Reservoirs in the Drainage Basins of Russian Arctic Seas

Water Resources - The space and time distribution of reservoirs over the drainage basins of Arctic seas within Russian Federation territory and the main rivers flowing into the Arctic Ocean is...     

Analysis of river runoff in the Poyang Lake Basin of China: long-term changes and influencing factors

An analysis of the variation characteristics and evolutionary trends in the runoff of five rivers in the Poyang Lake Basin was conducted using the MK trend test, Morlet wavelet transforms, correlation analyses, and other methods. For 1956–2011, the inflow runoff displays small, statistically insignificant trends. However, for 2000–2011, significant downward trends are present. River runoff in the basin is significantly correlated with precipitation, while water intake and use is less influential; the most significant impact on river runoff is climate variability. To analyse the effects of water conservancy project scheduling and operation, we also compare the inflow and outflow runoff processes of typical large reservoirs before and after peak reservoir construction. The scheduling and operation of large reservoirs in the five rivers is known to play a supplementary role in dry season inflow runoff. The recent reduction in inflow runoff was mainly caused by basin precipitation; reasonable scheduling of water conservancy projects in the five rivers plays a positive role in safeguarding the water required by the dry season ecosystem in Poyang Lake.     

Controls on Arctic glacier-fed river water temperature

The impact of climate change on Arctic rivers is expected to be severe. There is therefore a need for greater understanding of Arctic river temperature processes. This study quantifies the spatio-temporal variability of water temperatures in the Kårsa River, Sweden. Water temperature was monitored over two summers within the main proglacial channel and within braids fed by different sources. Longitudinal and lateral temperature patterns were assessed in relation to prevailing hydro-meteorology. Temperature metrics in the main channel increased with distance downstream but were moderated by a large lake, while temperatures in the braids were dependent upon channel source. The high temperature standard deviation and inter-site differences within the braids highlight the importance of braided channels for creating thermal habitat heterogeneity. Temperatures were dependent on hydro-meteorological conditions, with sensitivity to air temperature maximized during cooler, rainy conditions. These results shed new light on Arctic river temperature patterns and their controlling processes.     

Anthropogenic transformations of the hydrological-ecological state of rivers in the Russian Arctic

The dynamics of time and space variations in the composition of the aquatic medium is estimated and correlated with the governing factors of anthropogenic impact. The role of anthropogenic component is shown to be determining in the formation of the hydrochemical regime in Russian Arctic rivers.     

Analysis of trends in annual streamflow to the Arctic Ocean

There is increasing interest in the magnitude of the flow of freshwater to the Arctic Ocean due to its impacts on the biogeophysical and socio‐economic systems in the north and its influence on global climate. This study examines freshwater flow based on a dataset of 72 rivers that either directly or indirectly contribute flow to the Arctic Ocean or reflect the hydrologic regime of areas contributing flow to the Arctic Ocean. Annual streamflow for the 72 rivers is categorized as to the nature and location of the contribution to the Arctic Ocean, and composite series of annual flows are determined for each category for the period 1975 to 2015. A trend analysis is then conducted for the annual discharge series assembled for each category. The results reveal a general increase in freshwater flow to the Arctic Ocean with this increase being more prominent from the Eurasian rivers than from the North American rivers. A comparison with trends obtained from an earlier study ending in 2000 indicates similar trend response from the Eurasian rivers, but dramatic differences from some of the North American rivers. A total annual discharge increase of 8.7 km³/y/y is found, with an annual discharge increase of 5.8 km³/y/y observed for the rivers directly flowing to the Arctic Ocean. The influence of annual or seasonal climate oscillation indices on annual discharge series is also assessed. Several river categories are found to have significant correlations with the Arctic Oscillation, the North Atlantic Oscillation, or the Pacific Decadal Oscillation. However, no significant association with climate indices is found for the river categories leading to the largest freshwater contribution to the Arctic Ocean.     

Impact of cascade reservoirs on continuity of river water temperature: A temperature trend hypothesis in river

Water temperature is an important habitat factor in river ecosystems that exhibits the characteristics of continuous change. Dam construction disrupts the continuity of river water temperature and reset it, thus exerting sharp rise/decrease on the characteristics of water temperature change. The effect of a dam on river continuity is directly related to the dam size. To explain this relationship, two rivers in China were selected: one river without reservoirs and one river with cascade reservoirs. Through the analysis of the longitudinal change of water temperature in free-flowing rivers, we found that water temperature changes continuously and steadily in the longitudinal direction. Based on this, a temperature trend hypothesis in river was proposed, and the discontinuity of the water temperature in the reservoir section was evaluated. The results are as follows: (1) In mixed reservoirs, river water temperature remained as continuous as free-flowing rivers. However, the river water temperature had a large discontinuity in the stratified reservoir. (2) Water residence time was used as an indicator of the continuity of reservoir water temperature. (3) Selective withdrawal of stratified reservoirs in January could not remove the discontinuity caused by itself, but it worked in June.     

What about reservoirs? Questioning anthropogenic and climatic interferences on water availability

Water resources in semi-arid regions like the Mediterranean Basin are highly vulnerable because of the high variability of weather systems. Additionally, climate change is altering the timing and pattern of water availability in a region where growing populations are placing extra demands on water supplies. Importantly, how reservoirs and dams have an influence on the amount of water resources available is poorly quantified. Therefore, we examine the impact of reservoirs on water resources together with the impact of climate change in a semi-arid Mediterranean catchment. We simulated the Susurluk basin (23.779-km²) using the Soil and Water Assessment Tool (SWAT) model. We generate results for with (RSV) and without reservoirs (WRSV) scenarios. We run simulations for current and future conditions using dynamically downscaled outputs of the MPI-ESM-MR general circulation model under two greenhouse gas relative concentration pathways (RCPs) in order to reveal the coupled effect of reservoir and climate impacts. Water resources were then converted to their usages – blue water (water in aquifers and rivers), green water storage (water in the soil) and green water flow (water losses by evaporation and transpiration). The results demonstrate that all water resources except green water flow are projected to decrease under all RCPs compared to the reference period, both long-term and at seasonal scales. However, while water scarcity is expected in the future, reservoir storage is shown to be adequate to overcome this problem. Nevertheless, reservoirs reduce the availability of water, particularly in soil moisture stores, which increases the potential for drought by reducing streamflow. Furthermore, reservoirs cause water losses through evaporation from their open surfaces. We conclude that pressures to protect society from economic damage by building reservoirs have a strong impact on the fluxes of watersheds. This is additional to the effect of climate change on water resources.     

Reproductive seasonality of the fish fauna and limnoecology of semi-arid Brazilian reservoirs

The native fish fauna commonly found in the drainage basins of rivers and reservoirs of Latin America, including those of the semi-arid Northeastern Brazil, are representatives of the Neotropical region. This work reports on the reproductive ecology of five commercially important and consumable native fish species, in relation to rainfall and hydrological variables of the semi-arid reservoirs in Brazil. Pluviometric precipitation, temperature, pH, dissolved oxygen and electrical conductivity of the water were registered, and maturation of fish gonads was assessed on a monthly basis. This region is characterized with short spells of rain interspersed with long dry season and rainfall seems to be the main environmental factor which modulates the timing of the spawning period of fish. Construction of reservoirs without adequate facilities for fish migration has an adverse impact on the migratory fish species which are of commercial and ecological importance to semi-arid Northeastern Brazil.     

Arctic Climate and Water Change: Model and Observation Relevance for Assessment and Adaptation

The Arctic is subject to growing economic and political interest. Meanwhile, its climate and water systems are in rapid transformation. In this paper, we review and extend a set of studies on climate model results, hydro-climatic change, and hydrological monitoring systems. Results indicate that general circulation model (GCM) projections of drainage basin temperature and precipitation have improved between two model generations. However, some inaccuracies remain for precipitation projections. When considering geographical priorities for monitoring or adaptation efforts, our results indicate that future projections by GCMs and recent observations diverge regarding the basins where temperature and precipitation changes currently are the most pronounced and where they will be so in the future. Regarding late twentieth-century discharge changes in major Arctic rivers, data generally show excess of water relative to precipitation changes. This indicates a possible contribution to sea-level rise of river water that was previously stored in permafrost or groundwater. The river contribution to the increasing Arctic Ocean freshwater inflow is similar in magnitude to the separate contribution from glaciers, which underlines the importance of considering all possible sources of freshwater when assessing sea-level change. We further investigate monitoring systems and find a lack of harmonized water chemistry data, which limits the ability to understand the origin and transport of nutrients, carbon and sediment to the sea. To provide adequate information for research and policy, Arctic hydrological and hydrochemical monitoring needs to be extended, better integrated and made more accessible. Further water-focused data and modeling efforts are required to resolve the source of excess discharge in Arctic rivers. Finally, improvements in climate model parameterizations are needed, in particular for precipitation projections.     

Temporal and spatial characteristics of dissolved organic carbon in the Wujiang River,Southwest China

River systems play an important role in the global carbon cycle. Rivers transport carbon to the ocean and also affect the carbon cycle in the coastal ocean. The flux from land to the ocean is thought to be a very important part of the land carbon budget. To investigate the effect of dam-building on dissolved organic carbon(DOC)in rivers, three reservoirs of different trophic states in the Wujiang basin, Guizhou Province, were sampled twice per month between May 2011 and May 2012. Temporal and spatial distributions of DOC in the reservoirs and their released waters were studied. It was found that different factors controlled DOC in river water, reservoir water, and released water. DOC in the rivers tended to be affected by primary production. For reservoirs, the main controlling factors of DOC concentration varied by trophic state. For the mesotrophic Hongjiadu Reservoir, the effect of primary production on DOC concentration was obvious. For the eutrophic Dongfengdu Reservoir and the hypereutrophic Wujiangdu Reservoir, primary production was not significant and DOC came instead from soil and plant litter.     

On the flux of water and sediment into the Northern Adriatic Sea

This paper focuses on the delivery of water and sediment to the northern Adriatic to better understand the short-term evolution of continental margin sedimentation under natural and human impact. For that reason, the Po and six Apennine rivers (Metauro, Musone, Potenza, Tronto, Chienti and Pescara) are investigated. The climate-driven hydrological model HydroTrend is used to simulate discharge and sediment loads where observational data are limited. The northern Apennine hinterland has a significant impact on the sediment flux leaving the Po River, contributing 56% of the sediment it delivers to the Adriatic Sea. The Po River experienced a strong decrease in its sediment load (17.2–6.4 Mt/yr) across 1933–1987, in contrast to a small increase in its water discharge. The rivers draining the southern Apennine hinterland contribute more than 50% of the sediment load entering the Adriatic Sea, and this is in spite of human modification of their discharge through numerous small reservoirs that invariably reduce a river's sediment load. As a result, hyperpycnal flows, which historically carried 20–40% of the sediment flux from these Apennine rivers, become rare. Sediment load reduction is also reflected by retreat of the Apennine coastline. Based on the ART model (used in HydroTrend), the total sediment load to the northern Adriatic is 43 MT/yr where the northern Alpine rivers contribute 8 MT/yr, the Po River 13 MT/yr and the Apennine rivers contribute 22 MT/yr.     

Climatic and geographic patterns of river runoff formation in Northern Eurasia

Siberian rivers are of global importance as they impact on the freshwater budget of the Arctic Ocean, which affects the Thermo-Haline circulation in the North Atlantic Ocean. Siberian rivers, in particular the tributaries to the larger rivers, are under-represented in the international river-regime databases. The runoff of three Russian rivers in the Central Siberian taiga (Kureyka, Karabula and Erba) is modelled to analyse the relative influence of climate. In addition three rivers (Rhine, Maas and Odra) in Western Europe are similarly assessed as a control. The results show that the role of precipitation and autocorrelation as factors in the formation of river runoff is stronger under oceanic climate conditions, increasing from the central regions of Northern Eurasia towards the Arctic Ocean in the North and the Atlantic in the West. At the same time the influence of summer temperatures is weakened. The formation of Northern Eurasian river runoff appears to be influenced by periodically thawing top horizons of permafrost soil. Time served as an indicator for land use change after inclusion of meteorological data in the models. Maas and Erba showed a significant influence of the time factor. For the Erba the onset of agricultural land use in the catchment coincides with a drop in runoff. A similar causal relationship is suggested for the Maas. Land use can change the formation of runoff, which in turn can be used as an environmental indicator for sustainable land use.     

Dynamics of the Yenisei and Pur River Deltas

Variations in the mouth areas of the Yenisei and Pur rivers over the period of 50 years were revealed on the basis of comparison of topographic maps prepared in the 1950s and space images made from the Landsat satellite in 1973 (MSS System) and 1999, 2000 (ETM System). Maps of the drainage network dynamics were compiled; they show that, over a period of many years, mouth areas of northern rivers undergo slow but steady changes, which are indicative of the continuing protrusion of deltas into bays at a rate up to 20 m/year, the increment in mouth areas reaching 0.05–0.07% a year. As noted, secondary water streams die off under the condition of flow concentration in main branches, and small islands get integrated. It was found that, over the period under study, natural variations in the level of the receiving water body and human-induced changes in river basins (construction of a chain of reservoirs) did not have considerable impact on dynamic processes occurring in deltas.     

Conceptualizing delta forms and processes in Arctic coastal environments

Climate warming in the Arctic directly causes two opposite changes in Arctic coastal systems: increased melt‐water discharge through rivers induces extra influx of sediments and extended open water season increases wave impact which reworks and erodes the shores. A shoreline change analysis along the southern coast of Disko Island in western Greenland was conducted with aerial photographs and satellite images from 1964, 1985, and 2012. The decadal morphologic evolution of this 85 km section showed that large parts of the coast had undergone very limited changes. However, two deltas were highly dynamic and popped up as hotspots. The Tuapaat delta and Skansen delta showed large progradation rates (1.5 and 7 m/yr) and migration of the adjacent barriers and spits. The dynamic behavior at the delta mouths was mainly caused by classic delta channel lobe switching at one delta (Tuapaat), and by a breach of the fringing spit at the other delta (Skansen). The longshore and cross‐shore transports are responsible for reworking the sediment with a result of migrating delta mouths and adjacent subaqueous mouth bars. Seaward progradation of the deltas is limited due to the steep nature of the bathymetry in Disko Bay. Finally, a schematic conceptual overview of processes and associated morphological responses for deltas in Arctic environments is presented, including the climate drivers affecting delta evolution. Copyright © 2016 John Wiley & Sons, Ltd.     

Biogeochemical responses over 37 years to manipulation of phosphorus concentrations in an Arctic river: The Upper Kuparuk River Experiment

The climate of the Arctic region is changing rapidly, with important implications for permafrost, vegetation communities, and transport of solutes by streams and rivers to the Arctic Ocean. While research on Arctic streams and rivers has accelerated in recent years, long-term records are relatively rare compared to temperate and tropical regions. We began monitoring the upper Kuparuk River in 1983 as part of a long-term, low-level, whole-season phosphorus enrichment of a 4–6 km experimental reach, which was subsequently incorporated into the Arctic Long-Term Ecological Research (Arctic LTER) programme. The phosphorus enrichment phase of the Upper Kuparuk River Experiment (UKRE) ran continuously for 34 seasons, fundamentally altering the community structure and function of the Fertilized reach. The objectives of this paper are to (a) update observations of the environmental conditions in the Kuparuk River region as revealed by long-term, catchment-level monitoring, (b) compare long-term trends in biogeochemical characteristics of phosphorus-enriched and reference reaches of the Kuparuk River, and (c) report results from a new ‘ReFertilization’ experiment. During the UKRE, temperature and discharge did not change significantly, though precipitation increased slightly. However, the UKRE revealed unexpected community state changes attributable to phosphorus enrichment (e.g., appearance of colonizing bryophytes) and long-term legacy effects of these state changes after cessation of the phosphorus enrichment. The UKRE also revealed important biogeochemical trends (e.g., increased nitrate flux and benthic C:N, decreased DOP flux). The decrease in DOP is particularly notable in that this may be a pan-Arctic trend related to permafrost thaw and exposure to new sources of iron that reduce phosphorus mobility to streams and rivers. The trends revealed by the UKRE would have been difficult or impossible to identify without long-term, catchment level research and may have important influences on connections between Arctic headwater catchments and downstream receiving waters, including the Arctic Ocean.     

Cd, Cr, Cu, Ni and Pb in the water column and sediments of the Ob-Irtysh Rivers, Russia

Concentrations of Cd, Cr, Cu, Ni and Pb were determined in filtered water, suspended particulate matter, and bottom sediments from a 2000 km section of the Ob and Irtysh Rivers. Dissolved Cd, Cr, Cu and Ni concentrations are similar to, or higher than, results from other Russian Arctic and large world river-estuaries. Concentrations of Cd, Cr, Cu, Ni and Pb in suspended particulate matter are generally comparable to results from other Russian Arctic and large world rivers and estuaries. Comparison of trace metal ratios in crustal material and suspended particulate matter and bottom sediment suggests that the source of Cr, Cu and Ni is continental weathering. Particulate Cd and Pb are elevated relative to their crustal abundance, suggesting a source of these metals to the Ob-Irtysh in addition to continental weathering.     

Analysis of Many-Year Variations in River Runoff into the Arctic Ocean

Statistical analysis of long-term hydrological observations has shown that the interannual variations in the total river runoff into the Arctic Ocean can be considered as a stationary process. Similar are the variations in the annual runoff of the Ob, Lena, and rivers of the northwestern Asia. However, some components of the total runoff into the Arctic Ocean feature distinct and fairly complicated disturbances in the homogeneity of runoff variations. For example, variations in the annual runoff of the Yenisei River have a distinct nonmonotonic trend: the runoff systematically decreased till the late 1950s and increased since the late 1960s. The rivers of the European part of the Arctic Ocean drainage basin featured a decrease in the amplitude of variations in runoff during the past decades. Rivers of the northwestern America and northeastern Asia featured a regular increase in the amplitude of runoff variations and their autocorrelation since the late 1960s.     

滨海地区基于避咸蓄淡模式的供水安全临界流量研究——以粤港澳大湾区珠澳供水为例

枯水期咸潮入侵已经严重威胁到了感潮河流区域供水安全.本文通过构建避咸蓄淡供水模型,耦合了咸度预测、河库联合供水调度和供水安全分析模块,为依赖感潮河流为水源地的区域供水安全管理提供了一种整体思路和决策方法.以面向粤港澳大湾区珠海东部及澳门的珠江三角洲磨刀门水道取供水为例,基于潮汐、径流和风等因子及咸度实测数据,较好地拟合了基于BP神经网络的咸度预测模型,及含氯度与超标时间的曲线函数,建立了上游来水和咸度超标时间之间的联系,得到了避咸蓄淡取水时机.咸度预测与当地河库联合供水调度相结合,得到了上游枯水期来水过程的当地区域供需平衡状况.枯水期不考虑水库调蓄的资源性缺水临界需水量为3.22亿m³,水库参与调蓄的工程性缺水临界需水量为3.75亿m³.通过供水安全分析模块,基于设定的风险阈值和临界阈值识别出了不同需水规模的上游来水临界流量特征.对于当地规划的需水规模4.23亿m³,期望上游枯水期临界流量均值约为3372 m³/s.整体上来说,需水规模越大,对上游来水期望的临界流量越大,但同时还与枯水期流量分布有关.