Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 erent peri- ff , and S. Gao 1 , X. Zou 3 erent from downstream to upstream , F. Bai ff 3 , J. Li 1 9114 9113 , Y. Yang 1 , Y. P. Wang 2 , J. Jia 1 This discussion paper is/has beenSciences under (HESS). review Please for refer the to journal the Hydrology corresponding and final Earth paper System in HESS if available. Ministry of Education Key Laboratory for Coast and Island Development, Key Laboratory of Submarine Geo-Sciences, Second Institute of Oceanography, Qingdao Institute of Marine Geology, Qingdao 266071, China of the Changjiang;mainly after from 2003, the upstream although areas,large the the extent silt from clay and the component erosion sand of componentsthe may the have sediment mid-lower been be source and derived estuarine of still to reach thecould a main originated estuarine-coastal not channel. be deposits Thus, represented associated by withcaution the the should upstream Changjiang be sources taken alone. in This tracingand observation the implies sediment modeling that sources, the interpreting sediment sedimentshelf records, areas. dynamic processes over the estuary-coastal-continental ment load of the Hanof and the Jialing Changjiang Rivers. became AfterBefore 2003, a 2003, channel the major erosion various source of sub-catchmentssea of the as may main the the be river sediment sources evaluated of discharging bybecause the the analyzing into sediment sedimentary the the entering materials sediment sea. the were components delivered in directly from the the deposition upstream area, portions mulation areas (i.e., theods estuarine and, and on such adjacent asedimentary coastal basis, record. waters) discussed during The about the results di load environmental indicate of change the that signature main the in streamsections, timing the of due the of Changjiang to reduction was the in di step-wise variations reduction the periods in sediment were the observed:2003–2010. sediment 1956–1969, In 1970–1985, load addition, 1986–2002, the of and proportion theRiver of continuously the sub-catchments, increased sediment and load before four originating 2003, from due the to Jinsha the sequential reduction in the sedi- The variations in sedimentRiver by load human and activities compositionment were load from analyzed. in The tributaries the temporal-spatial ofwere main variations determined. the river in of We Changjiang the the identified sedi- Changjiang the under grain the size impact variation of of dam emplacement the sediment in the accu- Abstract Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/11/9113/2014/ 11, 9113–9143, 2014 doi:10.5194/hessd-11-9113-2014 © Author(s) 2014. CC Attribution 3.0 License. 1 Nanjing University, Nanjing 210093,2 China State Oceanic Administration,3 Hangzhou 310012, China Received: 7 June 2014 – Accepted: 18Correspondence July to: 2014 J. – H. Published: Gao 1 ([email protected]) August 2014 Published by Copernicus Publications on behalf of the European Geosciences Union. Variations in the characteristics of Changjiang sediment discharging into the sea due to human activities J. H. Gao 5 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent tributaries ff erent sub-catchments, ff erent periods is critical to the anal- ff erent periods (Lu et al., 2003). Therefore, the ff 9116 9115 erent tributaries. There have been studies about the ff erent sub-catchments to the marine deposits and de- erent rock properties and climate types; therefore, the ff ff ect. The importance of these two features lies in that they reflect ff This paper aims to (1) study the temporal-spatial variations of sediment load of the The Changjiang is one of the largest rivers in the world. A portion of the sediment Sediment provenance tracing is a major method used to study the spatial-temporal Because marine deposits consist of the materials from di are highly variable (Wang et al.,iment 2006). yield The varied from spatial-temporal the patternsthe tributaries of main changes the river sed- of the the sediment Changjianggrain contribution during size di of and each composition tributary ofload to the of sediment the might Changjiang vary River. with decreases in the sediment main river of theically Changjiang analyzing under the the variationsChangjiang in impact catchment; sediment of (2) load dams identify originating emplacement, the from by tributaries grain systemat- within size the and composition variations of the to dam emplacement and soil/waterthe conservation dam projects interception (Yang et accounted al., for2014). 2002), 90.10 % The of of which Changjiang the catchment sediment consistsdle load of reduction and numerous (Gao lower branches, et reaches and al., itsphysical have upper, di and mid- chemical properties of the sediment originating from di shelf regions and predicting thechange, response sea of level the change, marine and sedimentary human system activities. to climate from the Changjiang catchment formsthe a other large portions delta system escapeChina (Milliman from et Sea, the al., and delta 1985); Okinawa and and Trough,mentation thereby are and biochemistry exerting transported of a to these considerable areas thethe impact (Liu sediment Yellow et on load Sea, al., of the East 2007; the sedi- Dou Changjiang et into the al., sea 2010). was Recently, reduced considerably in response modify the “end-member” characteristics.in Therefore, the knowledge catchment about sedimentysis composition the of during variations the di changeterrestrial in sediment end-members. the Furthermore, mineralogy thisaccurately and knowledge analyzing is geochemical the also features sediment meaningful and for origin the and distribution selection of of estuary coast-continental 2013). However, variations in the composition of sediments supplied by a catchment (Morton and Hallsworth, 1994; Svendsen and Hartley, 2002; Yang et al., 2009; He et al., Farnsworth, 2011; Yang et al., 2011).ations However, less in attention has the been grain paidtogether size to with the and vari- composition its of e the sediment sediment in contribution response of totermine di human the mineralogy activities, and geochemistry characteristics. distribution patterns of terrestrialvalid sediments and in accurate end-member continental components margins; onchemical the thus, basis characteristics constructing of of the mineralogical catchment and sediment geo- is a prerequisite for such an analysis sediment load reduction andthe alterations sediment in originating sediment fromimpact grain di of size human and activity theiment (particularly proportion discharge large into of hydrologic the project) sea,tative on rivers by changes (i.e., analyzing in Milliman, the the 1997; long-term sed- Syvitski, 2003; variation Syvitski trends and of Saito, represen- 2007; Milliman and the geomorphology and eco-environmentregions of (Gao estuarine, and coastaland Wang, and 2008; products continental Gao of shelf etment the transport al., catchment-coast pathways 2011). system, from Thus,climate including catchment change the those to and source-sink continental human associated processes activities,Nittrouer, margins with 2002; have under Gao, received sedi- 2006). the increasing impact attention (Driscoll of and variations in the sediment characteristics at the deposition site should result from both Human activities inenvironmental river changes catchments in coastal havesediment oceans flux exerted (Syvitski into significant et the sea al.,tivities impacts has 2005). (Vörösmarty drastically on Recently, et decreased the the al., under global the 2003; eco- influence Walling, of 2006), human resulting ac- in considerable changes in 1 Introduction 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , originates 2 km 6 erent mineralogy ff 10 × 9118 9117 erent periods; and (3) discuss the significance of ff from 5 smaller tributaries (the Gan, Fu, Xin, Rao, and Xiu Rivers) ff erent entrances. Four tributaries enter Lake Dongting from the south ff Most of the Changjiang drainage basin was developed in the Yangtz block. Aside stream to downstream). Four gaugingthe stations Pingshan are located station at for the upstream the tributaries: Jinsha River, the Gaochang station for the Min River, 3.1 Data sources Data for theChangjiang River annual are regularly sedimentand collected we by acquired load the the Ministry annualin and sediment of load the Water suspended data Resource main for of 26tions sediment reach China, hydrological covers stations and grain a distributed seven 55main size of year reach period the i.e., of (1956–2010). the tributaries. Five Zhutuo, the The Cuntan, gauging Yichang, dataset stations Hankou, are for and situated these Datong in stations gauging the (from sta- up- intermediate grade were only2007). sparsely observed in these regions (Zheng and Zhang, 3 Material and method and geochemical characteristics (Table 1). Specifically, quaternarydominant phase sediment in is the the pre- uppermostgreen Tibet Plateau schist-amphibolite area, faces with in somein metamorphic South Southwest rocks Qinghai of China Province, are whereasate covered adjacent rocks by districts (the various Yungui plateau rocks,Panxi, and such and Sichuan as Basin), Guizhou), purple Emeishan andet shale basalt felsic (Yanyuan-Lijiang, al., and and carbon- 2006). maficthe Clastic mid-lower intrusive rocks portion rocks and of (Western the felsic Sichuan) Changjiang magmatic basin. (Zhou In rocks contrast, are metamorphic extensively rocks of distributed low- in from the complex Meso-CenozoicArchean tectonic metamorphic activities, rock, diversemagmatic lithologies Paleozoic and ranging carbonate clastic from and rocks,system and clastic Quaternary (Wu rocks, sequences et Meso-Cenozoic cangion al., also to 2005). be another found (Yang These et within al., rocks the 2004), are and they heterogeneously are exposed characterized by from di one re- from the Changjiang to the East China Sea. channel at the Chenglingji gauging stationfreshwater (Dai lake et in al., China, 2008). and PoyangLake Lake it receives is directly runo the exchanges largest and interactsand with discharges the freshwater river. into Poyang theestuarine Changjiang reach at of Hukou the (Shankmanet ChangjiangThe al., extends local 2006). from The water Datong and (tidalquantity limit) sediment in to supply the comparison from river withstation this mouth. is that part a from of critical river the basin station; upstream. is its Therefore, much records the smaller are Datong in often gauging used to represent the sediment flux basin. The catchmenthills area with of elevations this ofsecond section largest less freshwater mainly lake than in comprises 200 China,Lake m alluvial and via part (Yin plains of five et the and di main al.,and river low flow 2007). southwest, enters Dongting The and Dongting water Lake from is Dongting the Lake flows into the Changjiang main river The Changjiang, with a drainage basinin area the of Qinghai-Tibet approximately 1.80 Plateau andThe flows upper reach 6300 km of eastward the(Fig. toward river, 1), the from the East is upstream China the sourcemain Sea. major to upstream sediment-yielding the river Yichang area gauging has ofRivers. station the four The entire major upper catchment reach tributaries,1000 (Shi, region i.e., m a.s.l. 2008). is the The typically (Chen Jinsha, mountainous, et Min,Datong with gauging al., Jialing, an station, 2001). and elevation with exceeding The Wu threethe large mid-lower Dongting inputs Lake reach joining drainage the extends basin, main from the stream Hanjiang Yichang in River, this to and section: the the Poyang Lake drainage changes in sediment characteristics in the sedimentary environment. 2 Regional setting sediment entering the sea during di 5 5 20 25 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (3) (2) (4) (1) was erent larger k ff d C was obtained k for samples for lower than 1.96 i C m values calculated with were defined as C k . The intersection point of d 2 C was calculated as k and 1 C 9120 9119 0.05, a positive Man-Kendal statistics = ) was located within the confidence interval, pro- n P ≤ ...n k ), where the accumulative number ≤ 1,2 ...n n 2 = k ...x ( 3 1,2,3 5) 2 x ) was calculated, and the normally distributed statistic , i = + C 2 n ≤ k x k ≤ , j 1 k and ] x 72 ≤ ] 1)(2 ( k 1 ≤ k 1) d − (1 = C [ d 2 [ t − j k is the forward sequence, and the backward sequence UB 4 E ( X k i k ( k − var > x k m k i = p 1 d ] x = k = k i ] X = d k [ k = d [ k E Var d The mean and variance of the normally distributed statistic expressed as (Hamed and Rao, 1998) metric competitors (Serrano et al.,was 1999). Trend conducted analysis based of on the sedimentand this load method. partial changes Before autocorrelation using functionshydrological the data. were M–K The used test, results to the indicatedthe that autocorrelation examine data. there the was The autocorrelation no modified significantload of M–K autocorrelation all data: in method waswhich used to analyze variations in the sediment 3.2 Analytical methods The Mann–Kendall test (M–K test)analyze is long-term a hydro-meteorological nonparametric time method, serials andtest (Mann, it 1945; does has Kendall, been not 1955). used assume This to any distribution form for the data and is as powerful as its para- entrances where the Changjiang river dischargesjiangkou, into Dongting Shadaoguan, Lake: Ouchi the (Kang), Mituoshi, Xin- andstation Ouchi monitors the (Guan) Dongting stations; Lake and waterhydrological entering the stations the Chenglingji main are river distributed offor the in the Changjiang. the Six Gan Poyang River, Lake theRiver, system: the Lijiadu Wanjiabu the station station Waizhou for for the station the the Xiu Hukou Fu River, station the River, for Hushan theof station where Meigang the for the station the Changjiang. Poyang for Rao Lake River, the water and Xin discharges toward the main river Huangzhuang station is thehydrological control stations distributed gauging in station theat Dongting for Lake the the system: four Han four tributaries stations River.River, are the There entering located Taojiang are Lake station ten Dongting forthe the i.e., Zi Shimen the River, Station the Xiangtan for Taoyuan station station the for for Li the the River; Yuan River, Xiang and and five stations are situated at the five di the Beibei station for the Jialing River, and the Wulong station for the Wu River. The UF 4.1 Stepwise reduction in the sedimentAs load shown of the in tributaries Fig.correlation 2, with the their sediment cumulative reservoir load storage of capacity the (CRSC), seven suggesting tributaries that exhibited a negative Then, the normalized variable statistical parameter UF than 1.96 indicates an significantindicates increasing a trend; significant while decreasing trend. a negative 4 Results where UF using the same equationprogressive but and with retrograde a series retrogradethe were sample. two The lines, named viding the beginning of thedistribution step at change the significant point level within of the time series. Assuming normal 5 5 20 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − , exhib- value in 1 in 1999– − 1 1 − − in 1956–1998 1 − in 1986–2002. Due 1 − in 1989–2010. In addition, 1 − erent sections of the main river ff erences in the sediment load vari- ff in 1985–1998 and 27 Mt yr in 1986–2002; correspondingly, the sed- 1 in 2003–2010 and that of Datong station − 1 1 − − 9122 9121 ers from the most serious water and soil erosion area in in 1968–1988 and then 9 Mt yr ff 1 in the same time period. − 1 − in 1956–1985 to 404 Mt yr 1 in 1999–2010. Although the CRSC of the Min River catchment is low − 1 − Overall, there were significant temporal-spatial di The CRSC of the three mid-stream sub-catchments of the Changjiang exhibited The Han River was an important sediment source for the middle portion of the ations of the Changjiang main river: the sediment load began to decrease later in neglected in these previousbegan studies. to The decrease sediment afterfrom load 533 1985: of Mt yr the the upstream sedimentiment Changjiang load load of of the theto Datong the Yichang station Three further station Gorges decreased decreased Damstation to (TGD) decreased 340 emplacement considerably Mt in yr to 2003, 55decreased Mt the to yr sediment 152 Mt load yr of Yichang contrast, the sediment loadbecause of the the annual sediment Datong load stationvious supplied by studies decreased the have to Han suggested 445 River that Mt decreasedsea the by in began sediment 95 to 1970–1985 load Mt. decrease from Pre- in thethis the Changjiang decreasing 1980s entering (Yang the trend et al., alreadyment 2002); occurred however, load we in of demonstrate 1970, that the and Han the River impact on of the the sediment reduced flux sedi- of the Changjiang into the sea was Due to discrepancies among the sedimentthe load variations decreasing of the trends seven sub-catchments, ofwere the also sediment inconsistent load (Fig.the in 4): the Datong, from di Hankou, downstream1969, Cuntan, to 1969, Zhutuo, 1985, upstream, 1991, and 1999, the andsediment Pingshan sediment 2001, load respectively, stations suggesting load that began of began the to downstream the to decrease sediment earlier decrease load than in of theited the upstream fluctuations Datong from sediment station, 1956 load. with to Although an 1969, average the value quantity of generally remained 503 Mt at yr a high level. In sediment load began to decrease laterlocations. at upstream locations compared to downstream 4.2 Spatial-temporal sediment load variations of the main river spatial variation trends of the sediment loads of the seven tributaries indicated that the the Jialing River, 1994 for the Min River, and 2001 for the Jinsha River. The temporal- in 1957–1967 to 28 Mt yr the reduction in the sedimentcorrelated load with entering the the Dongting increase and in Poyang the Lakes CRSC. was highly rapid increasing trends afterthe Poyang the Lake, Han 1960s, River, and and1984, Dongting Lake respectively the began (Fig. to sediment decrease 3). loadstream in However, 1963, Changjiang of the 1968, began the and sediment to loads decrease catchment1980s), in of and of the the the 1970s sediment four (with loads rivers a began of significant to reduction the decrease in up- in the 1984 for the Wu River, 1985 for Changjiang before 1968. However, due to damHan emplacement, River the increased average CRSC stepwise ofthen the from 55.4 3.7 % % in in 1989–2010.seven 1957–1967 Currently, tributaries to the contributing 45.8 Hanjing % to River in thehibited has Changjiang. a 1968–1988 the stepwise Thus, and reduction highest the for average CRSC the sediment of three load the aforementioned ex- period, i.e., from 125 Mt yr (1.72 % in 2010), theCRSC. sediment Due load to the still rapid continuouslyin increase decreased in 1985 with the and increases CRSC of in 9.291956–1984, % the the decreased Jialing in River sharply 1998, catchment to to the2010. 4.49 125 As % sediment Mt yr the load, CRSC insharply increased terms decreased to from of 5.42 33 %, Mt theduced the (1956–1983) 154 to average Mt to 13 yr sediment Mt 20 Mt load (1994–2010) (1984–1993) when of and the the then CRSC Wu increased further River to re- 7.82 % in 1994. River catchment, which su the Changjiang catchment, is(Shi, the major 2008). sediment Due source toin of reservoir the 1998, construction, upstream and the Changjiang to the CRSC 185 drastically average Mt yr increased sediment to load 5.57 % decreased from 245 Mt yr dam emplacement caused a continuous decrease in the sediment load. The Jinsha 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | of 50 D 50 erent erent D ff ff ranged 50 D and sediment load moved variation interval gradually 50 50 D D from the Datong station was not as 50 D was 0.017 mm in 1960–1969, 0.012 mm 50 ) of suspended sediments from the Yichang D 50 9124 9123 D variation range of the two stations did not overlap 50 D erent sub-catchments. The temporal-spatial discrepancy among the ff of the Yichang station was greater than that of the Datong station in 1960–1969, periods 50 D The sand fraction of the Yichang station, ranging from 30 to 32 %, remained stable In addition, the degree of inter-annual variation in the upstream sediment grain size Changjiang entering the seato changed the considerably TGD during emplacement: the the 2003–2010 sediment period proportion due due to channel erosion of the main sha, Jialing, and Hanrespectively, Rivers, of and the the sediment threeRiver to rivers decreased, contributed the 35.0, Datong the 24.3, station.spectively, Jinsha and As of 19.0 and the the %, Jialing sediment sedimentwhereas load Rivers load the of accounted at contribution the of the for Han theperiod, Datong 46.7 due Han station to and River the during decreased reduced 27.6 sediment %, to thesha yield 5.8 in River re- 1970–1985 %. the to During period, Jialing the River, the thethat sediment 1986–2002 contribution of of load the the of Jin- the Jialing Datong River station decreased further to increased 15.0 %. to The 64.2 % composition and of sediment from the The sediment load fromsupplied the by Changjiang entering di thesediment sea load mixes variations weatheringsea of products sub-catchments to caused decrease1956–1969, the and the sediment resulted sediment load in load entering changes of the the to Datong the station sediment mainly composition originated (Fig. from the 7). Jin- In periods exhibited no clearcomponents changed variations, considerably. the inter-annual variation range and sediment 5 Discussions 5.1 Variations in the composition of sediment entering the sea during di fraction decreased to 10.4Datong % station (Fig. could 6). be The dividedsand into variation reached two in 17.5, stages: 57.7, the the and40.7 sediment content %, 24.8 %, fractions grain respectively, respectively, for size in in clay, silt, of 1960–1985,average 1986–2010. and and the value 32.4, The of 26.9, above the and analysis grain suggests size of that the although sediment the entering the sea during the di Furthermore, after 2003, the clay content further increased to 49.5 %, and the sand from 1960 to 2002. However,increased from 1960–1969 from to 14.2 1985–2002, the to clay 31.8 content % fraction and the silt fraction decreased from 54.4 to 37.0 %. size variations of the Yichang andthe Datong stations in the fourand stages the also two indicated stations that werethe similar Yichang in station 1970–1985 was and less 1986–2002;from than after 0.003–0.007 that 2003, mm of the for the2003–2010, Yichang Datong suggesting station. station that Furthermore, and the 0.008–0.013after mm 2003. for Datong station in creasing trend was recorded in 2002 (0.09 mm) and 2003–2010continuously (0.10 decreased mm). during the fournarrowed, stages, and i.e., the the distribution rangefrom of the the data top point left of that corner of to the the bottom Datong right station corner generally in shifted the vertically coordinate downward. system; The however, sediment grain ment grains size downstreamThe of variation the in the reservoirs medium become grainstation size significantly (Fig. ( 5) finer indicated (Xu, thatin 2005). the 1970–1985, average 0.009 mm inthe 1986–2002, sediment and grain 0.004 size mm from in theing upstream 2003–2010, trend. Changjiang suggesting In exhibited that a contrast, continuous thesignificant decreas- decreasing as trend that of fromin 1960–1969 the (0.12 Yichang mm) was station similar during to the that in four 1970–1985 stages: (0.13 mm), the and average a slight de- periods were observed: 1956–1969, 1970–1985, 1986–2002, and 2003–2010. 4.3 Variations in the grain sizeBecause of most the sediment of entering the the coarse-grained sea sediment is intercepted by reservoirs, the sedi- upstream locations than in downstream locations, and four stepwise reduction stage 5 5 20 25 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- ff (Li et al., 2011), 3 − after 2003. Furthermore, the quantity of 1 − 9126 9125 , was underestimated 62 Mt yr 1 − environment Actually, the record of the Datong station is not the real sediment flux of the The above analysis indicated that as the sediment load entering the sea decreased, the major source of claydue in to the sediment the of drastic the decrease upstream in Changjiang the during sediment this load period of the Jialing River. that the sediment from1992). the In Changjiang 1986–2002, mainlythe the originated Changjiang Jinsha from catchment, River these accounting becamesea; two thus, for the rivers the 64.2 major detrital % (Lin, mineralload sediment of tracing of yield the results the source sediment of upstream thisand of load period portion the entering Jialing indicated of and the that Changjiang Min theChangjiang Rivers mainly sediment (Wang provided originated et less from sediment al.,supplied to the 2006). by the Due Jinsha the mid-lower to reaches Jinsha River, of and the the Jialings clay River fraction (Lin, of 1989), the the sediment Jinsha River was is mainly certain to be sediments, respectively (Thiry, 2000; Garzantiresults and concerning Andó, 2007). the However,ent sediment the periods tracing source were inconsistent of (Wangwith et the the al., variations Changjiang 2006), in and catchment thethe sediment these during Jinsha composition. discrepancies During correlated and di 1970–1985, Jialingtherefore, the Rivers contribution the to of results the of sediment the load detrital entering and the clay sea mineral reached analysis 74.3 of %; this period indicated Generally, catchment sediments intochange information, the thereby sea becomingcatchment contain an changes rich important (Brown catchment et mediumtics environmental al., for of 2009). the identifying Changjiang The previous enteringet variations the al., in sea 2001); have the traditionally however, sediment been thesea characteris- slow load, changed and grain rapidly gradual size, (Saito in andcharacteristics recent of composition decades, the of resulting sediment sediment enteringand in entering clay the rapid the minerals sea. changes are As in widely important the used tracers, to mineralogy detrital trace mineral the provenance of fine and coarse grained sediment load of the Changjiang entering the sea. 5.2 Implications of the changes in sediment composition for the sedimentary the erosive sediment of mid-lower and estuarine reach accounted for 63.0 % of the iment load reduction, the estuarinetation river channel status of before the the Changjiangcially stayed late after in of 2003) sedimen- 1990s, (Li,status and 2007; of Wang then et the converted al., estuarine intoload 2009). reach erosion variation In of of status addition, the the (espe- the Datongsediment Changjiang sedimentation/erosion station load (Fig. was of Datong 8). also station According correlatedestuarine and to the reach, to the sedimentation/erosion and relationship the rate assuming between of sediment the the the a main sediment real river bulk of sediment density loadof of 214 of 1.23 Mt t yr m the Changjiang entering the sea, in terms of the quantity portion of the mainstation. river became the greatest source of sedimentChangjiang load into of the the sea, but Datong merelydue the to sediment the delivery adjustment to estuary of of estuarine the main Changjiang, river channel. Attributing to the upstream sed- position were mainly determinedJinsha, by Jialing, the and Han changes Rivers inof i.e., with the the the sediment Han sequential and contributions reduction JialingJinsha in of River Rivers, the the continuously the sediment increased, loads proportion whereas of thethe proportion the other of sediment the sub-catchments load sediment originating remained loadload from from of stable. the the Overall, Datong during stationmid-lower mainly this stream originated period, channel from the upstream ofsediment of the sediment the (Yang Changjiang Changjiang, et was and al., one the 2011). of However, major after sinks 2003, of channel the erosion upstream of the mid-lower In addition, the Jialing andload Han of the Rivers Datong only station, contributed respectively. 4.3 and 5.3 %although of the the sediment average sedimentcomposition grain changed size displayed considerably. Before no 2003, clear the variations, variations the in sediment the sediment com- river reached 48.0 % and that of the Jinsha River decreased dramatically to 24.1 %. 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | of sand to the sedi- 1 − erent periods. Estuary-coastal- ff erent sediment components had ff of silt, and 20 Mt yr 1 − 9128 9127 of clay, 43 Mt yr 1 − erent grain sizes of the sediment entering the sea also indicated ff The patterns ofRiver sediment have delivery been changed, from resulting the in sub-catchments spatial-temporal of changes in the the Chnagjiang sediment erent origins. Briefly, due to the impact of human activities, which has intensified at an acceler- After the emplacement of the TGD in 2003, the clay, silt, and sand fractions originat- In addition, the di 1. ff observed in the sedimenthysteretic? record What of is the thenamic East retardation environment China of time? Sea the Under shelfall Changjiang the these area? estuary questions conditions Is will and of the have East more a response uncertainty, China complicated and Sea deserve dy- continental to study shelf, further. 6 Conclusions ment behavior of thewhich should Changjiang also estuary be and consideredis when the calculated, the Zhejiang-fujian modeled sediment and coastal transportment predicted. process mud going of In area, from these terms the areas ofresponse source the to to process variations sink, of in one the can the catchment pose sediment sedi- the composition following of questions: the Could Changjiang the catchment be tions in the sedimentscientific characteristics problems when entering tracing thecally sediment sea modeling sources, will estuary-coastal-continental interpreting shelf inevitably records,tigated. areas, result and which As dynami- in should serious far bein as further end-member inves- sediment components provenance inducedChangjiang tracing by catchment, is changes the of concerned, end-memberto the due components sediment trace to composition of the the in onethe sediment variations the phase sediment origin cannot component of be variations another used entering phase. the For sea will the inevitably sediment change dynamic the process, sedi- di ated rate, the sediment load,from component, the composition, Changjiang and mineralogy changedcontinental characteristics considerably shelf during areas di are the final destination of catchment sediments; thus, varia- by a single sediment component origin when the di component sources from the Changjiang entering the sea could not be represented greater than 55.8 and 74.1 %.Datong These station data mainly imply originated that from thesand the clay fractions upstream fraction of of largely the the comprised sediment Changjiang,reaches the of and of erosive the the sediment silt main and of riverupstream the channel. of mid-lower The and the eroded estuarine Changjiang, “older” andgeochemical sediment is characteristics also characterized of derived by the from theafter upstream the homologous 2003, sediment the mineralogy (Kang tracing and et resultsorigin al., of (He clay 2009). minerals et Therefore, merely al., reflectof 2013), the the and fine-grained “older”, that sediment coarser of sediment the source. detrital This mineral phenomenon mainly indicates reflects that the all information sediment Lake contributed 13 Mt yr ment load of Datong stationof in the 2003–2010, corresponding which sediment accounted componentcontribution of for of 27.1, Datong strong station 55.8 erosion (Table and of 2). the 74.1 Consideringfractions % estuarine the reach, into the the real sea proportion coming of silt, from and the sand erosive sediment of main river channel, may be because all of the sedimentthough components the mineralogy were characteristics derived of fromcontinuously, the the a Changjiang various homologous catchment sub-catchments source, sediment as al- changed sea the may sources be of evaluated by the analyzing sediment the entering sediment the components ining the from deposition the area. upstream Changjiangof decreased sediment dramatically. originating With from regardriver, the to the Poyang the erosive Lake amount sediment and of Han the River to main the river Changjiang channel main (Yichang-Datong) and Dongting that the clay, silt, and sand fractionDatong of station the during Yichang station the werewhich 1960–1969, greater implied than 1970–1985, those that and of the the 1986–2002 sedimentoriginated periods fraction (Table from of 2), clay, the silt,tween upstream and the sand river Changjiang water entering and without the the riverbed. regard sea Thus, mainly the to above analysis sediment also demonstrates exchange that be- 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | mann, T., Macaire, J. J., Moldenhauer, K. M., ff 9130 9129 The study was supported by the National Basic Research Program of more than 55.8 % ofthe silt main and river 74.1 channel. % of sand wereBefore supplied 2003, by the various the sub-catchments eroding asthe bed the sea of sources may of be the sediment evaluatedtion entering by area; analyzing after the 2003, sedimentsociated the components with sediment in the source the Changjiang of deposi- couldalone. not the be estuarine-coastal represented deposits by as- the upstreamSuch sources changes indicatesources, interpreting that sediment caution records, and should modeling the be sediment dynamic taken pro- in tracing the sediment load within the main1956–1969, stream, 1970–1985, and 1986–2002, four and stepwise 2003–2010. reduction stages wereBefore observed: 2003, the variations inmainly the determined sediment by composition the at changessha, the in Jialing, marine the and sites sediment Han were contribution Rivers.Changjiang After made supplied 2003, by around channel the 63 % erosion Jin- of of the the sediment mainBefore load river 2003, into of the the the clay, sea. silt,from and the sand upstream fractions regions enteringof the the of sea clay the mainly component river. originated of However, the after sediment 2003, was only originated around from the 27 % upstream areas; cesses over the estuarine, coastal and continental shelf areas. 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E.: Fromcatchment sedimentary sediment flux, records Geomorphology, to 108, sediment 35–47, budgets: 2009. Multiple approaches to 4. 5. 2. 3. Hamed, K. H. and Rao, A. R. :AHe, modified M. Y., Mann–Kendall Zheng, trend H. B., test Huang, for X. autocorrelated T., Jia, data, J. T., J. and Li, L.: Yangtze River sediments from source Garzanti, E. and Andó, S.: Heavy mineral concentration in modern sands: implications for Gao, J. H., Jia, J. J., Kettner, A. J., Xing, F., Wang, Y. P.,and Gao, S.: The impact of reservoirs on Gao, S., Wang, Y. P., and Gao J. H.: Sediment retention at the Changjiang sub-aqueous delta Gao, S. and Wang, Y. P.: Changes in material fluxes from the Changjiang River and their im- Driscoll, N. and Nittrouer, C.:Gao, Source S.: to Sink Catchment-coastal studie, interaction Margins in Newsletter, 5, the 1–24, Asia-Pacific 2002. region, in: Global Change and In- Dou, Y. G., Yang, S. Y., Liu, Z. X., Clift, P. D., Yu, H., Berne, S., and Shi, X. F.: Clay mineral Dai, S. B., Lu, X. X., Yang, S. L., and Cai, A. M.: A preliminary estimate of human and natural Chen, Z., Li, J., Shen, H., and Wang, Z. H.: Yangtze River of China: historical analysis of Brown, A. G., Carey, C., Erkens, G., Fuchs, M., Ho References China (Grant No. 2013CB956503)41376068). and the Natural Science Foundation of China (Grant Nos. Acknowledgement. 5 5 30 25 20 15 10 15 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | n, London, 1955. ffi 9132 9131 ects on sediment yield in the upper Yangtze River, Geogr. Res., 27, 800– ff Plain and its paleoenvironmental implicaion,Chinese). J. East China Normal Univ., 1, 92–98, 2005 (in Land., 34, 1587–1593, 2009. sediments and their tracing(in implications, Chinese, with Acta English Sedimentologica Abstr.). Sinica, 24, 570–578, 2006 continental origin, Earth-Sci. 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Yangtze X.: River Two unique weathering regimes in the Changjiang and Yang, S. L., Zhao, Q. Y., and Belkin, I. M.: Temporal variation in the sediment load of the Yangtze Xu, J. X.: Variation in grain size of suspended load in upper Changjiang River and its tributaries 5 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 1 − ) Sand (Mt y 1 − 9136 9135 ) Silt (Mt y 1 − Yichang Datong Yichang Datong Yichang Datong Sketch of the Changjiang catchment and location of the hydrologic stations for the Time Period Clay (Mt1960–1969 y 1970–19851986–20022003–2010 78 105 128 78 27 86 113 297 48 257 212 291 257 174 25 172 159 77 63 134 102 50 3 27 Annual quantities of clay, silt, and sand at the Yichang and Datong stations during erent periods. ff Table 2. di Figure 1. Changjiang catchment. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

in

at aat and and also also

1985 , - average average Hankou, Hankou,

were were 1999 1970 an decrease earlier earlier than

,

ady occurred occurred ady in e

catchments, catchments, the Previous studies Previous 1991 - Datong, . , decreas the the

1985 95 Mt main river main , the 1969 began began to

,

Datong Datong station, with the the in in 1969 respectively.

1969, the quantity generally remained remained generally quantity 1969, the , 2 to to C

decrease decrease different different sections of the main river and

Datong Datong station decreased to 445 Mt 1956 13 1

9138 9137 C

the the the the Changjiang entering the sea began to the the of of

began began to

from from denotes sediment sediment load variations of the seven sub s

▲ ations from ations the the and and

● Although Although the sediment load of . ); however, we demonstrate that this decreasing trend alre trend decreasing this that demonstrate we however, ); ed fluctu sediment sediment load in the the sediment load iment iment load the by supplied Han decreased by River , he symbol exhibit T ): ): from downstream to upstream, the sediment load of

, 1 - and and Pingshan station emporal sediment load variations of sediment emporal

t , crepancies crepancies among - sediment sediment load Fig. Fig. 4

Relationship between the reduction in sediment load and cumulative reservoir stor- M–K trends of the sediment load for the Jinsha, Min, Jialing, Wu, and Han Rivers and K trends of the sediment load for the Jinsha, Min, Jialing, Wu, and Han Rivers and the Poyang and In In contrast Yang et al., 2002 al., et Yang - M 503 Mt 503 Mt y

. patial suggested suggested that the sediment load S Due Due to dis 1980s (

ure ure 3 Figure 3. the Poyang and Dongting Lake system. age capacity index indefined as the the tributaries ratio andthe of contributed main the catchment. river. Data reservoir The regardingChina storage reservoir Reservoir reservoir capacity Name construction storage and (Ministry originate capacity average of from Water annual The index Resources water Code is of For discharge the People’s of Republic of China, 2001). Figure 2. have have the value of of value high level. because the annual sed Cuntan, Cuntan, Zhutuo 2001, suggesting respectively, that the downstream sediment load the upstream decreasing decreasing trends of the inconsistent ( 4.2 Fig system. Dongting Lake

262 260 261 256 257 258 259 255 251 252 253 254 249 250 247 248 246 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

d of of the the s 1969, 1969, in in the on -

1 - he symbol decrease T Due Due to 1956

: Yichang Yichang station 2002. - the the sediment sediment load of the 1986 he in in sediment sediment load variati T

2002; 2002; correspondingly, the 1 - - . the the 1986 in Han River Han River on the flux sediment of the ediment ediment load of

1 - the the : : the s erent gauging stations of the Changjiang main

ff of of Datong station decreased to 152 Mt y 14 9140 9139 began began to decrease later in than locations in upstream spatial differences spatial in differences 003, the sediment load of station Yichang

- in in these previous studies and and that

sediment load sediment of 1985 to 404 Mt y -

2010 2010. - - 1956 reduced reduced 003 in four four stepwise reduction stage periods were observed 1

- the in in 2 respectively. significant significant temporal , 1 - 2 and 2003 and erent periods at the Yichang and Datong stations. Data are not available began began to decrease after 1985 , ff C , and re re Datong Datong station further decreased to 340 Mt y Mt Mt y we of of the sediment load gauging stationsfor different of the Changjiang main river. the the and 2002

. - 1 C to to 55 Mt y Relationship between the medium grain size of suspended sediments and the sedi- M–K trends of the sediment load for di into into the sea was neglected

K trends - M

denotes .

1985, 1986 1985, ▲ - Overall, Overall, there Figure 5. river. Figure 4. for the Datong station in 1968–1970, 1972–1973, and 1975. ment load during di and and

Figure 4 Figure ●

the Changjiang main river: the the river: Changjiang main load sediment downstream locations 1970 same time period time same sediment sediment load of Three Gorges Dam (TGD) emplacement in 2 considerably Changjiang upstream Changjiang decreased from 533 in in 1970, and the of impact

278 277 276 273 274 275 272 268 269 270 271 266 267 263 264 265 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 9142 9141 erent periods, and the pie charts represent the sediment load erent sub-catchments to the sediment load from the Changjiang ff ff erent periods. Gray bars denote the sediment load variations from ff erent tributaries to the Datong station. ff Contribution of di Distribution of the suspended sediment grain size of the Yichang and Datong stations erent tributaries during di ff Figure 7. entering the sea duringdi di contribution of the di Figure 6. in 1960–1969, 1970–1985, 2002, and 2003–2010. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 9143 Relationship between the sediment load of Datong station and the sedimenta- Figure 8. tion/erosion rate of therate from main Li, river 2007). of estuarine reach (the data of the sedimentation/erosion