TAM

1. Venezuela Colombia Ecuador OBI Napo TAM Solimoes OBI OBI Amazonas OBI Marañon TAM TAM TAM Huallaga Madeira Brasil PVE PVE PVE PVE Ucayali Peru SRE BOR REQ Bolivia CAE GUA Beni Mamoré BOR SRE BOR SRE BOR SRE REQ REQ REQ CAE CAE CAE GUA GUA GUA FIGURE 1 FIGURE 3 Data is available from HYBAM program (Hydrogeodynamic of the Amazon Basin.www.ore-hybam.org) : B C A OBIDOS TAMSHIYACU PORTO VELHO Annual mean runoff (Qmean), maximum and minimum annual runoff (Qmax and (Qmin) in Porto Velho (PVE. Madeira River), Tamshiyacu (TAM. Anazonas River) and Obidos (OBI. Amazon River) for the 1974 – 2004 period (Figure 1 and Table 1), and in sub basins inside the TAM watershed (Requena –REQ, Ucayaly River-, San Regis –SRE, Marañon River- and Borja -BOR, Upstream Marañon River-) and inside the PVE watershed (Guayaramerin –GUA, Mamoré River- and Cachuela Esperanza -CAE, Beni River-) (Figure 1 and Table 1). Mean rainfall data is computed in TAM, PVE and OBI basins. TABLE 1 FIGURE 4 B -0.32%/year A C -0.41%/year -0.77%/year -0.10%/year -0.60%/year -0.68%/year TABLE 2 Qmin Qmax Qmean + - B C A E F D • Callède, J., Guyot, J.L., Ronchail, J., L’Hôte, Y., Niel, H., de Oliveira, E., 2004. Evolution du débit de l’Amazone à Óbidos de 1902 à 1999. Hydrological Sciences journal 49, 85-97. • Espinoza, J.C, Fraizy, P., Guyot, J.L., Ordoñez, J.J., Pombosa, R., Ronchail, J., 2006. La variabilité des débits du Rio Amazonas au Pérou. Climate Variability and Change-Hydrological impacts. IAHS Publ. 308: 424 – 429. • Espinoza, J.C., Ronchail, J., Guyot, J.L., Filizola, N., Noriega, L., Ordonez, J.J., Pombosa, R., Romero, H., 2007a. Spatio – Temporal rainfall variability in the Amazon Basin Countries (Brazil, Peru, Bolivia, Colombia and Ecuador). International Journal of Clinatology. Submitted 2007. • Espinoza, J.C., Ronchail, J., Guyot, J.L., Filizola, N., Noriega, L., Ordonez, J.J.,Vauchel, P., Fraizy P. 2007b. Main rivers discharge trend in the Amazon Basin. In Preparation. • Marengo, J., Tomasella, J., Uvo, C., 1998. Long-term stream flow and rainfall fluctuation in tropical South America: Amazonia, eastern Brazil, and northwest Peru. Journal of Geophysical Research 103, 1775 – 1783. • Molinier, M., Guyot, J.L., de Oliveira, E., Guimarães, V., 1996. Les régimes hydrologiques de l’Amazone et de ses affluents. L’hydrologie tropicale: géoscience et outil pour le développement, Paris, Mai 1995. IAHS Publ. 238: 209 – 222. • Labat, D., Ronchail, J., Guyot, J.L., 2005. Recent advances in wavelet analyses: Part 2 – Amazon, Parana, Orinoco and Congo discharges time scale variability. Journal of Hydrology 314, 289 – 311. • Richey, J.E., Nobre, C., Deser, C., 1989. Amazon river discharge and climate variability. Science 246, 101 – 103. • Rocha, H.R., Nobre, C.A., Barros, M.C., 1989. Variabilidade natural de longo prazo no ciclo hidrológico da Amazônia. Climanálise 4(12), 36 – 42. • Ronchail, J., Guyo,t J.L, Espinoza, J.C, Callède, J., Cochonneau, G., de Oliveira, E., Ordeñez, J.J., Filizola, N., 2006. Impact of the Amazon tributaries on flooding in Obidos. Climate variability and Change – Hydrological Impacts (Procceedings of the Fifth FRIEND World Conference held at Havanna, Cuba, November 2006), IAHS Publ. 308, 2006, 220-225. • Zeng, N., J. Yoon, J. Marengo, A. Subramaniam, C. Nobre, and C. Birkett, 2007: Causes and impact of the 2005 Amazon drought. Science (submitted). REFERENCES HYDROCLIMATIC VARIABILITY IN THE ANDEAN REGION OF THE AMAZON BASIN ESPINOZA VILLAR Jhan Carlo1,2,3, GUYOT Jean Loup1,2, RONCHAIL Josyane1,3,4, CHAVARRI Eduardo1,2, FRAIZY Pascal1,2, GUYOMARD Marine1,5, NORIEGA Luis1,6, de OLIVEIRA Eurides1,9, ORDÓÑEZ Juan Julio1,7, POMBOSA Rodrigo1,8, VAUCHEL Philippe1,2,6. INTRODUCTION The Amazon Basin (AB) is the major hydrological basin in the world (6.106Km2, Molinier et al., 1996). Discharge variability has been studiedin the main stream(Richey et al., 1989; Costa and Foley, 1999) and a strong variability since the 1970’s has beenput in evidence by Callède et al. (2004) and Labat et al. (2005). Few studies analyzed the regional hydroclimatic variability (Rocha et al., 1989; Marengo et al., 1998; Ronchail et al., 2006; Espinoza et al., 2006),though strong runoff events occurred lately, as the dramatic low flow in the western basins in 2005 (Zeng et al., 2007). Nevertheless, what is the main runoff variability in the Andean rivers of the AB? Is the evolution of mean values the same than for extreme values? DATA The rainfall and runoff annual cycle in TAM, PVE and OBI show a strong seasonality in the tropical PVE basin, but is more regular in TAM and OBI because they drain tropical and equatorial regions (Fig. 3A, B and C). RESULTS AND DISCUTIONS Trend tests (parametric Pearson and non-parametric and rank based Spearman and Kendall coefficients) are applied. The interannual rainfall and runoff evolutions reveal a strong diminution in TAM and PVE and no trend in OBI, during the 1974 – 2004 period (Fig. 4A B and C). A Qmean and Qmin diminution in TAM and PVE (significant at the 99% level), and no trend in Qmax is observed for the 1974 – 2004 period (Figure 5 A, B and C, and Table 2). OBI do not display any significant trend during this period. In Andean rivers sub basins, strong trends are detected for the 1990 – 2005 period (Figures 5 D, E and F and Table 2). Inside PVE, trends are negative, strong in GUA and weak in CAE. Toward north, a strong diminution is observed in REQ, but trend is positive and strong in SRE (in Qmax and Qmean principally). In BOR no significant trend is observed. FIGURE 5 CONCLUSIONS AND PERSPECTIVES Strong runoff trends are noticed in the Andean rivers of the AB during the 1974 – 2004 period. An opposition is put in evidence between a negative trend in many shouthern tropical basins specially in Qmin and Qmean and a positive trend in a small northern equatorial basin, especially in Qmax. These trends are consistent with rainfall variability (Espinoza et al., 2007a). The resultant runoff diminution in the Andean rivers of the AB and the absence of trend in the mean stream at Obidos, suggest that the Andean rivers of AB cause extreme low stage values in OBI and that increasing high flow values should be registered in other basins. So, what is the trend in the other Amazon sub basins (Espinoza et al., 2007b)? Any way, what is the origin of these trends: regional and/or global climate changes or human impacts as deforestation? 1 HYBAM. 2IRD/UNALM-PERU. 3LOCEAN/IPSL-FRANCE. 4UNIVERSITÉ PARIS 7-FRANCE. 5 ENS-FRANCE.6SENAMHI BOLIVIA. 7SENAMHI PERU. 8INAMHI ECUADOR. 9ANA BRAZIL. Correspondence to: ESPINOZA VILLAR J.C. LOCEAN. Boite 100, 4 Place Jussieu, 75252. Paris Cedex 05, France. jhan-carlo.espinoza@locean-ipsl.upmc.fr.