Stott T. A, Mount, NJ. (2007) Sustainability in Alpine Proglacial Zones: Using the 2003 European...

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Sustainability in Alpine Proglacial Zones: Using the2003 European Heat Wave to Assess the

Implications of Global Warming on SedimentTransport Processes

Tim Stott and Nick Mount

THE INTERNATIONAL JOURNAL OF ENVIRONMENTAL, CULTURAL, ECONOMIC AND SOCIAL SUSTAINABILITY http://www.Sustainability-Journal.com First published in 2007 in Melbourne, Australia by Common Ground Publishing Pty Ltd www.CommonGroundPublishing.com. © 2007 (individual papers), the author(s) © 2007 (selection and editorial matter) Common Ground Authors are responsible for the accuracy of citations, quotations, diagrams, tables and maps. All rights reserved. Apart from fair use for the purposes of study, research, criticism or review as permitted under the Copyright Act (Australia), no part of this work may be reproduced without written permission from the publisher. For permissions and other inquiries, please contact <[email protected]>. ISSN: 1832-2077 Publisher Site: http://www.Sustainability-Journal.com THE INTERNATIONAL JOURNAL OF ENVIRONMENTAL, CULTURAL, ECONOMIC AND SOCIAL SUSTAINABILITY is a peer refereed journal. Full papers submitted for publication are refereed by Associate Editors through anonymous referee processes. Typeset in Common Ground Markup Language using CGCreator multichannel typesetting system http://www.CommonGroundSoftware.com.

Sustainability in Alpine Proglacial Zones: Using the 2003 EuropeanHeat Wave to Assess the Implications of Global Warming onSediment Transport ProcessesTim Stott, Liverpool John Moores University, Merseyside, UKNick Mount, University of Nottingham, UK

Abstract: The International Panel for Climate Change (2001) reported that average global surface air temperature increasedby 0.6±0.2 °C since the late 19th century and is projected to increase by 1.4–5.8 °C between 1990–2100 (approx 0.2 to 0.5°C per decade). The response of hydrological systems, erosion processes and sedimentation in Alpine regions could thereforealter significantly due to climate change. Suspended sediment fluxes in the Glacier Noir proglacial zone in the Ecrins Na-tional Park, French Alps, have been monitored for 15-20 days in July 2003, 2004, and 2005. Discharge and turbidity weremonitored at 10-min intervals and suspended sediment concentrations in 60-72 water samples collected in each season ata range of discharge values were obtained gravimetrically, and used to calibrate turbidity sensors from which suspendedsediment loads were estimated. Excluding rainstorms in 2005, the common data from 11-17 July for each melt season allowus to assess the impact of the unusually warm 2003 melt season when a Europe wide heat wave prevailed for over threemonths. Daily mean daily air temperature at the site in 2003, 2004 and 2005 was 16.5, 10.4 and 14.0 °C; correspondingdaily mean discharge was 5.5, 1.1, and 3.0 m³ sֿ¹ (or 171, 36 and 95% of the 3-year mean) and daily mean suspended sed-iment load was 777, 27, 343 t respectively (or 203, 7 and 90% of the 3-year mean). These data suggest that rises in temper-ature as predicted by current global warming models could propagate disproportionate increases in suspended sedimentloads. An improved understanding of suspended sediment dynamics in proglacial zones is important since such zones arelikely to expand in a warmer climate. Proglacial zones may become evenmore important in controlling downstream suspendedsediment loads, which have important implications for the hydroelectricity industry, stream ecology, river sedimentationand channel dynamics in lowland river systems.

Keywords: Global Warming, Proglacial Zones, Suspended Sediment Loads

Introduction and Aims

THE INTER-GOVERNMENTAL PANELon Climate Change (IPCC, 2001a) indicatedthat the average global surface air temperat-ure increased by 0.6 ± 0.2 °C since the late

19th century and is projected to increase by 1.4 – 5.8°C over the period 1990–2100 and Jones et al.,(1990) reported that global mean surface air temper-ature increased by 0.3 to 0.6 oC over the past 100years. IPCC (2007) has more recently confirmed this.The extent of global snow cover has decreased by10% since late 1960s (IPCC, 2001a). The impact ofglobal warming on water resources has been receiv-ing attention from hydrologists in recent years(Hansen and Lebedeff, 1987; Oerlemans et al., 1998;Singh and Kumar, 1997; Jones, 1999; Singh andBengtsson, 2005) who have modeled increasedevaporation rates from snowfed basins and increasedmelt from glacierized basins. Continued warming ofthe Earth-atmosphere system is likely to change bothtemperature and precipitation (Singh and Kumar,1997) which may affect both the quantity and qualityof freshwater resources. Letréguilly and Reynaud’s(1990) analysis of long-term records on glacier

fluctuations and mass loss and retreat of mountainglaciers, support the change in the climate in the pastcentury. While some glaciers like Nigardsbreen(Norway) and Franz Josef Glacier (New Zealand),have shown an advancing trend (Oerlemans et al.,1998), on the whole a widespread retreat of mountainglaciers has been reported in non-polar regions dur-ing the 20th century (Singh and Bengtsson, 2005)and these glaciers and ice caps are projected to con-tinue their widespread retreat during the 21st century.

The areal extent of glacierization in the EuropeanAlps has reduced by 30–40% since the middle of the20th century, whereas the volume of ice has beenreduced by 50% (Haeberli and Beniston, 1998) andup to half of Europe's alpine glaciers could disappearby the end of the 21st century IPCC (2001b). Underthe warmer climate, the proportion of solid precipit-ation in the total will reduce, resulting in a decreasein snow accumulation. Haeberli and Beniston (1998)performed simulations for double-CO2 scenarios inthe European Alps using regional climate models(RCM) with a 20-km horizontal grid which predictedgenerally higher winter temperatures, a more markedincrease in summer temperatures, indications that

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temperature increases more at higher elevations thanat lower altitudes, and higher/more intense precipit-ation in winter (but much dryer conditions in sum-mer). Under such conditions, they conclude that theAlps would lose major parts of their glacier coverwithin decades, and lower limits of permafrost occur-rence in the Alps could rise by several hundredmetres. Pronounced disequilibria in the water cycle,in mass wasting processes, and in sediment fluxcould ensue, as well as in growth conditions of veget-ation. Analysis of climate data by Demmer andMooers (2005) suggested that the Lewis glacier onSouth Sister Mountain, Oregon, USA, sits on thelocal glaciation threshold. Mean annual temperaturemidway along the profile was estimated at -2 oC,which along with the annual precipitation, placesLewis glacier at or outside the limits of sustainability.Their paper concludes by saying ‘Farewell oldfriend’.

The response of hydrological systems, erosionprocesses and sedimentation in Alpine regions islikely to alter significantly due to global warming.Proglacial zones are likely to expand due to changesin erosion rates and sediment delivery from glaciers,suspended sediment yields may change (Warburton,1999; Hodgkins et al., 2003) and changes in sedimentstorage in proglacial zones (Maizels, 1979; Warbur-ton, 1990; Harbor & Warburton, 1993) may be animportant aspect of alpine fluvial systems for determ-ining response to environmental change (Phillips,1991). Suspended sediment yields are seen as a par-ticularly sensitive parameter of environmental change(Walling, 1995) since suspended sediment loads instreams and rivers tend to be supply-controlled,whereas coarser bed load is hydraulically controlled.Thus, ‘suspended sediment fluxes are likely to bemore responsive to climate-driven environmentalchange, other factors being equal’ (Hodgkins et al.,2003, p.105).

In this study streamflow (Q) and suspended sedi-ment concentrations (SSC) in a proglacial stream inthe Ecrins National Park, French Alps (Fig. 2) weremonitored in the summers of 2003, 2004 and 2005.Summer 2003 was exceptionally hot in France andadjacent countries (Beniston, 2004), and this studyuses this heat wave as a possible indication of futureconditions under global warming. Table 1 presentsten years of monthly mean air temperature data forEmbrun (44°34' N, 6°30' E, altitude 871 m, Fig. 2)in the Ecrins region of the French Alps with predictedmelt season temperatures for the study site at theGlacier Noir (44°55' N, 6°25' E, altitude 1908 m)(1997-2006). A lapse rate relationship establishedduring July 2004 between Embrun daily mean tem-peratures and those at the study site was used topredict monthly mean temperatures at the study site,which for May -August 2003, can be seen to be

substantially higher than both 2004, 2005 and the1997-2006 mean. Since the monitoring for this studytook place in July 2003, 2004 and 2005, Fig. 1presents the July data only for 1997-2006. It showsan upward trend in July monthly mean air temperat-ure and shows the higher 2003 mean as comparedwith the ten year mean. A Students’ t-test showedthe difference in daily mean air temperatures for thetwo months of July 2003 and July 2004 to be statist-ically significant (T = 27.3, p < 0.01, n = 1585). Julyand August 2003 were exceptionally hot in Franceand surrounding countries (Beniston, 2004) with 14802 more deaths than expected in France in August2003 reported by the National Institute of Health andMedical Research, widespread forest fires and excep-tional rock falls in the Alps.

Based on this contrast in air temperatures betweenthe 2003 and the 2004-05 melt seasons, this studyaimed to quantify the differences in air temperature,discharge and suspended sediment load between a‘future’ warmer scenario, as witnessed during the2003 heatwave and ’normal’ conditions, as in 2004and 2005.

Study AreaThe Torrent du Glacier Noir (44°55' N, 6°25' E,altitude 1908 m) is one of two obvious watercoursesflowing onto the Pre de Madame Carle (Fig. 2). Thetorrent emerges from the Glacier Noir (Fig. 3A), adebris covered glacier, via two sub-glacial conduitswhich meet 0.5 km from the snout, and then flowover coarse moraines for a further 0.6 km to whereit joins the Torrent du Glacier Blanc to form theTorrent de St. Pierre. The gradient is steep (averageis 0.18 m m-1 over this 1.1 km, compared to the av-erage gradient of the Pre de Madame Carle which is0.04 m m-1), it has a boulder bed and step-pool se-quences in its long profile. The basin area drainingto the monitoring station is ~15 km2, approximately37% of which is ice covered.

MethodsThe monitoring site was established in each seasonat a stable cross-section where a bridge crosses theTorrent du Glacier Noir (Fig. 2) and rock filled gabi-ons form a stable channel margin (Fig. 3B). A stageboard, a High Range Partech IR15C Turbidity Sensor(0-10 000 mg/L range), a Druck pressure transducer,and an air temperature (AT) thermistor (placed inStevenson screen 1.25 m above ground level) wereinstalled in the same location in each season. Datafrom all sensors were logged at 10-min intervalsfrom 9-24 Jul-03 (16 days), from 7 Jul – 4 Aug-04(29 days) and from 10-21 Jul-05 by Grant and Sentrydata loggers. In this paper only complete days which

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were deemed to be unaffected by rain storms are in-cluded in the dataset.

Linear mV to stage rating relationships were estab-lished (r2 = 0.96, n=16) at the site and a linear stagev discharge (Q) rating relationship was achieved us-ing the velocity-area method (Herschey, 1978). Ve-locity was gauged from the bridge using a Braystokeimpellor type flow meter at 0.6 depth at six verticals(1 m apart) at 11 different stage values on 19-Jul-03(between 07:00 and 16:00) and checked again onseveral occasions in Jul-04 (n=11, r2 = 0.94) and Jul-05. The highly turbulent nature of the flow in thesechannels led us to repeat velocity readings 10 timesat each vertical at the same stage based on whichstandard error estimates ranged from 0.07 to 0.21(mean = 0.13) m s-1. The errors in our cross-sectionarea estimates are likely to be lower than these, sug-gesting that discharge values may be associated witherrors in the range 0.1 to 0.3 m3 s-1.

A Sigma 900 portable water sampler deployed atthe monitoring site retrieved water samples at prede-termined time intervals (usually half-hourly, 1-hr or5-hr intervals), collecting 74, 72 and 55 watersamples in the 2003, 2004 and 2005 field seasonsrespectively. The intake tube of the sampler was fit-ted with a stainless steel filter which admitted sedi-ment of a maximum size of 2 mm. The sampler wasset up to flush the intake tube once prior to pumpinga 0.5 L sample into each of 24 bottles. The intakenozzle was fixed to the stage board next to the turbid-ity sensor, 0.15 m above the bed, so as to remainwithin the flow at all times. The highly turbulentnature of the flow suggested that suspended sedimentis extremely well mixed and that values sampled atthe stream margin were representative of the wholecross-section (see Gurnell et al., 1992 and Wiseman,2005). Water samples were filtered through WhatmanGF/D 8 μm filters in the field and filters were re-turned to the laboratory in Liverpool John MooresUniversity for standard gravimetric analysis. Repeatweighing of filters suggests that standard errors arearound 0.15 mg. We therefore estimate that suspen-ded sediment processing is likely to be associatedwith errors of ± 10 mg, and the measurement ofvolume ± 5 ml, giving overall error of about 3%.Some fine particles (< 8 μm) may have passedthrough the filters. A sample of ten filters ranging inSSC from 75 – 1426 mg/L were analysed for theirparticle size distribution using a Malvern Mastersizer.The proportion of fines < 8 μm ranged from 0 to 24%with a mean of 11.5%. This suggested that at least10% of the suspended sediment is finer than the 8μm pore size of the filters used, though it is not pos-sible to estimate how much of this passed throughfilters compared with how much was trapped, butthis analysis showed that some is certainly trapped.In low flow conditions, these fines could make up a

reasonable proportion of the total suspended sedi-ment load, and this should be borne in mind whenexamining the results which follow.

Separate suspended sediment concentration (SSC)and turbidity (T) relationships were derived for eachseason (Fig. 4) and used to predict 10-min SSC fromwhich daily mean and total suspended sediment load(SSL) was computed.

Results

Air Temperature, Discharge andSuspended Sediment Load in the, TorrentDu Glacier NoirAir temperature (AT) and discharge (Q) time seriesare compared for the three seasons (Fig. 4). Both ATand Q records reveal a pronounced diurnal pattern.The Q pattern is entirely temperature driven in 2003(there was no rainfall at all). In 2004 approximately5 mm of rain fell on 16-Jul-04 but this had no discern-able effect on Q and there was a short-lived 4-hrstorm which delivered ~ 10 mm of rain on 11-Jul-05which did increase Q (Fig. 4) but had a relativelysmall effect on the daily mean SSL. 11-Jul is there-fore included in the datasets. The early part of the2004 and 2005 records, 11-14-Jul, were significantlycooler than the second half (14-17-Jul), with corres-pondingly lower Q. The considerably lower Q recor-ded throughout the 2004 period is likely to be partlya result of lower temperatures both during the mon-itoring period and early in the season (Table 1)combined with the possibility of less snowfall overthe previous winter (see discussion). However, eventhough temperatures on the afternoon of 15-Jul-04peaked at 25.6 oC, the Q peak 2:30 h later remainedlow (4.8 m3 s-1). In contrast, on 23-Jul-04 the AT at15:30 h that afternoon also peaked at 25.6 oC but onthis occasion the Q peak at 18:10 h (2: 40 h later)was 7.3 m3 s-1. Thus, Q seemed to be more respons-ive to increases in AT later in the 2004 ablation sea-son. AT in the previous days, weeks and months(Table 1) is likely to have an impact on Q as thesnow line rises, the snowpack extent shrinks, glacialstorage increases and sub-glacial drainage conduitsbegin to develop (Rothlisberger and Lang, 1987).

The SSC dynamics in the 2003 and 2004 seasonshave been discussed elsewhere (Stott and Mount,2007). In this paper we present daily mean AT, Qand SSL data for the common parts of the three abla-tion seasons which were deemed to be unaffected byrainstorms (Table 2). Standard errors (SE = s / √ n,where s = standard deviation and n = 144) for eachdaily load were calculated from the 144 instantaneousloads per day (computed for each 10-min period).The large number of values over the 7-day periods(n = 1008) means that estimates of standard error of

125TIM STOTT, NICK MOUNT

the mean are small and we are confident that thereare real differences in AT (T = 27.3, p < 0.01, n =1008) and Q (T = 102.9, p < 0.01, n = 1008) betweenthe three seasons. Expressed as percentages of the3-year mean, AT in 2003 was 121%, in 2004 was76% and in 2005 was 103%, Q in 2003 was 171%,in 2004 was 36% and in 2005 was 95% and SSL in2003 was 203%, in 2004 was 7% and in 2005 was90% of the 3-year mean. Fig. 6 summarises thesedata which illustrate how relatively small changesin AT can produce significant changes in Q and evengreater changes in SSL. These differences in thesensitivity of Q and SSL to changes in AT have im-portant implications as global warming proceeds.The high July 2006 monthly mean AT of 22.2 oC atEmbrun (Table 1) was the second highest Julymonthly mean in the last 10-years and was onlyslightly lower than July 2003 (22.5 oC) during theEuropean heat wave (Beniston, 2004), although theMay-06, Jun-06 and Sep-06 monthly means werelower than in 2003. Nevertheless, given the apparentsensitivity of Q and SSL to changes in AT, the 10-year trend for July monthly means (Fig. 1) shouldbe a cause for some concern.

DiscussionExperiments undertaken by Gurnell and Warburton(1990) at the Glacier de Tsidjiore Nouve and BasGlacier d’Arolla in Switzerland, reported that SSCseries derived from 1.5-min turbidity records werecharacterised by frequent short flushes which forman important component of the SSL (46 and 37%respectively for the two aforementioned glaciers).Even the 10-min record used in this study may wellhave ‘missed’ important information and could resultin underestimates of SSL by this method also.However, for the purposes of this study, we areconfident that by applying the same techniques tothe 2003, 2004 and 2005 datasets, we are making afair comparison and we assume that the errors andlimitations apply equally to all three seasons sincethe monitoring, sampling and analysis techniqueshave been deliberately kept consistent in each season.Table 1 clearly demonstrates the inter-annual variab-ility and shows the exceptionally warm air temperat-ures in April-July 2003. Not only was the daily meanair temperature at the study site for 11-17 Jul-03 5.1oC higher than for Jul-04, and 2.5 oC higher than for11-17 Jul-05, but the preceding months of the abla-tion season were also much warmer than the 1997-2006 average (Table 1) and warmer than in 2004. Incontrast, the April – July 2004 and 2005 ablationseasons were cooler than the same months in 2003,and with the exception of May-05, April, May andAugust in 2004 and 2005 were cooler than the 1997-2006 10-year average.

Parallels may be drawn between the results fromthis study and the likely impacts of higher alpinesummer temperatures as a result of global warming.Global climate models (GCM) such as the Hamburgclimate model (Timmreck et al., 1999) typically ad-opt changes in temperature in the range 1 to 3 oC andprecipitation changes between -10 and +10%. Singhand Kumar (1997) used the UBC watershed modelto simulate the hydrological response of the Himalay-an Spiti River basin under the changed climaticscenarios indicated above. For example, an increaseof 2 oC in air temperature enhanced annual snowmeltrunoff, glacier melt runoff and total streamflow inthe range 4-18%, 33-38% and 6-12% respectively,whereas the effect of change in precipitation (P -10%to P + 10%) suggested a linear increase in snowmeltrunoff and total streamflow, while glacier melt runoffis inversely related to changes in precipitation. Undera warmer climate scenario, Singh and Kumar con-clude that snowmelt runoff and glacier melt runoffcause an earlier response of total streamflow and achange in flow distribution.

In the Ecrins, a mean monthly regional air temper-ature increase of ~2.0 oC over most of the 2003 abla-tion season was shown to increase daily mean dis-charge for the 11-17 July dataset to 171% of the2003-05 daily mean, as compared to 30% and 93%for the 2004 and 2005 periods respectively. For SSLsthe equivalent figures were 203% for 11-17 Jul-03,compared with 7% and 90% in 2004 and 2005.Clearly there are a number of factors which can affectthis pattern. First, the amount of winter snowfallhigher up in the basin will influence summer melt-water Q. As a crude indicator, Jan-Jul precipitationtotals for Embrun (44°34' N, 6°30' E, altitude 871m) were 341 mm in 2003, 247 mm in 2004 and 271mm in 2005. While totals up on the Glacier Noirabove the study site are likely to be considerablyhigher, with a greater proportion falling as snow,these figures do give some indication that the higherprecipitation in Jan-Jul 2003 may have resulted in agreater availability of snow for melting by the higher2003 ablation season temperatures. These facts needto be borne in mind when interpreting these findings,as does that fact that much of the lower Glacier Noiris covered in a thick layer of debris (Fig. 3A) whichmay result in different melt responses in the threeseasons. Second, suspended sediment supply is ofmajor importance. It could be that the high SSLs inJuly 2003 resulted in removal of available sedimentin sub-glacial, ice marginal and proglacial storagezones, so that the SSLs in July 2004 were substan-tially lower because the sediment supply had beenexhausted in the previous season (Gurnell, 1987). Itcould take several ‘normal’ seasons for this sedimentsupply to be replenished. It is also important to notethat this study only presents data for a small part of


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the total melt season, where rain storms have had nosignificant impact and so it is not possible to com-ment on how these findings might scale-up to thewhole melt season, or indeed to changed precipitationpatterns. Clearly, in a global warming scenario wheremean monthly temperatures rose by T+2.0 oC year-on-year, the system would be unlikely to be able tosustain the sorts of Qs and SSLs seen in the Torrentdu Glacier Noir in July 2003. Caution should there-fore be exercised in extrapolating the differences inSSLs reported here to multiple future seasons in awarmer climate. Thirdly, there is a question aboutsuspended sediment storage between the glaciersnout and the monitoring site, a distance of around1 km.

Warburton (1999) suggests that proglacial riversystems provide the key link between glacial pro-cesses and the wider environment and addresses thequestion of sediment storage. Warburton (1990)found that 23% of the sediment yield of Bas Glacierd’Arolla, Switzerland, was derived from the progla-cial zone, whereas Maizels (1979) reported that 16%of the fluvial sediment from Glacier des Bossons,France, was redeposited in the proglacial valleysandur. Hodgkins et al. (2003) showed a net increase(aggradation) in suspended sediment storage in theproglacial area of the Finsterwalderbreen glacier inSvalbard in the 1999 ablation season, while in con-trast the 2000 ablation season showed a net decreasein storage (denudation). Orwin and Smart (2004)found that the proglacial area was the source for upto 80% of the total suspended sediment yield trans-ferred from the Small River Glacier basin in Canada.Distinguishing the proportion of sediment load de-rived from contemporary erosion, as opposed to thatreworked from stored sediments (Harbor & Warbur-ton, 1993), is clearly important. In glacierised basins,where sediment transport often takes place in large,discontinuous events at diurnal and seasonal times-cales (Bogen, 1980; Fenn, 1989; Gurnell et al., 1994;Hodgkins, 1996; Stott and Grove, 2001), quantifyingtransport rates of sediment entering proglacial zonesis a particularly important aspect to an understandingof sediment transfer across such zones. Stott andMount (2007) presented data which suggest thatsediment storage between the glacier snout and themonitoring site used in this study may be importantand future work is planned to investigate this. As faras the conclusions for this study are concerned, wemust assume that any processes of sediment storageover the 7-day periods in each of the three seasonsequally affect the datasets in each season, makingcomparisons between the seasons fair. However,further work is needed to verify this.

We believe that the dataset presented here offersan unique field-based example of how globalwarming could impact upon suspended sediment

loads in European Alpine proglacial environments.These results could be useful in future calibration ofmodels of sediment transfer from mountain to pied-mont zones in other mountainous regions of theworld. For example, Singh and Kumar (1997) usedthe Hamburg climate model to simulate changes intemperature and precipitation over the Indian subcon-tinent and simulated the hydrological response ofthe Spiti basin under the changed climate scenarios.However, their work did not extend to assessing theeffects of the changed hydrological responses onsediment loads. Many authors who work on suspen-ded sediments refer to high suspended sediment loadsas ‘sediment pollution’ (e.g. Marks and Rutt, 1997).Cleaning sediment from drinking water to make itpotable can be a costly process. Enhanced sedimentpollution in less developed parts of the world suchas those studied by Kumar and Singh (1997) maywell be an additional problem which needs to betaken into account if a sustainable water supply is tobe ensured in future. Ariztegui (2005) has highlightedthe impact which recent environmental change canhave on freshwater systems. Changes to freshwatersupplies can have devastating effects on populationand Ariztegui warns that a good understanding ofthe causes and processes behind environmental de-gradation is critical to develop strategies that guaran-tee future cultural sustainability

Hydropower, large and small, is one of the mostimportant of the “renewables” for electrical powerproduction worldwide, providing 19% of the world’selectricity (Paish, 2002).. The World HydropowerAtlas (2000) published by the International Journalof Hydropower and Dams, reported that the world’stechnically feasible hydro potential is estimated at14,370 TWh/year, which equates to 100% of today’sglobal electricity demand. The economically feasibleproportion of this is currently considered to be 8080TWh/yr. Small-scale hydro which draws water dir-ectly from streams and rivers with no dam or waterstorage, is one of the most cost-effective and envir-onmentally benign energy technologies to be con-sidered for rural electrification in less developedcountries. The European Commission have a targetto increase small hydro capacity by 4500MW (50%)by the year 2010. The UK has 100MW of existingsmall hydro capacity (under 5MW) operating fromapproximately 120 sites, and at least 400MW of un-exploited potential. With positive environmentalpolicies now being backed by favourable tariffs for‘green’ electricity, the industry believes that smallhydro will have a strong resurgence in Europe in thenext 10 years, after 20 years of decline. Paish (2000)concludes by pointing out that turbines need to beprotected from all the debris that is commonly foundin rivers. If sediment enters intake pipes and comesinto contact with turbines, it can be highly abrasive


and result in high maintenance and/or repair costs toequipment. A better understanding of sediment dy-manics, and the likely changes in future, will be im-portant to operators of hydro electric schemes as itwould allow the planning of sediment flushing eventsand intake of water at times when suspended sedi-ment loads are at their lowest.

ConclusionsComparison of 7-day monitoring periods in July2003, 2004 and 2005 in the Torrent du Glacier Noir,Ecrins massif, SE France, showed that, excludingsignificant rainstorms on 18-19 July 2005, the com-mon data from 11-17 July for each melt season allowus to assess the impact of the unusually warm 2003melt season when a Europe wide heat wave prevailedfor over three months. Daily mean air temperaturesat the site in 2003, 2004 and 2005 were 16.5, 10.4and 14.0 oC, corresponding daily mean dischargewas 5.5, 1.1, and 3.0 m3 s-1 (or 171, 36 and 95% ofthe 3-year mean) and daily mean suspended sedimentloads were 777, 27, 343 t respectively (or 203, 7 and90% of the 3-year mean). These data suggest thatrises in temperature as predicted by current globalwarming models are likely to propagate dispropor-tionate increases in suspended sediment loads in

Alpine proglacial environments Such changes insuspended sediment loads have important implica-tions for sediment delivery from mountain to pied-mont zones, for stream ecology, for downstreamchannel stability and flood risk and for the hydro-electric industry.

AcknowledgementsWe thank Joel Faure and the Ecrins National ParkAuthority for granting permission to conduct thisstudy within the National Park. Liverpool JohnMoores University and Birkbeck College, Universityof London supported staffing and equipment usedfor this project. Hamish McGowan and David Pageof The University of Queensland, Brisbane, arethanks for allowing use of the University’s MalvernMultisizer.

Dr Tim Stott, Reader in Physical Geography &Outdoor Education, Liverpool John Moores Univer-sity, I. M. Marsh Campus, Barkhill Road, LiverpoolL17 6BD, UK Email: [email protected]

Dr Nick Mount, Lecturer in Physical Geography,School of Geography, University of Nottingham,University Park, Nottingham NG7 2RD, UK Email:[email protected]

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Table 1: Ten Years of Monthly Mean Temperatures (oC) in the French Alps (1997-2006)

1997-2006

2006200520042003200220012000199919981997Month

MeanEMBRUN, 44°34' N, 6°30' E, altitude 871 m

1.60.1-0.7-0.40.62.53.21.13.12.33.8January3.01.5-0.62.50.55.14.54.4-0.16.95.7February6.94.75.55.67.88.47.76.86.179.5March9.29.9999.9108.19.38.68.19.6April14.313.314.412.614.713.115.215.515.714.614May18.418.919.118.221.519.717.118.516.617.716.3June20.122.219.720.222.519.920.217.919.920.618July20.016.418.519.9231921.720.619.920.820.4August16.017.415.916.515.814.712.916.517.515.217.9September11.81312.312.19.111.514.511.511.69.912.6October5.4*n/a4.64.66.87.35.54.94.53.17November2.1*n/a-1.83.23.14.31.24.21.12.31.7December

10.79.710.311.311.311.010.910.410.711.4EMBRUN Mean

STUDY SITE, GLACIER NOIR BRIDGE 44°55' N, 6°25' E, altitude 1908 m6.87.26.76.77.27.26.26.86.56.27.0April9.59.09.58.69.78.910.010.110.29.69.3May11.611.912.011.613.312.411.011.710.711.310.5June12.613.712.412.613.812.512.611.412.512.811.5July12.510.611.712.514.112.013.412.812.512.912.7August10.411.110.310.710.39.78.710.711.210.011.4September

16.416.116.117.916.115.916.416.416.216.0EMBRUN Apr – Sep mean10.610.410.411.410.410.310.610.610.510.4GLACIER NOIR

Apr-Sep meanAll temperatures at study site predicted from Embrum data using a lapse rate equation based on July 2004daily means y = 0.53x + 1.19R2 = 0.69*** (n = 16). n/a = data not available at time of writing (Nov-2006); * mean based on 9 years, excludes2006.


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Table 2: Daily Mean Air Temperatures (AT), Discharge (Q) and Suspended Sediment Loads (SSL) for11-17 July (No Rain Storms) for 2003, 2004 and 2005 Seasons

% of 3-yearmean

Mean17-Jul16-Jul15-Jul14-Jul13-Jul12-Jul11-Jul

Daily meanair temper-ature (AT)oC

12116.516.013.516.117.118.518.316.220037610.412.26.39.98.316.07.512.6200410314.017.416.716.013.912.011.510.82005

13.73-yearMEAN

Daily meandischarge(Q) m3/s

1715.54.94.75.35.65.66.16.12003361.20.60.50.61.01.61.72.12004933.02.92.92.73.03.03.42.92005

3.23-yearMEAN

% of7-dayTOTAL

Daily meansuspended 7-day

TOTALsedimentload (SSL)t

685438203776.9140 ±10

157 ±8

639 ± 85800 ±121

900 ±167

1419 ±53

1383 ±44

2003

2.4191727.315 ±0.4

104 ±21

39 ± 315 ± 19 ± 0.43 ±0.07

7 ± 0.32004

30240090342.9778 ±47

448 ±40

346 ± 22406 ± 27139 ±9

162 ±10

121 ± 62005

2677374382.43-yearMEAN


Fig. 1: July Monthly Mean Air Temperature at Embrun (44°34' N, 6°30' E, Altitude 871 m) in the Ecrins Region,SE France with Monthly Mean Temperature for Torrent Du Glacier Noir Bridge Monitoring Site (44°55' N,

6°25' E, Altitude 1908 m) Predicted from a Lapse-rate Relationship (1997-2006)

Fig. 2: Location of Glacier Noir with Monitoring Station at Torrent Du Glacier Noir Bridge Indicated


132

Fig 3A: View of the Glacier Noir in July 2004 Showing the Main Sub-glacial Conduit from the Snout and theSmaller Stream Flowing from the Snow Patch on Left

Fig. 3B: View of the Monitoring Site Under the Bridge (Foreground) Looking at the Torrent Du Glacier NoirUpstream Towards the Glacier Noir

3A can be seen top right.

Fig. 4: Suspended Sediment Concentration (SSC) and Turbidity (T) Relationships for Torrent Du Glacier NoirDerived for Each Season, 2003-2005


Fig. 5: Air Temperature and Discharge 10-min Time Series Data for Torrent Du Glacier Noir 11-17 Jul 2003,2004 and 2005

Fig. 6: Daily Mean Air Temperature, Discharge and Suspended Sediment Load for Torrent Du Glacier Noir in2003, 2004 and 2005

About the AuthorsDr Tim StottDr Stott is a Reader in Physical Geography & Outdoor Education at Liverpool John Moores University wherehe is Curriculum Leader for Outdoor Education Programmes. His research interests are in fluvial geomorphologyand he currently works in proglacial areas in the French Alps where he is investigating the impacts of climatechange on glacial meltwaters and sediment transport processes. He has a long standing interest in environmentalsustainability which he pursues through his research, through his teaching in environmental education and via


134

his membership of organisations and professional bodies such as the Alternative Technology Association andRoyal Geographical Society.

Dr Nick MountDr Mount is a Lecturer in GIS and Physical Geography in the School of Geography and the University of Not-tingham, UK. His research interests are in fluvial geomorphology and GIS applications. He currently works inproglacial areas in the French Alps where he is investigating the impacts of climate change on glacial meltwatersand sediment transport processes.


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