Assessment of possible anthropogenic changes in the runoff of the Syr Darya River on the basis of a mathematical model

The development of a simulation model of water and salt balance for river basins with the predominance of irrigated agriculture is considered. The results of a simulation experiment for the assessment of possible anthropogenic changes in Syr Darya River runoff for some scenarios of the implementation of a set of resource-saving and environment protection measures are given.     

Assessment of the statistical significance of global changes in the annual river runoff in XXI century due to possible anthropogenic warming of climate

A number of uncertainties of forecasts of changes in the annual runoff depths at global scale, obtained using information on results of integration of 21 IPCC climate models is studied. Following possible errors of these forecasts are calculated: errors of models; differences between main (IPCC) scenarios of emission of greenhouse gases in the atmosphere and resultant changes of global temperatures; mistakes in estimates of average long-term observed values of the runoff depths for the “control” period. Global maps of a “significance index” of forecasted changes in the runoff depths (estimations of changes in the annual runoff depths divided by mean square root values of errors of these estimations) for 2025, 2050, 2075 and 2100 are presented. It is shown that the most significant global changes of the runoff depths (growth in the north of Eastern Siberia, of the Russian Far East, of North America, falling in the “Greater Mediterranean Region”) are predicted for the second quarter of 21st century. Further changes of the runoff amplify only in the Amazon basin (reduction, by 2075). Almost everywhere else (including almost all European territory of Russia, Western Siberia, south of Eastern Siberia and of the Far East) the significance of changes in the runoff depths during 21st century is negligible.     

Long-term variability of nitrate and nitrite nitrogen runoff in the Amur River near Khabarovsk

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.     

Estimating the sensitivity of mean annual runoff to climate change using selected hydrological models

Hydrological model sensitivity to climate change can be defined as the response of a particular hydrological model to a known quantum of climate change. This paper estimates the hydrological sensitivity, measured as the percentage change in mean annual runoff, of two lumped parameter rainfall-runoff models, SIMHYD and AWBM and an empirical model, Zhang01, to changes in rainfall and potential evaporation. These changes are estimated for 22 Australian catchments covering a range of climates, from cool temperate to tropical and moist to arid. The results show that the models display different sensitivities to both rainfall and potential evaporation changes. The SIMHYD, AWBM and Zhang01 models show mean sensitivities of 2.4%, 2.5% and 2.1% change in mean annual flow for every 1% change in mean annual rainfall, respectively. All rainfall sensitivities have a lower limit of 1.8% and show upper limits of 4.1%, 3.4% and 2.5%, respectively. The results for potential evaporation change are −0.5%, −0.8% and −1.0% for every 1% increase in mean annual potential evaporation, respectively, with changes rainfall being approximately 3–5 times more sensitive than changes in potential evaporation for each 1% change in climate. Despite these differences, the results show similar correlations for several catchment characteristics. The most significant relationship is between percent change in annual rainfall and potential evaporation to the catchment runoff coefficient. The sensitivity of both A and B factors decreases with an increasing runoff coefficient, as does the uncertainty in this relationship. The results suggest that a first-order relationship can be used to give a rough estimate of changes in runoff using estimates of change in rainfall and potential evaporation representing small to modest changes in climate. Further work will develop these methods further, by investigating other regions and changes on the subannual scale.     

Impacts of land-use and climate changes on surface runoff in a tropical forest watershed (Brazil)

ABSTRACT

Surface runoff generation capacity can be modified by land-use and climate changes. Annual runoff volumes have been evaluated in a small watershed of tropical forest (Brazil), using the Soil and Water Assessment Tool (SWAT) model. Firstly, the accuracy of SWAT in runoff predictions has been assessed by default input parameters and improved by automatic calibration, using 20-year observations. Then, the hydrological response under land uses (cropland, pasture and deforested soil) alternative to tropical forest and climate change scenarios has been simulated. SWAT application has showed that, if forest was replaced by crops or pasture, the watershed’s hydrological response would not significantly be affected. Conversely, a complete deforestation would slightly increase its runoff generation capacity. Under forecasted climate scenarios, the runoff generation capacity of the watershed will tend to decrease and will not be noticeably different among the representative concentration pathways. Pasture and bare soil will give the lowest and highest runoff coefficients, respectively.     

Effects of land use and climate variability on the main stream of the Songhua River Basin,Northeast China

ABSTRACT

In this study, three representative concentration pathways (RCPs) and 15 general circulation models of the Coupled Model Intercomparison Project Phase 5 were used to assess the behaviour of precipitation (P) and surface air temperature (SAT) over part of the Songhua River Basin. The Water Evaluation and Planning (WEAP) model linked with SAT and P was used for monthly simulation of streamflow to assess the influence of land use/land cover and climate change on the streamflow. The results suggest that, under RCP2.6, RCP4.5 and RCP8.5, the SAT over the study area may increase in the 21st century by 1.12, 2.44 and 5.82°C, respectively. Moreover, by the middle of the 21st century, streamflow in the basin may have decreased by 19%. The decrease in streamflow may be due to changed land use conditions and water withdrawal, having critical implications for management and future planning of water resources in the basin.     

Modes of low-frequency climate variability and their relationships with land precipitation and surface temperature: application to the Northern Hemisphere winter climate

Variations in the Earth's climate have had considerable impact on society sectors such as energy, agriculture, fisheries, water resources, and environmental quality. This natural climate variability must be documented and understood in order to assess its potential impacts, its predictability and relationships with human-induced changes. Understanding the mechanisms responsible for natural variability proceeds through a strategy based on the use of a hierarchy of climate models and careful data analysis. In this paper, we examine primarily climate fluctuations on interannual-to-decadal time scales and their climate signature in terms of precipitation and temperature. First, space and time characteristics of two of the major variability modes, the Southern Oscillation (and its associated teleconnection patterns) and the North Atlantic Oscillation, are documented with a focus onto the midlatitudes of the Northern Hemisphere. Then, the current hypothesis regarding the nature of these modes (forced, coupled or internal) are reviewed based on both simulation results and statistical data analyses. Next, we address the potential predictability of seasonal surface temperature and land precipitation using an ensemble of atmospheric model simulations forced by observed sea surface temperatures. Finally, we review the relationships between the atmospheric variability modes and the recent low-frequency trends and suggest a possible influence of anthropogenic effects on these low-frequency variations.     

Impacts of climate variability and human activity on streamflow decrease in a sediment concentrated region in the Middle Yellow River

The Kuye River is the primary tributary located in the sediment concentrated regions in the Middle Yellow River in China. Significant decrease in streamflow has been observed in the Kuye River. The non-parametric Mann–Kendall test was applied to detect the change in annual streamflow for the period of 1960 to 2006. Mean annual streamflow in the Kuye River was 84.9 mm from 1960 to 1979 (period I), while it decreased to 58.2 mm from 1980 to 1998 (period II) and 20.5 mm from 1999 to 2006 (period III), respectively. The climate elasticity method and the hydrological modeling method were individually employed to assess the impact of climate variability and human activities on the decrease in streamflow. The results showed that climate variability was responsible for 29.6 and 27.1 % of the streamflow decrease from the climate elasticity method and the hydrological modeling method, respectively; while human activities accounted for 70.4 and 72.9 % of the streamflow decrease in period II. In period III, climate variability contributed 40.9 and 39.3 % of the streamflow decrease from the climate elasticity method and the hydrological modeling method, respectively; while human activities accounted for 59.1 and 60.7 % of the streamflow decrease. Therefore, human activities were the main reason of the streamflow decrease. Soil conservation measures (planting trees, improving pastures, building terraces and sediment-trapping dams) and coal mining led to the streamflow reduction in the Kuye River.     

Research on runoff forecast approaches to the Aksu River basin

The Aksu River (the international river between China and Kirghiz) has become the main water source for the Tarim River. It significantly influences the Tarim River’s formation, development and evolution. Along with the western region development strategy and the Tarim River basin comprehensive development and implementation, the research is now focused on the Aksu River basin hydrologic characteristic and hydrologic forecast. Moreover, the Aksu River is representative of rivers supplied with glacier and snow melt in middle-high altitude arid district. As a result, the research on predicting the river flow of the Aksu River basin has theoretical and practical significance. In this paper, considering the limited hydrometeorological data for the Aksu River basin, we have constructed four hydrologic forecast approaches using the daily scale to simulate and forecast daily runoff of two big branches of the Aksu River basin. The four approaches are the upper air temperature and the daily runoff correlation method, AR(p) runoff forecast model, temperature and precipitation revised AR(p) model and the NAM rainfall-runoff model. After comparatively analyzing the simulation results of the four approaches, we discovered that the temperature and precipitation revised AR(p) model, which needs less hydrological and meteorological data and is more predictive, is suitable for the short-term runoff forecast of the Aksu River basin. This research not only offers a foundation for the Aksu River and Tarim Rivers’ hydrologic forecast, flood prevention, control and the entire basin water collocation, but also provides the hydrologic forecast reference approach for other arid ungauged basins.     

Research on runoff forecast approaches to the Aksu River basin

The Aksu River (the international river between China and Kirghiz) has become the main water source for the Tarim River. It significantly influences the Tarim River's formation, development and evolution. Along with the western region development strategy and the Tarim River basin comprehensive devel-opment and implementation, the research is now focused on the Aksu River basin hydrologic charac-teristic and hydrologic forecast. Moreover, the Aksu River is representative of rivers supplied with gla-cier and snow melt in middle-high altitude arid district. As a result, the research on predicting the river flow of the Aksu River basin has theoretical and practical significance. In this paper, considering the limited hydrometeorological data for the Aksu River basin, we have constructed four hydrologic forecast approaches using the daily scale to simulate and forecast daily runoff of two big branches of the Aksu River basin. The four approaches are the upper air temperature and the daily runoff correlation method, AR(p) runoff forecast model, temperature and precipitation revised AR(p) model and the NAM rainfall-runoff model. After comparatively analyzing the simulation results of the four approaches, we discovered that the temperature and precipitation revised AR(p) model, which needs less hydrological and meteorological data and is more predictive, is suitable for the short-term runoff forecast of the Aksu River basin. This research not only offers a foundation for the Aksu River and Tarim Rivers' hydrologic forecast, flood prevention, control and the entire basin water collocation, but also provides the hydrologic forecast reference approach for other arid ungauged basins.     

Study on snowmelt runoff simulation in the Kaidu River basin

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 sta-tion 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.     

Natural and anthropogenic long-term variations of water runoff and suspended sediment load in the Huanghe river

The hydrographic, climate, hydrological, and landscape features of the Huanghe R. Basin are considered. Water runoff and suspended sediment load in the Huanghe R. are shown to have dropped significantly in 1950–2009 under the effect of regional climate changes and economic activity in the basin. Water balance method and the concept of flow transport competency were used to assess the contribution of natural and anthropogenic factors (decline in precipitation, water withdrawal for economic needs, and the effect of reservoirs) to the decrease in river water runoff and suspended sediment load.     

Dynamic-stochastic models of rainfall and snowmelt runoff formation

Abstract

Possibilities for the development of dynamic-stochastic models of runoff formation with random inputs are discussed. Two models are described: the first allows the calculation of the statistical distribution of the maximum discharges of rainfall floods, and the second the statistical distribution of snowmelt flood volumes. Meteorological inputs are generated by the Monte- Carlo method. Physically-based models are used for the transformation of input data into runoff. The various models are applied to observation data from two watersheds.     

Water and sediment runoff at the Amazon River mouth

The regime and budget of water and sediment runoff in the mouth area of the Amazon River are discussed. New values of the water and sediment runoff at the terminal cross section (the town of Obidos) and at its outflow into the Atlantic Ocean have been obtained on the basis of observational data. It turned out that the water runoff value was markedly higher and the sediment runoff value was lower than it had been considered previously.     

Investigating the ability of a land surface model to reproduce river runoff with the accuracy of hydrological models

The ability of the physically-based Soil Water-Atmosphere-Plants model, describing the processes of heat and water exchange between the land surface and the near-surface atmosphere, to reproduce hydrographs of daily river runoff is examined and compared with the Sacramento conceptual hydrological model, which has demonstrated the best performance in the International Model Parameter Estimation Experiment. Model simulations were carried out for 12 river basins with the area of ～10³ km² in the southeastern USA for the period of 1960–1998, of which the first 20 years were used to calibrate both models, while the last 19 years were used to validate them. The daily runoff hydrographs reproduced by the Soil Water-Atmosphere-Plants model, calibrated using different methods with the aim to maximize its accuracy, were compared with observational data and the results from the Sacramento model.     

Biotesting in the Assessment of Environmental and Toxicological State of Water Bodies in Lower Don River Basin

The toxicity of river water in the Lower Don basin was studied using biotesting with different biological objects. Water taken from most examined reaches of the Don and its tributaries was shown to exert toxic effect on crustaceans, algae, protozoa, and Rotifera.     

On the potential for climate change impacts on marine anthropogenic radioactivity in the Arctic regions

Current predictions as to the impacts of climate change in general and Arctic climate change in particular are such that a wide range of processes relevant to Arctic contaminants are potentially vulnerable. Of these, radioactive contaminants and the processes that govern their transport and fate may be particularly susceptible to the effects of a changing Arctic climate. This paper explores the potential changes in the physical system of the Arctic climate system as they are deducible from present day knowledge and model projections. As a contribution to a better preparedness regarding Arctic marine contamination with radioactivity we present and discuss how a changing marine physical environment may play a role in altering the current understanding pertaining to behavior of contaminant radionuclides in the marine environment of the Arctic region.     

Assessing the impacts of land cover and climate on runoff and sediment yield of a river basin

ABSTRACT

This study investigated the impacts of changes in land cover and climate on runoff and sediment yield in a river basin in India. Land Change Modeler was used to derive the future land cover and its changes using the Sankey diagram approach. The future climatic parameters were derived from five general circulation models for two emission scenarios with representative concentration pathways (RCPs) 4.5 and 8.5. The land cover and climate change impacts on runoff and sediment yield were estimated using SWAT model. The results show important changes in land cover and indicate that urban and agricultural areas strongly influence the runoff and sediment yield. Among the land cover and climate change impacts, climate has more predominant (70%–95%) impact. Runoff and sediment yield are likely to decrease in both RCP scenarios in the future period. The impacts of land cover changes are more prominent on sediment yield than runoff.     

Assessing the effects of climate change and human activities on runoff variations from a seasonal perspective

Stochastic Environmental Research and Risk Assessment - Previous studies attempting to quantify the contributions of climate change and human activities to runoff variations in a changing...