Nival Regime Research Articles

Recent multi-year streamflow regimes and water budgets of hillslope catchments in the Canadian High Arctic: evaluation and comparison to other small Arctic watershed studies

This study evaluates whether a recent decline in snowcover extent for circumpolar regions is matched by changes in the seasonal streamflow regime of several small hillslope catchments on Bathurst and Melville Islands. This includes shifts in the timing of initiation, peak discharge and impacts on the spring–summer water budgets. Paired catchments (West and East) at the Cape Bounty Arctic Watershed Observatory (CBAWO) on Melville Island (74.9°N, 109.5°W) have been studied from the pre-snowmelt season to early August since 2003. They are low-rolling tundra catchments between 8.0 and 11.6 km2 in area. Likewise, within the Polar Bear Pass (PBP) watershed, Bathurst Island (75.7°N 98.7°W), two hillslope basins, Windy Creek (4.2 km2) and Landing Strip Creek (0.2 km2) have been investigated since 2007. Detailed snow surveys were conducted each spring and streamflow estimates were made using the mid-section velocity method. Nival regimes continue to dominate in these basins but runoff ratios are variable between catchments, across islands, and from year-to-year. In comparison to earlier streamflow studies across the Queen Elizabeth Islands (QEIs), an earlier response to peak discharge and start of flow for these hillslope streams is confirmed. Water budgets for PBP, CBAWO differ from other small Arctic watersheds.

Hyperconcentrated flows on a forested alluvial fan of eastern Canada: geomorphic characteristics, return period, and triggering scenarios

ABSTRACTThe assessment of the dominant flow type on alluvial fans usually refers to two categories: debris‐flow fans (i.e. sediment gravity flows) and fluvial fans (i.e. fluid gravity flows). Here we report the results of combined morphometric, stratigraphic and sedimentological approaches which suggest that hyperconcentrated flows, a transitional process rheologically distinct from debris flows and floods and sometimes referred to as debris floods, mud floods, or transitional debris flows, are the dominant fan building process in eastern Canada. These flows produce transitional facies between those of debris flows which consist of a cohesive matrix‐supported diamicton, and those of river flows which display more distinct stratification. The size of the blocks in the channels and the abrasion scars at the base of several trees attest to the high transport capacity of these flows. The fan channels are routed according to various obstacles comprised primarily of woody debris that impede sediment transit. However, these conditions of sediment storage are combined with readily available sediment due to the friable nature of the local lithology. Tree‐ring analysis allowed the reconstruction of eight hydrogeomorphic events which are characterized by a return period of 9.25 years for the period 1934–2008, although most of the analyzed events occurred after 1970. Historical weather data analysis indicates that they were related to rare hydrometeorological events at regional and local scales. This evidence led to the elaboration of weather scenarios likely responsible for triggering flows on the fan. According to these scenarios, two distinct hydrologic regimes emerge: the torrential rainfall regime and the nival regime related to snowmelt processes. Hydrogeomorphic processes occurring in a cold‐temperate climate, and particularly on small forested alluvial fans of north‐eastern North America, should receive more attention from land managers given the hazard they represent, as well as because of their sensitivity to various meteorological parameters. Copyright © 2014 John Wiley & Sons, Ltd.

Implications of climate change scenarios for agriculture in alpine regions — A case study in the Swiss Rhone catchment

Coping with climate change in agriculture requires knowledge of trends in agro-climatic conditions with a focus at the smaller scales where decisions are taken. As part of the EU FP7 ACQWA project, the situation was analyzed for agriculture in the case of the Swiss Rhone catchment (Valais) where cultivation of permanent crops (orchards and vineyards) and livestock production are the most important agro-economic activities. The aim of this study was to use daily data from four downscaled and bias corrected transient climate change scenarios to analyze changes in water and temperature related indices over the period 1951–2050 for three locations (Aigle, Sion, Montana) that are representative of different production zones in the catchment. The results indicate that most relevant implications are caused by projected changes in temperature and not in precipitation. They indicate an extension of the thermal growing season with potentially positive effects on pasture and livestock production, most pronounced at the mountain site (Montana), but a trend towards increasing risks of frost in permanent crops and in heat stress for livestock at the valley bottom (Aigle, Sion). The increase in water requirement for irrigation in 2021–2050 relative to 1981–2009 is moderate (4–16%, depending on location). However, in years with low amounts of snow and rain, in small catchments with a nival regime, reduced water supply by rivers could restrict the surface area of grassland that can be irrigated, particularly during springtime. It is concluded that coping with heat-related risks may be most needed at the lower cropland and pasture sites while water-related issues would become more relevant in more elevated locations where pasture-based livestock production is the dominant type of agricultural land use.

Prediction of stream‐flow regime using ecological classification zones

AbstractHydrologic classification is useful for data organization, transfer of model parameters and estimation of hydrologic sensitivity to disturbance and climatic change. Stream‐flow regime has frequently been used as a basis for classification, typically by mapping regimes defined by stream‐flow data from a gauging network. As an alternative, we hypothesized that ecological classification systems can predict stream‐flow regime because they are based on the same characteristics that control run‐off generation (soils, climate and topography). A multivariate regression tree (MRT) was used to relate stream‐flow regime to the fractional coverages of the Biogeoclimatic Ecological Classification (BEC) zones within the catchment for gauged streams in British Columbia, Canada. Although the MRT identified a realistic set of regimes, only a small number of BEC zones were used as predictors, reflecting bias in the gauging network. To avoid this bias, we used a water balance model to compute mean monthly stream flow for 932 ungauged basins in British Columbia that were generated with areas between 10 and 1000 km2; these monthly stream flows were used to train an MRT model based on BEC zone coverages. This model predicted the regime at gauged basins nearly as accurately as the water balance model for pluvial, nival and glacier‐supported nival regimes. Difficulties occurred in smaller basins and in specific regions where the local BEC zones were not included as predictors. Coastal hybrid nivo–pluvial regimes were poorly predicted. With further development, ecological classification systems could have great value as a tool for hydrologic classification for both research and operational applications. Copyright © 2013 John Wiley & Sons, Ltd.

Impacts of climate change in three hydrologic regimes in British Columbia, Canada

Hydrologic modelling has been applied to assess the impacts of projected climate change within three study areas in the Peace, Campbell and Columbia River watersheds of British Columbia, Canada. These study areas include interior nival (two sites) and coastal hybrid nival–pluvial (one site) hydro-climatic regimes. Projections were based on a suite of eight global climate models driven by three emission scenarios to project potential climate responses for the 2050s period (2041–2070). Climate projections were statistically downscaled and used to drive a macro-scale hydrology model at high spatial resolution. This methodology covers a large range of potential future climates for British Columbia and explicitly addresses both emissions and global climate model uncertainty in the final hydrologic projections. Snow water equivalent is projected to decline throughout the Peace and Campbell and at low elevations within the Columbia. At high elevations within the Columbia, snow water equivalent is projected to increase with increased winter precipitation. Streamflow projections indicate timing shifts in all three watersheds, predominantly because of changes in the dynamics of snow accumulation and melt. The coastal hybrid site shows the largest sensitivity, shifting to more rainfall-dominated system by mid-century. The two interior sites are projected to retain the characteristics of a nival regime by mid-century, although streamflow-timing shifts result from increased mid-winter rainfall and snowmelt, and earlier freshet onset. Copyright © 2012 John Wiley & Sons, Ltd.

Hydro-meteorological trends in semi-arid north-central Chile (29–32°S): water resources implications for a fragile Andean region

Changes in hydro-meteorological historical records are of considerable importance for future planning. This study analyses trends of hydro-climatological indices of annual and seasonal precipitation, temperature and discharge in the “Norte Chico” region of Chile (29–32°S), located in the Central Andes. It addresses how these trends possibly impacted on the water resources in a nival regime, typical for arid mountainous regions. Homogenous records were tested against monotonic trends using the non-parametric rank-based Mann-Kendall test. The results suggested, at a very high confidence level, a strong warming signal trend over recent decades, consistent at the annual and seasonal levels. Furthermore, warmer days are observed in summer, especially at higher elevations. The region also experienced a shift in the rainy season over the last 42 years. However, an increase in precipitation was observed over recent decades, whereas an annual decrease was the general tendency when the whole century was considered. Changes in discharge were not unequivocal and glacier retreat has been compensated for possibly by an increase in snowmelt in recent years. Hence, in an under-studied area, from the hydrological perspective, this work provides some insights for a better understanding of changing hydrological processes in the mid-latitude Andes Cordillera. Editor Z. W. Kundzewicz Citation Souvignet, M., Oyarzún, R., Verbist, K.M.J., Gaese, H. and Heinrich, J., 2012. Hydro-meteorological trends in semi-arid north-central Chile (29–32°S): water resources implications for a fragile Andean region. Hydrological Sciences Journal, 57 (3), 479–495.

Detection of dual effects of degradation of perennial snow and ice covers on the hydrologic regime of a Himalayan river basin by stream water availability modeling

Summary In river basins where melt water from snow and ice constitutes a dominant component of stream discharge during summer, degradation or reduction of perennial snow and ice covered areas ( SCA P ) has a profound effect on stream water availability in those basins. Degradation of SCA P that includes glaciers is a globally widespread phenomenon observed in the recently past decades; its cause has been attributed to global warming and its consequence is expected to dramatically alter the flow regimes of the rivers draining the terrains. The predicted change in flow regime is an initial increase in summer flows in the early decades of 21st century followed by sharp decline of the same during the later parts of the century. Estimation of SCA P within the Upper Indus Basin (UIB), straddling the western ranges of the Greater Himalayas, Karakoram Mountains, and the eastern mountain ranges of the Hindu Kush, shows that from 1992 to 2010 there has been about 2.15% reduction in SCA P . A spatially distributed basin-scale stream water availability model is presented to calculate monthly river discharges at critical hydrologic junctions within UIB. Model calculations for the years 1992, 2000, and 2008, show that due to the degradation of the SCA P within the basin, there has been significant decrease in summer discharges at various hydrologic junctions. The percentage decline in flows varies from 10% to 22%, depending on the locations of the junctions within the basin. The space-dependence of these variations reflects differential degradation of SCA P in various parts of the basin. Furthermore, the time of peak discharge at all of the hydrological junctions has shifted from middle/late summer to late spring/early summer as another outcome of SCA P reduction. Such temporal shifting of nival regimes to early part of warmer season has also been predicted by global warming models. However, the case study presented here for a major Himalayan river basin demonstrates that such shifting of peak discharge in the time domain can also take place simply due to retreat of the equilibrium line. Thus, the effects of a warming climate have possibly been already set within UIB. Instead of experiencing an increased pulse of summer flows for the next few decades, summer flows within this basin are expected to decline. Changes in the timing of peak flows can have adverse effects on multipurpose water resources management without appropriate adaptation and mitigation measures. Monthly average stream flow data with 35 year period of record from a key gauging station support the findings of the model results. Similarly, digital maps of SCA P at different time periods within a key catchment of UIB, containing one of the major glaciers, show retreat of glacial lobes and significant decrease in total SCA P taking place during the past decades.

Uncertainty in the impacts of projected climate change on the hydrology of a subarctic environment: Liard River Basin

Abstract. Like many high latitude areas, the mountainous region of subarctic Canada has experienced recent warming and is an area of large inter-annual temperature variations, most notably during the winter. Quantifying how climate tendencies affect streamflow, especially in the spring melt season, is critical not only to regional water resource management, but to understanding the influence of freshwater on the Arctic sea-ice cover and global climate system. The impact of projected atmospheric warming on the discharge of the Liard River is unclear. Here, uncertainty in climate projections associated with GCM structure (2 °C prescribed warming) and magnitude of increases in global mean air temperature (1 to 6 °C) on the river discharge are assessed using a well-tested, semi-distributed hydrological model. Analyses have shown that the hydrological impacts are highly dependant on the GCM scenario. Uncertainties between the GCM scenarios are driven by the inconsistencies in projected spatial variability and magnitude of precipitation, rather than warming temperatures. Despite these uncertainties, the entire scenario simulations project that the subarctic nival regime will be preserved in the future, but the magnitude of change in river discharge is highly uncertain. Generally, spring freshet will arrive earlier, autumn to spring discharge will increase whereas summer flow will decrease, leading to an overall increase in annual discharge.

Sustainability of water resources management in the Indus Basin under changing climatic and socio economic conditions

Abstract. Pakistan is highly dependent on water resources originating in the mountain sources of the upper Indus for irrigated agriculture which is the mainstay of its economy. Hence any change in available resources through climate change or socio-economic factors could have a serious impact on food security and the environment. In terms of both ratio of withdrawals to runoff and per-capita water availability, Pakistan's water resources are already highly stressed and will become increasingly so with projected population changes. Potential changes to supply through declining reservoir storage, the impact of waterlogging and salinity or over-abstraction of groundwater, or reallocations for environmental remediation of the Indus Delta or to meet domestic demands, will reduce water availability for irrigation. The impact of climate change on resources in the Upper Indus is considered in terms of three hydrological regimes – a nival regime dependent on melting of winter snow, a glacial regime, and a rainfall regime dependent on concurrent rainfall. On the basis of historic trends in climate, most notably the decline in summer temperatures, there is no strong evidence in favour of marked reductions in water resources from any of the three regimes. Evidence for changes in trans-Himalayan glacier mass balance is mixed. Sustainability of water resources appears more threatened by socio-economic changes than by climatic trends. Nevertheless, analysis and the understanding of the linkage of climate, glaciology and runoff is still far from complete; recent past climate experience may not provide a reliable guide to the future.

Statistical downscaling of river flows

summary An extensive statistical ‘downscaling’ study is done to relate large-scale climate information from a general circulation model (GCM) to local-scale river flows in SW France for 51 gauging stations ranging from nival (snow-dominated) to pluvial (rainfall-dominated) river-systems. This study helps to select the appropriate statistical method at a given spatial and temporal scale to downscale hydrology for future climate change impact assessment of hydrological resources. The four proposed statistical downscaling models use large-scale predictors (derived from climate model outputs or reanalysis data) that characterize precipitation and evaporation processes in the hydrological cycle to estimate summary flow statistics. The four statistical models used are generalized linear (GLM) and additive (GAM) models, aggregated boosted trees (ABT) and multi-layer perceptron neural networks (ANN). These four models were each applied at two different spatial scales, namely at that of a single flow-gauging station (local downscaling) and that of a group of flow-gauging stations having the same hydrological behaviour (regional downscaling). For each statistical model and each spatial resolution, three temporal resolutions were considered, namely the daily mean flows, the summary statistics of fortnightly flows and a daily ‘integrated approach’. The results show that flow sensitivity to atmospheric factors is significantly different between nival and pluvial hydrological systems which are mainly influenced, respectively, by shortwave solar radiations and atmospheric temperature. The non-linear models (i.e. GAM, ABT and ANN) performed better than the linear GLM when simulating fortnightly flow percentiles. The aggregated boosted trees method showed higher and less variable R 2 values to downscale the hydrological variability in both nival and pluvial regimes. Based on GCM cnrm-cm3 and scenarios A2 and A1B, future relative changes of fortnightly median flows were projected based on the regional downscaling approach. The results suggest a global decrease of flow in both pluvial and nival regimes, especially in spring, summer and autumn, whatever the considered scenario. The discussion considers the performance of each statistical method for downscaling flow at different spatial and temporal scales as well as the relationship between atmospheric processes and flow variability.

The transboundary Mures/Maros catchment - a review

Scattered and partly unpublished data are compiled and commented in this review of the transboundary (Romania/Hungary) Mures/Maros River Basin (catchment area 28,310 km 2 , river length 789 km, mean annual discharge 184 m 3 /s). Main characteristics of the Mures/Maros River are a conductivity mostly >100 μS/cm due to prevailing calcareous rocks, a nival hydrological regime (mean annual precipitation 520-1000 mm), and high pollution through mining (heavy metals), industry (toxicants, thermal), agriculture (fertilizers, pesticides) and domestic waste (organic C, N. P). Some 750 km or 33 % of monitored river course were in EU-WFD quality classes III-V. Pollution locally affects phytoplankton, periphyton, macroinvertebrates and fish communities. However, habitat heterogeneity and biodiversity are generally high due to mostly intact, near natural hydromorphological structures reflecting moderate human technical impacts, although gravel exploitation is considerable. This literature review is aimed at providing basic limnological information as the foundation of future scientific research into the catchment.

Morphodynamics of Cold High Latitude Semiarid Regions: The Example of Ellef Ringnes Island, Nunavut*

In this paper we use the example of Ellef Ringnes Island, Nunavut, to examine active geomorphic processes in a high latitude semiarid region. The spectacular landscape of Ellef Ringnes Island is principally the result of fluvial erosion controlled by geological structure. The nival regime concentrates flow in a brief late-spring period which provides strong erosive capabilities for rivers in spite of low annual precipitation. Other processes related to the cold environment produce a variety of minor landforms such as patterned ground, mud flows associated with ground ice, and solifluction lobes.

Large canyons in Dinaric and Prokletije mountains region of Montenegro

Montenegro occupies relatively small, southeastern part of the Dinaric mountains. Geological composition, which is predominantly carbonate, enabled formation of a great number of deep canyons and gorges. Canyons of Montenegro were formed in several ways, during multiple phases. Regardless of polygenetic and polymorphic character of the canyons, they can be classified into three main groups. By incision of melt-water rivers of Pleistocene glaciers, deep and particularly narrow canyons of small width were formed. The rivers that presently flow through these canyons have a nival regime - during the summer, their discharge is minimal, or they completely dry out. Depths of these canyons are up to 500 m. Rivers that directly feed into the Adriatic sea are of torrential character. They have pluvial regime, and dry out during the summer. Their canyons are short, several hundreds of meters deep. Deepest and longest canyons have been formed by incision of rivers that have changed their regimes during a longer period of time. Melt-water of Pleistocene glaciers has incised the greatest parts of canyons at the beginning of Holocene. Presently, river courses have nival-pluvial regime. In this group, single-phase and multiple-phase canyons can be distinguished (alteration of erosional and accumulation processes). Depths of these canyons exceed 1000 m.

Multidecadal variations and decline in spring discharge in the Canadian middle Arctic since 1550 AD

Annually laminated (varved) sediments from Sanagak Lake in the Canadian middle Arctic were used to reconstruct past spring discharge. Two years of sediment transport observations demonstrate that sediment delivery in this nival regime is limited primarily to the short period of maximum discharge. Interannual variability in catchment snow water equivalence (SWE) was the primary control over the length of the peak discharge period, resulting in substantially increased sediment transport and deposition in the lake in years with higher SWE. Analysis of annual sediment accumulation reveals high interannual variability with a persistent 64–80 year frequency as well as a prominent decline, particularly since 1820 AD. These spectral results suggest a linkage between the Atlantic Multidecadal Oscillation (AMO) and snowfall conditions through persistence of the characteristic frequency since 1550 AD.

Floodplain environmental change during the Younger Dryas and Holocene in Northwest Europe: Insights from the lower Kennet Valley, south central England

Many lowland rivers across northwest Europe exhibit broadly similar behavioural responses to glacial–interglacial transitions and landscape development. Difficulties exist in assessing these, largely because the evidence from many rivers remains limited and fragmentary. Here we address this issue in the context of the river Kennet, a tributary of the Thames, since c. 13,000 cal BP. Some similarities with other rivers are present, suggesting that regional climatic shifts are important controls. The Kennet differs from the regional pattern in a number of ways. The rate of response to sudden climatic change, particularly at the start of the Holocene and also mid-Holocene forest clearance, appears very high. This may reflect abrupt shifts between two catchment scale hydrological states arising from contemporary climates, land use change and geology. Stadial hydrology is dominated by nival regimes, with limited winter infiltration and high spring and summer runoff. Under an interglacial climate, infiltration is more significant. The probable absence of permafrost in the catchment means that a lag between the two states due to its gradual decay is unlikely. Palaeoecology, supported by radiocarbon dates, suggests that, at the very start of the Holocene, a dramatic episode of fine sediment deposition across most of the valley floor occurred, lasting 500–1000 years. A phase of peat accumulation followed as mineral sediment supply declined. A further shift led to tufa deposition, initially in small pools, then across the whole floodplain area, with the river flowing through channels cut in tufa and experiencing repeated avulsion. Major floods, leaving large gravel bars that still form positive relief features on the floodplain, followed mid-Holocene floodplain stability. Prehistoric deforestation is likely to be the cause of this flooding, inducing a major environmental shift with significantly increased surface runoff. Since the Bronze Age, predominantly fine sediments were deposited along the valley with apparently stable channels and vertical floodplain accretion associated with soil erosion and less catastrophic flooding. The Kennet demonstrates that, while a general pattern of river behaviour over time, within a region, may be identifiable, individual rivers are likely to diverge from this. Consequently, it is essential to understand catchment controls, particularly the relative significance of surface and subsurface hydrology.

Comparative analysis of glacial and nival streamflow regimes with implications for lotic habitat quantity and fish species richness

AbstractGrowing interest in the differential responses of glacial and nival rivers to climatic forcing, and in ecological distinctions between the two streamflow regimes, suggests the need for a better comparative understanding of how the annual hydrologic cycle differs with presence or absence of catchment glacial cover. In this study, timing and magnitude characteristics of the average annual hydrographs of five glacierized and four nival catchments in the southwestern Canadian subarctic are empirically identified and compared. Likely effects upon fish habitat are qualitatively assessed, and net fisheries potential is tentatively investigated using taxa richness data. The chief hydrological conclusions at P < 0.05 using Kolmogorov–Smirnov and empirical orthogonal function analyses are: (1) catchment glacial cover results in freshets that are longer, larger, and peak later than those experienced by the nival regime; (2) the winter baseflows of glacial rivers are also much higher on a unit‐catchment‐area basis; and (3) basin scale and degree of catchment glacial cover are of comparable importance in determining the magnitude of the annual hydrologic cycle. These differences arise from the greater availability, both in volume and over time, of meltwater in glacial catchments, which in part reflects the consistently negative alpine glacial mass balances observed both in the present study area and globally under historical climatic warming. Such regime distinctions result in increased spawning season and winter aquatic habitat availability, which may in turn offset negative habitat characteristics previously identified for glacial river ecosystems. While previous studies have suggested that glacial influences tend to decrease macroinvertebrate diversity and increase salmon populations, preliminary analysis of available fish species presence/absence data from the current study area tentatively appears to suggest similar or, perhaps, slightly higher fish taxa richness relative to nival streams; in all three cases, however, catchment lake cover may play a key hydroecological modifying role. The results strongly confirm and extend existing understanding of glacial–nival regime differences with respect to both streamflow and fisheries ecology, and raise new questions for future research. Copyright © 2005 John Wiley & Sons, Ltd.

Hydrological Response of a Patchy High Arctic Wetland

High Arctic patchy wetlands are ecological oases in a polar desert environment and are vulnerable to climatic warming. At present, understanding of their responses to external factors (climate and terrain) is limited. This study examines a wetland located in a topographic depression maintained by seasonal snowmelt, ground ice melt and lateral inflows. The wetland is located on Cornwallis Island, Nunavut, Canada. Hydrological, climatological and soil observations were made over several summers with different weather conditions. The summers of 1996 and 1997 were cool and wet but the summer of 1998 was warm and dry. The melt in 1996 was rapid due to rain on snow events and only lasted six days. Deeper snow in 1997 prolonged the melt season to 18 days. A shallow snow-cover in 1998 and early melt depleted the snow by early June. Surface, groundwater and storage fluctuations in the wetland were dictated by snowmelt, rainfall, evaporation loss from the wetland and lateral inputs which in turn were controlled by the melting of the late-lying snow storage in the catchment. Soil factors influence the spatial variations in ground thaw which affects the surface and subsurface flow. Streamflow response of the wetland reflects a nival regime and augmentation of streamflow thoughout the summer season in all three years is supported by multiple water sources: ground ice melt and suprapermafrost water from a large late-lying snowpack. Overall, this study suggests that the survival of some patchy wetlands depends on their interaction with the surrounding basin, with a dependency probably being more important during warm and dry seasons.

High-Resolution Measurements of Water Discharge, Sediment, and Solute Transport in the River Zackenbergelven, Northeast Greenland

The climatic control on fluvial fluxes of sediments and solutes from arctic terrestrial ecosystems to the hydrographically sensitive and highly productive marine ecosystem are considered to be an important feedback mechanism in relation to the understanding of global change. High temporal resolution data are presented on water discharge, suspended sediment transport, and solute chemistry in the river Zackenbergelven draining a catchment of 512 km2 in High Arctic Northeast Greenland. Variations of water quality and water discharge in the river are discussed in relation to climate, water balance, and drainage basin dynamics. The temporal variations in water composition in the river can be separated into three characteristic periods. During the early part of the season, snow melt in the lowland areas produces an ion pulse. Later in the season, when the active layer in the permafrost develops, the water quality is mainly influenced by water draining through and from the active layer. In the latest part of the season, when air temperature reaches the annual maximum, and drainage from the lowland areas ceases, the river water mainly originates from glaciers and snow patches on the high-lying plateaus above 1000 m a.s.l. The fluxes of sediments and solutes from the catchment seems to be especially sensitive to even slightly changing climates during the mid period. It is concluded that the river regime is intermediate between the “arctic nival regime” and the “proglacial regime,” and it is suggested that the Zackenbergelven drainage basin is representative for Northeast Greenland drainage basins with no connection to the Greenland Ice Sheet in the more continental part of the land fringe outside the ice sheet.

High-Resolution Measurements of Water Discharge, Sediment, and Solute Transport in the River Zackenbergelven, Northeast Greenland

The climatic control on fluvial fluxes of sediments and solutes from terrestrial ecosystems to the hydrographically sensitive and highly productive marine ecosystem are considered to be an important feedback mechanism in relation to the understanding of global change. High temporal resolution data are presented on water discharge, suspended sediment transport, and solute chemistry in the river Zackenbergelven draining a catchment of 512 km2 in High Arctic Northeast Greenland. Variations of water quality and water discharge in the river are discussed in relation to climate, water balance, and drainage basin dynamics. The temporal variations in water composition in the river can be separated into three characteristic periods. During the early part of the season, snow melt in the lowland areas produces an ion pulse. Later in the season, when the active layer in the permafrost develops, the water quality is mainly influenced by water draining through and from the active layer. In the latest part of the season, when air temperature reaches the annual maximum, and drainage from the lowland areas ceases, the river water mainly originates from glaciers and snow patches on the high-lying plateaus above 1000 m a.s.l. The fluxes of sediments and solutes from the catchment seems to be especially sensitive to even slightly changing climates during the mid period. It is concluded that the river is intermediate between the arctic nival regime and the proglacial regime, and it is suggested that the Zackenbergelven drainage basin is representative for Northeast Greenland drainage basins with no connection to the Greenland Ice Sheet in the more continental part of the land fringe outside the ice sheet.

Late Devensian river and floodplain dynamics and related environmental change in northwest Europe, with particular reference to a site at Woolhampton, Berkshire, England

Marked fluctuations in Late-glacial climate are correlated with significant changes in river behaviour and floodplain environment across much of northwest Europe. Evidence from a new site in the Kennet Valley provides a rare comprehensive picture of varying fluvial regime and local vegetation during this interval. Chronological control for the site is provided by biostratigraphical and morphostratigraphical correlations with other sites in the region, and by radiocarbon dating of carefully selected material. Preservation of the sedimentary sequence was facilitated by its occurrence within a large depression in the underlying bedrock. The origin of this depression is uncertain, perhaps reflecting subsidence or scour. Following the Last Glacial Maximum, a nival regime braided river dominated by floods deposited sandy gravels under stadial conditions. A large channel infilled by fine sediments during the latter part of the Windermere Interstadial indicates a fall in flow competence at a time of increased floodplain vegetation, most notably the appearance of tree birch. Variations in sediments and vegetation suggest fluctuations in the floodplain environment, reflecting complex vegetation dynamics and possibly climate forcing. During the Loch Lomond/Younger Dryas Stadial, a nival, braided regime was re-established, accompanied by the disappearance of tree birch.