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Hydro-climatology: Variability and Change Edited by STEWART W. FRANKSUniversity of Newcastle, NSW, Australia

EVA BOEGHRoskilde University, Denmark

ELEANOR BLYTHCentre for Ecology and Hydrology, UK

DAVID M. HANNAHUniversity of Birmingham, UK

KORAY K. YILMAZMiddle East Technical University, Ankara, Turkey

The hydro-climatological approach of this volume illustrates the scientific and practical value of considering hydrological phenomena and processes in a climate context to improve understanding of controls, process interaction, and past and future variability/change. Contributions deal with understanding hydrological systems given historic observed climate variability, or utilise climate models to project future climate scenarios and then assess the resultant hydrol-ogical consequences. Human interventions – water storages, extrac-tion, irrigation, land-use change – i.e. the societal context, are also considered. The interdisciplinary approach reveals information and perspectives that go beyond the study of climate and hydrology alone.IAHS Publ. 344 (2011) 254 + x pp. ISBN 978-1-907161-19-3 £58.00

Preface

This volume includes a selection of peer-reviewed papers presented at the Hydro-climatology – Variability and Change symposium as part of the XXVth International Union of Geodesy and Geophysics (IUGG) General Assembly held in Melbourne, Australia, in July 2011. The symposium was jointly sponsored by the International Association of Hydrological Sciences (IAHS) international commissions and working groups: ICCLAS, ICSW, HYDROMET) and the International Association of Meteorology and Atmospheric Sciences (IAMAS).

The aim of the symposium was to collate studies on the role of climate variability and change on the land surface hydrology, as well as the role of hydrological dynamics in affecting climate system processes. Hence, the symposium documents the multiple interactions and feedbacks between land surface hydrology and climatology.

Approximately half of the papers presented here deal with understanding aspects of hydrological systems given historic observed climate variability and/or change. Conversely, a number of papers utilise climate models to project future climate scenarios and then assess the resultant hydrological consequences.

By necessity, study of land surface hydrology often includes human intervention in hydrological processes – water storages, extraction, irrigation, land-use change, etc. As such, the study of hydrology and climate at the land surface interface provides a human societal context for climate variability and change.

It is hoped that the hydro-climatological approach taken by many papers in this volume illustrates the scientific and practical value of considering hydrological phenomena and processes in a climate context to improve understanding of controls, process interaction and past and future variability/change. We believe such an interdisciplinary approach reveals new information and perspectives that go beyond the study of climate and hydrology alone.

We hope that the diverse range of case studies (in terms of geographical location, methodologies and hydrologically-relevant variables) presented herein provides a useful sharing of insight and experience.

The editors would like to thank all symposium participants for their scientific contributions. We express special thanks to Cate Gardner, Penny Perrins and Frances Watkins of IAHS Press for their professional approach and help with the processing of the manuscripts.

Stewart W. FranksUniversity of Newcastle, Australia

Eva Boegh Roskilde University, Denmark

Eleanor BlythCentre for Ecology and Hydrology, UK

David M. Hannah University of Birmingham, UK

Koray K. YilmazMiddle East Technical University, Ankara, Turkey

Contents

Preface by Stewart W. Franks, Eva Boegh, Eleanor Blyth, David M. Hannah & Koray K. Yilmaz

v

Drought risks and impact on water resources in part of northern Nigeria Olusegun Adeaga

1

Kohonen Self-Organizing Map as a software sensor estimator of reference crop evapotranspiration Adebayo Adeloye & Rabee Rustum

7

Pan evaporation trend for the Haihe River basin and its response to climate change

Zhenxin Bao, Jianyun Zhang, Guoqing Wang, Guobin Fu, Cuishan Liu & Xiaolin Yan

15

Calibration of an evapotranspiration model using runoff records and regional evapotranspiration Zoubeida Bargaoui & Ahmed Houcine

21

Developing a feedbacks toolkit for regional water resource assessments E. M. Blyth & C. M. J. Jacobs

27

Hydrological validation of statistical downscaling methods applied to climate model projections Marie Bourqui, Thibault Mathevet, Joel Gailhard & Frederic Hendrickx

32

Pathologies of hydrological models used in changing climatic conditions: a review L. Coron, V. Andréassian, M. Bourqui, C. Perrin & F. Hendrickx

39

Variability, change and prediction of hydro-climatic elements in the Hai River basin, China Xiangyi Ding, Yangwen Jia, Jinsheng Jia, Huaidong Zhou & Yuchun Wang

45

Evaluation of energy balance, combination and complementary schemes for estimation of evaporation A. Ershadi, M. F. McCabe, J. P. Evans & J. P. Walker

52

Temporal changes in annual rainfall in the “Top End” of Australia Wayne D. Erskine, Michael J. Saynor & Maureen Townley-Jones

57

Water and ice regimes of the rivers of European Russia under climate change Natalia Frolova, Svetlana Agafonova & Dmitry Nesterenko

63

Statistical downscaling of daily rainfall for southeastern Australia Guobin Fu & Stephen P. Charles

69

Non-stationary analysis of spatial patterns of extreme rainfall events in West Africa Sandra G. García Galiano & Juan D. Giraldo Osorio

75

Evolution des principales caractéristiques de la saison des pluies au Burkina Faso à partir des données pluviométriques de cinq modèles climatiques régionaux (MCR) / Evolution of main rainy season characteristics in Burkina Faso derived from rainfall data of five regional climate models (RCM) Boubacar Ibrahim, Harouna Karambiri & Jan Polcher

82

The effects of the 2007–2008 drought on water resources in Ilam Province, Iran Haji Karimi & Sadegh Alimoradi

87

Changes of pan evaporation and its influencing factors in different climate zones of China Cuishan Liu, Jianyun Zhang, Guoqing Wang & Ruimin He

93

Recent increased frequency of drought events in Poyang Lake Basin, China: climate change or anthropogenic effects? Yuanbo Liu, Ping Song, Jian Peng, Qiaoni Fu & Cuicui Dou

99

Hydro-climatological variability in the Murray-Darling Basin Natalie Lockart, Dmitri Kavetski & Stewart W. Franks

105

Explaining annual streamflow variability of Amazonian rivers Alan V. Lopes & John A. Dracup

112

Agronomie et climatologie d’un bassin de 100 000 km2 en Afrique de l’Ouest / Agronomy and climatology of a 100 000 km² watershed in West Africa S. Louvet, K. Delarue, J. E. Paturel, G. Mahé, M. Vaksman, L. Tiganadaba, N. Vigaud, P. Roucou, N. Rouché & M. Koité

118

Variabilité spatio-temporelle passée et future de la pluie sur le basin du Bani en Afrique de l’Ouest / Past and future spatiotemporal variability of rainfall of the Bani catchment in West Africa S. Louvet, J. E. Paturel, G. Mahé, N. Vigaud, P. Roucou, N. Rouché & M. Koité

125

Le fleuve Niger et le changement climatique au cours des 100 dernières années / The River Niger and climate change over 100 years G. Mahé, G. Lienou, F. Bamba, J. E. Paturel, O. Adeaga, L. Descroix, A. Mariko, J. C. Olivry, S. Sangare, A. Ogilvie & J. C. Clanet

131

Estimation of the flooded area of the Inner Delta of the River Niger in Mali by hydrological balance and satellite data G. Mahe, D. Orange, A. Mariko & J. P. Bricquet

138

Numerical modelling and land–atmosphere feedback of drought in southeast Australia X. H. Meng, J. P. Evans & M. F. McCabe

144

Simulation of the impacts of climate change on the water budget of the Xitiao River catchment, China Xingguo Mo & Dejuan Meng

150

Separation of climate and anthropogenic influences on Columbia River mean flow and sediment transport Pradeep K. Naik & David A. Jay

157

Hydro-climatic variability of the Hadejia–Jama’are river systems in north-central Nigeria Shakirudeen Odunuga, Ifeyinwa Okeke, Ademola Omojola & Lekan Oyebande

163

Analysis of extreme daily rainfall in southeast Asia with a gridded daily rainfall data set Keisuke Ono & So Kazama

169

Modelling maximum precipitation in a mountainous area of Greece under global warming Dionysia Panagoulia & Chrys Caroni

176

River runoff response to climate changes in Poland (East-Central Europe) Joanna Pociask-Karteczka

182

Non-linearity of the runoff response across southeastern Australia to increases in global average temperature David A. Post, Jin Teng, Francis H. S. Chiew, Biao Wang, Jai Vaze & Steve Marvanek

188

How could hydro-climatic conditions evolve in the long term in West Africa? The case study of the Bani River catchment D. Ruelland, L. Collet, S. Ardoin-Bardin & P. Roucou

195

Trends in hydro-meteorological variables in the Brahmaputra basin in India and their impact on flood events U. C. Sharma & Vikas Sharma

202

Estimation of evapotranspiration in the Brígida River basin, Brazil, by satellite remote sensing Richarde Marques Silva, Leonardo Pereira e Silva,

208

Celso Augusto Guimarães Santos & Suzana Maria Gico Lima Montenegro

Satellite-based tracking of water surface variation of Poyang Lake during the last three decades Ping Song & Yuanbo Liu

215

Calibration of hydrological models for medium-term streamflow prediction in a changing climate Jin Teng, Francis H. S. Chiew, Jai Vaze & David A. Post

221

Trends in precipitation extremes and long-term memory of runoff records in Zhejiang, East China Ye Tian, Yueping Xu, Martijn J. Booij, Qingqing Zhang & Shengji Lin

227

Climate variability and water security for power generation Adam M. Wyatt & Stewart W. Franks

233

Evapotranspiration observation and data analysis in reed swamp wetlands Shiguo Xu & Tao Ma

239

Assessment of flash flood events using remote sensing and atmospheric model-derived precipitation in a hydrological model Ismail Yucel & Fatih Keskin

245

Key word index 253

________________________________________________________________________________________________Hydro-climatology: Variability and Change (Proceedings of symposium J-H02 held during IUGG2011 in Melbourne, Australia, July 2011) (IAHS Publ. 344, 2011) 1-6

Drought risks and impact on water resources in part of northern NigeriaOLUSEGUN ADEAGADepartment of Geography, University of Lagos, [email protected]

Abstract Knowledge concerning various aspects of drought and water scarcity is required to predict and to articulate strategies to minimize the effects of future events. This paper investigated drought episodes in northern Nigerian using the Standardized Precipitation Index (SPI) for monthly rainfall standardization at temporal scales of 6 and 12 months. The region has been hit by droughts with maximum severity in the 1980s. The Sahel savannah is more prone to extreme drought with great magnitudes while the Guinea and Sudan savannahs are more prone to mild to moderate drought. Hence, there is a call for people-oriented national drought policies and preparedness.Key words drought; northern Nigeria; rainfall; standardized precipitation index (SPI); recurrence interval

________________________________________________________________________________________________Hydro-climatology: Variability and Change (Proceedings of symposium J-H02 held during IUGG2011 in Melbourne, Australia, July 2011) (IAHS Publ. 344, 2011). 7-14

Kohonen Self-Organizing Map as a software sensor estimator of reference crop evapotranspiration

ADEBAYO ADELOYE1 & RABEE RUSTUM2

1 School of the Built Environment, Heriot-Watt University, Edinburgh, [email protected]

2 College of Engineering, University of Dammam, Saudi Arabia

Abstract Reference crop evapotranspiration (ETo) estimation is of importance in irrigation water management for the calculation of crop water requirements and its scheduling, rainfall–runoff modelling and numerous other water resources studies. This paper developed the Kohonen Self-Organizing Map (KSOM), unsupervised artificial neural networks software sensors to predict the ETo. This was achieved by using the powerful clustering capability of the KSOM to analyse the multi-dimensional data array of estimated Penman-Monteith ETo and different subsets of input climatic variables. Data obtained at two locations, Edinburgh (UK) and Udaipur (India), were used in order to demonstrate the versatility of the approach. The findings indicate that the KSOM-based ETo estimates were in good agreement with those obtained using the conventional FAO Penman-Monteith formulation at both locations. A further comparison of the KSOM estimates with other commonly used empirical methods for the ETo, e.g. Thornthwaite, Priestley-Taylor and Hargreaves, showed that the former were far superior. This offers significant potential for accurate estimation of the ETo in regions of the world where the needed climatic data are unavailable for the implementation of the full Penman-Monteith formulation. Key words reference crop evapotranspiration; crop water requirements; Kohonen Self-Organizing Map; neural networks; FAO Penman-Monteith method


Pan evaporation trend for the Haihe River basin and its response to climate change

ZHENXIN BAO1,2, JIANYUN ZHANG1,2, GUOQING WANG1,2, GUOBIN FU3, CUISHAN LIU1,2 & XIAOLIN YAN1,2

1Nanjing Hydraulic Research Institute, Nanjing 210029, [email protected], [email protected]

2Research Center for Climate Change, MWR, Nanjing 210029, China3CSIRO Land and Water, Private Bag 5, Wembley WA 6913, Australia

Abstract The Mann-Kendall trend test technique was used to detect the pan evaporation trend for the Haihe River basin (HRB). The results showed that there was a statistically significant decreasing trend of pan evaporation in the HRB during the last 50 years. An empirical formula (E-THWS formula) for calculating pan evaporation was proposed with temperature, relative humidity, wind speed and sunshine duration, to investigate the possible reasons. The results indicated that the positive impacts of increasing temperature and decreasing relative humidity on pan evaporation were offset by the negative impacts of the decreasing trends of sunshine duration and wind speed, which were the dominant factors resulting in pan evaporation decrease in HRB. Key words pan evaporation trend; Mann-Kendall test; E-THWS formula; climate change; Haihe River basin, China


Calibration of an evapotranspiration model using runoff records and regional evapotranspiration

ZOUBEIDA BARGAOUI & AHMED HOUCINENational Engineering School of Tunis, ENIT, BP 37 1002 Tunis, [email protected]

Abstract Modelling the time distribution of soil moisture is a key issue for biomass evaluation and is often adopted for deriving drought awareness indices. A vertically-averaged water budget over the root zone is implemented to estimate the evapotranspiration flux at daily time step for a lumped watershed. The water balance is computed including evapotranspiration, runoff, leakage and capillary rise components, as well as the concept of contributing area. Soil property-related parameters are derived according to pedotransfer functions, while parameters linked to the resistance of vegetation to evapotranspiration and to watershed area contributing to runoff are considered as data driven and are subject to calibration. The contributing area is assumed to be indexed by the soil moisture content. The model is calibrated using daily hydro-meteorological data (solar radiation, air temperature, air humidity, mean areal rainfall) as well as daily runoff records and also average annual evapotranspiration. The latter is referred to as regional evapo-transpiration because it is estimated using an empirical sub-model based on annual rainfall and potential evapotranspiration data from at-site and surrounding stations. Acceptable solutions are identified according to a compromise between the Nash coefficient for monthly runoff and relative bias for average annual evapotranspiration. The case study is a watershed of 250 km2 in an arid climate. Meteorological and

hydrological data are available for a 10-year calibration period and a 4-year validation period. It is found that the parameter linked to the resistance of vegetation to evapotranspiration is the most subject to uncertainty. Key words evapotranspiration; bucket model; soil moisture; contributing area

________________________________________________________________________________________________Hydro-climatology: Variability and Change (Proceedings of symposium J-H02 held during IUGG2011 in Melbourne, Australia, July 2011) (IAHS Publ. 344, 2011) 27-31 .

Developing a feedbacks toolkit for regional water resource assessments

E. M. BLYTH1 & C. M. J. JACOBS2

1 CEH, Wallingford, Oxfordshire, [email protected]

2 Wageningen UR, Alterra, Earth System Science–Climate Change, Wageningen, The Netherlands

Abstract There is a need to include the atmospheric feedbacks that alter evaporative demand in a region when water availability is changed. This is because the water resource implications of large-scale irrigation or soil water depletion cannot be assessed unless the subsequent changes to air temperature, humidity and cloudiness are accounted for. Here, we propose a simple tool that can be used to assess such feedback strengths anywhere in the globe, although it will not always be appropriate. The tool is based on a simple box model for the planetary boundary layer, assuming a semi-permeable lid at the top, but taking advection into account as well. Sample calculations with a prototype of the tool and an analysis of atmospheric data in North America showed that atmospheric feedbacks can play an important role in water resource assessments in some regions. If the region has a relatively straightforward feedback regime dominated by one-dimensional feedback processes, this can be quantified using the simple tool. Key words water resource management; evapotranspiration; land–atmosphere feedback


Hydrological validation of statistical downscaling methods applied to climate model projections

MARIE BOURQUI1, THIBAULT MATHEVET2, JOEL GAILHARD2 & FREDERIC HENDRICKX1

1 Electricity of France R&D, 6 quai Watier, 78401 Chatou, [email protected]

2 Electricity of France - DTG DMM 21, avenue de l’Europe BP 41, 38040 Grenoble CEDEX 09, France

Abstract Understanding the impacts of climate change projections on the hydrological cycle is a great challenge for the hydrometeorological community. The RIWER 2030 project aims at evaluating the impacts of climate change on two French watersheds with major issues of water management. Climate change impact studies use a mixture of GCM, RCM and downscaling methods to generate local watershed climate input time-series for hydrological models to generate streamflow time-series. This modelling chain

mailto:[email protected]

is rather complex and each step can strongly impact hydrological projections. Before using such a chain, we consider that downscaling methods must be validated on past observations. This paper aims to assess the ability of downscaling methods and hydrological models to reproduce past climate and hydrological observed series and trends. Three downscaling methods (based on analog approaches) were applied on a reanalysis of atmospheric pressure fields over the 1953–2002 period to generate climate time-series. Then, downscaled precipitation and temperatures were coupled to two hydrological models (lumped and semi-distributed) to generate streamflow time-series. Downscaling methods performances were assessed on precipitation and temperatures at different spatial and temporal scales. Hydrological model simulations were also used for a complete assessment on potential evapotranspiration, snow water equivalent and streamflows. The results show a relatively good ability of downscaling methods to reproduce climate observations and to yield good hydrological simulations. However, low flows depend strongly on downscaling methods and hydrological model performance. Downscaling methods are sometimes not able to reproduce an observed trend, which is highly questionable when used for climate change impact studies.Key words analog methods; statistical downscaling; rainfall–runoff models; past climate validation


Pathologies of hydrological models used in changing climatic conditions: a review

L. CORON1,2, V. ANDRÉASSIAN2, M. BOURQUI1, C. PERRIN2 & F. HENDRICKX1

1 EDR R&D, Chatou, [email protected]

2 Cemagref, Antony, France

Abstract Characterizing the impact of climate change on hydrology is not as simple as feeding a previously calibrated hydrological model with future climate scenarios. Nevertheless, hydrological modelling is often considered as a small contributor to the overall uncertainty in climate change impact studies. Running a model under conditions that can be significantly different from those used for calibration raises questions relative to the actual extrapolation capacity of the model. As hydrological models (as complex as they may be) are always a simplification of reality, they can never fully integrate all aspects of the rainfall–runoff relationship. Consequently, we prefer to consider them as patients that can certainly be in good health in average conditions, but may also be affected with pathologies when exposed to unusual conditions (namely conditions they have not been properly trained or structured for). Focusing on the robustness issues linked with non-stationary climatic conditions, this paper reviews some of the typical pathologies rainfall–runoff models can suffer from when asked to predict discharges under climate conditions different from the calibration ones.Key words hydrological model; climate change; model calibration; parameter stability

________________________________________________________________________________________________Hydro-climatology: Variability and Change (Proceedings of symposium J-H02 held during IUGG2011 in Melbourne, Australia, July 2011) (IAHS Publ. 344, 2011) 45-51.

Variability, change and prediction of hydro-climatic elements in the Hai River basin, China

XIANGYI DING, YANGWEN JIA, JINSHENG JIA, HUAIDONG ZHOU & YUCHUN WANGChina Institute of Water Resources and Hydropower Research, Beijing, China [email protected]

Abstract Many observational facts and studies have shown that the hydro-climatic conditions in the Hai River basin, which is the political and cultural centre of China, changed significantly over last half of the 20th century. This study attempts to evaluate the variability and change of hydro-climatic elements in the basin including precipitation, temperature, evapotranspiration and runoff, based on observations and a hydrological model, as well to predict the trends of these elements under a changing environment. Specifically, the temporal variations and sudden changes of precipitation, temperature, evapotranspiration and runoff during the last 50 years (1956–2005) in the basin are analysed using the moving-average method, linear regression method and Mann-Kendall method. For future conditions, the precipitation and temperature data are obtained from the average data set of 20 global climate models using the REA (reliability ensemble averaging) method, together with future land-use data based on national land-use planning documents, and evapotranspiration and runoff data obtained through hydrological model simulations. Thus, the prediction of the elements under a changing environment can be given. The results indicate that: (1) during 1956–2005, the temperature significantly increased and the estimated sudden change time was 1964, while the precipitation and evapotranspiration significantly decreased and the estimated sudden change time was 1961, the surface runoff also significantly decreased and the estimated sudden change time was 1963; (2) during 2021–2050, evapotranspiration will increase by 7.1%, surface runoff will decrease by 9.8% and the variation within a year may increase; runoff in flood seasons especially July and August may increase, but decrease in the remaining months. This study may provide decision support for integrated management and planning of water resources in the highly water-stressed basin.Key words variability; change; prediction; hydro-climatic elements; Hai River, China


Evaluation of energy balance, combination, and complementary schemes for estimation of evaporation

A. ERSHADI1, M. F. McCABE1, J. P. EVANS2 & J. P. WALKER3

1 School of Civil and Environmental Engineering, University of New South Wales, Sydney, Australia2 Climate Change Research Centre, University of New South Wales, Sydney, Australia3 School of Civil and Environmental Engineering, Monash University, Clayton, Australia

[email protected]

Abstract A comparison between three basic techniques for estimation of actual evapotranspiration, namely: the Energy Balance, the Combination, and the Complementary approaches, is undertaken. We utilize Monin-Obukhov Similarity Theory (MOST) as a framework for the energy balance method, the single-layer Penman-Monteith method for the combination approach, and the Advection-Aridity method as the complementary approach. Data from three flux tower stations are used to evaluate model estimated heat fluxes at short time steps. The results indicate advantages and/or limitations of each method under different conditions, highlighting issues in application of the Advection-Aridity technique in dry conditions and energy balance methods over sparse canopies.Key words evapotranspiration; evaluation; energy balance; Penman-Monteith; Advection-Aridity method


Temporal changes in annual rainfall in the “Top End” of Australia

WAYNE D. ERSKINE1,2, MICHAEL J. SAYNOR2 & MAUREEN TOWNLEY-JONES3

1 School of Environmental & Life Sciences, The University of Newcastle, PO Box 127, Ourimbah NSW 2258, [email protected] and [email protected]

2 Physicochemical Processes Group, Environmental Research Institute of the Supervising Scientist, GPO 461, Darwin NT 0801, Australia

3 School of Mathematical & Physical Sciences, The University of Newcastle, PO Box 127, Ourimbah NSW 2258, Australia

Abstract CUSUM (cumulative deviations from the mean) analysis of up to 136 years of annual rainfall at 15 stations in the northern part of the Northern Territory (Australia) revealed alternating periods of above- and below-average rainfall that persisted for at least 6 years to many decades. The Kruskal-Wallis and Mann Whitney tests were used to show that consecutive time periods were usually statistically significantly different to each other. Furthermore, the wet periods were statistically identical to each other, as were the dry periods, but non-consecutive wet and dry periods were significantly different. The time and duration of these alternating wet and dry periods varied from station to station. Alternating, sub-decadal to multi-decadal, wet and dry periods also appear to be manifested in the streamflow record and have significant implications for water resource assessments, river channel dynamics and landscape processes.Key words alternating flood- and drought-dominated regimes; CUSUM; non-parametric statistics; Top End of Australia


Water and ice regimes of the rivers of European Russia under climate change

NATALIA FROLOVA, SVETLANA AGAFONOVA & DMITRY NESTERENKODepartment of Hydrology, Lomonosov Moscow State University, 119899 Leninskiye Gory, Moscow, [email protected]; [email protected]

Abstract Specific features of the water and ice regimes of the rivers of the European territory of Russia, as well as their spatial and temporal variability, were studied using up-to-date hydrometeorological data. Variations in the characteristics of the water and ice river regimes over the last 125 years are analysed. For some rivers, changes in the dates of the appearance of floating ice and then the break-up, due to changes in the air temperature and the rate of streamflow in rivers, are assessed. Special attention is paid to the factors that affect the formation of ice jams and their spatial and temporal variability for the northern rivers. Trends

of ice regime changes within the territory under study during recent decades have been revealed. It is shown that changes of ice regime are mainly defined by features of the water regime. The basic feature of modern changes in the hydrological regimes of rivers over a large part of the country is a significant increase of low flows, especially in winter. Within the European territory of Russia, for the majority of the rivers considered, significant positive trends of increased winter and summer–autumn low flows are apparent. It was concluded that there is an increase of natural regulation of river drainage.Key words ice and water regime; climate change; European Russia


Statistical downscaling of daily rainfall for southeastern AustraliaGUOBIN FU & STEPHEN P. CHARLESCSIRO Water for a Healthy Country Flagship and CSIRO Land and Water, [email protected]

Abstract An ensemble of stochastic daily rainfall projections has been generated for 30 stations across southeastern Australia using the downscaling Nonhomogeneous Hidden Markov Model (NHMM), which was driven by atmospheric predictors from four climate models for three IPCC emissions scenarios (A1B, A2, B1) and for two periods (2046–2065 and 2081–2100). The results indicate that the annual rainfall is projected to decrease for both periods for all scenarios and climate models, with the exception of a slight increase for one GCM for the A2 scenario in 2081–2100. However, there is a seasonal difference: two downscaled GCMs consistently project a decline of summer rainfall, and two an increase of summer rainfall. In contrast, all four downscaled GCMs show a decrease of winter rainfall. Since winter rainfall accounts for two-thirds of the annual rainfall and produces the majority of streamflow for this region, this decrease in winter rainfall would cause additional water availability concerns in the southern Murray-Darling Basin, given that water shortage is already a critical problem in the region. In addition, the annual maximum daily rainfall is projected to intensify in the future, particularly by the end of century; the maximum length of consecutive dry days is projected to increase and, correspondingly, the maximum length of consecutive wet days is projected to decrease. These changes in daily sequencing, combined with fewer events of reduced amount, would lead to drier catchment soil profiles and further reduce runoff potential, and hence also have streamflow and water availability implications.Key words Murray-Darling Basin; Nonhomogeneous Hidden Markov Model (NHMM); southeastern Australia; statistical downscaling; climate change


Non-stationary analysis of spatial patterns of extreme rainfall events in West Africa

SANDRA G. GARCÍA GALIANO & JUAN D. GIRALDO OSORIO Technical University of Cartagena, R&D Group of Water Resources Management, Department of Civil Engineering, Paseo Alfonso XIII, 52, 30203, Cartagena, Spain

[email protected] ; [email protected]

Abstract Heavy storm events frequently cause extensive damage, and often result in loss of life and


property. The objective of this work is to build maps of Annual Maximum Daily Rainfall (AMDR) for various return periods for the Senegal River Basin. However, traditional stationary analyses are not suitable, since meaningful trends have been detected in historical hydrometeorological time series. Therefore, the GAMLSS (Generalized Additive Models for Location, Scale and Shape) tool is applied to fit the parameters of the probability density functions (pdfs). AMDR time series were estimated using observed daily rainfall grids and regional climate models (RCMs). The wide divergence in predicted trends from RCMs imposes the use of ensemble pdfs, which can be built using bootstrapping techniques. The plausible AMDR maps associated with various quantiles, interpolated from these ensemble pdfs, could be used by stakeholders to develop strategies of mitigation and adaptation to climate change impacts on floods events.Key words non-stationarity; GAMLSS; regional climate models; bootstrapping; ensemble probability density function; maximum daily rainfall


Evolution des principales caractéristiques de la saison des pluies au Burkina Faso à partir des données pluviométriques de cinq modèles climatiques régionaux (MCR)

BOUBACAR IBRAHIM1, HAROUNA KARAMBIRI1 & JAN POLCHER2

1 Institut International d’Ingénierie de l’Eau et de l’Environnement (2iE), 01 BP 594 Ouagadougou 01, Burkina [email protected]

2Laboratoire de Météorologie Dynamique /IPSL/CNRS, Boite 99, 4 place Jussieu, F-75252 Paris Cedex 05, France

Résumé Dans un pays sahélien comme le Burkina Faso, l’évolution du climat peut être déterminée à travers les données des pluies journalières relevées au niveau des stations. Ces données ont permis de faire une caractérisation des saisons des pluies à partir de six paramètres pluviométriques, le début et la fin des saisons, la durée de la saison, le nombre de pluies, la pluie moyenne journalière et la pluie annuelle. La comparaison des paramètres pluviométriques issus des cinq modèles climatiques avec les observations a révélé des biais sur les données simulées. Pour rendre ces données simulées plus représentatives du climat de la zone, la méthode de correction des biais dite “quantile–quantile” est utilisée sur la période de 1961 à 2050 sur la base des écarts de la période de contrôle 1961–1990. Les données corrigées ne montrent aucun consensus entre les cinq modèles sur l’évolution future des six principaux paramètres de la saison des pluies.Mots clefs variabilité pluviométrique; modèle climatique régional; Sahel; Burkina Faso

Evolution of main rainy season characteristics in Burkina Faso derived from rainfall data of five regional climate models (RCM) Abstract In a Sahelian country like Burkina Faso, climate evolution can be assessed through daily rainfall data recorded at stations. The rainy season is characterized by six parameters: season onset, end of the rainy season, season duration, annual rainfall number, and daily rainfall average and annual rainfall amounts. Comparison of simulated data from five regional climate models with observed data showed some biases in the simulated data. The quantile–quantile method was used to correct biases in data from regional climate models for the period 1961–2050 based on deviations on the control period (1961–1990). The corrected data from the five regional climate models did not show the same trend regarding the future evolution of the six rainy season parameters. Key words rainfall variability; regional climate model; Sahel; Burkina Faso


The effects of the 2007–2008 drought on water resources in Ilam Province, Iran

HAJI KARIMI1 & SADEGH ALIMORADI2

1Agriculture faculty, Ilam University, Ilam, [email protected]

2Water Authority of Ilam Province, Ilam, Iran

Abstract The conditions of the 2007–2008 drought in Ilam Province, Iran, are inspected using the Standard Precipitation Index (SPI). The impacts of the drought on water resources of Ilam Province are evaluated. The data from climatology stations, hydrometric stations and groundwater observation stations were used in the analysis. The results showed that the drought intensity increased from southwest to northeast in the Province. This trend is the result of air masses originating from the Mediterranean area, which is situated west and southwest of the area, and the influence of the Zagros Mountain ranges. These mountains have a northwest–southeast trend and the moisture content of the air masses is reduced by the rainshadow effect. This drought decreased river discharges significantly and lowered the water table of alluvial aquifers.Key words drought; water resources; Ilam Province, Iran; SPI index


Changes of pan evaporation and its influencing factors in different climate zones of China

CUISHAN LIU1,2, JIANYUN ZHANG1,2, GUOQING WANG1,2 & RUIMIN HE1,2

1Nanjing Hydraulic Research Institute, Nanjing 210029, [email protected]

2Research Center for Climate Change, MWR, Nanjing 210029, China

Abstract Changing trends of observed pan evaporation are detected and its key influencing meteorological factors, which result in new changes in pan evaporation, are identified for different climate zones in China. The Mann-Kendall method is used to detect the variation trends of E601 pan evaporation over China from 1960 to 2006. The results show that during the last 50 years, temperature has presented a significantly increasing trend while E601 pan evaporation shows a decreasing trend for most climate zones of China before the late 1990s. After the late 1990s, pan evaporation has shown insignificant but increasing trends for some regions. The cause for the changing trend in pan evaporation and the reason for recent shifts in pan evaporation rates are analysed by considering thermal and turbulent conditions and the changing trends of the main influencing climate factors. The results show that daily temperature range, sunshine duration and average wind speed correlated well with the E601 pan evaporation, and the significantly decreasing trends of these influential factors are the main reason explaining the decreasing rates of E601 pan evaporation before the late of 1990s. Recent changes of these meteorological factors, together with a continuously increasing temperature trend can explain the changes in pan evaporation after the late 1990s.Key words pan evaporation; climate zones; changing trend; influencing factors; China


Recent increased frequency of drought events in Poyang Lake Basin, China: climate change or anthropogenic effects?

YUANBO LIU1, PING SONG1, JIAN PENG1, QIAONI FU1,2 & CUICUI DOU1,2

1 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, [email protected]

2 School of Earth Sciences and Engineering, Hohai University, Nanjing 210098, China

Abstract The Poyang Lake wetland of China is in the first batch of the Ramsar Convention List of Wetlands of International Importance. Poyang Lake’s surface area has decreased drastically in the past three decades, and hydrological droughts have occurred more frequently in the region in recent years. It is unclear which factors are responsible for the change and to what extent. This study utilized satellite remote sensing to investigate the recent increase of drought events in the region. The Moderate Resolution Imaging Spectroradiometer (MODIS) data were used to retrieve the lake variations in the last decade. The Global Precipitation Climatology Centre (GPCC) data sets were incorporated to analyse the water cycle in the basin. Our results revealed no significant increasing or decreasing long-term trend in precipitation. The lake surface reached minimum levels in the winters of 2003, 2006 and 2009, corresponding to three severe hydrological droughts in the basin. Case examinations showed less precipitation in 2003 and greater evapotranspiration in 2006, but this was not the case for 2009. The explanation is likely related to operation of the Three Gorges Dam, the largest dam in the world. Overall, the increased frequency of droughts was very likely related to the dam construction and operation and climate change, in addition to land-use and land-cover change.Key words Poyang Lake, China; multi-temporal satellite remote sensing; climate change; hydroclimatology


Hydro-climatological variability in the Murray-Darling Basin

NATALIE LOCKART, DMITRI KAVETSKI & STEWART W. FRANKSSchool of Engineering, University of Newcastle, Callaghan 2308, New South Wales, [email protected]

Abstract Investigations into the recent drought in the Murray-Darling Basin have brought to light confusion surrounding the cause and effect of temperatures, potential evaporation and actual evaporation. In this study, a simple coupled land surface–planetary boundary layer model is used to illustrate the role of soil moisture in controlling evaporation and temperature, and to explore the interaction between potential and actual evaporation and temperatures under drought conditions. We demonstrate that increased temperatures during drought conditions are a result of the reduced soil moisture and actual evaporation. It is also shown that potential evaporation is increased under drought conditions as a result of increased atmospheric moisture demand, which is itself due to the decreased actual evaporation.Key words evaporation; temperature; drought; soil moisture; Murray-Darling Basin

________________________________________________________________________________________________Hydro-climatology: Variability and Change (Proceedings of symposium J-H02 held during IUGG2011 in Melbourne, Australia, July 2011) (IAHS Publ. 344, 2011 112-117

Explaining annual streamflow variability of Amazonian rivers

ALAN V. LOPES & JOHN A. DRACUPCivil & Environmental Engineering Department, University of California, Berkeley, Davis Hall 612, California, [email protected]

Abstract Analysed in this study were the influence of El Niño events and the oscillation of the Intertropical Convergence Zone (ITCZ) on Amazonian rivers. Empirical orthogonal function analysis (EOF) was employed to quantify how much of the annual variability of Amazonian river discharges can be explained by El Niño events and anomalous ITCZ displacement. Normalized time series of the NINO 3.4 index and Atlantic Meridional Mode (AMM) index were analysed together with river discharge measurements at 13 sub-basins and longer reconstructed streamflow time series spanning over 60 years at four sites. The results show that the AMM index explains more of the streamflow annual variability than the NINO 3.4. The annual discharge variability of the rivers that drain from the south area of Amazonia (Xingu and Araguaia), were better explained by NINO3.4 than by AMM. However, a large part of the annual discharge

variability of the Amazonian rivers remains to be explained by other phenomena not considered here.Key words Amazon; streamflow; principal component analysis


Agronomie et climatologie d’un bassin de 100 000 km2 en Afrique de l’Ouest

S. LOUVET1, K. DELARUE1, J. E. PATUREL1, G. MAHÉ2, M. VAKSMAN3, L. TIGANADABA3, N. VIGAUD4, P. ROUCOU4, N. ROUCHÉ1 & M. KOITÉ5

1HSM/IRD, Montpellier, France [email protected]

2HSM/IRD, Rabat, Maroc 3 IER/CIRAD, Bamako, Mali4CRC, Dijon, France 5DNM, Bamako, Mali

Résumé Les régions sahéliennes sont considérées comme étant particulièrement vulnérables à la variabilité et au changement climatique pour deux raisons: le rôle prédominant de l’agriculture pluviale dans son économie et la faiblesse des structures de gestion. La réponse physiologique d’une plante aux variations climatiques est bien documentée mais l’extrapolation à une production alimentaire régionale reste encore très incertaine. Sur le Bani, affluent du fleuve Niger, des variables climatiques représentatives des contraintes agroclimatiques des cultures (dynamique de la saison des pluies et occurrence des événements extrêmes) ont été calculées à partir de données observées ou estimées à partir de données climatiques du futur (modèle régional climatique WRF). Des corrélations simples et multiples ont été établies entre les données du passé et des séries de rendements agricoles mais les résultats aboutissent à des régressions guère significatives. Le facteur climatique est une condition nécessaire mais non suffisante pour expliquer les rendements agricoles dans ces régions d’Afrique.

Mots clefs agroclimatologie; analyse statistique; rendement agricole; Sahel

Agronomy and climatology of a 100 000 km2 watershed in West AfricaAbstract Sahelian regions are considered as particularly vulnerable to climatic variability and change for two reasons: the dominant role of rainfed agriculture in their economies and their weakness of water resources management. The physiological response of an individual plant to the climatic variations of parameters is well documented, but extrapolation to regional food production still remains very dubious. On the Bani, a tributary of the Niger River in Mali, climatic variables representative of the agroclimatic constraints of the cultures (dynamics of the rainy season and occurrence of extreme events) were evaluated from observed past data and simulated future data (regional climatic model WRF). Simple and multiple correlations were established between past data and agricultural yields, but the relations are hardly significant. In these regions in Africa, the climate factor is certainly a necessary condition to explain the agricultural outputs, but not sufficient alone. Key words agricultural yields; agroclimatology; Sahel; statistic analysis


Variabilité spatio-temporelle passée et future de la pluie sur le basin du Bani en Afrique de l’Ouest

S. LOUVET1, J. E. PATUREL1, G. MAHÉ2, N. VIGAUD3, P. ROUCOU3, N. ROUCHÉ1 & M. KOITÉ4

1HSM/IRD, Montpellier, France [email protected]

2HSM/IRD, Rabat, Maroc 3CRC, Dijon France 4DNM, Bamako, Mali

Résumé Depuis 1970, sur le Bani, principal affluent du Niger supérieur, l’écoulement annuel a baissé de 69% alors que le déficit pluviométrique est compris entre 15% et 25% sur le bassin. Parmi les causes possibles les changements des caractéristiques pluviométriques sont à explorer. Quatre méthodes d’interpolation spatiale des champs de pluies ont été comparées sur des indices intra-saisonniers (nombre de jours secs, séquences sèches, EDI, SPI, etc.) pour la période 1950–2006. Cette étude a également été menée sur des données pluviométriques issues d’un modèle climatique régional (WRF) à l’horizon 2032–2041. La péjoration pluviométrique est imputable à la conjonction de plusieurs facteurs: un cœur de saison des pluies moins arrosé, une fin plus précoce, un nombre de séquences sèches en augmentation. Le modèle climatique régional prévoit des précipitations en hausse par rapport à la décennie 1981–1990, moins de séquences sèches et des vagues de sécheresse moins longues.Mots clefs Afrique de l’Ouest; mousson; précipitations; sécheresse; variabilité spatio-temporelle

Past and future spatio-temporal variability of rainfall of the Bani catchment in West AfricaAbstract Since 1970, on the Bani, main tributary of the upper Niger, annual discharges have decreased by 69% while annual rainfall has decreased only by 15% to 25% over the catchment. Among the possible causes for this very strong discharge decrease changes of precipitation patterns must be explored. Four different methods of spatial interpolation of rainfall fields were compared on intra-seasonal indices (number of dry days, the dry spells, EDI, SPI, etc.) for the period 1950–2006. This study was also conducted on simulated pluviometric data generated by a regional climatic model (WRF) for the 2032–2041 period. The pluviometric deficit is explained by a conjunction of many factors: an earlier end of rainy season, less precipitation during the core of it and an increase of the number of dry spells. The climatic model envisages an increase of annual precipitation amounts compared to the 1981–1990 period, fewer dry spells and shorter droughts.Key words drought; monsoon; rainfall; spatio-temporal variability; West Africa

________________________________________________________________________________________________Hydro-climatology: Variability and Change (Proceedings of symposium J-H02 held during IUGG2011 in Melbourne, Australia, July 2011) (IAHS Publ. 344, 2011 131-137

Le fleuve Niger et le changement climatique au cours des 100 dernières années

G. MAHE1, G. LIENOU2, F. BAMBA3, J. E. PATUREL4, O. ADEAGA5, L. DESCROIX6, A. MARIKO7, J. C. OLIVRY8, S. SANGARE9, A. OGILVIE10

& J. C. CLANET10 1 IRD, Université Mohamed V Agdal, BP 8967, 10 000 Rabat Agdal, Morocco

[email protected]é Yaoundé I, Yaoundé, Cameroun3Ecole Nationale d’Ingénieurs, Bamako, Mali4HydroSciences Montpellier, France5University of Lagos, Lagos, Nigeria6LTHE, Grenoble, France7Université de Bamako, Bamako, Mali8Carqueiranne, France9DNH, Conakry, Guinea

10 G-EAU joint research unit, IRD, Montpellier, France

Résumé Le bassin du fleuve Niger couvre 1.2 millions km2 et s’étend sur neuf pays en Afrique de l’Ouest. Son débit moyen à l’exutoire maritime est d’environ 6000 m3 s-1. La crue sur le cours principal en amont est formée au cours des 6–7 mois de la saison des pluies tropicales. Le régime hydrologique a évolué en raison du changement climatique et des impacts anthropiques. Il n’y a que peu de barrages sur le fleuve Niger, et les futurs ouvrages planifiés vont modifier son régime et les zones inondées. L’objectif de cette étude est de donner un aperçu global des changements hydrologiques du régime du Niger dans ses différents sous-bassins, afin d’évaluer les impacts des changements futurs. Les séries chronologiques à Koulikoro et pour les bassins amont montrent une forte variabilité interannuelle des débits depuis 1907, et une diminution profonde depuis 1970. Le déficit d’écoulement du Bani après 1970 est supérieur à celui des pluies, en raison de la baisse du niveau des eaux souterraines. A partir des images NOAA 1990–2000, on constate que les surfaces inondées ont diminué dans le Delta Intérieur. La crue sahélienne du Burkina-Faso et du Niger et celle de la rivière Sokoto au Nigéria a augmenté en raison de la dégradation des terres, en dépit de la baisse des pluies. Aujourd’hui, plus de la moitié du débit du bas Niger vient de la rivière Bénoué. Pour les bassins du Sahel, l’augmentation des eaux de ruissellement peut être étroitement liée à la déforestation. Mais la baisse très importante du niveau des eaux souterraines semble être liée au changement climatique. Les prochains grands changements viendront des futurs barrages, qui réduiront le pic de crue et les surfaces inondées, mais auront également des effets positifs pour la mobilisation des ressources en eau.Mots clefs Niger; Afrique de l’Ouest; changements climatiques; écoulement; Delta Intérieur; barrage

The River Niger and climate change over 100 yearsAbstract The Niger River basin covers 1.2 million km2 and extends over nine countries in West Africa. Its average discharge to the sea is about 6000 m3 s-1.The main upstream flood is produced during the 6–7 months of the tropical rainy season. The hydrological regime has been modified due to climatic and anthropogenic changes. There are only a few major dams on the River Niger, and future development plans will modify its regime and the flooded areas. The goal of this study is to provide a comprehensive overview of the hydrological changes of the Niger regime in its different sub-basins, in

order to assess the impacts of future changes. The time series at Koulikoro and for the upstream basins show a high interannual flow variability since 1907, and a strong decrease since 1970. The runoff deficit in the Bani River after 1970 is greater than the rainfall deficit, due to a decrease in the groundwater level. NOAA images for 1990–2000 indicate that the flooded surfaces have decreased in the Inner Delta. The Sahelian flood from rivers in Burkina-Faso and Niger, and from the Sokoto River in Nigeria, has increased due to land degradation, despite the reduced rainfall. Now, more than half of the water of the Lower Niger comes from the Benue River. For the Sahelian basins, the increase in runoff can be closely related to the deforestation, but the dramatic decrease of the groundwater levels seems to be related to climate change. In the future, large changes will come from the proposed dams, which will reduce the flood peaks and the flooded surface areas, but will also have positive effects on the management of water resources.Key words River Niger; West Africa; climate change; runoff; Inner Delta; dam


Estimation of the flooded area of the Inner Delta of the River Niger in Mali by hydrological balance and satellite data

G. MAHE1, D. ORANGE2, A. MARIKO3 & J. P. BRICQUET4

1 IRD, Université Mohamed V Agdal, BP 8967, 10 000 Rabat Agdal, [email protected]

2 IRD Vietnam, Quartier diplomatique Van Phuc, 298 Kim Ma, Bat 2G appt 202, Hanoi, Vietnam

3Université de Bamako, Bamako, Mali4HSM, Case MSE, BP 64501, 34394 Montpellier Cedex 5, France

Abstract The Inner Niger Delta in Mali is the largest flood plain of West Africa. It is an ecosystem where water regime, environmental dynamics and human activities (fishing, agriculture, livestock) are closely associated. It is home to a tenth of the population of Mali on an area of 35 000 km2. Rational management of this wetland subjected to a dry climate is essential for sustainable development in the region. Since the drought began around 1970, the Delta has been facing a problem of sustainability of renewable natural resources. Management strategies of these resources depend on the extent of flooded areas, the annual variability of which is still largely natural. The prediction of the flood extent, varying with runoff of the rivers Niger and Bani, is an important venture. Thus the objective of this study is the estimation of flooded areas of the Delta from conventional water balance methods and from analysis of satellite images. We examine the variability of the hydrological regime and processes of storage and release in the Delta. We then present the method of evaluation of flooded areas, from low-resolution multispectral data (1 km) NOAA/AVHRR for the period 1990–2000, using a distinction between the open water surfaces, vegetation cover and flooded vegetation. We then determine the flooded areas by this method and compare them with previous estimates. Finally, to produce a model for spatial-temporal forecasting of flooded areas, we study the correlations between the heights of water levels at gauging stations in the Delta and the flooded areas.Key words River Niger; West Africa; Inner Delta; flooded area; AVHRR


Numerical modelling and land–atmosphere feedback of drought in southeast Australia

X. H. MENG1, J. P. EVANS1 & M. F. McCABE2

1Climate Change Research Centre, University of New South Wales, Sydney, [email protected]

2School of Civil and Environmental Engineering, University of New South Wales, Sydney, Australia

Abstract Albedo and vegetation fraction play important roles in land–atmosphere interactions and local climate change. In this paper, the influence of these land surface parameters on the evolution of the drought that occurred in southeastern Australia between 2000 and 2008 is investigated. To examine the impact of variable land surface conditions on the hydrometeorology of the region, the Weather Research and Forecasting (WRF) model was used to perform a twin-study under two distinct scenarios. In the first instance, WRF was run in control mode with the default climatological surface albedo and vegetation fraction data sets. Then, these key surface variables were run in experiment mode with data sets derived from available satellite data. Comparison of these simulations demonstrates the importance of capturing the dynamic nature of land surface fields as the climate moves into, and then out of, a persistent multi-year drought. Both simulations capture the drought reasonably well, emphasizing changes in the large-scale circulation as a primary cause. Differences in the surface conditions do, however, provide local influence on the intensity and severity of drought.Key words Murray-Darling Basin; albedo; vegetation fraction; drought; land–atmosphere interaction


Simulation of the impacts of climate change on the water budget of the Xitiao River catchment, China

XINGGUO MO & DEJUAN MENGKey Laboratory of Water Cycle & Related Land Surface Processes, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China [email protected]

Abstract Climate change has been demonstrated to affect the water budget of a watershed by altering its ecohydrological processes. This study was conducted to quantify water budget changes in Xitiao River catchment from 1960 to 2009 using a distributed ecohydrological process-based model. The result showed that rise of temperature and declines of sunshine duration, air pressure and wind speed were significant, whereas the changes of precipitation and vapour pressure failed a significance test at α = 0.05. The annual evapotranspiration, precipitation and runoff increased during the last 50 years; however, only the evapotranspiration trend passed the significance test (α = 0.05).Key words climate change; ecohydrological process; water budget; VIP model; Xitiao River catchment, China



Separation of climate and anthropogenic influences on Columbia River mean flow and sediment transportPRADEEP K. NAIK1 & DAVID A. JAY2

1Agricultural Engineering and Water Resources, Ministry of Municipality Affairs and Urban Planning, PO Box 31126, Kingdom of Bahrain [email protected]

2Department of Civil and Environmental Engineering, Portland State University, PO Box 751, Portland, OR 97207, USA

Abstract Most analyses of hydrologic changes do not differentiate the contributions from climatic and human influences. Here, we separate human and climate influences on the Columbia River mean flow and sediment transport. The mean annual Columbia River virgin (naturalised) flow at The Dalles has decreased ~17%, 8–9% due to climate change and 7–8% due to irrigation water withdrawal. Climate impacts on the sediment discharge are larger than on streamflow because sediment discharge increases more than linearly with flow (QS ~ QR

n, n = ~2.4). Total sediment and sand transports have decreased >50% and >70%, respectively. Flow regulation (since 1970) has decreased peak spring flows by ~45% and increased flow during the rest of the year. The spring freshet flow decrease due to climate change is 8–9%; the decreases due to water withdrawal and flow regulation are about 11–12% and 26–27%, respectively. The peak freshet flow now occurs two to four weeks earlier than before 1900. Key words climate impact; human impact; climate change; El Niño Southern Oscillation; Pacific Decadal Oscillation; sediment transport; water withdrawal; flow regulation; reservoir manipulation; irrigation depletion


Hydro-climatic variability of the Hadejia-Jama’are river systems in north-central Nigeria

SHAKIRUDEEN ODUNUGA, IFEYINWA OKEKE, ADEMOLA OMOJOLA & LEKAN OYEBANDE Department of Geography, University of Lagos, Nigeria [email protected], [email protected]

Abstract The study investigates the hydrological fluxes and land-use dynamics of the Hadejia-Jama’are basin in north-central Nigeria for sustainable agricultural development. The empirical Thornthwaite model was used to determine the potential evapotranspiration (PE) loss taking into account the land-use dynamics obtained from change detection using Landsat TM of 1986 and 2006. Using the results obtained from land- use dynamics, multiplying factors were determined and future water balances computed for high and medium emission climate change (HCC; MCC) scenarios for 50 and 100 years. The results reveal that the basin is currently recording a water deficit and that this will increase by 0.52% for the 50-year MCC, 0.53% for the 100-year MCC, 7.25% for the 50-year HCC and 37.82% for the 100-year HCC in Nguru, relative to the 2006 water balance. Sustainable agricultural practices and appropriate dam optimization

techniques to ensure eco-friendly developments were recommended. Key words hydro-climatic; land use; water stress; climate change; Hadejia-Jama’are river systems, Nigeria


Analysis of extreme daily rainfall in southeast Asia with a gridded daily rainfall data set

KEISUKE ONO & SO KAZAMADepartment of. Civil Engineering, Tohoku University, Aoba 6-6-06, Sendai, Miyagi, 980-8579, [email protected]

Abstract The objective of this study is to estimate the daily extreme precipitation distribution in an Asian monsoon region considering orographic precipitation in mountainous areas. For this purpose, the APHRODITE data set and precipitation observations from 150 raingauges throughout Thailand were used as the main input. First, a bias-correction for underestimated precipitation in the APHRODITE data set was conducted based on the raingauge data. Secondly, a frequency analysis for estimating the extreme precipitation for different return periods was performed based on the bias-corrected APHRODITE data set and the raingauge data. For taking orographic precipitation effect into account, a regression relationship between the calculated extreme precipitation, elevation and latitude was developed using 150 raingauge data. Our results show that when orographic rainfall was incorporated, the extreme rainfall distribution was improved to show the characteristic of rainfall in mountainous areas.Key words APHRODITE data set; extreme rainfall; slope failure; orographic rainfall


Modelling maximum precipitation in a mountainous area of Greece under global warming

DIONYSIA PANAGOULIA1 & CHRYS CARONI2

1School of Civil Engineering, Dept of Water Resources & Environmental Engineering, National Technical University of Athens, 5 Heroon Polytechniou, 15780 Zografou, Athens, [email protected]

2School of Applied Mathematical & Physical Sciences, Dept of Mathematics, National Technical University of Athens, 9 Heroon Polytechniou, 15780 Zografou, Athens, Greece

Abstract We investigated the fit of generalized extreme value (GEV) distributions to maximum precipitation over the Mesochora mountainous catchment in central-western Greece under present and future climate scenarios. Precipitation was modelled as a stochastic process coupled with atmospheric circulation models. Automated objective classification based on optimized fuzzy rules was used to classify observed circulation patterns (CPs) and ECHAM4 General Circulation Model-generated CPs for 1CO2

and 2CO2 climate scenarios. The GEV distribution was fitted by maximum likelihood, allowing for non-stationarity over time in its location and scale parameters. The stationary model was adequate for historical data on annual daily maxima for 1972–1992 and also for 1CO2 for the period 1961–2000. However, the 2CO2 series for 2061–2100 required a cubic time trend in location to obtain a satisfactory fit (P<0.0001 by likelihood ratio test). This series declined to a minimum around 2080, followed by an increase to a maximum around 2092, and subsequently a further decline. Key words generalized extreme value distribution; maximum likelihood; global warming; annual maximum precipitation; likelihood ratio tests; non-stationarity; Greece


River runoff response to climate changes in Poland (East-Central Europe)

JOANNA POCIASK-KARTECZKAHydrology Department, Institute of Geography and Spatial Management, Jagiellonian University, [email protected]

Abstract Climate change in Poland is expressed primarily by a decrease in rainfall and an increase in winter air temperatures. The response of river runoff to climate change in Poland is uncertain. The mean annual flows of two major rivers crossing the country (the Vistula and the Oder) observed in the years 1901–2008 reveal the occurrence of periods of wet and dry years. No statistically significant trends were observed. The periodicity of runoff caused by different types of the atmospheric circulation is the only observed effect. Maximum discharges for 462 water gauges were analysed in the period 1951–2006. During the last 20 to 30 years neither the number, nor the relative magnitude of maximum river discharges for 462 water gauges in Poland have increased (1961–2006). They are even slightly smaller than in 1951–1980. However, a number of absolute maxima occurred in 1997 and 1979. There is a relationship between NAO and river flow – especially during snowmelt season in Carpathian Mountains catchments. Key words floods; atmospheric circulation; NAO; trends; Vistula River; Oder River; Carpathian Mountains


Non-linearity of the runoff response across southeastern Australia to increases in global average temperature

DAVID A. POST1, JIN TENG1, FRANCIS H. S. CHIEW1, BIAO WANG1, JAI VAZE1 & STEVE MARVANEK2

1 CSIRO Land and Water, GPO Box 1666, Canberra, ACT, Australia

[email protected] CSIRO Land and Water, Private Bag No. 2, Glen Osmond, SA, Australia

Abstract Many studies examining the impact of climate change on runoff use a technique whereby the changes in rainfall for a particular region are derived per degree of global warming. These changes in rainfall are then used to drive a rainfall–runoff model to produce a change in runoff, which can also be interpreted per degree of global warming. The technique assumes that the change in rainfall scales linearly with global average temperature. That is, a two degree increase in global average temperature will produce twice the change in rainfall as a one degree increase in global average temperature. This paper uses the CCCMA_T47, CCCMA_T63, CNRM and IAP global climate models (GCMs) to examine the nature of the relationship between runoff and global average temperature across a range of scales in southeastern Australia for projected temperature increases of 1.0, 1.3, 2.0 and 3.3 degrees, representing medium and high global warming scenarios for 2030 and 2060, respectively. Results indicate that for individual GCM grid cells (~40 000 km2) and most small catchments, the vast majority of runoff responses to increases in global average temperature up to 3.3 degrees are reasonably linear. This is particularly the case for large changes in runoff (>5% per degree global warming), and more so when the projected changes in rainfall are consistent across all seasons. However, small projected changes in rainfall may display a non-linear runoff response to increases in global average temperature, particularly when the seasonal response shows increases in rainfall in one season and decreases in another. In the vast majority of cases, this non-linearity takes the form of more runoff than expected for higher levels of global warming. At larger scales, when averaging across a number of GCM grid cells, differences in response between grid cells mean that the overall regional runoff response to increases in global average temperature can be non-linear. The implications of this finding are that regional-scale analyses of changes in runoff due to projected climate change require rainfall–runoff models to be run for each projected increase in global average temperature – simple linear approximations can only be used with prior knowledge of the nature of the relationship.Key words runoff; rainfall; climate change; southeastern Australia


How could hydro-climatic conditions evolve in the long term in West Africa? The case study of the Bani River catchment

D. RUELLAND1, L. COLLET2, S. ARDOIN-BARDIN3 & P. ROUCOU4

1 CNRS, 2 UM2, 3 IRD – UMR HydroSciences Montpellier, Place E. Bataillon, 34395 Montpellier Cedex 5, [email protected] Université de Bourgogne – Centre de Recherche en Climatologie, 6 Boulevard Gabriel, 21000 Dijon, France

Abstract This paper assesses the future variability of water resources in the long term over a large Sudano-Sahelian catchment in West Africa. Flow simulations were performed with a daily conceptual model. The climate models HadCM3 and MPI-M (based on SRES-A2) were used to provide future climate scenarios over the catchment. Outputs from these models were used to generate daily rainfall and temperature series for the 21st century according to: (i) application of the unbias and delta methods, and (ii) spatial and temporal downscaling. A temperature-based formula was used to calculate present and future potential evapotranspiration (PE). The daily rainfall and PE series were introduced into the calibrated and validated hydrological model to simulate future discharge. The model correctly reproduces the observed discharge at the basin outlet with the Nash-Sutcliffe efficiency criterion over 0.89, and the volume error close to null over 1952–2000. With regard to future climate, the results show clear trends of reduced rainfall with a continuing increase in PE over the catchment. This suggests that the catchment discharge could fall in the long term to the same levels as those observed during the severe drought of the 1980s.Key words hydro-climatic variability; climatic scenarios; hydrological modelling; River Bani; West Africa


Trends in hydro-meteorological variables in the Brahmaputra basin in India and their impact on flood events

U. C. SHARMA1 & VIKAS SHARMA2

1Centre for Natural Resources Management, V. P. O. Tarore, District Jammu 181133, J & K, India. [email protected]

2S. K. University of Agricultural Sciences & Technology, Chatha, Jammu 180009, J & K India.

Abstract The Brahmaputra River basin in India has an area of 1.94 105 km2. Floods are almost an annual feature in the basin, with variable magnitudes and frequencies. The annual rainfall variability index (RVI), monthly evaporation variability index and monthly maximum temperature variability index range from –1.77 to +1.85, –0.892 to +2.11 and –0.185 to +0.115, respectively. A negative relationship was found between the difference of monthly mean maximum and minimum temperature and rainfall, with gradient of up to –54.52 mm per C. To study hydro-meteorological variables, a long-term- multidisciplinary study has been in progress since 1983. Evaporation was relatively less during high rainfall months, resulting in higher runoff generation inducing floods.Key words hydro-meteorological variables; Brahmaputra basin, India; flood events


Estimation of evapotranspiration in the Brígida River basin, Brazil, by satellite remote sensing

RICHARDE MARQUES SILVA1, LEONARDO PEREIRA E SILVA2, CELSO AUGUSTO GUIMARÃES SANTOS2 & SUZANA MARIA GICO LIMA MONTENEGRO3

1 Federal University of Paraíba, Department of Geosciences, 58051-900 João Pessoa, PB, [email protected]

2 Federal University of Paraíba, Department of Civil and Environmental Engineering, 58051-900 João Pessoa, PB, Brazil3 Federal University of Pernambuco, Department of Civil Engineering, Laboratory of Hydraulic, Av. Acadêmico Hélio

Ramos, 50741-530 Recife, PE, Brazil

Abstract During the past two to three decades, significant progress has been made in estimating actual evapotranspiration using satellite remote sensing. Recently, the remote sensing and the techniques of geoprocessing have been used in diverse areas of research, mainly in environmental monitoring. The present study was intended to analyse the applicability of the SEBAL algorithm (Surface Energy Balance for Land) for energy balance estimation in the Brígida River basin, located in a semi-arid region of Brazil between 39°1156W longitude and 8°3855S latitude and 40°4936W longitude and 7°1543S latitude. Two TM - Landsat 5 images, orbit 217 and path 65, on 24 September 2009 and 16 July 1990, were

processed, organized and analysed in a Geographical Information System (GIS) environment from which surface albedo, vegetation indexes (NDVI, SAVI and LAI), surface temperature, soil heat flux, and evapo-transpiration were determined. The results showed that the reduction of vegetation cover is evident in the temporal and spatial analysis between the two periods. This reduction produced an increase of the temperature. The estimated evapotranspiration values were compared with the measured data at Araripina meteorological gauge. It was further observed that evapotranspiration increased gradually from 1990 to 2009, with an annual rate of about 10%. When comparing the mean annual evapotranspiration estimated from SEBAL and the observed data for each period, there is a satisfactory agreement.Key words SEBAL; semi-arid lands; water resources; Brazil


Satellite-based tracking of water surface variation of Poyang Lake during the last three decades

PING SONG1,2 & YUANBO LIU1

1 Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, [email protected]

2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Abstract Satellite-based observation provides an effective way to track water variations, since it can be used to retrieve many major hydro-physical variables, especially the water surface area. Here we used multi-satellite data to explore three-decade surface area variations of Poyang Lake, the largest freshwater lake in China. Our results revealed that the water area had declined generally in the last three decades. There existed a downtrend period of about 10 years. Generally, the decreasing trend of the decline was found to be significantly related to basin-scale climate change. Furthermore, the seasonal data demonstrated the remarkable change in surface area from over 3000 km2 in summer to less than 1000 km2 in winter. In the period examined, the lake surface area shrank to minimum values in 2003 and 2006. This was possibly related to land-use and land-cover change and construction of reservoirs in the basin, in addition to local climate change.Key words remote sensing; water surface area; NDWI; Poyang Lake, China; climate change


Calibration of hydrological models for medium-term streamflow prediction in a changing climate

JIN TENG, FRANCIS H. S. CHIEW, JAI VAZE & DAVID A. POSTWater for a Healthy Country National Research Flagship, CSIRO Land and Water, GPO Box 1666, Canberra, ACT 2601, [email protected]

Abstract Prediction of medium-term (1–10 years) streamflow has become more challenging under climate

change conditions. This paper presents results from a modelling study carried out to evaluate the performance of conceptual rainfall–runoff models in predicting medium-term streamflow using parameter values from model calibration against different periods of observed historical data. Four rainfall–runoff models are calibrated using the past 1 year, 2 years, 5 years, 10 years, 20 years and the entire historical daily climate and streamflow data for 20 catchments in southeastern Australia. The calibrated models are then used to predict the next 1 year, 2 years, 5 years and 10 years of streamflow. Calibrating hydrological models against the more recent data may give better medium-term streamflow predictions because the more recent data are likely to be of better quality, and they represent the current hydroclimate state and current land use and development. The results indicate that at least 10 years of data are needed for the model calibration to properly capture the range of hydroclimate variability. However, the modelling experiments here show little difference in the streamflow prediction results using parameter values from model calibrations against the past 10 or 20 years of data or the entire historical record. Key words streamflow prediction; rainfall–runoff model; model calibration; southeastern Australia


Trends in precipitation extremes and long-term memory of runoff records in Zhejiang, east China

YE TIAN1,2, YUEPING XU1, MARTIJN J. BOOIJ2, QINGQING ZHANG1 & SHENGJI LIN1

1 Institute of Hydrology and Water Resources, Zhejiang University, Hangzhou, China2 Department of Water Engineering and Management, University of Twente, Enschede, The Netherlands

[email protected]

Abstract Extreme weather events have a huge impact on human beings and therefore it is of vital importance to investigate trends in relevant climatological and hydrological variables. In this study, precipitation and streamflow trends in Zhejiang Province in east China are analysed. Trends in annual and extreme precipitation for 18 meteorological stations (data periods 42 to 58 years) are studied using the Mann-Kendall test. Trends in the plum season (May–July) and typhoon season (August–October) are analysed separately as well. The scaling properties of streamflow for three hydrological stations (data periods 47 to 57 years) are determined using the detrended fluctuation analysis (DFA) method. Results show a positive trend in annual precipitation in the east and a negative one in the west. The major part of Zhejiang shows a positive trend in extreme precipitation, being more significant for 95% non-exceedence values than for 99% non-exceedence values. Precipitation intensity exhibits an upward trend in most areas and in both plum and typhoon seasons, especially in the coastal areas. The results of the DFA method show that long-term memory properties exist for one year in all three rivers. This time scale can be explained since the main source of the streamflow variation comes from climatic variability and the fact that annual streamflow cycles did not change.Key words trends; precipitation; streamflow; Mann-Kendall; detrended fluctuation method; Zhejiang Province; China


Climate variability and water security for power generation

ADAM M. WYATT & STEWART W. FRANKSUniversity of Newcastle, Callaghan, New South Wales 2308, [email protected]

Abstract A reliable supply of fresh water is a critical component of coal fired power generation. During periods when water supplies are reduced, power generation may be limited, with obvious impacts on power consumers. Using the reconstructed historical streamflow series contained in the IQQM water allocation model, and simple water balance modelling, the water supply security of the Bayswater Power Station in the Hunter Valley, Australia, is assessed. The study revealed that the supply of water to the Bayswater Power Station is sensitive to extended dry periods, with some historical periods experiencing water shortfalls so severe that the station would be shut down without alternative water supplies.Key words climate variability; water supply security; water balance modelling; IQQM; Hunter Valley, Australia


Evapotranspiration observation and data analysis in reed swamp wetlands

SHIGUO XU & TAO MAInstitute of Water and Environment Research, Dalian University of Technology, No. 2 Linggong Road, Dalian 116024, [email protected]

Abstract Water is very important to wetlands. The state of water in a wetland determines the state of the ecosystem within it. In order to understand the water loss and water balance in wetlands, the evaporation from the water surface (Ew) and transpiration from vegetation (Tr) should be observed and calculated accurately. Taking Baiyangdian wetland in northern China as the experimental base, this study develops an on site monitoring system for evaporation and transpiration called the compensation Evapotranspiration Observation System (CETOS). The system includes two compensation cylinders and several observation cylinders set in the reed swamp wetlands. The compensation calculation of the observed data of the cylinders can reveal the amount of evaporation from the water surface, and the amounts of transpiration of reeds with different density. Using this method for the on-site experiment in Baiyangdian wetland, established that the accumulated evaporation from the water surface (Ew) was 442.2 mm in 2008, while the evapotranspiration from the reed belt (ET) was 2.85 times of Ew. In 2009, the corresponding amounts were 544.4 mm and 2.67 times, respectively. The data have been successfully used in the study of water resources plan of Baiyangdian wetland.Key words evapotranspiration; observation; compensation; wetlands; Baiyangdian wetland, China


Assessment of flash flood events using remote

sensing and atmospheric model-derived precipitation in a hydrological model

ISMAIL YUCEL1 & FATIH KESKIN2

1 Middle East Technical University, Civil Engineering Department, Ankara 06531, Turkey [email protected]

2 State Hydraulic Works, Ankara, Turkey

Abstract Remotely-sensed precipitation estimates and regional atmospheric model precipitation forecasts provide rainfall data at high spatial and temporal resolutions with a large-scale coverage, and can therefore be potentially used for hydrological applications for making flash flood forecasts and warnings. This study investigates the performance of the rainfall products obtained from the Hydro Estimator (HE) algorithm of NOAA/NESDIS and the Weather Research and Forecasting (WRF) model, and their use in a hydrological model (HEC-HMS) to simulate the catastrophic flood events which occurred in the Ayamama basin in northwest Turkey during 7–12 September 2009. The WRF model is also run with three-dimensional variational assimilation to obtain improved precipitation forecasts. The precipitation estimates at 4-km from the HE and WRF model, with and without assimilation, were evaluated against raingauge and radar data. The 4-km HE and WRF-estimated rainfall showed capabilities in capturing the timing of the flood events and to some extent the spatial distribution and magnitude of the heavy rainfall. Hydrological modelling based on HEC-HMS is applied using rainfall data from raingauges, radar, HE and WRF model. By use of surface hydrographs obtained from HEC-HMS, the HEC-RAS hydrological model is used to simulate inundation extent. The extent of the inundated areas in the river basin changes according to the peak discharges of the surface hydrographs used in the HEC-RAS module. Key words satellite rainfall; radar; hydrological model; flash flood; Turkey

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