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Impacts of climate change on surface hydrology in the source region of the Yellow River

Yuan, Feifei LU (2015)
Abstract (Swedish)
Popular Abstract in Swedish

Nästan 35% av den totala avrinningen i Gula floden härstammar från dess källområde och vattenförsörjningen nedströms är därför beroende av de rådande förhållandena i detta område. Minskad vattenföring i floden på grund av klimatförändringar förväntas leda till negativa konsekvenser för de 110 miljoner invånarna i avrinningsområdet och problem uppstår för såväl jordbruket som vattenförsörjningen av hushåll och industri. Denna studie behandlar därför klimatförändringars påverkan på källregionens ytvattenhydrologi. Målsättningen är att resultatet ska kunna användas för vattenresursplanering och bättre hantering av vattenresurserna i Gula flodens avrinningsområde. Hydroklimatiska trender och... (More)
Popular Abstract in Swedish

Nästan 35% av den totala avrinningen i Gula floden härstammar från dess källområde och vattenförsörjningen nedströms är därför beroende av de rådande förhållandena i detta område. Minskad vattenföring i floden på grund av klimatförändringar förväntas leda till negativa konsekvenser för de 110 miljoner invånarna i avrinningsområdet och problem uppstår för såväl jordbruket som vattenförsörjningen av hushåll och industri. Denna studie behandlar därför klimatförändringars påverkan på källregionens ytvattenhydrologi. Målsättningen är att resultatet ska kunna användas för vattenresursplanering och bättre hantering av vattenresurserna i Gula flodens avrinningsområde. Hydroklimatiska trender och variationer i klimatologi under de senaste 50 åren undersöktes för att identifiera förändringar över tid och rum. Analysen pekar på en årlig ökning i medeltemperatur över hela området och under de senaste decenniet har ökningen eskalerat. Förändringar i den årliga medelnederbörden varierade mellan stationerna, och generellt kunde en viss minskning ses. Årsflödet i floden har minskat påtagligt, allra mest sedan 1990-talet, men under de senaste åren har det synts tecken på en återgång mot högre flöden. En tydlig förändring av temperaturentrenden identifierades för 1998 och en liknande trendförändring av vattenflödet för 1990. Utifrån en säsongsanalys av vattenflödet kan sägas att en minskning har inträffat av nederbörden under sommarmonsunen (juli till september) samtidigt som medeltemperaturen har ökat för årets alla månader. På grund av den försvagade monsunen har medelavrinningen minskat med 0.74 mm/år över hela källregionen. Utöver detta kunde en statistiskt fastställd periodicitet av områdets medelnederbörd och temperatur på 2 till 4 år konstateras. En ännu tydligare 8-årsperiodicitet för vattenflödet var uppenbar från slutet av 1960-talet till början av 1990-talet. För en fördjupad förståelse av förändringarna i vattenflödet har hydroklimatiska trender och kopplingar mellan olika delavrinningsområden undersökts. Nederbörden under sommarmånaderna (juni till september) motsvara i Gula flodens källregion för ungefär 70% av den årliga avrinningen och är därför av stor betydelse för vattentillgången och därmed kommer de minskade flödena under monsunen att medföra vattenbrist för befolkningen i området. Därför har förändringarna av källregionens sommarnederbörd från 1961 till 2010 analyserats och satts i förhållande till jordens havsytvattentemperaturer, likaså till det kopplade systemet som beskrivs av Southern Oscillation Index (SOI). Nederbörden uppvisar en tydligt minskande gradient, från sydväst till nordöst, på grund av den försvagade sommarmonsunen. En uppdelning av regionen i tre områden med homogen nederbörd visar på en tydlig areell variation. Det nordvästra området (zon 1) hade en svagt ökande trend, medan mittendelen och området i sydöst (zon 2 och zon 3), där mest nederbörd faller, hade en statistiskt fastställd minskande trend. Hela regionens sommarnederbörd har visat på en statistiskt fastställd omvänd korrelation till yttemperatur i centrala Indiska oceanen med en fördröjning på 0-4 månader, och liknande relation till yttemperaturen i södra Indiska oceanen och Atlanten, med en fördröjning på 5-8 månader. Analyser av delområden visar på komplexa samband med olika havsområdens yttemperaturer som kan ytterligare förklara variationer i nederbörden. En korrelation konstaterades mellan sommarnederbörden i källregionen och SOI med en fördröjning på 0-2 månader. El Niño-Southern Oscillation (ENSO) påverkar sommarnederbörden i källregionen, och en övervägande omvänd korrelation tyder på att högre yttemperaturer i ekvatoriella Indiska oceanen under El Niño sammanfaller med mindre nederbörd i Gula floden källregion. Kopplingar mellan nederbörden i Gula floden källregion och andra kända globalt kopplade system har identifierats, för att kunna förutsäga sommarnederbörden med hjälp av dessa samband. Nederbörden är kopplad till den Nordatlantiska oscillationen, West Pacific Pattern, och ENSO, samt en omvänd relation till Polar Eurasian Pattern. Prognoserna för källregionens sommarnederbörd utifrån dessa samband är överlag bra och korrelationen mellan prognosen och den observerade nederbörden var generellt större än 0.6. En delvis modifierad nederbörds-avrinningsmodell (Xinanjiangmodellen) applicerades på Gula flodens källregion för att undersöka relationen mellan nederbörd och avrinning. Den potentiella evapotranspirationen i modellen beräknades med Blaney-Criddle-metoden och Monte Carlo-simulering användes för att optimera känsliga parametrar. Pearson-korrelationskoefficienten mellan observerad och simulerad avrinningen var upp till 0.87 under kalibrering och upp till 0.85 för validering. Således gav Xinanjiang-modellen generellt bra simulering av relationen mellan nederbörd och avrinning. Xinanjiang-modellen kan därför vara ett lämpligt verktyg för framtida vattenresurshantering rörande avrinningssimulering och översvämningsprognoser i Gula Flodens källregion. (Less)
Abstract
The source region of the Yellow River contributes about 35% of the total water yield in the Yellow River basin playing an important role for meeting the downstream water resources requirements. The declining water availability caused by climate change in the source region of the Yellow River is expected to have severe repercussions for the 110 million basin inhabitants in terms of water resources affecting agricultural productivity, municipal, and industrial water supply. Thus, this study investigated the impacts of climate change on surface hydrology in the source region of the Yellow River. The presented results have important implications for water resources management in the Yellow River.

Hydroclimatic trend and periodicity... (More)
The source region of the Yellow River contributes about 35% of the total water yield in the Yellow River basin playing an important role for meeting the downstream water resources requirements. The declining water availability caused by climate change in the source region of the Yellow River is expected to have severe repercussions for the 110 million basin inhabitants in terms of water resources affecting agricultural productivity, municipal, and industrial water supply. Thus, this study investigated the impacts of climate change on surface hydrology in the source region of the Yellow River. The presented results have important implications for water resources management in the Yellow River.

Hydroclimatic trend and periodicity during the last 50 years were investigated to identify significant changes in time and space over the study area. Results showed that mean annual temperature increased for all stations and it had an accelerated increasing trend during the last decade. Mean annual precipitation trends varied depending on station location; however, they were generally slightly decreasing. Annual streamflow decreased markedly especially from the 1990s but showed recovery during recent years. Statistically significant changes in trend occurred for temperature in 1998 and for streamflow in 1990. Based on the streamflow change point, seasonal analysis results showed that precipitation mainly decreased during the summer monsoon period (July-September) and temperature increased throughout the year. Corresponding to the weakened monsoon period the average runoff depth is decreasing by 0.74 mm/year over the whole area. Statistically significant 2 to 4-year periodicities for mean areal precipitation and temperature occurred over the area. For streamflow, an even stronger 8-year periodicity was revealed from the end of the 60s to the beginning of the 90s. Frequency analysis investigated the magnitudes of mean annual precipitation and discharge corresponding to a given frequency. Hydroclimatic trends and linkages at each sub-basin were investigated to further improve the understanding of observed streamflow changes.

The summer precipitation (June-September) in the source region of the Yellow River accounts for approximately 70% of the annual total playing an important role for water availability, and its decreasing trend will cause water shortage in the whole river basin. Hence, summer precipitation trends and teleconnections with global sea surface temperature (SST) and Southern Oscillation Index (SOI) from 1961 to 2010 were investigated. Results show that the precipitation has a strongly decreasing gradient from southeast to northwest due to the weakening summer monsoon, and a division of the region into three homogeneous precipitation zones shows marked spatial variability. The northwest part (zone 1) had a non-significantly increasing trend, and the middle and southeast parts (zone 2 and 3) that receive the most precipitation displayed a statistically significant decreasing trend. The summer precipitation in the whole region shows statistically significant negative correlations with the central Pacific SST for 0-4 month lags and with the southern Indian and Atlantic Ocean SST for 5-8 month lags. Analyses of sub-regions reveal intricate and complex correlations with different SST areas that further explain the summer precipitation variability. The SOI had significant positive correlations mainly for 0-2 month lag with summer precipitation. It is seen that El Niño Southern Oscillation (ENSO) events have an influence on the summer precipitation, and the predominant negative correlations indicate that higher SST in equatorial Pacific areas corresponding to El Nino coincides with less summer precipitation in the source region of the Yellow River.

The linkages between the precipitation and global teleconnection patterns were identified, and summer precipitation was predicted based on revealed teleconnections. It was found that precipitation in the study area is positively related to North Atlantic Oscillation, West Pacific Pattern and El Nino Southern Oscillation, and inversely related to Polar Eurasian pattern. Summer precipitation was overall well predicted using these significantly correlated climate indices, and the Pearson correlation coefficient between predicted and observed summer precipitation was in general larger than 0.6.

The performance of the Xinanjiang model for daily rainfall-runoff simulation in the source region of the Yellow River was evaluated. The Blaney–Criddle method was used to calculate the potential evapotranspiration as model input due to data scarcity of this area. The Monte Carlo method was used to optimize the sensitive model parameters. The resulting Pearson correlation coefficient between observed and simulated runoff for the calibration period was up to 0.87, and 0.85 for the validation period. Accordingly, the Xinanjiang model simulated the daily runoff series well in general. Thus, the Xinanjiang model can be a proper tool for further water resources management involving runoff simulation and flood forecasting in the source region of the Yellow River. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Chen, Deliang, Department of Earth Sciences, University of Gothenburg, Sweden
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Source region of the Yellow River, climate change, summer precipitation, ENSO, teleconnection pattern, sea surface temperature, Xinanjiang model, Rainfall-Runoff process
pages
157 pages
defense location
Lecture hall K:F, Kemicentrum, Sölvegatan 39, Lund University, Faculty of Engineering, LTH.
defense date
2015-06-10 10:15
ISSN
1101-9824
ISBN
978-91-7623-311-5
language
English
LU publication?
yes
id
35bedb51-9b1f-44d3-83e5-d6c3d3faf3c2 (old id 5366860)
date added to LUP
2015-05-11 09:27:45
date last changed
2016-09-19 08:45:00
@misc{35bedb51-9b1f-44d3-83e5-d6c3d3faf3c2,
  abstract     = {The source region of the Yellow River contributes about 35% of the total water yield in the Yellow River basin playing an important role for meeting the downstream water resources requirements. The declining water availability caused by climate change in the source region of the Yellow River is expected to have severe repercussions for the 110 million basin inhabitants in terms of water resources affecting agricultural productivity, municipal, and industrial water supply. Thus, this study investigated the impacts of climate change on surface hydrology in the source region of the Yellow River. The presented results have important implications for water resources management in the Yellow River.<br/><br>
Hydroclimatic trend and periodicity during the last 50 years were investigated to identify significant changes in time and space over the study area. Results showed that mean annual temperature increased for all stations and it had an accelerated increasing trend during the last decade. Mean annual precipitation trends varied depending on station location; however, they were generally slightly decreasing. Annual streamflow decreased markedly especially from the 1990s but showed recovery during recent years. Statistically significant changes in trend occurred for temperature in 1998 and for streamflow in 1990. Based on the streamflow change point, seasonal analysis results showed that precipitation mainly decreased during the summer monsoon period (July-September) and temperature increased throughout the year. Corresponding to the weakened monsoon period the average runoff depth is decreasing by 0.74 mm/year over the whole area. Statistically significant 2 to 4-year periodicities for mean areal precipitation and temperature occurred over the area. For streamflow, an even stronger 8-year periodicity was revealed from the end of the 60s to the beginning of the 90s. Frequency analysis investigated the magnitudes of mean annual precipitation and discharge corresponding to a given frequency. Hydroclimatic trends and linkages at each sub-basin were investigated to further improve the understanding of observed streamflow changes.<br/><br>
The summer precipitation (June-September) in the source region of the Yellow River accounts for approximately 70% of the annual total playing an important role for water availability, and its decreasing trend will cause water shortage in the whole river basin. Hence, summer precipitation trends and teleconnections with global sea surface temperature (SST) and Southern Oscillation Index (SOI) from 1961 to 2010 were investigated. Results show that the precipitation has a strongly decreasing gradient from southeast to northwest due to the weakening summer monsoon, and a division of the region into three homogeneous precipitation zones shows marked spatial variability. The northwest part (zone 1) had a non-significantly increasing trend, and the middle and southeast parts (zone 2 and 3) that receive the most precipitation displayed a statistically significant decreasing trend. The summer precipitation in the whole region shows statistically significant negative correlations with the central Pacific SST for 0-4 month lags and with the southern Indian and Atlantic Ocean SST for 5-8 month lags. Analyses of sub-regions reveal intricate and complex correlations with different SST areas that further explain the summer precipitation variability. The SOI had significant positive correlations mainly for 0-2 month lag with summer precipitation. It is seen that El Niño Southern Oscillation (ENSO) events have an influence on the summer precipitation, and the predominant negative correlations indicate that higher SST in equatorial Pacific areas corresponding to El Nino coincides with less summer precipitation in the source region of the Yellow River. <br/><br>
The linkages between the precipitation and global teleconnection patterns were identified, and summer precipitation was predicted based on revealed teleconnections. It was found that precipitation in the study area is positively related to North Atlantic Oscillation, West Pacific Pattern and El Nino Southern Oscillation, and inversely related to Polar Eurasian pattern. Summer precipitation was overall well predicted using these significantly correlated climate indices, and the Pearson correlation coefficient between predicted and observed summer precipitation was in general larger than 0.6.<br/><br>
The performance of the Xinanjiang model for daily rainfall-runoff simulation in the source region of the Yellow River was evaluated. The Blaney–Criddle method was used to calculate the potential evapotranspiration as model input due to data scarcity of this area. The Monte Carlo method was used to optimize the sensitive model parameters. The resulting Pearson correlation coefficient between observed and simulated runoff for the calibration period was up to 0.87, and 0.85 for the validation period. Accordingly, the Xinanjiang model simulated the daily runoff series well in general. Thus, the Xinanjiang model can be a proper tool for further water resources management involving runoff simulation and flood forecasting in the source region of the Yellow River.},
  author       = {Yuan, Feifei},
  isbn         = {978-91-7623-311-5},
  issn         = {1101-9824},
  keyword      = {Source region of the Yellow River,climate change,summer precipitation,ENSO,teleconnection pattern,sea surface temperature,Xinanjiang model,Rainfall-Runoff process},
  language     = {eng},
  pages        = {157},
  title        = {Impacts of climate change on surface hydrology in the source region of the Yellow River},
  year         = {2015},
}