Session 3: Case studies Session 3: Case studies Low flows and floods – Amazon Basin Low flows and floods – Amazon Basin Jean Loup GUYOT – IRD Lima – [email protected] - Jean Loup GUYOT – IRD Lima – [email protected] - www.mpl.ird.fr/hybam www.mpl.ird.fr/hybam UPS Toulouse UPS Toulouse ANA Brasília ANA Brasília UnB Brasília UnB Brasília UFF Niteroí UFF Niteroí UFRJ Rio de Janeiro UFRJ Rio de Janeiro INAMHI Quito INAMHI Quito SENAMHI Lima SENAMHI Lima UNALM Lima UNALM Lima SENAMHI La Paz SENAMHI La Paz UMSA La Paz UMSA La Paz
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Session 3: Case studies Low flows and floods – Amazon Basin Jean Loup GUYOT – IRD Lima – [email protected] - UPS Toulouse ANA.
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Session 3: Case studiesSession 3: Case studiesLow flows and floods – Amazon Basin Low flows and floods – Amazon Basin
Jean Loup GUYOT – IRD Lima – [email protected] - www.mpl.ird.fr/hybam Jean Loup GUYOT – IRD Lima – [email protected] - www.mpl.ird.fr/hybam
UPS ToulouseUPS ToulouseANA BrasíliaANA BrasíliaUnB BrasíliaUnB BrasíliaUFF NiteroíUFF NiteroíUFRJ Rio de JaneiroUFRJ Rio de JaneiroINAMHI QuitoINAMHI QuitoSENAMHI LimaSENAMHI LimaUNALM LimaUNALM LimaSENAMHI La PazSENAMHI La PazUMSA La PazUMSA La Paz
Rainfall stations from :Rainfall stations from :ANA (Brazil),ANA (Brazil),SENAMHI (Bolivia and Peru),SENAMHI (Bolivia and Peru),INAMHI (Ecuador)INAMHI (Ecuador)IDEAM (ColombiaIDEAM (Colombia
This methodology consists in assuming that for the same climatic zone under the same rainfall regime, the annual pluviometric totals are pseudo proportional, with a little random variation every year due to rain distribution in the zone.
To calculate this “Vector” station, the RVM applies the concept of extended average rainfall to the work period, which is an estimation of the average possible value that would have been obtained through continuous observations during the study period. Based on the above mentioned, the Least Squares Method is applied to find the Regional Annual Pluviometric Regional Indexes Zi and the extended average rainfall Pj. This may be calculated by minimizing the sum of the formula (1), where i is the year index, j is the station index, N is the number of years, and M is the number of stations. Pij is the annual rainfall in the station j, the year i; Pj is the extended average rainfall to the period of N years; and finally, Zi is the regional pluviometric index of the year i. The series of the chronological indexes Zi is called “Regional Annual Pluviometric Indexes Vector”.
Gauging stations from :Gauging stations from :ANA (Brazil),ANA (Brazil),SENAMHI (Bolivia),SENAMHI (Bolivia),INAMHI (Ecuador),INAMHI (Ecuador),HYBAM (Bolivia, Peru and Ecuador)HYBAM (Bolivia, Peru and Ecuador)
The trend analysis is made based on the calculation of the correlation coefficients, which are applied for evaluating the series trend. The correlation coefficients applied are: Pearson coefficient, which is parametric and measures the lineal correlation among variables, Spearman is non-parametric based on the range, and Kendall, also non-parametric based on the range and probability of the data occurrence order.
Annual Discharge Data (Óbidos gauging station, Brazil)Annual Discharge Data (Óbidos gauging station, Brazil)
2006
2005
Mean (no trend)
Max
Min
Nine events with runoff higher than 250 000 m3/s occurred between 1970 and 2005, while four have been observed since the beginning of the century,
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Annual Discharge Data (Tamshiyacu gauging station, Peru)Annual Discharge Data (Tamshiyacu gauging station, Peru)
-0.81% / year
Espinoza et al. (2006). Espinoza et al. (2006). IAHS Publ. IAHS Publ. 308, 424-429.308, 424-429.
Positive trend no significance90% Positive significance99% Positive significance99% Negative significance90% Negative significanceNegative trend no significanceno trend
TAMSAI
ACASER
CAR
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G-L
PVE
FVA
ITA ALT
OBI
Mean annual discharge trendMean annual discharge trend
TAMSAI
ACASER
CAR
MAN
G-L
PVE
FVA
ITA ALT
OBI
Positive trend no significance90% Positive significance99% Positive significance99% Negative significance90% Negative significanceNegative trend no significanceno trend
Max annual discharge trendMax annual discharge trend
TAMSAI
ACASER
CAR
MAN
G-L
PVE
FVA
ITAALT
OBI
Positive trend no significance90% Positive significance99% Positive significance99% Negative significance90% Negative significanceNegative trend no significanceno trend
Min annual discharge trendMin annual discharge trend
One long observed time serie : Negro River at Manaus (1903 - today)One long observed time serie : Negro River at Manaus (1903 - today)
Due to backwater effects, Negro River water levelsare controlled by theAmazon river near the confluence, like allmajors tributaries of theAmazon basin.
Meade et al. (1991). Meade et al. (1991). Environ. Geol. Water Sci. Environ. Geol. Water Sci. 18(2), 105-114.18(2), 105-114.
Richey et al. (1989). Richey et al. (1989). Science. Science. 246, 101-103.246, 101-103.-> No trend, links with ENSO events-> No trend, links with ENSO events
Milly et al. (2002). Milly et al. (2002). NatureNature, 415: 524-517., 415: 524-517.-> increasing floods-> increasing floods
One long reconstructed time serie : Amazon River at Óbidos (1903 - today)One long reconstructed time serie : Amazon River at Óbidos (1903 - today)
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dh = 83 cm
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Echelle ancienneEchelle actuelle
2 observed periods withoutnivel correction.The rating curve for the recent Period can not be used for thewhole period.-> be careful with publisheddischarge data (UNESCO)
Callède et al. (2004). Callède et al. (2004).
Max, Mean and Min annual discharges : Amazon River at Óbidos (1903 - 1999)Max, Mean and Min annual discharges : Amazon River at Óbidos (1903 - 1999)
The breaks and changes in the series are evaluated through different methods, using Kronostat software: the Buishand method, of Bayesian nature, based on changes of the series average. The Pettitt method is a non-parametric test based on changes in the average and the range of the series. Lee and Heghinian test are also used, which is other Bayesian method that uses the average as an indicator of change. Finally, Hubert segmentation is applied based on the significant difference of the average and the standard deviation among periods; for the search of multiple changes in the series.
Callède et al. (submitted). Callède et al. (submitted).
Runoff coefficient : Amazon River at Óbidos (1903 - 2003)Runoff coefficient : Amazon River at Óbidos (1903 - 2003)
Using Wavelet analyses to detect changes
Conclusion
Main results for the 1902 – 1999 period at Obidos are : i) increasing trends for annual mean discharge and annual flood discharge, ii) no tendency for low flows, and iii) a significant break for the maximum and mean time series in 1969-1970.
Using the HYBAM dataset for the whole Amazon basin, a first study has been realized for 30 years (1975-2005). Mean annual rainfall over the Óbidos drainage basin presents a decreasing trend of 0.32%/year, while mean annual discharge is stable. This difference between rainfall estimation and discharge can be the consequence of:• rainfall under estimation, mainly in the equatorial region (north Peru, Colombia) were rainfall data is rare,• impact of the deforestation : with the same rainfall, there is more runoff, etc…• and/or change in the rainfall regime, with higher intensity, i.e. more runoff.For the same period (1975-2005), annual flood discharges are increasing, while annual low flows are decreasing, traducing an increasing amplitude of discharge at the Óbidos station.
The study of these tendencies in the different sub basins should allow us to understand better the impact of the climatic variability in the Amazon basin.
=> More data is required, => We have to help the Andean countries in this way