang Jiande Wei Quanxi Shao Wanqiu Xing Bin Yong Zhongbo Yu Xiyun Jiao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(4):1117-1133
11.
Scaling properties of the runoff variations in the arid and semi-arid regions of China: a case study of the Yellow River basin 总被引:2,自引:2,他引:0
Qiang Zhang Chong-Yu Xu Tao Yang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(8):1103-1111
We analyzed long daily runoff series at six hydrological stations located along the mainstem Yellow River basin by using power
spectra analysis and multifractal detrended fluctuation analysis (MF-DFA) technique with aim to deeply understand the scaling
properties of the hydrological series in the Yellow River basin. Research results indicate that: (1) the runoff fluctuations
of the Yellow River basin exhibit self-affine fractal behavior and different memory properties at different time scales. Different
crossover frequency (1/f) indicates that lower crossover frequency usually corresponds to larger basin area, and vice versa, showing the influences
of river size on higher frequency of runoff variations. This may be due to considerable regulations of river channel on the
runoff variations in river basin of larger basin size; (2) the runoff fluctuations in the Yellow River basin exhibit short-term
memory properties at smaller time scales. Crossover analysis by MF-DFA indicates unchanged annual cycle within the runoff
variations, implying dominant influences of climatic changes on changes of runoff amount at longer time scales, e.g. 1 year.
Human activities, such as human withdrawal of freshwater and construction of water reservoirs, in different reaches of the
Yellow River basin may be responsible for different scaling properties of runoff variations in the Yellow River basin. The
results of this study will be helpful for hydrological modeling in different time scales and also for water resource management
in the arid and semi-arid regions of China. 相似文献
12.
A. V. Frolov 《Water Resources》2011,38(5):583-592
A model of long-term river runoff variations is proposed. The model is based on a difference stochastic equation of water
balance on a watershed. Precipitation and evaporation on the watershed are simulated by stochastic, dependent, non-Gaussian
Markov processes. Long-term river runoff variations are described by a component of three-dimensional non-Gaussian Markov
process. It is shown that the autocorrelation and skewness coefficients for river runoff can be negative. The proposed model
can be used to assess the effect of climate-induced variations in precipitation and evaporation regimes in a watershed on
long-term river runoff variations. 相似文献
13.
V. V. Shutenko I. I. Astapov N. S. Barbashina A. N. Dmitrieva R. P. Kokoulin K. G. Kompaniets A. A. Petrukhin I. I. Yashin 《Geomagnetism and Aeronomy》2013,53(5):571-579
The intensity of the atmospheric muon flux depends on many factors: the energy spectrum of primary cosmic rays and the state of the Earth’s heliosphere, magnetosphere, and atmosphere. The wide-aperture URAGAN muon hodoscope (Moscow, Russia, 55.7° N, 37.7° E, 173 m a.s.l.) makes it possible to investigate not only variations in the muon flux intensity but also temporal changes in the parameters of its angular distribution. These changes are analyzed using the vector of local anisotropy and its projections, which have different sensitivities to the parameters of modulation of both primary cosmic rays in the heliosphere and the Earth’s magnetosphere and secondary cosmic rays as they pass through the Earth’s atmosphere. The vector of local anisotropy is the sum of unit vectors (directions of the reconstructed muon tracks) normalized to the number of tracks. The results of an analysis of long-term variations in mean hourly projections of the vector of local anisotropy obtained from the 2007–2011 URAGAN hodoscope data are presented. 相似文献
14.
The current features of the space and time variations of river runoff in Kamchatka Krai have been considered. Two relatively long cycles have been shown to exist in water runoff variations in the major portion of the examined rivers. The renewable water resources were increasing until 1970–1980, while in the following years (up to 2010), they were gradually decreasing. Current data on river runoff were used to prove the existence of three zonal types of water regime in Kamchatka Krai; five azonal types of annual runoff distribution are characterized. One of them (nearly uniform annual distribution caused by the predominance of groundwater recharge) has been theoretically predicted in the classification proposed by M.I. L’vovich, though without factual confirmation. The specific features of water regime of rivers whose basins lie on the slopes of active volcanoes are considered for the first time. This type of regime typically shows alternating periods of the presence and absence of surface runoff in river channels, corresponding to the inflow of snowmelt or rainfall runoff at high level of subsoil water (when channel deposits are fully saturated with water) or at its low position (when moisture is deficient). 相似文献
15.
The spatial-temporal variations in the amount and biochemical composition of organic matter and the rates of its transformations in the ecosystems of the Russian part of the Sea of Azov are analyzed. Maximum OM concentrations are typical for Taganrog Bay. A characteristic feature of the Sea of Azov is a large proportion of particulate organic matter, which in summer in Taganrog Bay exceeded 35%. It is shown that not only the concentration of organic matter changes from season to season, but also its elementary (Corg, Norg, and Porg) and biochemical composition (proteins, carbohydrates, and lipids). The major biochemical compound of dissolved organic matter is shown to be carbohydrates (13–28%), and that of particulate matter is protein (44–51%). The hydrolytic (phosphatase and protease) and oxidation-reduction enzymes of electron-transport system demonstrate a high activity in summer. The estimated short turnover times of phosphates and protein suggest the rapid and complete utilization of organic matter in the Sea of Azov. 相似文献
16.
S. G. Dobrovol’skii 《Water Resources》2017,44(3):347-358
New approaches, methods, and formulas, proposed by the author, are used to study many-year and year-to-year variations of the annual, maximal, and minimal runoff of rivers in Baikal Lake drainage basin. The stationary character of most changes in the annual and maximal runoff (including major Baikal tributaries at the gages nearest to the lake) is demonstrated and the percentage of transient changes in the minimal runoff is shown to be close to the mean world characteristics. Some effects found in Baikal Basin have been generally recorded only in the data of runoff observations in much larger basins or globally: “the law of the power of minus 0.5” for the dependence of the coefficient of variation and the correlation between neighboring years on the mean runoff depth, a fixed structure of the orders of stochastic (autoregression models), the effect of bifurcation of the models of maximal and minimal runoff at the passage from drier to wetter watersheds. 相似文献
17.
《Continental Shelf Research》1995,15(8):981-1014
Low frequency sea-level variations and associated geostrophic currents in the central Great Barrier Reef (GBR) region near Townsville are studied using optimally-lagged multivariate regression. The analyses show that pressure-adjusted coastal sea levels and mid-shelf geostrophic currents are influenced predominantly by local along-shelf wind stress at the weather time-scale, and by climatic variables, such as atmospheric pressure and temperature, at seasonal and inter-annual time-scales. These forcing variables can specify sea levels over annual and inter-annual time-scales with a forecasting skill of 0.53 and 0.22, respectively (where 1.0 is perfect skill). Associated along-shelf geostrophic currents can be forecast with a skill of 0.57 over an annual time scale. If, instead, absolute coastal sea levels or offshore sea-level differences are used to specify the along-shelf geostrophic current, the forecasting skill is 0.75. A characteristic El Niño/Southern Oscillation (ENSO) response is detected for time periods up to 25 years in monthly sea-level both at Townsville and at western Pacific island sea-level stations. This spatially coherent response varies in intensity and phase within the Coral Sea. Sea-level differences show a pattern which characterizes known features of the large-scale circulation of the Coral Sea. These very low frequency sea-level variations in the Coral Sea must be taken into account to obtain accurate predictions of along-shelf geostrophic current variations on seasonal and inter-annual time scales. Regression analysis and a diagnostic river plume model show that the influence of the major rivers can produce sea-level changes due to buoyancy of order 5 cm. The corresponding errors in geostrophic velocities estimated using pressure-adjusted Townsville sea-level data alone are of order 5 cm s−1 rms. 相似文献
18.
Astronomical observations of time and latitude providing precise information on the motion of the earth as a whole (rotation and polar motion) point to the existence of secular and periodical variations due to tidal forces and geophysical and meteorological causes.Together with these variations, there is also evidence that the earth's crust is wandering as a result of the action of different forces, and the mean latitudes and longitudes of the observatories vary because of continental and/or local displacements.In this paper an analysis of a long series of latitude and time astronomical observations is carried out in order to investigate their long-term variations, and an important result is found: there is significant evidence for the existence of a relationship between the rotational accelerations of the earth and the variation in the positions of the mean rotation pole over periods of about thirty years. This result is discussed from the viewpoint of a deformable earth and/or crustal movements. 相似文献
19.
N. A. Gashkina 《Water Resources》2011,38(3):352-371
The results of large-scale studies of water chemistry in small lakes in European Russia were used to characterize the distributions
and ratios of biogenic elements and organic matter from the viewpoint of the zonal peculiarities of their turnover rate. Latitudinal
regularities were identified in the limiting of lake production with respect to major biogenic elements. A classification
of lakes is proposed, where the lakes are regarded as a system based on the percent distribution of organic carbon, nitrogen
and phosphorus forms, as well as the trophic status and the totality of indices characterizing the origin of OM and the extent
of its transformation. 相似文献
20.
Study on snowmelt runoff simulation in the Kaidu River basin 总被引:2,自引:0,他引:2
Alpine snowmelt is an important generation mode for runoff in the source region of the Tarim River basin, which covers four subbasins characterized by large area, sparse gauge stations, mixed runoff supplied by snowmelt and rainfall, and remarkably spatially heterogeneous precipitation. Taking the Kaidu River basin as a research area, this study analyzes the influence of these characteristics on the variables and parameters of the Snow Runoff Model and discusses the corresponding determination strategy to improve the accuracy of snowmelt simulation and forecast. The results show that: (i) The temperature controls the overall tendency of simulated runoff and is dominant to simulation accuracy, as the measured daily mean temperature cannot represent the average level of the same elevation in the basin and that directly inputting it to model leads to inaccurate simulations. Based on the analysis of remote sensing snow maps and simulation results, it is reasonable to approximate the mean temperature with 0.5 time daily maximum temperature. (ii) For the conflict between the limited gauge station and remarkably spatial heterogeneity of rainfall, it is not realistic to compute rainfall for each elevation zone. After the measured rainfall is multiplied by a proper coefficient and adjusted with runoff coefficient for rainfall, the measured rainfall data can satisfy the model demands. (iii) Adjusting time lag according to the variation of snowmelt and rainfall position can improve the simulation precision of the flood peak process. (iv) Along with temperature, the rainfall increases but cannot be completely monitored by limited gauge stations, which results in precision deterioration. 相似文献