Assessing Amur Water Regime Variations in the XXI Century with Two Methods Used to Specify Climate Projections in River Runoff Formation Model

A regional numerical physico-mathematical model of river runoff formation is used to study the possibility to assess long-term variations of water regime characteristics in the Amur R. in the XXI century. Two methods were used to specify climate projections as boundary conditions in the hydrological model: (1) based on the results of calculations with an ensemble of global climate models of CMI5 project, (2) based on data obtained by linear transformation of series of actual meteorological observations with the use of normal annual climate parameters calculated by climate models. The results of numerical experiments were used to analyze the sensitivity of the anomaly of Amur normal annual runoff to changes in the climate normals of air temperature and precipitation. The anomalies of normal annual runoff were shown to respond similarly (within the accuracy of sensitivity coefficient estimates) to changes in the appropriate climate normals, whatever the way of specifying climate projections.     

Assessing possible changes in Selenga R. water regime in the XXI century based on a runoff formation model

The runoff of the Selenga R., the largest tributary of Lake Baikal, in recent two decades corresponds to a low-water period. Such decrease can be due to the global climate processes, which have an effect on the amounts of precipitation onto and evaporation from Selenga drainage basin, which is located in arid climate zone. The adaptation of Ecomag software complex to simulating river runoff in the Selenga Basin based on global databases (relief, soils, vegetation, and weather information) is described. The model was calibrated and verified, and the statistical estimates of calculation efficiency were constructed. The obtained model of runoff formation in the Selenga Basin was used to assess the possible changes in the climate and water regime in the XXI century with the use of data of global climate models under different scenarios of greenhouse gas emissions. Throughout the XXI century, the Selenga R. runoff may decrease by 10–40%, depending on the forecasted climate conditions.     

Long-Term Variations of Water Runoff and Suspended Sediment Yield in the Parana and Uruguay Rivers

The hydroclimatic conditions of water runoff formation and the hydrography of Parana and Uruguay river basins in the South America are considered. A survey of the recent studies of the hydrological regime of these rivers is given. Observation data are used to evaluate the long-term average values of water runoff and suspended sediment yield in the Parana and Uruguay and their variations along the rivers. Characteristics of many-year runoff variations in the rivers were evaluated. A climate-induced increase was identified in the Parana and Uruguay water runoff, and the corresponding present-day trends in river runoff variations in both rivers were evaluated. The total water runoff and suspended sediment yield of the Parana and Uruguay into La Plata estuary were calculated. Water balance of the drainage basin of La Plata estuary was characterized.     

Current changes in river water regime in the Don River Basin

The formation and distribution of present-day water resources under the effect of changing climate are studied. Seasonal, annual, and many-year variations in the regime of spring-flood and dry-season runoff of rivers with drainage areas from 2000 to 20000 km², reflecting the zonal landscape-climatic conditions of runoff formation, are considered. It is shown that various and often contradictory demands of water users to water supply distribution over seasons of the year result in that the entire water management complex depends on not only the total volume of water resources, but also on the water regime characteristics of rivers in different phases of hydrological year. It was established that the climate changes recorded in the recent decades radically change the pattern of space and time variations in runoff characteristics.     

Runoff Formation Model for the Amur River Basin

ECOMAG software complex was adapted to simulate river runoff in the Amur basin using data from global databases (relief, soils, landscapes). The results of model calibration and verification were used to give a statistical estimate of the efficiency of river runoff calculation over a long period based on standard data of meteorological and water management monitoring. The results of calculations using the developed runoff formation model were used in the space and time analysis of the formation conditions of 2013 flood in the Amur basin.     

Estimation of uncertainty sources in the projections of Lithuanian river runoff

Particular attention is given to the reliability of hydrological modelling results. The accuracy of river runoff projection depends on the selected set of hydrological model parameters, emission scenario and global climate model. The aim of this article is to estimate the uncertainty of hydrological model parameters, to perform sensitivity analysis of the runoff projections, as well as the contribution analysis of uncertainty sources (model parameters, emission scenarios and global climate models) in forecasting Lithuanian river runoff. The impact of model parameters on the runoff modelling results was estimated using a sensitivity analysis for the selected hydrological periods (spring flood, winter and autumn flash floods, and low water). During spring flood the results of runoff modelling depended on the calibration parameters that describe snowmelt and soil moisture storage, while during the low water period—the parameter that determines river underground feeding was the most important. The estimation of climate change impact on hydrological processes in the Merkys and Neris river basins was accomplished through the combination of results from A1B, A2 and B1 emission scenarios and global climate models (ECHAM5 and HadCM3). The runoff projections of the thirty-year periods (2011–2040, 2041–2070, 2071–2100) were conducted applying the HBV software. The uncertainties introduced by hydrological model parameters, emission scenarios and global climate models were presented according to the magnitude of the expected changes in Lithuanian rivers runoff. The emission scenarios had much greater influence on the runoff projection than the global climate models. The hydrological model parameters had less impact on the reliability of the modelling results.     

Space and time variations of the runoff of Kamchatka Krai rivers

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).     

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.     

Hydrological and morphological processes in Senegal River mouth area

The main features of the structure and water regime of the mouth area of the Senegal River and their changes caused by river regulation in its upper reaches and within its delta area are considered. Data on water and sediment runoff of the Senegal River and their variations along the river are specified. River runoff was found to dramatically decrease in recent decades because of a drought. Zoning of river mouth area was carried out, and morphological processes in its estuary, in particular, the formation of a new outlet of the river into the ocean with the formation of a lagoon, are described.     

Transformation of estimated characteristics of the annual and maximal runoff in the major tributaries of Lake Baikal

Hydrometric data of recent years were used to evaluate the parameters of distribution of the annual and maximal runoff in the major tributaries of Lake Baikal: the Selenga, Upper Angara, and Barguzin. The estimates of the mean water content, maximal water discharges of spring flood and rain freshets were obtained. The comparison with analogous data of an earlier period often shows significant difference. Variations of the characteristics under consideration are taking place against the background of warming in the region since the early 1970s. The results of the current transformation of river runoff variations is a change in Baikal water regime, which determines the restructuring of hydrological processes in the lake.     

Changes to flood peaks of a mountain river: implications for analysis of the 2013 flood in the Upper Bow River,Canada

The mountain headwater Bow River at Banff, Alberta, Canada, was subject to a large flood in June 2013, over which considerable debate has ensued regarding its probability of occurrence. It is therefore instructive to consider what information long‐term streamflow discharge records provide about environmental change in the Upper Bow River basin above Banff. Though protected as part of Banff National Park, since 1885, the basin has experienced considerable climate and land cover changes, each of which has the potential to impact observations, and hence the interpretations of flood probability. The Bow River at Banff hydrometric station is one of Canada's longest‐operating reference hydrological basin network stations and so has great value for assessing changes in flow regime over time. Furthermore, the station measures a river that provides an extremely important water supply for Calgary and irrigation district downstream and so is of great interest for assessing regional water security. These records were examined for changes in several flood attributes and to determine whether flow changes may have been related to landscape change within the basin as caused by forest fires, conversion from grasslands to forest with fire suppression, and regional climate variations and/or trends. Floods in the Upper Bow River are generated by both snowmelt and rain‐on‐snow (ROS) events, the latter type which include flood events generated by spatially and temporally large storms such as occurred in 2013. The two types of floods also have different frequency characteristics. Snowmelt and ROS flood attributes were not correlated significantly with any climate index or with burned area except that snowmelt event duration correlated negatively to the Pacific Decadal Oscillation. While there is a significant negative trend in all floods over the past 100 years, when separated based on generating process, neither snowmelt floods nor large ROS floods associated with mesoscale storms show any trends over time. Despite extensive changes to the landscape of the basin and in within the climate system, the flood regime remains unchanged, something identified at smaller scales in the region but never at larger scales. Copyright © 2016 John Wiley & Sons, Ltd.     

Modeling of variations in river runoff on the East European Plain under different climates of the past

The results of modeling of the annual river runoff on the East European Plain, performed with the help of atmospheric general circulation models for the conditions of the present-day climate, the Atlantic Optimum of the Holocene, and the Cryochrone of the Late Pleistocene, are analyzed. The quality of modeling the present-day climate is assessed; the spatial scales, within which the model results are appropriate for using in hydrological calculations, are determined. The genesis of variations in the river runoff on the East European Plain in the epochs of the Holocene Optimum and Late-Pleistocene Cryochrone is investigated.     

Simulated runoff responses to land use in the middle and upstream reaches of Taoerhe River basin,Northeast China,in wet,average and dry years

Study on runoff variations and responses can lay a foundation for flood control, water allocation and integrated river basin management. This study applied the Soil and Water Assessment Tool model to simulate the effects of land use on annual and monthly runoff in the Middle and Upstream Reaches of Taoerhe River basin, Northeast China, under the wet, average and dry climate conditions through scenario analysis. The results showed that from the early 1970s to 2000, land use change with an increase in farmland (17.0%) and decreases in forest (10.6%), grassland (4.6%) and water body (3.1%) caused increases in annual and monthly runoff. This effect was more distinct in the wet season or in the wet year, suggesting that land use change from the early 1970s to 2000 may increase the flood potential in the wet season. Increases in precipitation and air temperature from the average to wet year led to annual and monthly (March and from June to December) runoff increases, while a decrease in precipitation and an increase in air temperature from the average to dry year induced decreases in annual and monthly (all months except March) runoff, and moreover, these effects were more remarkable in the wet season than those in the dry season. Due to the integrated effects of changing land use and climate conditions, the annual runoff increased (decreased) by 70.1 mm (25.2 mm) or 197.4% (71.0%) from the average to wet (dry) year. In conclusion, climate conditions, especially precipitation, played an important role in runoff variations while land use change was secondary over the study area, and furthermore, the effects of changes in land use and/or climate conditions on monthly runoff were larger in the wet season. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrological processes at an Arctic river mouth: Case study of the Colville River, Alaska, USA

Data on the Colville River mouth (Alaska, USA) are used to discuss the regularities in hydrological processes taking place in river mouth areas, functioning under extreme arctic conditions. Seasons and periods are recognized in the annual cycle of the Colville river mouth hydrologic regime. A thick ice cover commonly forms in winter in the river, its delta distributaries, and the offshore zone. Water salinity in under-ice water in the distributaries and near-delta river reach appreciably increases in late winter. The spring flood is very short; in this period, snowmelt water propagates toward the ocean first over ice and next under it. A wedge of freshened waters forms in the nearshore zone above fast ice. River runoff abruptly drops in the summer-autumn low-water period. The morphological processes in the distributaries and some ecological conditions in the delta are also discussed.     

The hydrological regime of large river basins in Northern Eurasia in the XX–XXI centuries

The ability of present-day climate models to reproduce the mean annual regime of river runoff and its within-year distribution is evaluated for major Eurasian basins, including the basins of the Volga and Amur and the major Siberian rivers: the Ob, Yenisei, and Lena. Estimates are made for possible variations in seasonal runoff and characteristics of daily precipitation (the amount, rate, and probability) in drainage areas for the late XXI century. The analysis involved the use of the results of calculations by climatic general circulation models carried out under international Coupled Model Intercomparison Project.     

Annual distribution of river runoff with estimated contribution of winter low-water season

Proportions of the overland, delayed, and groundwater runoff are given for different phases of the hydrological regimes of rivers under different landscape–climate conditions in Russia. The concept of runoff hydrological regime is in agreement with the formation features of the annual and seasonal runoff on small watersheds under current climate conditions. The increase in winter runoff is due to the impulse discharge regime of soil water and groundwater, which receive additional recharge during frequent thaws and at weak freezing of the aeration zone. Variations in the values of runoff, total precipitation, and mean temperature were shown to be both synchronous and periodic.     

Effect of Permafrost Rocks on Water Resources Formation in Eastern Siberia: Case Study of Some Rivers in Eastern Siberia

The study is focused on the specific features of water resources formation in Eastern Siberia under variable climate and regional occurrence of permafrost rocks. Expert estimates are given to the effect of greenhouse gas emissions on climate evolution in this large region. Under present-day climate conditions, featuring temperature rise and some increase in precipitation as resource-forming factors, the most significant changes are shown to have taken place in the formation of water resources and regime of dry-season runoff in individual rivers of Eastern Siberia, including the Lena, Indigirka, Kolyma, etc. Present-day resources of surface water and groundwater resources in the region are mapped and the dynamics of the annual and dryseason runoff of the rivers are plotted.     

Exposure of inner-shelf reefs to nutrient enriched runoff entering the Great Barrier Reef Lagoon: post-European changes and the design of water quality targets

We used historical flood plume extent data (modelled) to quantify the typical spatial extent of the summer runoff-seawater mixing zone of the Great Barrier Reef (GBR) lagoon. Spatially explicit analysis of the variability of in situ chlorophyll a concentrations (observed) across the runoff-seawater mixing zone, then allowed us to explore regional differences in the nutrient enrichment impact of runoff events from the various river systems that drain the GBR catchment. We demonstrate the existence of a discernable north-south gradient along the length of the GBR, such that for equivalent runoff:seawater dilutions ratios, lower levels of nutrient enrichment (as indicated by chlorophyll alpha observations) result from the river systems that drain the relatively undisturbed northern areas of the GBR catchment, compared to more human-impacted central and south areas. We identify a strong correlation between this north-south enrichment gradient and the flood concentration of dissolved inorganic nitrogen (DIN) entrained by the various river systems. By substituting the nutrient enrichment characteristics of the human-impacted river discharges with those of the undisturbed northern rivers, we provide a means to compare the short-term enriching 'footprint' for existing runoff intrusions with those that are likely to have occurred under pre-European catchment conditions. We demonstrate that under pre-European conditions, the nutrient enriching impact from river runoff was likely to have been largely constrained within 1-2 km of the coast, whereas existing conditions support the impact of reefs some 20-30 km off the coast. By using the developed spatial relations, we show that for the heavily human-impacted river systems, reductions in the end-of-river concentrations of DIN in the order 50-80% are needed in order to restore parity with pre-European conditions. We discuss these results in regard to developing end-of-catchment water quality targets for the region.     

Hydrological–morphological processes in the mouth area of the Congo R. and the effect of submarine canyon on these processes

The general geographic, hydrographic, climatic, and hydrological characteristics of the Congo R. basin are considered. The major features of the riverine and marine factors that have their effect on the hydrological regime and morphology of the delta and estuary of the Congo R. are identified; the effect of a submarine canyon on the morphological features of the estuary is analyzed in detail; and changes in river delta structure in the XX century and currently are considered. The hydrological—morphological characteristics of the largest mouths of African rivers, the formation conditions of water and sediment runoff, and variations of their deltas are compared.     

Formation of surface water quality in the basin of the upper reaches of the ural river under technogenic transformation of the environment

The natural conditions and the anthropogenic factors governing the formation of the environmental-hydrochemical situation in the rivers of the upper part of Ural R. basin are analyzed. Pollution transport is partially taking place under the conditions of hampered water exchange, caused by the structure of river channels and runoff regulation. The study confirms the uneven distribution of heavy metal concentrations in river water in different seasons, which is mostly due to differences in river runoff characteristics. The long duration and the high intensity of anthropogenic impact have considerably weakened the stability of river systems.