19820 September 1993
LATENDissemination Note # 5 Public Disclosure Authorized An Analysisof Flooding in the ParaniYParaguay River Basin
September1993 Public Disclosure Authorized Public Disclosure Authorized
,a,g-X Z S~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...N. ...
RobertJ. Anderson,Jr. Nelsonda FrancaRibeiro dos Santos
Public Disclosure Authorized HenryF. Diaz
The World Bank Latin America TechnicalDepartment t EnvironmentDivision
LATEN Dissemination Note # 5
An Analysis of Flooding in the Parana'/ParaguayRiver Basin
September 1993
Robert J. Anderson, Jr. Nelson da Franca Ribeiro dos Santos Henry F. Diaz
The World Bank Latin America & the Caribbean Technical Department Environment Division
FOREWORD
Late in 1991, unusually heavy rain began to fall in the catchment areas of the Parana, Paraguay, and Uruguay Rivers. In 'normalH years, the average precipitation in this basin varies between 200 mm per year in the western part, the mountain range of the Andes, and 2,000 mm in the southeastern part, consisting of the Iguazu River basin. The rains are almost incessant during the year in the southern and southeastern parts of the basin. This rainfall distribution produces high river flows in the basin that begin in October/Novemberand peak between February and June/July.
As in most flood years, torrential downpours in the Brazilian part of the Paran; River Basin between January and May 1992 produced massive flows in the Parana River. In addition, heavy rains in the middle to lower Paraguay River basin during March and May led to peak flows in this river that were coincident with the peak flows of the Parana River. The Parana thus peaked in April/May 1992 at almost four times the yearly average. The initial data on the 1992 flood indicate that the peak flow was about 56000 m3/s. This caused serious infrastructure damage and forced the evacuation of about 120,000 people from seven Argentine provinces - Buenos Aires, Chaco, Corrientes, Entre Rios, Formosa, Misiones, and Santa Fe. Although it is too early to attempt a precise estimate, indications are that the damage may be on the same order of magnitude as that caused by the 1983 flood, which cost about US$ 1 billion to repair. Apart from the capital stock damage, Argentina will also face substantial economic losses (e.g., lost production of grains, livestock, and cotton). Losses in Paraguay and Brazil were also severe.
In September, 1992, the World Bank approved a loan to Argentina to cover a portion of the costs of repairing the damage due to this flood. The Bank also initiated the identification of a possible subsequent operation that would aim at improving Argentina's preparedness to deal with severe flooding. During the processing of the rehabilitation operation, the Bank became aware of satellite imagery evidence that heavy siltation appears to be occurring along stretches of the Parani that are bordered by agriculture. This led the senior managementof the LAC Region to question whether deforestation may be making the basin more prone to floods. Regional senior management asked the Region's Technical Department to examine this issue.
Disentangling the impact of deforestation from other factors on flooding is a difficult undertaking under the best of circumstances. The quantity and quality of historical data on land-use changes and other interventions affecting the hydrology of the basin and basic hydrologic data are reasonably good by developing country standards. Records of Parana River flows exist since 1901 and land-use data extend back perhaps 40 years. There are, however, serious gaps in meteorological information, and the hydrology of this large basin is extremely complex. This paper, writtenby a team led by RobertJ. Anderson,Jr., formerlyof LATEN,and comprisedby Dr. Nelsonda Franca Ribeiro dos Santosof the Organizationof AmericanStates, and Dr. Henry F. Diaz of the NationalOceanic and AtmosphericAdministration, draws upon these data to reach preliminaryconclusions about the recent frequencyand severityof flooding,and about the possiblerole that land use changesmay be playing. During the preparationof the paper, Drs. Anderson,da Franca Ribeiro dos Santos, and Diaz benefittedfrom the commentsof workshopin whichseveral distinguishedscientists and practitionersparticipated.'
While the data are far from perfect, the evidenceexamined indicates that floodingin the ParanAfParaguaybasin has indeedbeen both more frequentand more severein recent years. Ten-yearflood dischargerates are now over 15% greater than they were in the early years of the 20th century. Mean dischargerates and extremelow dischargerates are higher too. The analysisalso showsthat changesin precipitationrates and patterns are by far the mostimportant explanatory factors in these observedchanges in streamflow. Recentprecipitation has been higher in the wet season, and lower in the dry season. Reservoirson the Upper Parand havealso playeda role, particularly in increasinglow flows. When these other factorsare held constant,there is no systematicevidence that any other factor such as land use changesin the upper basin is playinga significantrole in flooding.
Theseconclusions notwithstanding, the apparentlack of association betweenflooding and land use changesis no reason to be complacentabout these changes. Data examinedduring the course of the research - particularlythe satelliteimagery suggestive of heavy sedimentloads - suggestthat land use changesin the upper basins maybe exactinglarge private and social costs in terms of lost productivityin agricultureand infrastructure,and lost biodiversity.
Like other papers in this 'DisseminationNotesw series, the findings, interpretations,and conclusionsexpressed are entirelythose of the author(s) and shouldnot be attributedto the WorldBank, membersof its Board of ExecutiveDirectors, or the countriesthey represent.
DennisJ. Mahar Division Chief EnvironmentDivision Latin American& the Caribbean TechnicalDepartment
Workshopparticipants, in additon to theauthors, included Dr. KirkRodgers (Orgaiion of American States), Professor Rafael Bras (Massahusetts Instituteof Technology), Mr. StephenOliver (IBRD), Mr. ArmandoAraujo (IBRD), and Mr. Sri-RamAiyer (IBRD). AN ANALYSISOF FLOODING IN TIHE PARANA/PARAGUAYRIVER BASIN
Robert J. Anderson, Jr. Nelson da Franca Ribeiro dos Santos Henry F. Diaz'
'The authors are respectively Principal Sector Economist, India Country Department, The World Bank, Water Resources Senior Specialist, Department of Regional Developmentand Environment, and Climatologist,National Oceanic and Atmospheric Administration. Dr. Anderson led the team and was prinarily responsiblefor analysis and for preparation of the main body of the paper. Dr. da Franca Ribeiro dos Santos was primarily responsible for the preparation of Annexes A and C. Dr. Diaz was primarily responsible for preparation of Annex B.
The views expressed in this paper are solely those of the authors and do not necessarily reflect the views of organizations with which they are associated.
AN ANALYSISOF FLOODINGIN THE PARANAIPARAGUAYRIVER BASIN
Introduction
1. Torrentialdownpours in the Upper and MiddleParana River Basin betweenDecember 1991 and May 1992and in the Middle and Lower ParaguayRiver Basin betweenMarch and May producedmassive flooding in Argentina,Brazil, and Paraguay.These floods caused seriousinfrastructure damage and forced the evacuationof about 120 000 peoplefrom the Argentineanprovinces of BuenosAires, Chaco, Corrientes,Entre Rios, Formosa, Misiones, and SantaFe, as shown. In Paraguay,more than 70 000 peoplewere evacuatedin the cities of Asunci6n,Concepcion, Alberdi, and Pilar. In Brazi, heavyrains and the floods in these basins forced the evacuationof thousandsof peopleand also causedserious infrastructure damage. TableI: Most SevereMaximum Floods, 1901-92
ParanA-Posadas Paraguay-Asunci6n Parang-Corrientes Year m 3 /s date Year m3/s date Year m 3 /s date 1905 45 000 May 25 1983 11 740 May 29 1983 54 700 July 18 1983 43 330 July 12 1905 11 170 June 23 1992 50 800 June 8 1992 41 850 June 25 1992 10 530 June 1 1905 50 000 June 5 1990 37 500 Jan 25 1919 8 770 June 13 1966 43 800 March 1 1936 34 500 June 12 1982 8 730 July 29 1990 43 800 Feb 1 1987 34 500 May 23 1988 8 500 June 10 1982 42 600 Dec 11 1966 33 900 Feb 23 1931 8 240 July 1 1912 39 100 Jan 7 1923 33 750 June 21 1912 7 820 Jan 15 1929 39 100 March 10 1929 32 450 March 5 1979 7 580 June 14 1987 38 900 May 30 1982 31 350 Dec 5 1913 7 420 May 15 1923 38 100 June 27
2. The 1992 floods cappeda decade of unusual(by historicalstandards) flood activity. Five (5) of the ten (10) most severe (measuredin terms of annualdaily peak discharge) floods recorded in the Parani/ParaguayRiver Basin during this century have occurred since 1982 (TableI).
3. This apparentrecent "bunching"of relativelyserious flood events has led to speculationthat some systematicstructural changes (as opposedto purely randomvariations) may have occurredthat may have made/bemaldng the basin more prone to flooding. Any such changes,if present, clearly would have far-reachingimplications for the future developmentof the central-easternregion of SouthAmerica. The larger La Plata Basin, whichis comprisedby the Parand, Paraguay,and UruguayRiver Basinswith an area of 3.1 millionkm 2 in Argentina,Bolivia, Brazil, Paraguay,and Uruguay constitutesthe economic heart of this region. The ParanA/ParaguayRiver Basin encompasses2.6 million km2 (84% of the total area of the La Plata Basin)in the four countriesexcept Uruguay. It containsa multitudeof natural resources: water, minerals,and arable soils. As a result, the area has the most developedagricultural and industrialzones of the continent;it holds some of the more importanthydroelectric dams in Latin America(Itaipu and Yacyreta);it containsan extensiveriverine and terrestrialtransportation network; it generatesaround 80% of the Gross DomesticProduct of the countriesand it is home to some 100 millionpeople.'
4. Three major changeshave occurredsince the 1960sthat potentiallycould affect the hydrometeorologyof the region:
o Agriculturaland industrialproduction in the basin has grown rapidly and the frontier of agricultureand livestockproduction expanded. In Brazil, land in the Upper Parana Basin has been convertedfrom coffee plantationsto soybeansand sugar cane for alcoholfuel production. In the ParaguayBasin, deforestationand the expansionof the agriculturalfrontier to establish croplandand pasture, have been extensivein both the Brazilianand Paraguayanportions of the basin. These land use changesmay have increased runoff, streamflow,siltation and may be implicatedin recent flood episodes.
O Hydroelectricdevelopment, mostly in the Upper Parara Basin, has expanded significantly. Some 20 hydroelectricpower plants of more than 1000 MW includingbinational plants for Brazil-Paraguayand Argentina-Paraguayhave been installedor are under construction. Overallpotential in the basin is now approximately42,000 MW and the total amount of water stored in the reservoirsis approximately350,000 hm 3, of which 120,000hm 3 are active storage. Reservoiroperation may have increasedthe flow of the ParanaRiver at the confluencewith the Paraguayat the time that the ParaguayRiver peaks.
o Wet season rainfallin the region of the Paranaand ParaguayBasins has been relativelyhigh since the early 1980s, raising the possibilitythat a changein climate (as opposedto simplerandom variation in precipitation)may have occurred. It also begs the questionwhether any such change could be due to humaninfluences on the environment(e.g., increasedconcentrations of atmospheric'greenhouse' gases, worldwidedeforestation, stratospheric ozone depletion,and increasesin anthropogenicaerosol loading of the atmosphere could be contributingto these recent precipitationextremes).
'A basicdescription of the ParanL/ParaguayBasin is containedin AnnexA. 2 5. This paper examines some of the evidence bearing on these developments and their possible effects on the hydrometeorologyof the Basin. In particular, it considers two questions'
i Has flooding in the basin become more frequent and/or more severe?
ii Can observed variations in streamflow in the basin be explained by random variations in precipitation alone, or do other factors such as changes in climate, land use, or operations of reservoirs also appear to have played a role?
Definitive answers to these questions are beyond the reach of the paper given the present state of the data. This limitation notwithstanding,however, the evidence is reasonably strong that flooding was significantly (in a strict statistical sense) more frequent and more severe in recent years, and that this was due primarily to unusually concentrated (in time and space) precipitation. There is no strong statistical evidence to indicate that any other factor played a significant role in flooding. There is, however, some evidence that when precipitation is not extremely high, some change has taken place that causes streamflow to be greater than otherwise would have been expected.
Has Flooding Become More Frequent or Severe?
6. The data presently available only permit a partial and preliminary analysis of the frequency and severity of flooding in the Basin. This analysis is based on examination of discharge/stage extrema (i.e., maxima and minima) and mean discharges at a limited number of stations
Annual Maximum Daily Discharges/Stages Since 1900
7. Data on annual maximum daily discharge rates/stages at Corrientes are shown in Figure 1.2 Other things being equal, if flooding were no more frequent in the latter years of the sample than in the early years, the proportion of the time that peak discharges exceed a given level would be about the same as in the earlier years of the sample. Visual inspection of the data shown in Figures 1 is not conclusive, but does suggest some bunching of relatively high peak discharge rates toward the end of the sample period. A statistical analysis of the data in Annex C for Corrientes and other stations (based on binomial probability distributions estimated from the data in these tables) rejects the hypothesis that the frequency of extraordinary (i.e.. ten-year) floods was the same in the latter years of the sample (Table II). This conclusion is not sensitive to the point at which the sample is divided in the cases of Corrientes, Posadas, and Porto Murtinho. The frequency of extraordinary
2Annualmaximum daily dischargerates/stages at Corrientes,Posadas, Asuncidn, Porto Murtinho, Ladario, Guaira, and Jupia are reportedin AnnexC. 3 60000
50000 AII
40000
20000
t0000
0 i: :IiI,,ii:nt itt uuuu:i tt uu: uI 111111: Wtn
F"igure1: Corrientes - Annual Maximum Daily Discharge Rates (m3Is) floodsis significantlyhigher in each of these places over all divisionsof the sample,while floodingin Guaira, Asunci6n,and Ladaniois significantlymore frequentpi Ix when the sampleis split at 1980. Splittingthe data at 1970 or 1960yields inconclusive results at these latter sites.
8. To determinewhether the seveity o loo~dsappears to be increasing,log normal cumulativedistribution functions were fitted to the maximumdischarge data over two sample periods of equal length (1901-46and 1947-92)for Posadasand Corrientesand the resulting fits tested to determinewhether the distributionshad changedsignificantly between early and later sampleperiods. 3 The tests reject the null hypothesisthat the post-1947cumulative
3Thecumulative distribution functions were fitted by estimatingthe following expression by ordinary regressionmethods, N+1 whereF, is the reportedmaximum daily discharge rate in yeart, N is the totalnumber of yearsin the subsample,R, is the rank in the subsampleCin order of decreasingdischarge rates, with the highest dischargerate rankedfirst, andso forth)of thete observation,and e, is an errorterm. An analysisof variancetest wasperformed in the contextof theseregressions. This test partitionsthe data into two 4 Table II: Probability Analysis of Frequency of Extraordinary Floods
River Station SampleSplit At 1980 1970 1960 Paraguay Asuncion 0.00972 0.07492 0.22555 Porto Murthinho 0.00001 0.00001 0.00177 Ladario 0.02095 0.01069 0.25724 Parana Corrientes 0.00318 0.02346 0.00120 Posadas 0.00021 0.01193 0.00133 Guaira 0.16540 0.71984 0.37953
Table m: Estimated Flood Discharges (m31s) Corresponding to Alternative Return Periods (years)
StationlSample Significance Return Period (Years) l Subperiod Level of Test 10 20 50 100 Posadas 0.0990 1901-92 32700 36986 42653 46939 1901-46 32653 36968 42672 46987 1947-92 33653 38273 44382 49002 Corrientes 0.0000 1901-92 39204 44584 51696 57076 1901-46 37542 42659 49423 54540 ; 1947-92 41734 47694 55574 61535
distribution function is the same as the pre-1947 distribution function, although the significance level of the test at Posadas is only about 10% (Table Im). At both sites, higher flood peaks were associated with any given level of probability in the post-1947 period, or equivalently, the flood for any given return period was more severe.
9. While the samples of data analyzed as described above span relatively long time periods (i.e., 92 years in Corrientes and Posadas, and between 49 and 89 years at other locations), it should be kept in mind that a longer sample period might well lead to different
subperiods(in this case of equal length)and tests whetherthe estimatedcoefficients are, for statistical purposes,identical over the two subperiods.
5 conclusions. There exist referencesto extraordinaryfloods that occurredin Corrientesin 1612 and 1748 (stage< 10.50 m), as well as in 1812, 1858, and 1878. Table IV reports extraordinaryfloods in Corrientesprior to 1905 in comparisonwith the floods of 1983 and 1992. It is not clear whetherthis is a completerecord of extraordinaryfloods during the 1800s.However, these three large floods duringthe 1800sunderscore the point that, if the statisticalrecord could be extendedback into the 1800s,the conclusionsconcerning frequencyand severitystated above might not stand. Table IV: ExtraordinaryFloods in CorrientesBefore Prior to 1905Compared to the Floodsof 1905 and 1992
Year Stage lGM1 Discharge m m m3 /s 1812 9.53 50.93 58 000 1983 9.02 50.42 54 700 1858 8.93 50.33 52 000 1878 8.65 50.05 51 000 1992 8.64 50.04 50 800 1905 8.57 49.94 50 000 I-Gage-dacUmsbove swa level-Instituto Gcog~iScoMiIk, Aretn
Other StreamflowCharacterisics
10. Two other streamflowcharacteristics, annual minimum daily dischargerates and mean monthlydischarge rates were examinedto determinewhether changes appear to have occurred in these parametersas well. Figure 2 suggeststhat annual minimumdischarge rates have tendedto increase. Regressionestimation fitting log normal cumulativeprobability distributionsto the annual minimumdaily dischargerate data for Corrientesand Posadasand statisticaltesting confirms that minimumdaily flowswere significantlyhigher at these stationsduring the latter part of the sampleperiod.4
'Data on annual minimumdaily dischargerates/stages at Corrientes,Posadas, Guaira, Asunci6n, Porto Murtinho, and Ladario are reported in Annex C. Estimationand testing was carried out in accordancewith the proceduredescribed in footnote3 above.
6 258000-
20000
15000
10000
5000
20.1n a
Flgure 2: Annual Minimum Discharge Rates (m3Is) at Corrientes 4 ".0 1910-92,g
190_ -9
5.0
Jan Feb Mar Apr May Jun Jul Aug Gep Oct Nov Dec
Figure 3: Monthly Mean Discharge Rates (m3 /sec)at Corrientes
7 11. Figure 3 shows a distinctshift in the pattern of mean monthlyflows in Corrientes over two subperiods(1901-67 and 1968-92).5Visual inspection of the figure suggeststhat two changeshave occurred. First, mean dischargesseem generallyto have increased. Mean annualdischarge was between15 and 20 percent higher during the second subperiod(1968- 92) than in the earlier period. Second,there was a shift in the intra-annualpattern of discharges,with mean monthlyflows becomingmore uniformover the year due to significantlyhigher (in the secondsubperiod) mean flowsin the monthsof May through December. This latter shift in the distributionis what would be expectedto occur as a result of the operationsof reservoirsin the Upper Basin.
12. In sum, the analysesdescribed above suggestthat the entire streamflowdistribution was shiftedtoward higher values in the later years of the sampleperiod. Maximumannual daily dischargerates, minimumannual daily dischargerates, and mean annualdaily dischargerates all were higherin the later years of the sampleperiod. There is also some evidenceof a changein the intra-annualdistribution of streamflow.
What Accounts for Greater FloodFrequency and Severity?
13. The dischargedata reviewedabove thus are generallyconsistent with the hypothesis that floods were both more frequentand more severein the latter years of this century than in the earlier years. It is of fundamentalimportance for the future developmentof the Basin to try to understandwhether this is due to purely randomvariations in precipitationor whetherit representsa structuralchange in the hydrometeorologyof the basin.
14. This is a complexundertaking. Runoffwithin a basin dependsnot only on the amount of rainfall but also upon its temporaldistribution, vegetal cover, evapotranspiration, infiltrationrates, soil moisturestorage capacity, the amount of moisturein storage, surface storage, rate of groundwateroutflow, losses due to deep percolation,and a host of other factors. Many of these parametersare interrelated. An extensiveprogram of reservoir constructionover the sampleperiod on the Upper Parara introducesadditional complications. For these reasons, the analysispresented here is indicative,but not conclusive.
UnusuallyHeavy Precipitation
15. The most obviouspossible explanation for recent heavy floodingis that it could have been"causedby too much rain fallingin too short a period, or prolongedrain fallingon land that is already saturatedwith water."6 Figure 4 shows an annualtime series of precipitation anomalies(i.e., deviationsof precipitationfrom its meanvalue) over the region of the ParanA/ParaguayBasins during a three-monthperiod (March-May)derived from stationdata
'Data on mean monthlyflows are presentedin AnnexA. %Hamilton,Lawrence S. *TheRecent Bangladesh Flood Disaster Was No Causedby Deforestation Alone." EnvironmentalConservation, 1988, pp 369-370. 8 4
ma
2-
.~~~~~a
iO 20 30 40 50 60 70 80 90
|_PRECIP .MAXFLOW|
Figure4: March-May Preupitation Anomalies and Annual Maximum Daily Dischages at Corrientes (Normnalized) within this region.' Clearly, the temporal behavior of the rainfall anomaly sen'es agrees quite closely with that of the peak annual flow series. The correlation between the two series, weighted by the number of station at which measurements were taken for each observation, is roughly 0.95. This means that variations in weighted precipitation explain about 90% of the variation in the annual weighted maximum daiy discharge rate series. The correlation between the two unweighted series is about 0.67.
Ilhe March-May period was chosen because five of the ten maximum discharge rates recorded at Corrientes occurred in May, June or July. Two others occurred in March. See Table I.
9 TableV: RegressionResults for MonthlyPrecipitation and Mean MonthlyDischarge Rate Data
Regression1 Regression2 Coefficient t-statistic Coefficient t-statistic Constant 0.6241 0.8821 11.4019 13.5376 PRECIP 0.0256 7.9090 0.0107 5.0276 PRECIP(-1) 0.0423 12.6846 0.0325 15.8547 PRECIP(-2) 0.0228 6.7791 0.0136 6.5997 PRECIP(-3) 0.0113 3.3709 0.0029 1.4015 PRECIP(4) 0.0129 388398 0.0038 1.8169 PRECIP(-S) 0.0140 4.1640 0.0027 1.3181 PRECIP(-6) 0.0202 6.3313 0.0039 1.8969 AR(1) 0.7889 40.3219 R2 0.8004 0.9048 Dubin-Watson 0.6520 2.0502 Observations 1094 1093
16. Monthlydata on precipitationand streamflowalso shed some light on the extent to which precipitationaccounts for apparentdifferences in streamflowcharacteristics. Two regressionsreported in Table V suggestthe same relativelytight relationshipbetween precipitationand streamflowevident in the annualdata describedabove.' In the first regression,monthly mean dischargerates are regressedon monthlyprecipitation anomalies in the current month and six precedingmonths. The multiplecorrelation between the estimated linear combinationof explanatoryvariables and streamflowis a little greater than 0.7. The secondregression corrects for autocorrelationin residuals,increasing the multiplecorrelation coefficientto about 0.9.
Changesin the Structureof the Hydrometeorologyof the Basin
17. It is clear that variationsin precipitationexplain a great deal of the apparentshift in streamflowdistribution parameters and, more specifically,the recent spate of severe flooding in the Basin. This does not mean that other factors were unimportant. Three possibilities merit consideration:(i) climatechanges leading to increasedprecipitation, particularly in cntical monthsfor flooding;(ii) reservoir constructionand operation;and (iii) changesin land use that increase runoff.
'Tle regressionsreported in TableV, likethe correlationreported in paragraph15 basedon annual data, are weightedregressions. The weightingfactor applied to eachobservation was the numberof stationsreporting precipitation observations in each monthdivided by the meannumber of stations reporting.All of theconclusions reported here based on monthlydata also hold for regressionsdone with unweighteddata.
10 440.00
40. 00 20.00 l0.00
Jan Pab Mar APr way Jun Ju I Aug Sep OCt Nov Des
Figure 5: Mean MonthlyPrecipitation (mm)
18. Climate Change. Monthly precipitation data suggest that the rainy season has become somewhat wetter and the dry season slightly drier (Figure 5). Also note that relatively large positive March-May precipitation were more frequent in the 1980s and early 1990s than in earlier periods (Figure 3). These changes may represent a purely random perturbation (a statistically unlikely one, to be sure), a cyclical fluctuation, or a change in the climate of the region.
19. The climate change hypothesis is broadly consistent with extensive recent work on predicting global climate change and analyzing large scale atmospheric disturbances. Global climate models, developed to study the effect of accumulationof greenhouse gases in the earth's atmosphere, generally predict that precipitation in the vicinity of the basin will increase in the early and late months of the calendar year, as seems to be occurring (Figure 5). These models also predict that the El Nino phenomenon, which is empirically closely related to flooding in the ParanA/ParaguayBasin,' will intensify. However, due to the high variability present in precipitation data, considerably more data would be needed to discriminate statistically among the random perturbation, cyclical fluctuation, and structural climate change hypotheses.
20. Reservoirs. There has been a considerable expansion of active storage capacity in the Upper Parana River Basin over the last 40 years. Active storage has increased from 2500 hm3 in 1956, to over 150,000 hm3 today (see Table VI). Much of this capacity (approximately 125,000 hm3) came on line during the 1970s and 1980s. These reservoirs
'Annex B describesthe relationshipbetween El Nino phenomenaand floodingin the ParanTlParaguay Basin.
11 reducepeak floodsby roughly 10-20%during heavyrainfall months, and increaseninimum flows during the dry months. This may accountfor the fact that the statisticalresults on the stabilityof maximumdischarge rates as betweenearly and late periods are weakerat Posadas than they are at Corrientes, whichreceives unregulated flows from the ParaguayRiver and is well belowthe last reservoiron the ParanaRiver. 10 The effect of reservoirsis also reflectedin the data on low flow extrema: most of the extremelow flows recorded from 1901in Posadasand Corrientesoccurred prior to 1970.
Table VI: Brazilian Reservoirs - Upper Parana River Basin'
Active Year Storge tmulated Name of River hm' hm' the Dam 1956 2500 2500 Pizoto Grande 1958 0 2960 C o Grand0 1962 2890 850 lurann PSapn 1963 16089 1939 Furnas 1963 2556 2449 Bar Bonita net. 1966 04 24999 raninha 1968 1250 249 upin 1969 IS0 6399 Esiruito randc 1970 045 9444 Xavates paner 1971 1295 0739 'puar( g 1973 12866 3605 SolIhrn 1973 296 3901 PoateNova iota 1973 233 134 Pto Colombia rnd 1974 50 Voha Grand 1975 00 C84 PrDmiuJo 1975 310 S1994 ixndo 1975 2434 ahoono u 1976 700 1134 aprn 1978 790 924 Sio Smbo 1979 204 124 AguaVermIelba runde 1980 13600 5724 InhiPrn 1980 250 9974 Faz do Atia guaqu 1980 600 74 1982 300 T874ru Inrbc. ne 1982 12700 108S74 E io 1982 00 110874 Nova Avanhandava Mt. 1983 800 111674 1984 80 1S954 Santiago
1. DmimCauhw ag
21. Prior to 1970, mean monthlydischarges of the ParanaRiver at Posadaswere considerablylower during the monthswhen meanmonthly discharges of the ParaguayRiver reached their highestlevels. Since 1970, however, mean monthlydischarge rates at Posadas have increasedaround 15 to 30% during the mid monthsof the year, and hence coincide with the period of high average dischargerates in the ParaguayRiver. This change in the
"MTheresults on extremelow flows are equallystrong at both sites,however. 12 monthly distribution of streamflow could also be due to a change in the monthly distribution of precipitation, or in the intertemporal relationship between precipitation and streamflow in the Upper Parana Basin.
22. Deforestation/Land Use Changes. Significant changes in land use have taken place over the last 100 years in the upper and middle basins of both the Parana and Paraguay Rivers. Most of the land use changes in the Upper Paranr Basin took place in the 1930s and 1940s when land was put into coffee production, and again in the late 1960s when land was converted from coffee plantations to production of soybeans and sugar cane. In the Paraguay River Basin, particularly in Western Brazil and Eastern Paraguay where agricultural potential is greatest, there has been a progressive conversion of forest to agricultural land. In Paraguay in 1945, approximately 55% of the land area of the Eastern Region was forested. During the 1960s, the Paraguayan Government, under pressure to respond to growing demands for employment and income, began to encourage the expansion of the agricultural frontier to the east. As a consequence, forested areas in this region declined to about 45% by the mid-to-late 1960s, 35% by the mid-1970s, 25% by the mid-1980s, and only about 15% by the early 1990s.1'
23. Other things being equal, one would expect to observe an increase in streamflow associated with deforestation and/or other land use changes that tend to increase runoff.'2 The results on flooding frequency and severity reported above are thus broadly consistent with the land use effect hypothesis. They are, however, also consistent with the heavy rainfall hypothesis. Some additional examination of the data is thus necessary to discriminate between these hypotheses. Consistent time series data on land use in the Basin are not presently available. It is not possible, therefore, to proceed directly by introducing land use variables into the regression analysis to determine whether or not they contribute significantly to explaining streamflow variations. Inferences of the possible effect of land use changes can only be drawn indirecty by analyzing whether the rainfall-runoff relationship seems to have changed in ways that could be explained by land use changes. To this end, note that if land use change were an important contributor to streamfiow, the relationship between precipitation and streamflow should differ between early and late subsamples: in particular, the same rainfall should generate more streamflow in the later part of the sample period than in the early part.
24. This possibility was investigated using the two sets of data (i.e., annual and monthly) on precipitation and streamflow analyzed above. First, the annual data on March-May
"Bozzano,Bernado and Jorg H. Weik.El Avancede la Deforestaciony el ImpactoEconomico. Serie N. 12. Proyectode Planificaciondel Manejode los RecursosNaturales (MAG/GT-GTZ). Asunci6n, Noviembre1992. 'A detaileddiscussion of hypothesesconcerning relationships between land use changesand runoff is availablein Hamilton,Lawrence S. TropicalForested Watersheds: Hydrologic and Soil Responseto Major Uses or Conversions,(Boulder: WestviewPress), 1983.
13 Table VII: Analysis of Variance Test for Stability in the Relationship Between Precipitation Anomalies and Annual Maximum Daily Discharge Rates (F-test Significance Level)
Sample Period i 1901-92 1901-60 1961-92
Sample Break Point 1930 0.7863 1940 0.3481 0.5517 1950 0.0986 0.8292 1960 0.0344 1965 0.0126 1970 0.0314 1975 0.0025 0.2996 1980 0.0003 0.1717 1985 0.8691
Regressions CONSTANT 30581.507 27670.084 31295.372 PRECIP 112.189 35.020 123.705 R2 0.8538 0.6270 0.5668 Durbin Watson 1.5397 1.9169 1.5566
precipitationanomalies and amual maximumdischarge rates were split into early and late subsamplesand examinedto see whetherthe relationshipbetween precipitation anomalies and maximumdischarge discussed in paragraph 15 is stable C(ableVIU). Three differentsample periods (1901-92, 1901-60,and 1961-92)are considered. The first column of the table reports results obtainedanalyzing the data from the full sampleperiod. The numbers reportedin the upper sectionof the table (i.e., the rows in the 'Break Point' section of the table) are F-statisticprobabilities associated with an analysisof variance test like that describedin footnote3. The numbersreported in the lower sectionof the table are regressionsummary statistics." 3
25. The probabilitiesshown in Table VII are interpretedas follows. Considerthe period 1901-92. When the 1901-92sample is dividedinto two subsamples- for example 1901-79
1 Theresults reported in TableVII are based on weightedregressions in whichthe number of stations reportingprecipitation observations is relativeto the meannumber of stationsover the wholesample period(i.e., 1901-92)is usedas the weightingfactor. This givesmore weight to observationsthat are basedon moremeasurements of precipitation.An analysis(not reported in detailhere) paralleling that in Table VII was carried out using unweighted regressions. The results and conclusions of this unreported analysis are exactly the same as those reported here.
14 and 1980-92- the probabilityis only 0.0003of gettingan F-statisticas large as was obtainedin the analysisof variancetest if the relationshipbetween precipitation anomalies and maximumdischarges were in fact the same in both subsamples.
26. Three conclusionsflow from the results (and, more importantly,the pattern of results) summarizedin the table. First, the data stronglyreject the hypothesisthat the relationship betweenMarch-May precipitation anomalies and maximumdischarge rates was unchanging. For break pointsat 1960 or after, the test rejects the null hypothesis(i.e., no change)at the 0.035 level of significanceor better. Second,the changein the relationshipappears to occur sometimein the 1950sor 1960s. As can be seen in the columnheaded "1901-92",the null hypothesiswould be rejectedonly at muchlower levelsof significance(i.e., higher probabilityvalues) if the samplewere splitat 1950or 1940. This conclusionis confirmedby two additionalcuts of the data. In the columnof the table headed "1901-60",stability of the regressionrelationship within the 1901-60subperiod is examined. As can be seen, the test fails to reject the null hypothesisat any reasonablelevel of significance(i.e., the highest level of significanceobtained is 0.55). The sameresult is obtainedfor tests of splits within the subsample1961-92 (i.e., the highestlevel of significanceobtained is 0.17). Third, the regressioncoefficients behave qualitatively as they wouldbe expectedto if some changehad occurred whichincreased the runoffproduced by any givenquantity of rainfall: the coefficientof the precipitationvariable (PRECIP) is muchhigher in the second subsample (1961-92)than it is in the first (1901-60),taldng a valueof "123" versus "35".
27. The relationshipbetween monthly precipitation and averagestream flowsexhibits this same generalpattern of -instability (TableVmI). The relationshipis significantlydifferent in the latter part of the sampleperiod. However,analysis of the post-1960data indicates significantdifferences in the relationshipwithin the post-1960sample subperiod. 28. The statisticalrelationship between precipitation and streamfiowis widelyheld to be highly nonlinearand to dependcrucially on the temporalpattern of precipitationas well as its amount. At higher precipitationrates, other thingsbeing equal, streamflowshould increase more than in proportionsince the other ways in whichprecipitation can be 'dissipated" (e.g., infiltration,evapotranspiration, surface retention) have very definitemaxima. The results reported in Tables VII and VIII could thus simplybe a reflectionof the fact that precipitation has been far above "nonnal"throughout much of the 1980sand early 1990s. In the annual data, the fact that the coefficientof the precipitationvariable in the second subperiodis over three times as large as it is in the first subperiod(i.e., 123 versus 35), whichwould be an implausiblylarge effect to attributeto structuralchanges in rainfall-runoffrelationships, suggeststhat nonlinearitymay be at work. In the monthlydata, the instabilityof within subsampleregression coefficient in the post-1960period could also be associatedwith nonlinearity.
29. If nonlinearitywere Ie explanationfor apparentchanges in the relationshipbetween precipitationand streamflow,we shouldexpect to find significantdifferences between relationshipsfitted to subsamplesclassified by precipitationranges, and little if any
15 Table VIII: Test of Stability of Statistical Relationship Between Monthly Precipitation and Mean Monthly Mean Discharge Rates at Corrientes (F-test Significance Level)
SamplePeriod 1901.01-92.08 1901.01-59.12 1960.01-92.08 SampleBreak Point 1930.01 0.1183 0.9737 1940.01 0.0333 0.0374 1950.01 0.0001 0.4341 1960.01 0.0000 1975.01 0.0000 1980.01 0.0000 1985.01 0.0000
Table IX: Test of Stability of Statistical Relationship Between Precipitation Anomalies and Annual Maximum Discharge Rates: Marimum Flood and Non-Maximum Flood Years
Nul Hypothesis F-test Levelof Significance Relationshipbetween precipitation anomaliesand maximumdischage rates fittedto data for 1905,1912, 1923,and 0.9998 1929is statisticaUyindisinguihable from the elationshipfitted to data for 1966, 1982, 1983, 1987, 1990,and 1992. Relationshipbetween precipitation anomaliesand maximumdischarge rates fitted to pre-1960years other than 1905, 1912, 1923,and 1929is stadsticaly 0.5757 indistinguishablefrom the relationship fittedto post-1960years other than 1966, 1982, 1983, 1987, 1990and 1992.
difference between early and late subsamples within precipitation ranges. If nonlinearity were an explanation, along with some time varying factor such as land-use change, then significant differences would be expected both between subsamples defined by precipitation ranges and within subsamples defined by precipitation ranges across time.
16 30. Supportfor the "nonlinearityhypothesis" is providedby further analysisof both annual maximumand monthlymean data alongthese lines. Table IX reports the results of analysisof variancetests for differencesbetween subsamples when the annual data are partitionedinto 4-subsamples:(i) pre-1960years in whichone of the ten highestmaximum dischargerates occurred (i.e., 1905, 1912, 1923, 1929); (ii) other pre-1960years; (iii) post- 1960 years in whichone of the ten highestmaximum discharge rates occurred (i.e., 1966, 1982, 1983, 1987, 1990,and 1992);and (iv) other post-1960years. If nonlinearitywere responsiblefor the apparentstructural instability in the annualrainfall-runoff relationship, relationshipsfitted to the data thusly disaggregatedmight not show significantdifferences betweenearly and late periods. In fact, tests fail to reject the null hypothesesthat pre- and post-1960relationships between precipitation anomalies and maximumdischarge rates were the same in the pre- and post-1960periods.
Table X: Test of Stability of Relationship Between monthly Precipitation and Monthly Mean DischargeRates - Data Grouped by Three-MonthCumulative Precipitation
ThroeMonth Cumulative Precipitation F-testLevel of Significance CP < 190 0.0120 190 <= CP < 240 0.0000 240 <= CP < 290 0.0087 290 <= CP < 330 0.0232 330 <= CP < 370 0.0106 370 <= CP < 410 0.9077 410 <= CP <460 0.1634 460 <= CP < 520 0.5812 520 <= CP 0.0393
31. Monthlyprecipitation and mean dischargedata, when disaggregatedby level, also fail to show consistentlysignificant differences between relationships fitted to pre- and post- 1960 data. Two differentdisaggregations were examined. In the first, the 12 monthsleading up to the flood events at Corrientesshown in Table I are separatedfrom the other observations(Table X). The test fails to reject the null hypothesisthat pre- and post- 1960 relationshipsare identicalin this subsample. The hypothesisof stabilityis stronglyrejected, however,in the complementarysubsample. The second disaggregation(Table XI) divides the sampleinto 9 subsamplesbased on the cumulativeprecipitation over three months(i.e., the current and two precedingmonths). In general, tests show significantdifferences betweenearly and late periods at lower cumulativeprecipitation levels, but differences betweenearly and late periods at higher cumulativeprecipitation levels tend to become insignificant.
17 Table XI: Test of Stability of Relationship Between Monthly Precipitation and Monthly Mean DischargeRates - Data Grouped by Three-Month Cumulative Precipitation
Three MonthCumulative Precipitation F-testLevel of Significance CP < 190 0.0120 190 <= CP < 240 0.0000 240 <= CP < 290 0.0087 290 <= CP < 330 0.0232 330 <= CP < 370 0.0106 370 <= CP < 410 0.9077 410 <= CP < 460 0.1634 460 <= CP < 520 0.5812 520 <= CP 0.0393
Conclusions
32. Taken together,these results tend to suggestthat the unusuallyheavy precipitation of the 1980sand early 1990swas the most importantfactor accountingfor the floodingof these years. There is no consistentstatistical evidence in the data examinedhere that any other factor playeda significantrole. This conclusionis not surprising. When precipitationis concentratedin time and space, as it typicallyis during flood years, it simplyoverwhelms other factors: floodingwill occur other factorsnotwithstanding. There is some evidencein the data examinedhere that, at less extremelevels of precipitation,the basin may be producingmore runoff todayfor a given quantityof precipitationthan it did in the early years of the century.
33. In sum, the conclusionsthat emerge from the previousanalysis are as follows:
o Floodingwas both more frequentand more severe in the latter part of the 1900s than previously;
o Extremelow flows were both less frequentand less extremein the latter part of the 1900sthan previously;
o Total streamflowwas greater and its intra-annualdistribution different than in the latter part of the sampleperiod than during the early years;
o Variationsin precipitationexplain much of the variation in streamflowsand flooding;
0 Changes in intra-annual variation in streamflow appear to be due to some combinationof changesin the intra-annualdistribution of precipitation,and to
18 the operationof reservoirson the Paranawhich delay the propagationof floods;and o There is no consistentevidence, statistical or otherwise,that changesin rainfall-runoffdynamics associated with land use changeshave playedan importantrole in recentflooding in the Basin.
19
Annex A: Description of the Parana/Paraguay River Basin
1. This annex summarizesbasic information and data on the Parana/Paraguay River Basin. Much of this information derives from international compacts established to manage the basin's resources.
Intergovernmental Cooperation on Hydrometeorology in the La Plata Basin
2. In 1969, the Foreign Affairs Ministers of Argentina, Bolivia, Brazil, Paraguay and Uruguay signed the Plata Basin Treaty in an effort to institutionalize the Plata System. An IntergovernmentalCoordinating Committee-CICwas created to promote, coordinate, and implement the multilateral actions as defined by the Ministers including the hydrometerology and floods in the Basin. Several resolutions dealing with floods have been approved by the Ministers. (Table A. 1)
3. Furthermore, expert Groups and Ad hoc Working Groups on Hydrometeorology and Flood Warning System were formed and have met with the CIC periodically since 1982, in order to exchange information and recommend actions to be considered by the Foreign Affairs Ministers. Consequently, the countries have established an information exchange network, especially for periods of flood warning. Selected stations of the flood warning system are shown in Table A.2.
Table A. 1: Plata Basin Resolutions Dealing with Hydrology and Floods
ResolutionNo. Meeting Year 88 IX 1977 Paraguayriver hydrometeorologicalnetwork 91 IX 1977 Exchangeof Hydrometerologicalinformation among the Plata Basin countries 153 XI 1980 Floods in the ParaguayRiver 174 XII 1981 Floodsin other internationalrivers 176 XII 1981 Plata Basinhydrometerological network 195 XVI 1986 Plata Basinflood warning system 2Ex flEx 1986 Technicalcooperation actions including water resources 302 XVII 1987 Flood warningsystem and water quality
The Paranf River Basin
4. The Parana River Basin is the most important in the La Plata Basin system due to the magnitude of its discharges, the extension of its area, and its overall length. It encompasses 1 510 000 km2 (excluding the area of the Paraguay River Basin, its most important tributary). Of this area, 890 000 km2 is located in Brazil, 565 000 km2 in Argentina, and 55 2000 km2 in Paraguay. The total area including the Paraguay River extends to 2 605 000 km2 . Its length from its origins at the Paranaiba River until the confluence with the Uruguay River reaches 3 740 km. The ParanA is divided into the Upper Parana ( 972 050 km2 upstream of its confluence with the Paraguay River), the Middle Parana (between the confluence with the Paraguay River and the Salado River) and the Lower Parana (from the confluence with the Salado River to the confluence with the Uruguay River)
Table A.2: Parand-Paraguay Flood Warning System-Selected Stations
Observations River Station Area km2 since Country Parana Jupia 478 000 1926 Brazil Parana Sao Jos6 670 000 1963 Brazil Parana Guafra 802 150 1921 Brazil Iguagu Salto Cataratas 67 300 1915 Brazil Parana R-8 Itaipu 901 545 1976 Brazil Parana Libertad 910 000 1931 Argentina Parana Posadas 933 600 1901 Argentina Paraguay Ladario 258 000 1900 Brazil Paraguay Porto Esperanga 363 500 1963 Brazil Paraguay Porto Murtinho 474 500 1939 Brazil Paraguay Concepcidn 600 000 1910 Paraguay Paraguay Asunci6n 797 000 1904 Paraguay Tebicuary V. Florida 21 000 1945 Paraguay Paraguay Pilar 925 000 1917 Paraguay Bermejo El Colorado 91 950 1969 Argentina Parana Corrientes 2 067 050 1903 Argentina Parand SantaFe 2 457 050 1925 Argentina ParanE Rosario 2 480 000 1884 Argentina
5. The distinguishing feature of the Upper Parana is its delineation in "stepped' plateaus, creating 'saltos" in the river channel, now flooded by the reservoirs of hydroelectric dams. Other smaller falls and the presence of rapids, the majority of which are now also flooded by the reservoirs of around 40 hydroelectric dams, characterize the landscape. Most of the reservoirs were constructed between 1960 and 1990 in the Braziian portion of the basin.
6. The width of the Paran River vaies dramaticaly from 4 000 m north of town of Guaira in Brazil to 60 m below Itaipu Dam. Near Posadas, in Argentina, its width ranges
Annex A - September 2, 1993 -2- between 150 and 2 500 m. Downstream of Posadas, the river flows through a series of islands, covering a 25 km-wide area. The river is 4 200 m wide at Corrientes, 2 600 m at Bella Vista, and 2 300 m near Santa Fe. However, its flood plain gradually spreads out, especially over its right bank, which is lower than its left bank. The width of this flood plain varies between 13 km near Corrientes to about 56 km near Rosario-Victoria. The delta of the river is 18 km wide at its beginning, growing to a width of about 60 km. Then through its numerous branches, the Parana flows into the La Plata..
The Paraguay River Basin
7. The Paraguay River Basin encompasses 1 095 000 km2, of which nearly 365 000 km2 are in Brazil, 365 000 km2 in Paraguay, 182 500km2 in Argentina, and 182 500 km2 in Bolivia. The origin of the Paraguay is found in Brazil, and the river, after flowing 2 800 km (Table A.3) reaches the Parana river, north of the Argentinean cities of Corrientes and Resistencia. In its northeast portion (i.e., the Bafiadosof Izozog in Bolivian territory), the basin boundaries are not clearly defined.
8. Excluding the headwaters of the Pilcomayo and the Bermejo, which descend from the Argentine-Bolivianplateau in the Andes, and in the southern part of the left banks of the Paraguay River, between the Apa River and its confluencewith the Parana - which presents a wavy relief with slopes of certain magnitudes- the rest of the river basin extends over an immense alluvial plain, very slight slope and extensive flood plains.
9. In the Upper Paraguay, the river banks are low and prone to floods, creating a zone known as the 'Pantanal' , a vast flood plain that covers close to 100 000 knmand that is periodically covered by water. The terrain slope is very slight, as is the slope of the river channel. The river bed is sandy, very unstable, and the river meanders. There are some rocky stretches, but they do not affect the general character of the river.
10. In the area that extends from the Apa River to the confluence with the Tebicuary, the flood plain is restricted to a width that varies from 5 to 10 km, occupying mainly the right bank. The mouth of the Paraguay river extends from this point until its confluence with the ParanA (approximately 130 km). During floods, water rises over both banks in this region, occupying a strip of land 10 and 15 km wide. The major characteristics of the Paraguay river in this section are the enormous amount of sediments carried from the Bermejo River, and the backwater phenomena produced by the waters from the Paranr at its confluence with the Paraguay River.
Annex A - September 2, 1993 -3- Table A.3: Limits and Slopes- Paraguay River'
Zones Limits Distances MedianSlopes/ Observations Lower Confluence-TebicuaryRiver (260 km 130 km 5 cm/km. Sufferseffect Paraguay south of Asuncion) of the Parana whenthe river is rising. The BermejoRiver is at km 87 and Pilar is at km 89. Middle Tebicuary-ApaRiver (an 927, bordering 797 km 6 cm/km. Asunci6nis at Parguay Brazil-Paraguay) km 390 and Concepcidn at km 700. Upper Apa River-headwaters(km 2 800) 1 873 km 3,1 cm/km.Includes the Paraguay Pantanal.Porto Murtinho is at kan999, Porto Esperancaat km 1395, and Ladariois at km 1 530. 1I-AS, 1992
Basic Basin Parameters
11. The concluding section of this annex (previous studies) contain a listing of data sources and of relevant previous studies of the hydrometeorologyand floods of the ParanA and Paraguay river basins'. Many of these have been utilized in the preparation of this paper. A wealth of information remains to be exploited, however.
12. The hydrometeorolgy of the Paranr-Paraguay River Basin is very complex. Several small sub-basins have particular hydrological characteristics. Previous studies of the basin have divided it into seven major sub-basins (EBY,1979):
'Data presentedin AnnexC on annualmaximum and minimumdaily floods and stages,mean monthly flow and stages, and annualand monthlyprecipitation at selectedstations were provided by the Instituto Nacionalde Cienciay TecnicaHidricas (Argentina), Departamento Nacional de Aguase EnergiaEletrica (Brazil),and Direccionde Meteorologiae Hidrologiaand AdminsitracionNacional de Navegaciony Puertos (Paraguay).
Annex A - September 2, 1993 -4- * Upper ParaguayRiver UpsreamPorto Esperan- * Upper ParmnfRiver upstreamGuafa (363500 km) (802 150 kn2)
* Middle ParaguayRiver between P. Esperanzaand * Upper PamnrRiver between Guain and Asunci6n (433 500kmn) Confluence(169 900 km:
* Lower ParaguayRiver between Asunci6nand Confluence (29S000 km)
* MiddleParani River between Confluenceand Santa Fe/ Parani (390 000 kin)
* Lower ParaniRiver downam SantaFeI Pararn (197 950 km2)
Precipitation
13. The runoff basins of the Parana and Paraguay Rivers are located in a region of heavy precipitation that is prevalent almost throughout the year. Situated east of the Andes, between approximately 150 S and 30 0 S, the region is subject to rain-producing systems of both tropical and extratropical (frontal-type)origins. The annual mean rainfall in the Parana basin varies from 1100 to 1600 mm, except in the upper basins of the Tiete, Paranapanema and Iguacu with the annual mean reaching 2 200 mm. In the Paraguay Basin, it varies from 400 to 1800 mm.
Mean Discharges
14. The Parana river system, shows a predominance of summer-fall discharges over those of winter-spring. The variability is more evident in the upper portion -due to the tropical regime of rains- with high waters between December and April, pealing in February, and a period of low waters in the winter, with minimums in August and September. South of Guaira, the tributaries of the Parant, like the Iguagu, exhibit a somewhat different seasonal pattern: lower waters in the summer, and high waters in the winter and spring due to the greater persistence of rains during the entire year. After its confluence with the Paraguay, which also exhibits increased flows during the winter (June, July) due to the retardation effect created by the Pantanal, the flows in the Parana exhibit less seasonal variability. Table A.4 summarizes the mean monthly and mean annual discharges for 1901-1992, 1901- 1967 and 1968-1992.
15. An analysis of the origin of the Parani River flow is shown in Table A.5. Roughly 78% of the mean annual flow originates in the Upper Parand. From Corrientes to the confluence with the Uruguay River (around 540 000km2) the discharge of the Parani River increases only 10%, less than 2 000 m3/s. Generally, the rainfall in the Upper Parana (i.e., upstream of.Guaira) is the main source of the flows in the Middle and Lower Parana river, but in some years torrential rains between Guafra and the confluence with the Paraguay River (including the Iguacu River Basin) and between Asunci6n and Confluence are the main cause of the floods registered in Asunci6n, Posadas, Corrientes and downstream.
AmnexA - September 2, 1993 -5- Table A.4: Mean Montly Discharge in Posadas and Corrientes-ParandRiver 1OOm3Is
Station Period I F M A M I Jl A S 0 N D AVG Poudas 1901- 14.9 16.5 15.7 13.6 12.0 12.0 10.5 9.0 9.3 10.8 11.0 11.9 12.3 1992 Poaadas 1901- 14.5 16.3 16.1 13.6 11. 11.2 9.6 8.1 8.3 10.1 10.2 11.1 11.7 1967 Pouda 1968 16.1 16.8 14.7 13.7 13.5 13.9 12.9 11.4 12.0 12.9 13.1 14.1 13.8 1992
Corrients 1901- 17.6 20.3 20.3 18.6 16.7 17.0 15.1 11.6 12.2 13.8 14.2 15.0 16.1 1992 Corrientes 1901- 16.7 19.6 20.S 18.5 15.8 15.8 13.8 11.3 10.7 12.5 13.1 13.0 15.2 1967 Corentes 1968- 20.1 22.1 19.8 19.0 19.1 20.2 18.6 16.1 16.1 17.2 17.1 18.0 18.6 1992
16. An analysis of the ozigin of the Parand River flow is shown in Table A.5. Roughly 78% of the meanannual flow originatesin the Upper Parani. From Corrientesto the confluencewith the UruguayRiver (around540 000km2) the dischargeof the Parand River increasesonly 10%, less than 2 000 m3/s. Generally,the rainfallin the Upper Parari (i.e., upstreamof Guaira)is the main source of the flowsin the Middle and Lower Parand river, but in some years torrentialrains betweenGuafra and the confluencewith the ParaguayRiver (includingthe IguacuRiver Basin) and betweenAsunci6n and Confluenceare the main cause of the floods registeredin Asunci6n,Posadas, Corrientesand downstream.
17. The hydrologicalregime of the Upper Paraguayin Cuiabais similar to the Upper Parand, but the principalcharacteristic of the ParaguayRiver regime is the intra-annual variationwhich occurs along its course. In the Upper Paraguay,before reachingthe lower and flood-pronearea of the Pantanal, the maximumlevels are reached in February and the minimumsin August-September.However in Corumba,Ladario, and in the Middle Paraguayin Asunci6nand Concepci6n,the period of high flowsis practicallyreversed, with the maximumin June-July,and the minimumin December-January.This waterflowpattern variationis causedby the storageeffect producedby the Pantanal, which creates a delay of about 3 monthsin the flood propagation,before arriving in Asuncionand at the confluence with the Parana.
Annex A - September 2, 1993 -6- Table A.5: Origin of the Dischargesof the Paranf River in Posadas and Corrientes
Flow in AreaKm 2 Percent Originatedfrom Area km2 Posadas' 933 600 78% UpstreamGaufra 802 150 12% IguaquRiver Basin 68 000 10% Intermediatearea 63 450 Corrientes' 2 067 050 72% Upstream Posadas 933 600 16% UpstreamAsunci6n 797 000 12% Intermediatearea 336 450 CorrienteS2 2 067 050 61 % Upstream Guafra 802 150 17% betweenGuafra and the ParaguayRiver 169 900 22% Paraguay River Basin 1 095 000 I-ELETROBRAS, 1978 2-EBY, 1979
Minimum Discharges
18. The percentage of the occurrence of annual extreme low flows and stages in selected stream flow gauging stations of the Paraguay and Parana rivers are shown in Table A.6. Most of the extreme low flows occurs in November, December, in the Paraguay river. From August to October, November, and even December, and January in the Parana River. In the Iguacu River they may occur during the whole year especially in January, May, and August.
Maximum Discharges
19. Most of the maximum annual floods in the Upper Parana (Guafra and Posadas) occur in January, February and March while in the Middle and Lower Paraguay (Asunci6n), they occur in May, June, and July.2 In the Middle Parana (Corrientes), they occur in February and March. In the Iguacu River Basin (Cataratas) floods occur generally in October, November and in June and July. The percentage of the occurrence of annual maximum floods in each month of the year for those stations is shown in Table A.7.
20. High precipitation in the lower part of the Upper Parani Basin is more effective in producing peak discharge at Guaira (and Posadas) than the same average basin rainfall spread uniformly over the basin or concentrated in the upper end.
21n the ParaguayRiver Basinthe volumeand durationof the floodsare as importantas the peak flood due to the area, shapeand topographyof the basin.
AnnexA - September2, 1993 -7- Table A.6: Percentage of Occurrence of Eitreme Low Flows and Stages by Month
River Station J F M A M J JI A S O N D % Paraguay Ladario 19 2 * 0 0 * 0 2 7 13 29 28 100 ParanA Guafra 4 0 0 0 0 * 1 16 40 28 7 4 100 Iguagu Cataratas 14 6 4 9 21 6 1 13 7 7 4 8 100 Parana Posadas 9 * 1 0 4 2 5 21 24 16 11 7 100 Parana Corrientes 12 1 0 4 1 0 10 28 22 12 12 100
Table A.7: Percentage of the Occurrence of Annual Maximum Floods by Month'
River Station J F M A M J JI A S O N D % Parang Guaira 19 2727 7 6 4 0 1 0 1 2 6 100 Iguagu Cataratas * 5 5 8 2 14 15 6 5 22 12 6 100 Parana Posadas 19 29 19 5 5 10 2 0 2 4 5 9 100 Paraguay Asunci6n 13 7 2 5 7 30 10 i 2 4 3 6 100 Parand Corrientes 8 23 25 9 3 11 4 0 1 3 1 12 100
i-It should be notedth the mots ezxtorimay floods in Poadas and Comfent occurrd in May, June, and July.
The most criticalconditions for floodsat Guafra,(Posadas and Corrientes),would be with storms over the whole ParandBasin for the first few months,giving high base flows and peak discharges from the upper part of the basin, followedlater by stormsconcentrated in the lower part of the Upper Basin. This combinationshould produce the greatestpeak dischargeat Guafra,Posadas and Corrientes(ELETROBRAS/ANDE, 1972). This is whatoccurred in 1982, 1983,and 1992,for example.
21. The flood-travel time in the ParanA River between Jupia and Corrientes, and Salto Osorio and in the Iguagu River between Salto Cataratas is shown in Table A.8. (ELETROBRAS, 1978). According to EBY, 1979 the flood-travel time between Posadas and Corrientes in the Parna river is 5 days and between Corrientes and Rosario 30 days (i.e., 788 km at 0.3 mls).
AnnexA - September2, 1993 -8- 22. Table A.9 presents the difference between ordinary and extraordinary floods according to EBY, 1979 (An extraordinary flood is considered equal or superior to a 10 year recurrence flood.)
Table A.8: FloodTravel rime in Parana and IguaguRivers
Distance Flood Travel Velocity River Zone km days m/s Parana Jupia-Guarfa 499 4 1.4 Parana Guafa-Posadas 664 2 3.8 Parana Posadas-Corrientes 376 5 0.9 Iguagu S. Osorio-S.Cataratas 270 1 3.1
Table A.9: Ordinary and Extraordinary Floods in the Parana and Paraguay Rivers
Warning Extraordinary Gauge River Station Ordinary Floods Datum Floods abovesea level m m3/s m m31s m Paraguay Ladario 4.0 82.15 Paraguay P. Murtinho 6.0 70.15 Paraguay Asunci6n 4.5 4000 6.3 6300 53.09 Parana Guafra 2.0 15000 2.8 24000 218.00 Parana Posadas 3.5 21000 6.0 30000 73.09 Parana Corrientes 5.5 24000 7.0 35000 41.40
23. In the Iguagu Basin, due to its area, topography, and shape, the peak floods are high, but for shorter periods of time. The maximum peak floods recorded since 1926 in the Iguacu river basin are:
1983July 31 000 m3/s 1987May 17 500 m3/s 1938 July 15 500 m3/s 1936June 28 600 m31s 1928May 17 500 m3/s 1937 Nov 15 000 m 3 /s 1992May 18 700 m3/s 1932April 16 000 m'/s 1989June 14 900 m3/s
Annex A - September 2, 1993 -9- Table A.10: Sedimentsin the ParanA - Paraguay river basins
Mean Sedimementston/year Annual (*106) Flow 1977' 1992 River Site W/s3 Observations ParanA Guaira 9350 23.72 Since 1982, most of the sediments are depositedin the reservoirof Itaipu dam. Parana Confluence 12000 26.5 6* Includesthe Paraguay contributionof the Iguaguriver basin and other tributaries Paraguay Asunci6n 2750 4.3 4.5* Most of the sedimentsof the Brazilianportion are depositedin the Pantanal Paraguay ConfluenceParang 4000 100.9 100* Includesthe contributionof the Bermejoriver basin Parana Corrientes 16000 126.1 106* Most of this sedimentreaches the port of Buenos Aires
I-EBY, 1979 2-ELETROBRAS, 1992 *-Estiriated
Sedimentation
24. At present, data for only two years (1977 and 1992) have been obtained and examined. These are shown in Table A.10.
25. In 1992 ELETROBRAS published an updated report on the sedimentological conditions of the most important Brazilian rivers. This report shows three areas of higher production of sediments in the Paran6/Paraguay River Basin, mainly caused by the erosion of sedimentary rocks, mostly sandstone. In the Parand River Basin, the areas are located in the upper part of the Araguari river (Paranaiba basin) and between the Paranapanema and Ivaf rivers (Caiud sandstone). Both areas are upstream from Guaira and the Itaipu dam. In the
Annex A - September 2, 1993 -10- Paraguay River Basin the area of high production of sediments is located in the upper part of the Pantanal.
26. As far as the Paraguay River Basin is concerned most of the sediments in the Brazilian portion are deposited in the Pantanal. The same occurs with the production of sediments in the Parana River that remain deposited in the reservoirs of the hydroelectric dams.
27. The most important production of sediments in the Parana/Paraguay River Basin occurs in the Bermejo River Basin (94 350 km2) that originates in the Andean slopes of Argentina and Bolivia. Almost 100 000 000 tons of sediments are transported each year into the Paraguay and Parani Rivers.
Previous Studies
The La Plata Basin
AISIKS,E.G. 1985. 'La Gran Crecidadel Rfo Paranade 1983".Buenos Aires
CIC. 1982. 'Reunionesde las ContrapartesTecnicas para el Programade AlertaHidrol6gicade la Cuencadel Plata". Alsothe reportsfrom 1984,1989, and 1991meetings held in BuenosAires.
COIMBRA,R.M., OLIVEIRA,E., CUDO,K.J. 1992. "MonitoramentoQuantitativo e Qualitativo das Aguasda Bacia do Prata' (ProjetosAlerta Hidrologico e Qualidadedas Aguasdo CIC - Comit6 IntergovernamentalCoordenador da Baciado Prata). Brasfia.
DIAZ, H.F. 1993. 'TemporalPatterns of Precipitationin the Paranaand ParaguayRiver Basinsand its Relationshipto the El NinloPhenomenon". National Oceanic and AtmosphericAdminstration. EnvironmentalResaearch Laboratories. Boulder. Colorado.
DNAEE. 1987. 'Inventariodas Estac6esPluviom6tricas". Brasilia
DNAEE. 1987. 'Inventariosdas EstacoesFluviometricas". Brasilia
EBY. 1979. "Estudiode CrecidasRfos Paranay Paraguay. Estudiorealizado por MOTOR COLOMBUSY Asociadospara EntidadBinacional Yacireta. Buenos Aires-Asunci6n.
ELETROBRAS.1992 'Diagn6sticodas Condi06esSedimentologicas dos Principais Rios Brasileiros". Institutode PesquisasHidraulicas-IPH. Rio de Janeiro.
OEA. 1969. 'Cuenca del Plata. Estudiopara su Planificaci6ny Desarrollo.Inventario de Datos Hidrol6gicosy Climatol6gicos".Informe del estudiollevado a cabopor la Unidadde Recursos Naturalesen 1967 y 1968.Washington, D.C.
OEA. 1971. 'Inventarioy Analisisde la Informaci6nBasica sobre RecursosNaturales". Cuencadel Rfo de la Plata. Estudiopara su Planificaciony Desarrollo.Washington, D.C.
AnnexA - September2, 1993 -11- OEA. 1969. " Indice Anotado de los Trabajos Aerofotograficos y de los Mapas Topograficos y de Recursos Naturales". Cuenca del Rio de la Plata. Estudio para su Planificaci6n y Desarrollo. Washington D.C.
OEA. 1985. 'Infraestructura y Potencial Energetico en la Cuenca del Plata'. Washington, D.C.
The Paraguay River Basin
ANNP. 'Anuarios Hidrograficos". Asunci6n
ARMADA NACIONAL. "Anuarios Hidrograficos'. Asuncidn
ARMADA NACIONAL. 1979. 'Estudio del Comportamientodel Rfo Paraguay y su Litoral Desde Concepcidn Hasta Confluencia'. Asuncion.
CARVALHO, N. de O., AYRES R.M., ROCHA, J.P.G. 1992. 'Estudos Sedimentoldgicosda Bacia do Sao Lourengo, MT'. ELETROBRAS/Universidade Federal de Mato Grosso. Cuiaba.
CARVALHO, N. de O., MONTEIRO, A.E. 1991. 'Sistema de Alerta e Provisao de Cheias do Pantanal'. ELETROBRAS/ Companhiade Pesquisas de Recursos Minerais. Rio de Janeiro.
DMH. 1992. 'Balance Hidrico Superficial de Paraguay". Asunci6n.
DNPVN. 1973. 'Estudo Hidrologico do Rio Paraguai. Perfodo 1966-1972 Relat6rios Parciais e Relat6rio Final'. Hidrologia Comercial Ltda. Rio de Janeiro
DNOS. 1974."Estudos Hidroldgicos da Bacia do Alto Paraguai%.4 Volumes. Rio de Janeiro.
GIUSTI, E. V., LOPEZ M.A., 1984. 'On the Hydrology of the Paraguay River'. USGS. Selected Papers in the Hydrologic Sciences. Reston.
HALCROW AND PARTNERS. 1973. 'Estudio de Navegabilidad del Rfo Paraguay al sur de Asuncicn'. Asunci6n.
JICA. 1985. 'Storm Drainage System. Improvement in Asuncion City'. Asunci6n.
LOPEZ, M.A. et alli. 1983. 'Hydrologic Hazards in Paraguay with Special Reference to the floods of 1983.' USGS. Reston.
OEA. 1974. 'Alta Cuenca del Rio Bermejo. Argentina-Bolivia'. Estudio de los Recursos Hidricos. Washington, D.C.
OEA. 1977. "Cuenca Inferior del Rfo Bermejo. Argentina". Programaci6n para su Desarrollo. Washington, D.C.
OEA. 1975. ' Proyecto Aquidaban. Desarrollo de la Regi6n Nororiental del Paraguay". Washington, D.C.
Annex A - September2, 1993 -12- OEA. 1979. "Caracteristicas da Vegetacio da Bacia do Alto Paraguai" Informe preparado por el consultor Jorge AdAmolipara o 'Estudo de DesenvolvimientoIntegrado da Bacia do Alto Paraguai (EDIBAP)". Brasilfa.
OEA. 1992. "Proyecto de Reconstrucci6ny Desarrollo Integrado del Area Meterol6gica de Asunci6n y de los Entidades de Concepci6n, Alberdf, Pilar Afectadas por Inundaciones." Informe de las Misi6n Preliminar de la OEA/DDRMA. Washington.
PNUD. 1975. "Proyecto de Mejoramientode la Navegaci6ndel Rfo Paraguay". PAR/TS/006. Asunci6n.
PNUD. 1979. "Estudio de Inundaciones del Rfo Paraguay". Asunci6n.
PNUD. 1980. 'Modelos Estadlsticospara Previsi6n de Niveles del rfo Paraguay". PAR1801002. Asunci6n.
SUDECO. 1979. "Estudo de DesenvolvimentoIntegrado da Bacia do Alto Paraguai-EDIBAP". Convenio Governo Brasileiro PNUD-OEA Brasfia.
USCE. 1972. 'Application of the SSARRmodel to the Upper Paraguay River Basin". Portland, Oregon.
UNESCO/UNDP. 1973."Hydrologicalstudies of the Upper Paraguay River Basin (Pantanal) (1966- 1972) Technical Report". Bra. 66.521. Paris.
Parang River Basin
AyEE/DNCPyVN/CONCAP. 1973. "Estudio Hidrol6gico y Sedimentol6gicodel rio Alto Parand." Buenos Aires.
AyEE. 1970. "Resumen de la Estadfstica Hidrol6gica Hasta 1967". Buenos Aires.
AyEE. 1960. "Estudio Hidrol6gico del Rio Alto Parana". Buenos Aires.
AHLQUIST, 0. 1906. "La Gran Creciente de 1905 del Rio Parana y sus Afluentes". Buenos Aires.
BERGER-BROKONSULTA.B. 1973. "Mejoramientode la Navegaci6n del Rfo Parana. Buenos Aires.
BRAZILIUNDP. 1966. "Power Study of South Central Brazil-SaoPaulo Group-Hydrometerology Report."Appendix No. 8. Canambra Engineering Consultants Limited. Montreal.
CARVALHO, N. de O., CATHARINO, M.G. 1992. 'Avaliacao do ssoreamento do Reservatorio da UHE Itaipu". ELETROBRAS, Diretoria de Planejamento e Engenharia. Rio de Janerio.
CARVALHO, N. de O., 1991. 'Producbo de Sedimentosda Area de Contribuisao ao Reservat6rio de Itaipu". I Reuniao sobre Erosao e Sedimenta§bo,Curitiba.
Annex A - September 2, 1993 -13- COMIP. 1977. 'Aprovechamiento del Rfo Paranl en el Tramo Limitrofe Comprendido Entre la Desembocaduradel Rfo Iguazd y la Seccidn Encanaci6n- Posadas, con particular atenci6n a la zona de Corpus-Fase I" . Lahymer-Harza y Asociados. Buenos Aires.
CONCAP. 1970. 'Modelo Matematico de la Cuenca del Plata - Informe Preliminar de la Fase I - Factibilidad Tecnica de las Fases 2-3". Buenos Aires.
CONCAPlDNCPyVN/AyEE. 1973. 'Estudio Hidrol6gico y Sedimentol6gicodel rio Alto ParanA". Buenos Aires.
COTTA, D. 1973. "Influencia Sobre el Rfo Parana del Material Sdlido Transportado por el Rfo Bermejo. Buenos Aires
DNCPyVN. 'Anuarios Hidrograficos". Ministerio de Economfa de la Replblica Argentina. Buenos Aires.
EBY. 1973. "Estudio de Factibilidad Tecnica, Econ6mica y Financiera para el Desarrollo del Rfo Parand en el Area Yacyreta - Apipe". Consorcio Harza y Asociados. Asuncidn. Buenos Aires.
ELETROBRAS/ANDE. 1972. "Rio ParanAStudy. Appendix A. Hydrology and Meterology", prepared by EECO-International Engineering Company of San Francisco, California and ELC- Electroconsult of Milan, Italy. Rio de Janeiro/Asunci6n.
ELETROBRAS. 1978. "Estudo da Genese das Vaz6es do Rio ParanA". 5 volumes realizados pelo Consorcio Nacional de Engenheiros Consultores SA. Sao Paulo.
ELETROBRAS/GCOI. 1992. "AnAliseda Operacao de Controle de Cheias para as Bacias dos Rios Parana e outros na Estagao Chuvosa 1991/1992". Subcomite de Estudos Energeticos. Rio de Janeiro.
ELETROBRAS/GCO1.1992 'Analise da Operacao Hidraulica dos Aproveitamentos da Bacia do Rio Iguagu durante a Cheia Maio-Junho de 1992." Grupo de Trabalho de Hidrologfa Operativa. Rio de Janeiro.
EINSTEIN, H.A. 1972. -Report on the Sediment Problems Connected with the Apip6 Project on the ParanARiver. Buenos Aires.
FESQUET, H.B. 1975. 'Pron6stico de la Fecha de Culminaci6n de las crecientes del Rio Parana". Publicaci6n N°15, Serie Hidrometeorol6gica. Buenos Aires.
INCyTH. 1975. 'Cuenca Superior del Rfo Parana - Estudio de la Crecida Maxima Probable". Buenos Aires.
OEA. 1973. *Noroeste do Estado do Parana-Brasil. Estudo para o Controle da Erosao". Washington, D.C.
PNUD. 1977. 'Proyecto Mejoramiento de la Navegacidn del Rio Parana, Mediciones de Transporte de Sedimentos en el rfo Parana a altura de Corrientes", por J. Lelievre y E. Navntoft. Buenos Aires.
PNUDIINCYTH. 1974. "Estudio del Sistema Fluvial Parang-Santa Fe' SFIARGI66I521. Buenos Aires.
Annex A - September 2, 1993 -14- RAFFO, J.M. 1951. 'Pron6stico de las Crecientes del Rfo Parana, S.M.N., Publicaci6n N02. Serie Hidrometeoroldgica.Buenos Aires.
STUCKRATH, T. 1969. 'Movement of Ondulation on the Bed of the Parang River". Buenos Aires.
VANONI, V. 1967. "Review of SedimentationProblems of the Proposed Parana-Fe Tunnel". Buenos Aires.
ACRONYMS
ANNP Administaci6nNacional de Navegacidny Puertos (Paraguay)
AyEE Agua y Energia Electrica (Argentina)
CFI Consejo Federal de Inversiones (Argentina)
CIC Comite IntergubernamentalCoordinador de la Cuenca del Plata
COMIP ComisionMixta Argentina Parguaya del rfo Parang
CONCAP Comisi6nNacional de la Cuenca del Plata (Argentina)
DEPVN Departamientode Puertos y Vfas Nagigables (Aregentina)
DRDE Department of Regional Development and Environment
ELETOBRAS Centrais Eletricas Brasileiras SA
DMH Direcci6n de Meteorologfae Hidrologfa (Paraguay)
DNAEE Departamento Nacional de Aguas e Energia Eletrica(Brazil)
DNCPyVN Departamento Nacional de Construcciones Portuarios y Vfas Navigables (Argentina)
DNPVN Departamento Nacional de Portos e Vias Navegaveis (Brazil)
DNOS Departamento Nacional de Obras de Saneamento (Brazil)
EBY Entidad Binacional YaciretA(Argentina/Paraguay)
EDIBAP Estudo para o DesenvolvimentoIntegrado da Bacia do Rio Paraguai (Brazil)
GCOI Grupo Coordenador para a Operagao Interligada (Brazil)
JICA Japan International Cooperation Agency
IECO/ELC Consultoras "Intemational Engineering* San Francisco / "Electroconsult" Milan
IGH Instituto Geogrlfico Militar (Argentina)
Annex A - September 2, 1993 -15- INCyTH Instituto Nacional de Ciencia y Tdcnica Hfdricas (Argentina)
IPH Instituto de Pesquisas HidrAulicas(Brazil)
LAC Latin America and the Carribbean
MIT MassachusettsInstitute of Technology
NOAA National Oceanic and Atmospheric Administration
OAS Organization of American States
SMN Servicio Meterol6gico Nacional (Argentina)
SUDECO Superintendenciado Desenvolvimentoda Regiao Centro Oeste (Brazil)
SUCCE Subunidad Central de Coordinacidn para la Emergencia del Ministerio del Interior (Argentina)
UNDP United Nations Development Programme (PNUD in spanish)
UNESCO United Nations Educational, Scientific, and Cultural Organization
USAID United States Agency for InternationalDevelopment
USCE United States Corps of Engineers, North Pacific Division
USGS United States Geological Survey
AnnexA - September2, 1993 -16- Annex B: Large Scale Atmospheric Disturbances and Flooding in the Parana/ParaguayRiver Basin
1. Large-scale atmospheric disturbances and their temporal variability may play a role, via precipitation, in producing year-to-year changes in streamflow in the Parana\Paraguay Basin. In particular, a characteristic feature of the climate of the tropical Pacific Ocean is a biennial tendency in equatorial sea surface temperature (SSI) and associated atmospheric fields such as the surface winds, sea-level pressure, and rainfall. In general, conditions along the equatorial Pacific are such that warm surface waters and heavy rainfall are restricted to its western areas (west of the International Dateline). During so-called El Nifio events, warm equatorial Pacific waters are found much further east than usual, heavy rainfall shifts eastward, and between about December and March, can become excessive along the normally dry coasts of southern Ecuador and Peru.
2. The shifts in rainfall pattems in the tropical Pacific perturb large scale atmospheric circulation patterns all over the globe. Because the weather patterns associated with El Nino events can persist for about one year, the anomalous weather conditions that can be experienced in those regions affected by the phenomenon can also be long-lasting.
3. In 1991-92, a moderate El Nifo event occurred in the Pacific. In the last decade, we have experienced three moderate to very strong El Nifio events - in 1982-83, 1986-87 and in 1991-92. The 1982-83event is considered the strongest such event in this century. The type of climatic anomalies experienced in any one part of the world depends on its geographic location, and it also tends to be seasonally dependent.
4. The pattern of anomalously high and low precipitation is quite characteristic of the typical season response to El Nino events in this region (Kiladis and Diaz, 1989'; Diaz and Kiladis, 19922). In particular, heavier than normal rainfall is experienced in the Parana/Paraguary Basin and along the northern coast of Peru, and dryer than normal weather is experienced in the Nordeste region of Brazil. Although this is the typical or characteristic response of the precipitation regime in South America, it does not necessarily occur in every El Nifio event to the same degree, whether in its spacial features or in its seasonal distribution. Nevertheless, the frequency with which this typical response is observed, and the fact that significant alterations of the normal climatologicalfeatures in the affected regions can occur, suggest that having knowledge of the expected climatic patterns when an El Niino event is underway would be helpful in planning for the safety of life and property.
'Kiladis,G.N. and Diaz, H.F., 1989:Global climatic anomalies associated with the extremesof the SouthernOscillation. Journal of Calimate,2:1069-1090.
2Diaz,H.F. and Kiladis,G.N., 1992:Atmospheric teleconnections associated with the extremephases of the Southern Oscillation.In Diaz, H.F. and Markgraf, V. (eds.), El Mflo: Historical and PaleoclimaticAspects of the SouthernOscilation, CambridgeUniversity Press, Cambridge,pp. 7-28. Table B. 1 shows a close correspondence between El Nino events and the occurrence of extra- ordinary floods'.
Table B.1: El Niiio Episodes and Floods in the ParanDIParaguay River Basin'
El Nifno Yearof Year of Occurrence Extraordinary (warmevent) FloodsRecorded 1991 1992 1986 1987 1982 1982-83 1976 1977 1972 1974 1965 1965-66 1963 1963 1957 1957 1953 1954 1951 1951 1939 1939 1932 1932 1930 1931 1925 1926 1923 1923 1918 1919 1913 1913 1911 1912 1904 1905 1877 1878
3Extraordinaryflood years are years in whichan extraordinaryflood (i.e. 10-yearsflood) occurred at one or more of the folowing sites: Jupia, Guafra, Posadas,Corrientes, Ladario, Porto Murtinhoor Asunci6n.
ANNEX B -AugUSt 31, 1993 -2- 5. The warm events in the Pacific are not the only critical feature of this phenomenon. The Southern Oscillation (SO), a large scale "seesaw" of atmospheric mass between the western and eastern tropical Pacific, is also an important tropical feature.
6. In essence, the SO defines two predominant climate regimes in the tropical Pacific Ocean. In one mode, sea-level pressures (SLP) are relatively high over the subtropical South Pacific and the Southeast Trades are strong, upwelling along the equator is well developed, and rainfall is heavier than usual in the western tropical Pacific, while very dry conditions prevail along the equator east of the dateline and along the Peruvian coast. In the other mode, pressure gradients are weaker, and, in response, the Southeast Trades are also weakened resulting in anomalously warm water along the Equator from the coast of South America to the dateline, and anomalously heavy rainfall over these same areas. The El Nino is the manifestationof the latter extreme phase, whereas, so called "La Nifia" events comprise the opposite phase of the SO. Some of the great droughts of this century in parts of the Parana/Paraguay Basin have occurred in association with La Nina events.
7. Table B.2 summarizesthe impact of the extremes in the El Nihio/SouthernOscillation (ENSO) in terms of the average percent of normal annual peak flow measured during warm and cold ENSO events in this century for the available streamflow record at the three recording sites. The figures show that the climatic patterns associated with the extreme phases of the ENSO phenomenon have resulted in about a 20% differential in peak flows on the Upper Parand-ParaguayRiver Basin. The data displayed in Figures of the main text suggest that since the about the early 1980s wet season rainfall and annual peak streamflow in the region of the Parana and Paraguay River Basins have been relatively high. The question thus arises as to whether the recent increase in wet season rainfall represents a change in climatic conditions (i.e., a structural change), or whether it is simply a random perturbation within the same climatic structure. Indeed, if this increase to a higher level of runoff is real and climatically driven, this would have serious implications for the planning of development projects that are affected by streamflow levels.
Table B.2: Mean Deviationfrom Long Term Mean Annual MaximumDaily Discharge (percent of normal)
GaugingSite El Nifno La NifiaYear Posada 110 93 Corriente 113 89 Asuncion 118 94
ANNEX B-August 31, 1993 _3.
ANNEX C: DATA TABLES
This annex presents in tabular fonn the data that were used in the analyses reported in the text of the paper. These data are available in Lotus format on request from Robert J. Anderson, Jr.
Table C.1 Parana River in Posadas: Mean Monthly Discharges
Table C.2 Parana River in Corrientes: Mean Monthly Discharges
TAbleC.3 Parana River: Extreme Annual Low Flows
Table C.4 Paraguay River: Extreme Annual Low Flows/Stages
Table C.5 Parana River: Annual Maximum Daily Discharges
Table C.6 Paraguay River: Annual Maximum Daily Discharges/Stages
Table C.7 Monthly Precipitation in the Parana/Paaguay Basin I Table C.1 Parana river in Posadas Mean monthly dischargs m/s *1000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
1900 1901 21.6 23.9 21.2 20.5 16.3 12.2 10.2 14.7 9.2 7.9 6.4 10.6 14.5 1902 15.3 14.8 19.9 16.7 14.4 16.0 10.7 7.6 9.2 10.8 12.4 17.7 13.8 1903 13.6 16.3 16.9 10.7 9.7 9.6 9.0 8.6 6.2 9.2 9.5 9.7 10.7 1904 17.5 16.9 12.1 9.0 7.7 7.9 11.0 8.1 9.8 12.8 16.6 13.9 11.8 1905 20.1 23.8 20.4 19.7 29.4 25.5 17.1 14.7 12.5 10.7 9.1 13.1 18.0 1906 19.7 23.3 23.5 22.4 13.5 13.4 10.2. 7.7 7.2 7.7 7.9 9.7 13.8 1907 17.2 17.6 19.9 12.5 10.6 12.0 12.9 9.9 15.9 17.3 17.1 16.3 14.9 1908 18.6 22.4 16.7 12.1 10.7 10.4 9.2 8.8 8.3 13.4 14.2 15.5 13.3 1909 13.6 13.7 13.4 11.4 9.5 9.8 7.7 5.7 5.7 7.6 9.6 9.8 9.7
1910 10.9 15.6 14.9 12.1 9.1 10.2 8.8 8.1 7.2 8.7 7.3 6.2 9.9 1911 7.7 10.4 9.0 11.2 10.1 8.7 9.9 10.1 13.0 18.9 14.8 22.1 12.2 1912 21.5 22.1 23.8 16.9 13.1 11.7 8.8 8.9 9.1 10.6 12.8 12.3 14.2 1913 16.9 14.9 13.8 11.9 9.3 8.7 7.3 6.6 6.8 5.9 5.6 5.6 9.4 1914 8.5 12.4 13.0 9.5 6.8 8.7 12.8 8.6 8.4 10.1 12.8 12.7 10.3 1915 10.8 8.4 7.7 9.5 10.4 13.7 8.1 6.6 9.7 16.3 10.5 9.8 10.1 1916 10.7 13.7 12.0 12.0 8.8 8.3 8.4 6.2 8.4 8.9 5.1 7.9 9.2 1917 12.4 14.6 15.3 12.8 9.6 7.2 7.0 5.5 5.5 8.7 6.7 6.3 9.3 1918 8.9 15.6 12.9 9.3 8.4 12.1 9.0 8.0 7.2 10.5 11.0 12.3 10.4 1919 12.5 19.4 15.2 14.2 13.7 14.5 10.8 7.5 8.2 10.7 17.3 16.7 13.3
1920 18.0 17.9 17.7 13.3 10.0 9.7 11.3 8.5 8.9 9.5 11.6 14.0 12.5 1921 18.7 23.0 17.0 13.6 9.0 8.5 8.6 7.8 11.0 12.9 7.2 6.1 11.9 1922 11.4 17.8 20.9 18.9 18.7 18.1 14.4 12.6 10.1 10.7 9.6 9.8 14.4 1923 13.0 15.5 17.0 16.9 13.9 19.7 12.4 8.4 11.6 13.9 16.9 11.4 14.2 1924 11.6 16.0 17.5 13.4 11.6 12.3 8.8 6.7 5.8 4.8 5.5 7.2 10.1 1925 13.4 9.5 8.3 8.8 9.7 7.6 6.6 4.9 4.5 7.2 11.2 13.8 8.8 1926 19.1 22.6 17.3 21.5 16.1 15.4 15.5 9.8 8.7 7.1 8.6 10.7 14.1 1927 18.3 15.9 17.0 13.1 9.3 9.2 7.7 6.0 13.0 9.2 12.7 7.1 11.5 1928 6.6 11.7 13.9 16.2 13.4 17.7 11.7 11.6 11.1 17.7 9.3 11.5 12.7 1929 21.5 27.0 27.1 18.2 12.3 13.2 9.2 8.1 14.2 16.2 13.8 12.4 16.0
1930 16.4 20.6 15.6 11.6 10.6 8.5 7.0 7.4 7.5 12.4 13.4 14.1 12.0 1931 19.6 19.2 24.6 19.3 19.9 17.9 13.0 8.8 10.8 10.4 8.8 12.6 15.4 1932 15.6 19.5 17.8 19.3 14.6 15.1 11.9 9.2 9.0 13.6 9.7 15.8 14.2 1933 17.8 16.6 14.1 11.0 9.5 7.1 6.5 5.5 5.4 7.1 6.9 8.3 9.6 1934 12.6 12.3 11.4 9.9 8.9 6.2 5.1 4.3 4.7 6.2 4.3 9.0 7.9 1935 14.4 15.5 17.1 13.7 10.6 11.0 9.5 12.2 10.6 24.8 14.7 12.3 13.9 1936 16.5 9.5 13.5 10.9 10.6 16.5 8.9 9.7 10.3 8.6 7.6 9.9 11.0 1937 19.1 15.0 14.6 13.3 10.9 9.8 7.1 6.1 6.3 9.5 15.2 13.9 11.7 1938 15.5 17.1 12.3 11.7 12.8 14.2 15.7 8.7 6.7 6.5 8.3 9.6 11.6 1939 14.6 16.0 12.7 10.6 11.7 10.0 9.3 6.6 7.0 6.8 12.8 19.4 11.4
1940 17.3 17.5 18.1 15.0 12.9 10.1 8.0 7.0 5.3 5.0 8.7 10.2 11.2 1941 13.8 15.9 11.3 10.1 14.1 9.9 8.9 12.1 9.2 10.9 11.8 17.8 12.1 1942 14.6 16.5 19.3 18.6 15.6 14.3 11.7 9.3 8.3 9.7 7.6 9.6 12.9 1943 16.1 18.8 17.7 12.6 9.0 11.5 7.9 7.0 6.0 9.3 11.4 10.1 11.4 1944 10.6 10.5 15.0 10.4 7.5 5.8 4.7 3.7 3.6 3.1 6.7 7.5 7.4 1945 7.1 14.9 15.3 14.7 9.6 7.5 10.3 5.8 4.7 5.5 7.3 12.2 9.5 1946 20.0 23.1 24.4 16.7 13.6 13.1 16.5 9.6 7.3 10.7 10.1 11.8 14.7 1947 14.8 18.0 21.7 18.6 13.8 12.2 9.7 9.4 12.4 12.9 9.4 10.4 13.6
Page 1 Table C.1 Parana river in Posadas Mean monthly dischargs mI/s *1000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann 1948 14.4 16.4 16.3 13.6 9.2 8.3 6.4 8.4 5.9 7.5 10.8 9.5 10.5 1949 10.8 15.5 15.0 10.8 9.6 8.8 6.1 6.1 6.3 6.3 5.8 7.7 9.0
1950 11.2 17.9 18.1 14.3 10.9 8.7 8.1 5.8 6.3 9.5 8.9 12.7 11.0 1951 14.3 21.4 23.0 15.8 9.4 8.1 7.2 5.5 6.5 9.7 9.1 10.2 11.7 1952 7.7 13.0 18.1 13.7 7.9 9.2 7.6 5.2 6.4 11.7 12.5 7.9 10.1 1953 9.0 8.5 8.5 11.2 8.1 8.2 5.7 4.4 7.4 11.7 14.0 10.8 8.9 1954 11.7 12.2 12.2 8.3 16.4 18.4 12.4 7.4 7.5 11.0 7.8 7.5 11.1 1955 9.2 9.0 8.3 10.3 9.5 15.2 14.1 8.2 8.9 5.8 7.2 7.7 9.4 1956 12.5 8.7 10.7 14.3 15.2 17.6 12.7 14.9 10.3 8.2 7.3 7.3 11.6 1957 13.0 17.6 16.0 15.4 11.4 9.6 15.0 18.9 21.1 13.9 12.3 12.8 14.7 1958 10.5 16.6 14.4 13.1 10.1 11.3 8.5 8.6 11.3 10.1 11.3 12.1 11.4 1959 14.5 18.9 14.4 14.7 10.4 9.3 7.2 7.2 6.5 7.0 7.1 9.7 10.5
1960 11.2 16.6 15.2 12.5 9.7 8.9 8.1 8.7 8.4 9.7 12.9 11.1 11.0 1961 17.6 16.9 23.8 18.8 15.2 11.6 8.7 6.5 8.3 9.4 12.0 10.4 13.2 1962 12.1 16.5 18.4 12.8 9.5 8.8 6.5 5.6 7.5 12.5 9.8 11.0 10.9 1963 18.8 17.2 13.7 11.4 8.5 7.4 5.7 4.9 4.6 8.0 16.0 10.2 10.5 1964 7.9 13.5 12.5 10.9 9.5 7.5 7.6 8.4 8.2 8.0 8.5 10.1 9.4 1965 32.0 19.4 23.5 16.5 19.6 14.1 17.8 11.4 9.9 16.6 14.0 20.1 16.2 1966 22.0 23.6 21.3 15.3 11.3 10.6 9.8 7.6 8.6 10.8 13.5 11.4 13.8 1967 17.2 18.8 19.8 13.0 9.3 9.5 8.9 8.0 8.1 7.1 8.0 11.5 11.5 1968 14.0 13.2 12.6 9.1 8.3 6.4 6.0 5.6 5.2 7.0 8.4 8.6 8.7 1969 12.5 10.3 9.3 10.6 8.5 13.2 9.1 5.8 4.8 11.9 13.4 10.6 10.0
1970 11.8 13.2 15.5 9.3 8.5 9.1 11.1 5.7 7.6 11.7 7.6 9.6 10.0 1971 18.0 9.5 10.6 9.7 12.1 13.7 12.4 9.5 7.5 9.4 7.2 10.2 10.8 1972 11.7 16.9 16.5 12.9 8.5 10.5 10.7 12.1 15.3 22.0 17.0 17.2 14.3 1973 18.4 19.6 15.3 14.4 12.3 12.7 13.7 11.6 14.2 15.2 12.6 12.0 14.3 1974 19.4 15.9 14.8 18.5 12.5 12.5 13.6 9.8 10.5 8.3 11.2 11.2 13.1 1975 15.6 13.5 12.6 12.4 9.7 9.2 9.0 9.5 10.2 15.6 12.5 16.0 12.1 1976 15.3 16.7 15.0 13.1 9.8 16.1 10.7 12.9 12.8 13.0 15.7 17.6 14.0 1977 22.7 24.6 11.6 14.4 10.7 10.5 9.4 8.7 8.8 9.5 10;3 14.7 12.9 1978 15.9 12.6 12.6 9.2 8.0 9.0 10.5 10.6 10.9 8.6 10.0 9.9 10.7 1979 13.0 15.3 13.6 10.5 15.3 10.2 9.5 11.0 12.8 13.9 15.8 15.0 13.0
1980 15.7 22.0 19.8 13.3 13.3 11.1 11.2 10.8 13.4 13.3 12.3 13.5 14.1 1981 18.9 16.5 10.9 10.0 11.0 9.6 0.6 8.4 8.. 9.9 11.0 19.7 11.9 1982 18.7 19.1 16.8 18.2 11.5 15.0 21.6 13.2 11.1 9.3 19.3 27.0 16.7 1983 24.9 29.9 31.7 24.1 30.7 34.6 33.7 19.7 19.7 24.9 22.1 19.8 26.3 1984 21.6 17.1 12.0 12.4 11.9 14.1 11.5 14.0 12.6 13.3 15.1 15.3 14.2 1985 13.5 19.3 17.5 16.7 15.9 13.1 12.2 12.6 12.3 10.3 11.0 10.2 13.7 1986 9.9 12.3 12.8 13.0 14.2 13.0 12.4 12.3 12.8 12.8 11.3 12.1 12.4 1987 10.4 15.4 12.5 13.8 20.5 18.0 15.0 11.6 10.8 12.2 15.4 13.2 14.0 1988 13.9 14.1 16.2 13.3 16.5 16.8 12.2 11.2 12.5 8.8 11.4 9.9 13.0 1989 15.0 21.5 16.3 13.5 13.8 12.5 12.4 15.3 20.6 14.6 12.7 12.8 15.1
1990 26.9 16.7 11.6 13.2 14.5 19.0 15.6 16.7 20.5 18.9 16.2 13.7 16.9 1991 11.2 17.9 13.1 19.6 14.7 13.4 12.9 11.2 10.0 12.7 11.S 14.3 13.5 1992 13.5 17.8 15.0 17.5 24.8 24.8 16.3 15.0 15.0 16.2 17.0 17.9 17.6
Page 2 Table C.2 Parana river in Corrientes Mean monthly dischargs m/a *1000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
1900 1901 17.0 17.9 16.6 15.9 13.5 10.6 9.4 12.4 9.6 7.9 6.7 9.5 12.2 1902 15.2 14.4 19.2 19.3 15.0 16.6 12.8 8.6 9.7 10.7 11.4 18.7 14.3 1903 13.1 15.9 20.4 14.3 12.5 12.3 11.1 10.2 7.5 8.5 11.2 13.1 12.5 1904 20.1 19.2 14.4 11.1 9.2 9.4 12.9 10.3 11.4 15.1 20.2 21.8 14.6 1905 25.1 27.0 29.0 25.1 31.7 40.3 28.3 24.0 19.7 17.5 15.5 17.4 25.0 1906 21.5 24.7 24.5 26.0 15.6 15.0 13.0 10.4 9.4 8.8 7.8 9.1 15.4 1907 16.5 17.4 21.8 13.3 11.0 12.0 12.7 10.0 14.6 17.2 19.6 17.2 15.3 1908 21.7 26.4 22.9 17.2 14.2 17.2 14.3 11.7 9.2 15.4 18.5 20.7 17.4 1909 18.2 16.5 16.9 16.1 13.5 13.8 10.1 7.4 6.6 8.1 10.4 11.6 12.4
1910 11.9 16.7 18.6 16.7 14.9 12.8 10.2 9.6 7.6 8.9 8.2 7.6 12.0 1911 7.7 11.5 11.8 14.3 13.9 12.7 12.4 12.9 14.0 21.9 16.9 30.2 15.0 1912 33.8 28.7 31.7 23.8 18.0 16.0 12.7 11.8 11.1 13.2 14.5 15.1 19.2 1913 18.9 20.3 18.8 19.9 18.2 15.8 13.3 11.4 11.3 10.3 9.3 7.5 14.6 1914 9.7 13.8 16.6 15.3 12.9 11.9 14.8 11.4 10.3 12.1 16.2 20.7 13.8 1915 15.1 11.8 9.9 15.7 15.4 18.4 10.7 7.5 10.0 17.2 12.0 11.8 13.0 1916 11.5 17.5 14.5 14.1 11.5 12.3 11.7 9.1 9.4 9.6 6.5 7.6 11.3 1917 12.4 15.6 17.8 15.2 12.4 9.4 9.0 8.0 7.5 10.8 8.8 6.6 11.1 1918 9.1 16.6 16.3 13.2 12.0 17.4 14.9 10.5 8.2 10.9 13.1 14.9 13.1 1919 14.2 20.9 20.6 16.9 18.1 23.6 20.6 11.5 10.2 11.2 20.0 25.5 17.7
1920 25.8 24.3 25.9 20.1 15.1 15.0 17.4 15.1 13.7 16.3 17.2 22.3 19.0 1921 25.2 33.1 27.3 25.2 17.1 14.5 14.7 13.2 14.2 22.2 13.8 9.3 19.1 1922 12.4 23.1 26.7 26.4 26.5 27.2 24.0 19.9 15.7 13.9 13.1 12.4 20.1 1923 15.8 20.7 20.4 21.7 19.2 24.4 21.9 12.8 14.5 18.8 24.4 19.0 19.4 1924 16.8 18.2 21.0 17.4 13.5 15.8 12.8 9.1 8.2 6.9 6.9 8.0 12.9 1925 14.6 12.9 10.4 11.8 15.1 11.9 9.0 7.2 6.3 8.4 13.2 16.9 11.5 1926 20.2 30.9 23.2 25.3 22.2 20.4 16.0 13.2 12.1 10.4 11.2 13.0 18.1 1927 20.4 20.9 20.3 16.5 12.8 11.5 10.4 8.5 13.5 11.0 14.6 8.8 14.0 1928 8.5 12.5 15.3 21.7 21.1 24.0 18.3 13.9 14.5 22.4 15.7 13.1 16.7 1929 24.3 33.6 35.5 25.4 16.5 16.4 12.8 11.2 16.8 23.6 19.5 14.6 20.7
1930 21.0 26.1 23.5 15.4 14.7 13.5 10.7 10.4 10.6 13.1 18.2 16.7 16.1 1931 25.5 23.5 32.3 27.0 28.9 29.1 22.0 14.4 14.6 15.3 14.5 16.3 21.9 1932 19.1 23.1 23.8 25.7 22.7 22.5 19.8 15.4 13.9 19.3 15.6 20.1 20.1 1933 22.1 22.6 20.6 15.9 13.9 11.7 10.6 9.5 8.8 9.9 9.8 9.3 13.7 1934 13.9 14.9 13.8 13.2 12.8 8.9 7.7 7.1 6.9 7.6 6.3 9.0 10.2 1935 16.1 17.2 22.1 16.7 13.6 13.7 13.4 16.7 13.6 29.0 23.2 17.6 17.8 1936 21.3 12.4 14.5 12.2 12.7 20.1 12.6 11.5 10.9 9.6 8.2 9.5 13.0 1937 19.2 18.5 16.7 15.0 13.4 12.4 9.0 7.5 7.6 9.1 14.2 15.4 13.1 1938 16.2 21.9 15.1 13.4 13.5 16.8 19.6 9.9 7.2 6.7 8.4 9.5 13.1 1939 14.7 16.8 15.6 15.1 14.8 14.2 12.2 8.4 8.4 9.4 14.8 26.5 14.2
1940 22.2 20.6 23.4 22.5 19.8 18.1 14.7 13.6 10.8 8.5 10.5 12.9 16.5 1941 14.7 19.0 14.8 19.8 17.6 13.8 12.0 14.0 10.5 12.1 12.4 20.9 15.1 1942 18.4 17.9 22.2 23.5 23.2 22.8 18.5 13.9 11.4 13.3 10.7 10.5 17.2 1943 15.9 20.9 20.6 16.1 11.1 14.5 12.3 9.8 8.4 11.2 14.3 14.1 14.1 1944 12.9 11.7 17.3 13.2 9.4 7.7 6.7 5.6 4.9 4.7 6.7 8.0 9.1 1945 7.3 14.7 18.4 17.4 12.0 9.2 12.1 8.6 7.5 7.9 8.7 11.8 11.3 1946 21.1 28.0 31.1 25.0 19.3 21.1 21.9 16.1 10.3 12.5 13.9 14.8 19.5 1947 17.4 21.5 24.8 26.1 19.4 18.7 15.4 13.8 14.9 17.4 12.3 10.8 17.7
Page 1 Table C.2 Parana river in Corrientes Mean monthly dischargs m/s *1000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann 1948 15.3 18.1 19.5 17.7 12.3 10.7 8.5 9.6 7.3 8.4 11.7 10.4 12.4 1949 11.9 17.1 18.7 13.2 12.3 12.0 10.0 8.0 7.5 6.9 6.4 8.3 11.0
1950 14.1 21.0 23.9 21.4 14.9 13.2 13.0 9.3 8.1 11.1 10.6 14.7 14.6 1951 15.0 25.3 30.5 25.4 13.5 11.2 9.9 8.1 7.2 7.6 10.9 12.5 14.7 1952 9.2 15.2 21.5 20.4 12.1 13.5 11.8 9.1 8.8 13.8 16.4 11.6 13.6 1953 10.3 10.1 9.9 13.3 12.7 13.6 10.3 7.4 8.6 13.2 19.9 14.4 12.0 1954 14.4 15.2 16.9 11.6 19.0 27.7 21.5 13.5 11.1 15.6 12.5 8.7 15.6 1955 10.3 11.3 10.5 14.2 13.0 17.9 20.8 10.6 11.6 7.3 8.4 8.3 12.0 1956 14.0 12.4 12.8 19.6 23.0 25.6 20.3 22.3 15.7 13.4 13.1 10.9 16.9 1957 14.2 21.7 23.4 20.9 17.4 15.4 19.3 24.1 26.4 22.8 16.1 16.4 19.9 1958 15.0 19.9 19.1 18.6 16.1 15.7 12.9 13.0 14.2 16.6 17.6 20.6 16.6 1959 22.6 29.3 22.9 22.4 18.2 16.4 14.1 12.8 13.2 13.7 12.7 15.4 17.7
1960 17.3 22.7 20.9 17.9 13.8 13.2 12.8 11.7 12.3 13.3 19.1 15.0 15.8 1961 20.6 21.2 30.1 30.5 26.1 19.5 15.4 11.1 11.4 12.8 15.3 15.8 19.1 1962 14.8 19.2 23.3 18.0 12.7 11.5 8.9 7.9 8.5 14.2 11.6 11.2 13.5 1963 20.8 22.7 18.5 16.7 12.9 12.0 10.2 8.4 7.7 8.8 18.8 14.2 14.2 1964 9.7 13.7 16.9 15.0 15.5 10.3 9.0 9.0 10.1 9.3 9.5 11.3 11.6 1965 17.1 24.5 31.1 25.1 26.1 25.0 22.3 15.2 12.9 19.6 19.6 23.2 21.8 1966 33.3 33.4 36.6 26.6 17.9 15.0 13.1 10.1 10.2 10.8 15.7 13.2 19.6 1967 20.2 22.3 26.0 18.4 11.6 10.9 10.6 9.6 9.2 8.2 8.6 11.6 13.9 1968 14.0 17.4 14.7 11.0 9.8 8.3 7.7 7.1 6.6 8.1 11.1 9.0 10.4 1969 16.1 12.6 11.1 12.6 10.9 17.4 12.5 7.6 6.1 12.7 16.0 14.9 12.5
1970 12.5 15.3 17.7 12.1 9.9 10.0 13.0 7.4 8.1 13.7 9.3 9.1 11.5 1971 22.4 16.7 15.2 15.3 16.9 16.5 16.0 11.8 8.8 10.1 8.6 10.2 14.0 1972 12.5 16.6 20.7 15.8 10.5 13.6 13.1 12.9 18.2 26.3 20.1 25.8 17.2 1973 23.8 26.3 21.5 18.5 17.4 16.6 18.4 14.1 17.0 18.3 15.1 14.8 18.4 1974 23.1 24.7 19.7 26.7 18.0 18.2 19.1 14.9 15.5 11.7 14.2 14.3 18.3 1975 19.9 17.9 16.2 16.4 14.9 12.7 12.3 12.6 13.1 19.7 16.8 21.4 16.2 1976 20.6 22.1 20.1 17.6 12.8 20.0 13.9 15.3 15.9 16.0 20.0 20.3 17.8 1977 28.5 34.0 18.9 18.6 15.8 13.8 14.4 12.7 12.3 12.8 12.9 18.7 17.7 1978 19.1 18.3 16.5 13.1 11.0 12.0 12.7 14.8 13.8 11.8 13.0 13.2 14.1 1979 15.8 19.8 19.4 16.2 21.3 19.0 17.5 18.6 20.4 22.0 23.7 22.3 19.7
1980 21.1 29.4 28.9 18.3 18.8 18.6 18.3 17.6 19.5 19.4 18.7 18.9 20.6 1981 25.7 27.5 18.6 15.5 17.6 15.0 13.9 12.7 12.1 13.0 13.6 22.7 17.3 1982 27.0 24.7 22.5 27.6 18.0 21.4 32.2 25.5 20.2 17.7 24.9 40.6 25.2 1983 38.3 40.4 45.3 38.2 46.5 50.2 48.2 33.5 25.4 33.3 29.1 25.7 37.8 1984 27.3 22.9 15.6 17.6 19.6 20.7 16.4 16.8 15.7 16.9 19.4 21.5 19.2 1985 18.8 24.2 24.0 25.3 24.7 22.8 18.9 20.2 19.5 14.8 14.1 11.7 19.9 1986 10.9 13.1 16.9 19.8 21.0 20.3 18.0 15.3 14.2 16.4 13.7 14.1 16.2 1987 15.0 19.0 18.5 18.7 26.0 28.5 22.2 16.4 13.6 13.4 17.9 16.6 18.8 1988 16.4 16.5 19.4 16.4 20.8 24.7 20.3 18.2 17.6 13.0 13.4 10.6 17.3 1989 14.4 25.6 23.0 19.4 18.4 16.6 18.0 19.6 28.4 23.2 18.7 14.8 19.9
1990 26.3 27.2 13.8 16.8 21.2 27.8 21.7 21.4 28.1 25.6 22.5 17.3 22.4 1991 13.0 19.7 16.3 23.6 21.0 17.1 18.0 14.1 12.5 15.4 13.6 16.4 16.7 1992 18.9 21.0 19.7 23.3 34.2 42.3 27.4 21.5 20.7 23.5 26.8 26.6 25.5
Page 2 Table C.3 Parana River Extreme Annual Low Flows
Guaira Posadas Corrientes Year Date Discharge Date Discharge Date Discharge
1900 1901 Nov 5699 Nov 1902 6154 Aug 6949 Aug 1903 7902 Oct 5520 Oct 1904 5962 Aug 6097 May 1905 8330 Nov 8061 1906 Nov 14107 Sept 6686 1907 Nov 7291 Aug 8376 Aug 1908 8851 Sept 7983 1909 Sept 8477 Aug 5378 Sept 6096 1910 Dec 5026 Dec 1911 6115 Jan 5061 Jan 1912 6077 Aug 7404 1913 Sept 10216 Dec 4991 1914 Dec 6531 May 5096 Jan 1915 8452 Aug 5096 Aug 1916 6470 Nov 4271 1917 Nov 5962 Sept 4102 1918 Dec 5962 Sept 5735 1919 Sept 7181 Oct 6724 Oct 8501 1920 Sept 7175 Sept 1921 2302 Dec 5307 Dec 8477 1922 Dec 1 3850 Jan 6464 Jan 9107 1923 Jan 1 5100 Aug 7519 Aug 11452 1924 Sept 29 3350 Nov 4169 Oct*NoV 6271 1925 Sept 1 2500 Sept 3539 Sept 5812 1926 Sept 1 2550 Oct 6097 Oct 9316 1927 Aug 14 4600 Aug 5879 Dec 8138 1928 Sept 30 3500 Jan 5807 Jan 7902 1929 Oct 1 3600 Aug 7213 Aug 10762
1930 Sept 30 3600 Oct 5735 Oct 8927 1931 Oct 1 3900 Aug 7634 Sept 12662 1932 Sept 24 4450 Aug*Sep 7299 Sept 12795 1933 Nov 24 3350 Sept 4749 Dec 7203 1934 Nov 16 2500 Nov 3572 Nov 5431 1935 Sept 1 2700 July 7519 June 11238 1936 oct 13 3800 Nov 6464 Nov 7269 1937 Sept 28 3350 Sept 5378 Oct 6674 1938 Oct 1 3400 Oct 5237 Oct 5906 1939 Sept 4 3350 Oct 5166 Sept 6756 1940 Sept 29 2900 Oct 4474 Oct 8306 1941 Oct 1 2900 Nov 7404. Jan 8526 1942 Sept 1 4450 Nov 6649 Nov 9529 1943 Sept 12 3400 Sept 5166 Sept 8019 1944 Oct 10 3500 Oct 2928 Oct 4552 1945 Oct 1 2600 Sept 4406 Jan 6154 1946 Oct 1 3200 Sept 6538 Sept 9475 1947 Oct 1 4800 Dec 6986 Dec 9030
Page 1 Table C.3 Parana River Extreme Annual Low Flows
Guaira Posadas Corrientes Year Date Discharge Date Discharge Date Discharge 1948 Oct 10 3200 Sept 5026 Sept 6674 1949 Oct 20 2000 Oct 5378 Nov 6000
1950 Sept 7 2700 Aug 5378 Sept 7763 1951 Sept 1 2700 Aug 5378 Oct 6390 1952 Sept 1 2950 Sept 4338 Sept 7603 1953 Aug 24 2700 Aug 3836 Aug 6592 1954 Nov 11 2950 Nov 5520 Dec 8090 1955 Oct 6 2600 Oct*Dec 5378 Oct 6861 1956 Oct 1 2800 Dec 5378 Dec 9965 1957 Dec 1 4100 June 8376 Jan 10762 1958 Aug 31 4200 Aug 6170 Sept 10674 1959 Oct 1 3250 Oct 5413 Nov 11118
1960 Oct 2 3250 July 6060 Aug 9992 1961 Oct 16 3900 Aug 6097 Oct 9882 1962 Aug 29 4300 Sept 5202 Sept 7313 1963 Sept 22 3600 Sept 3935 Sept 7181 1964 Sept 28 3800 Jan 6097 Sept 7856 1965 Oct 1 4350 Sept 9176 Sept-Oc 11982 1966 Aug 30 5000 Sept 6686 Oct 8725 1967 Sept 1 5050 Oct 6464 Oct 7763 1968 Oct 10 3750 Sept 4852 Sept 6430 1969 Sept 24 3150 Sept 4440 Sept 5868
1970 Sept 1 3630 Aug 4957 Sept 6430 1971 Aug 29 4500 Nov 5988 Nov*Dec 7247 1972 Sept 1 4500 May 7789 May 9691 1973 Sept 1 5750 Aug 9748 Aug 12400 1974 Sept 29 5500 Oct 7213 Oct 10998 1975 Sept 5 5600 Sept 7289 Sept 10558 1976 Aug 1 5900 May 8653 May 11329 1977 Aug 25 6200 Aug 7827 Sept 11856 1978 Sept 1 6400 May 7289 Oct 10674 1979 Aug 19 6500 July 8455 Jan 12761
1980 Aug 1 6900 June 9790 May 16862 1981 Sept 23 5800 July 7062 Sept 11793 1982 Sept 1 6600 Oct 5520 Oct 13193 1983 Oct 1 8050 Sept 13944 Sept 23124 1984 July 5 7000 July 10205 Aug 13787 1985 Nov 29 7800 Dec 8894 Dec 10329
1986 Nov 8 - 6400 Jan 7673 Jan 9609 1987 Jan 1 6900 Jan 8336 Oct 12206 1988 Jan 1 7130 Oct 6761 Dec 9772 1989 Dec Jan 8693 Jan 9449
1990 Dec 31 7950 March 10457 March 12465 1991 Sept 9339 Nov 11028 1992 Aug 7300 Jan 11526 Jan 15708
Page 2 Table C.4 Paraguay River - Extreme Annual Low Flows and Stages
Ladario Porto Murtinho Asuncion Year Date Discharge Date Discharge Date Discharge
1900 Jan 1 0.79 1901 Nov 4 1.12 1902 Novl 1.17 1903 Oct 3 0.31 1904 1905 Dec 28 1.90 1906 Nov 11 0.85 1907 Dec 1 1.10 1908 Jan 1 1.50 1909
1910 1911 1912 1913 1914 1915 Nov 2 0.00 1916 Nov 1 0.02 1917 Dec 1 0.33 1918 Jan 1 0.78 1919 Jan 1 0.79
1920 Nov 1 1.36 1921 Dec 31 1.45 1922 Nov 23 1.02 1923 Dec 1 1.14 1924 Nov 1 0.34 1925 Dec 1 0.46 1926 Jan 1 0.68 1927 Nov 11 0.50 1928 1929 Jan 1 0.85
1930 Jan 1 1.05 1931 Nov 1 1.67 1932 Jan 1 1.90 1933 Dec 7 1.18 1934 Feb 28 0.00 1935 Dec 1 1.44 1936 Nov 11 0.00 1937 0.12 1938 Sept 4 0.00 1939 Sept 9 0.00 Oct 10 1.13
1940 Oct 1 0.05 Oct 1 1.30 1941 Oct 16 0.00 Nov 4 1.57 1942 Nov 1 0.14 Nov 1 1.60 1943 Jan 1 0.73 Nov 1 2.26 1944 Sept 28 1.01 1945 Sept 1 0.07 Oct 10 1.08 1946 Jan 1 1.90 1947 Dec 24 0.86 Dec 1 2.26
Page 1 Table C.4 Paraguay River - Extreme Annual Low Flows and Stages
Ladario Porto Murtinho Asuncion Year Date Discharge Date Discharge Date Discharge 1948 Oct 4 1.28 1949 Oct 1 1.26
1950 Nov 21 1.02 Dec 1 1.86 1951 Dec 6 0.87 Nov 14 2.17 1952 Dec 29 2.19 1953 Nov 17 0.57 Dec 26 2.04 1954 Nov 1 0.70 Dec 30 1.80 1955 Nov 30 0.07 Dec 3 1.51 1956 Dec 1 1.92 1957 Jan 1 0.64 Jan 1 1.94 1958 Jan 1 1.63 Feb 8 3.17 1959 Dec 30 1.53 Dec 22 3.00
1960 Dec 30 2.72 1961 Nov 27 2.15 1962 1963 Dec 1 0.16 1964 Sept 26 0.81 1965 Oct 1 0.87 1966 Oct 11 0.00 Oct 16 1.28 1967 Sept 6 0.00 Oct 18 0.80 1968 Oct 3 0.00 Nov 1 0.94 1969 Aug 8 0.00 Sept 28 0.86
1970 Nov 11 0.00 Oct 1 0.98 1971 Sept 25 0.73 1972 Oct 1 0.77 1973 Oct 12 0.00 Oct 5 1.25 1974 Oct 1 0.08 Oct 1 1.31 1975 Dec 1 1.30 Nov 23 2.80 1976 Dec 12 3.10 1977 Jan 1 3.11 1978 Dec 5 1.95 Dec 25 3.96 1979 Dec 16 3.78
1980 Dec 1 1.89 Dec 12 3.99 1981 Dec 6 1.71 Dec 4 3.66 1982 Dec 1 3.43 1983 Feb 1 3.54 1984 Jan 1 3.91 1985 Dec 31 2.82
Page 2 Table C.5 PARANA RIVER - ANNUAL MAXIMUM DAILY DISCHARGES
Year Jupla Guaira Posadas Corrientes m/s date m/s date m/a date m/s date
1901 25800 Feb 17 19400 Feb 22 1902 24500 Dec 1 23000 April 10 1903 20100 Feb 24 22100 March 25 1904 21100 Jan 31 25700 Dec 31 1905 45000 May 25 50000 June 5 1906 26150 April 1 27800 April 17 1907 23650 March 6 24300 March 14 1908 26600 Feb 7 29400 Feb 12 1909 15450 June 1 21300 Jan 2
1910 18850 March 2 22000 March 3 1911 29550 Dec 30 33200 Dec 31 1912 29800 Jan 2 39100 Jan 7 1913 20800 Jan 27 24200 Feb 1 1914 17050 Nov 17 22500 Dec 16 1915 24650 Oct 11 24100 June 6 1916 18100 Feb 7 20100 Feb 12 1917 19850 Mar 8 22100 March 13 1919 21850 June 21 24800 June 26 1919 27550 Nov 29 31000 Dec 6
1920 23450 Jan 7 30000 Jan 13 1921 23700 Feb 11 25800 Feb 13 36000 Feb 20 1922 19800 April 2 25050 April 2 30500 July 5 1923 19600 March 18 33750 June 21 38100 June 27 1924 19000 March 9 18850 March 10 22200 March 14 1925 11400 Nov 28 17250 Dec 15 18600 Dec 19 1926 22000 April 7 25700 April 15 27000 Jan 30 33400 Feb 5 1927 19000 March 12 21000 Jan 21 21000 Jan 28 24300 Feb 3 1928 11600 Feb 12 15300 March 26 29600 Oct 22 31000 Oct 27 1929 26300 Feb 19 34900 March 3 32450 March 5 39100 March 10
1930 18900 Feb 8 21300 Feb 11 23600 Feb 15 30100 Feb 22 1931 25500 Feb 22 32800 March 1 29900 March 3 36000 March 10 1932 14600 Jan 30 20200 Feb 5 26750 April 24 32100 April 29 1933 14700 Jan 31 19400 Jan 23 19700 Jan 26 24600 Feb I
Page 1 Table C.5 PARANA RIVER - ANNUAL MAXIMUMDAILY DISCHARGES
Year Jupia Guaira m/a Posadas date m/a Corrientes 1934 date 11200 Jan 18 e/ date 13600 Dec 31 r/s date 1935 17000 Feb 14650 Jan 27 20 19000 16300 Feb 2 1936 13700 March 12 27650 March 8 16700 Oct 13 33500 1937 Jan 9 34500 Oct 23 14900 Jan 20 June 12 31900 24700 Jan 19 June 17 1938 12800 Dec 24 25800 Nov 21 15200 Jan 29 25800 Jan 27 1939 15100 Jan 4 25100 July 4 16800 Jan 10 26800 July 9 26600 Dec 7 31000 Dec 12 1940 17400 Feb 22 20900 1941 12800 Feb 28 21550 Jan 8 16400 Jan 21 25600 1942 Feb 11 23750 April 7 15300 March 14 Feb 13 25500 20000 March 21 April 27 1943 19700 22000 April 19 Jan 31 21000 25700 March 1944 Feb 3 21700 29 11900 Feb 23 Feb 8 23000 15700 March 21 Feb 13 1945 15900 17400 March 24 Feb 14 17700 20000 March 1946 Feb 19 17800 28 19500 Jan 10 Feb 22 20100 25900 March 5 March 8 1947 21800 March 28500 March 6 21 26500 March 33700 March 12 1948 14600 28 2i500 March March 21 17400 30 29600 April 1949 Feb 25 18800 9 15500 Feb 17 Feb 25 21500 17300 March 6 March 4 17300 March 8 20400 March 20 1950 15000 Feb 14 20300 March 6 1951 17700 Jan 22300 March 9 30 23000 26800 March 15 1952 19300 Feb 5 25800 March 18 21400 March 22 33200 1953 March 25 20900 March 27 9740 March 28 March 28 25700 11100 Apr1l 4 March 31 1954 12500 19450 Nov 4 Feb 22 17900 23200 Nov 1955 May 24 23900 8 9740 Jan 27 June 19 30600 13100 June 23 June 24 1956 12600 22900 June 24 Jan 7 1850o 27300 July 1957 June 15 22050 1 17400 March 1 June 7 29200 i18oo Feb 38 June 13 1958 17000 26150 Sept 27 Jan 29 18000 32400 oct 1959 Feb 4 17800 4 15600 March 26 Feb 7 20200 Feb 9 23300 Dec 31 23800 Feb 12 33800 Feb 19 1960 15000 Jan 28 17900 Feb 2 17800 1961 20200 Feb 25 Feb 5 25300 March 23500 Feb 24 1962 15200 6 26650 March March 22 18400 18 35100 March 1963 March 22 20700 25 16600 Jan 2 Feb 27 24500 1964 21200 Jan 25 March 11 13200 Feb 26 21750 Nov 9 20300 Feb 24400 Feb 1 1965 23 20500 19300 March 11 Feb 25 22700 25800 March 8 March 2 1966 20100 30300 Dec 23 Feb 13 27400 36400 Dec 1967 Feb 22 33900 29 15000 Feb 17 Feb 23 43800 20100 Feb 22 March l 21700 March 9 27200 March 14
Page 2 Table C.5 PARANA RIVER - ANNUAL MAXIMUM DAILY DISCHARGES
Year Jupia Guaira Posadas Corrientes rn/a date m/s date m/s date m/s date 1968 11600 March 3 18300 Jan 23 18800 Jan 39 21300 Feb 3 1969 8680 Nov 19 13900 Nov 24 23100 Jan 1 23500 Jan 16
1970 14800 March 3 17100 March 7 17100 March 12 19600 March 19 1971 11500 Dec 12 16800 Jan 10 23450 Jan 3 27200 Jan 19 1972 12400 Dec 12 20000 Oct 17 24600 Oct 10 29800 Dec 11 1973 13400 April 6 22130 Jan 28 25050 Jan 31 29900 Feb 9 1974 18soo March 26 22880 April 2 23500 Jan 27 30400 Feb 2 1975 11000 Jan 9 16250 Jan 6 22850 Dec 11 26600 Dec 17 1976 14100 Dec 17 19770 Dec 31 21050 June 10 24400 June 17 1977 21270 Feb 6 28250 Feb'13 28000 Feb 15 36700 Feb 21 1978 l8830 Jan 1 19890 Jan 29 19700 Jan 31 25000 Feb 5 1979 15180 Jan 29 17400 Feb 27 25500 May 17 29800 May 23
1980 19000 Jan 31 26380 March 7 26850 March 8 34100 March 15 1981 13070 Dec 21 21250 Dec 29 25900 Dec 30 31000 Feb 5 1982 21220 March 27 27190 Dec 1 31350 Dec 5 42600 Dec 11 1983 28160 Feb 12 39850 June 15 43330 July 12 54700 July 18 1984 16080 Jan 7 19840 Aug 9 23100 Jan 6 28800 Jan 19 1985 16040 Feb 15 19550 Feb 18 21750 Feb 19 28300 Feb 23 1986 7920 April 3 15140 May 21 21000 May 22 27200 May 28 1987 7350 Jan 1 21310 May 23 34500 May 23 38900 May 30 1988 13970 March 10 17020 March 14 23450 May 27 26900 June 3 1989 12520 Feb 19 31250 Sept 16 35200 Sept 23
1990 16040 Jan 9 34180 Jan 19 37500 Jan 25 43800 Feb 1 1991 22380 Jan 13 21390 April 11 22800 April 14 27500 April 22 1992 16680 May 6 22520 May 9 41850 June 25 50800 June 8
Page 3 I Table C.6 PARAGUAY RIVER - ANNUAL MAXIMUM DAILY STAGES AND DISCHARGES
Year Ladario Porto Murtinho Asuncion m date m date m W/s date 1900 4.32 June 25 1901 4.39 June 10 1902 5.00 June 4 1903 2.71 May 16 1904 5.00 June 3 6.40 6320 Dec 11 1905 6.62 May 11 8.80 11170 June 23 1906 5.61 May 6 5.38 4980 Jan 1 1907 3.69 July 13 3.60 3320 Dec 31 1908 3.69 July 23 5.96 5730 March 21 1909 2.77 May 27 5.31 4900 Jan 1
1910 2.00 March 23 3.31 3110 March 19 1911 2.17 June 21 7.00 7280 Dec 31 1912 5.10 June 17 7.30 7820 Jan 15 1913 6.39 April 8 7.08 7420 May 15 1914 3.57 July 10 5.84 5540 Nov 30 1915 1.51 April 12 4.84 4400 June 9 1916 3.26 July 25 4.85 4410 Feb 20 1917 5.13 June 18 3.89 3550 Oct 16 1918 3.45 July 22 5.40 5010 June 18 1919 3.00 July 8 7.78 8770 June 13
1920 6.37 May .12 6.14 5950 Dec 6 1921 6.07 April 7 6.02 5780 July 18 1922 4.26 June 12 5.99 5740 Jul 30 1923 5.50 June 14 5.85 5560 Nov 19 1924 3.41 July 4 3.57 3300 Jan 1 1925 2.30 July 20 4.94 4500 May 13 1926 5.47 June 18 4.85 4410 May 28 1927 4.07 July 2 3.42 3190 May 5 1928 2.87 July 9 5.46 5080 June 17 1929 5.31 June 4 4.35 3940 Oct 16
1930 5.20 June 6 4.80 4360 Feb 17 1931 5.50 June 3 7.52 8240 July 1 1932 5.98 May 27 5.91 5630 July 4 1933 5.11 May 16 4.96 4520 Feb 1
Page 1 Table C.6 PARAGUAY RIVER - ANNUAL MAXIMUM DAILY STAGES AND DIScHARGEs
Year Ladario Porto Murtinho m Asuncion date m 1934 date m 3.99 July 1 m/s date 1935 5.74 2.87 June 11 2800 May 12 1936 2.25 5.03 June 12 4600 Aug 23 1937 2.43 5.04 July 12 4610 June 21 1938 1.60 3.52 June 9 3260 May 21 1939 2.01 3.26 June 16 3.16 3070 Feb 18 June 6 4.60 4170 June 1940 14 5.03 June 12 1941 6.49 May 25 1.96 May 28 6.36 6260 3.94 April June 10 1942 5.25 1 4.50 June 28 6.06 4080 April 23 1943 5.03 Oct 5 5.06 June 23 5.46 4630 June 22 1944 2.05 Aug 12 5.07 June 13 3.98 4640 Nov 28 1945 5.24 May 25 3.11 June 19 5.64 2970 Jan 1 1946 Aug 24 3.02 4.15 July 15 2900 Sept 1947 5.79 July 21 13 4.57 July 6.50 6470 a 6.04 May June 1 1948 1.92 24 5.43 June 26 2.78 5040 June 3 1949 5.32 June 19 1.48 May 3 5.83 1910 May 3 Auq 13 3.61 3330 July 1 1950 5.07 June 8 5.65 1951 4.15 Aug 19 4.12 June 26 3740 April 1952 4.90 March 24 22 4.64 5.27 4860 July 3 5.49 June 6 1953 May 26 4.52 2.86 July 1 4100 4.27 June June 11 1954 4.42 17 4.87 July 14 4430 June 6 1955 4.96 June 4 2.64 July 6.38 6290 a 3.66 July June 18 1956 4.30 12 3.01 August 3 6.16 2890 July 15 1957 4.19 Sept 21 6.45 July 22 5.60 6400 May 17 1958 5.01 Aug 10 5.45 June 25 6.20 5060 April 11 1959 5.91 Oct 1 6.02 May 9 7.75 5780 oct 23 Aug 5 5.80 5500 Oct 17 1960 4.92 May 25 5.42 June 1961 4.34 29 5.20 June 21 6.20 4780 Jan 1 1962 2.25 July 1 6.05 June 10 5820 May 20 1963 2.28 4.47 June 19 2420 May 28 1964 4.09 1.33 April 1 3710 June 1965 2.60 April 17 27 2.74 April 8 4.40 3980 4.80 May May 2 1966 2.48 22 6.77 May 22 4.66 6900 June 1 1967 1.63 April 9 4.85 April 24 3.06 4410 Jan 26 March 14 2.62 2640 April 1
Page 2 Table C.6 PARAGUAYRIVER - ANNUAL MAXIMUM DAILY STAGES AND DISCHARGES
Year Ladario. Porto Murtinho Asuncion m date m date m m/e date 1969 2.05 June 6 4.36 Jan 30 2.34 2450 Feb 2 1969 1.80 May 31 3.82 May 9 4.50 4080 May 12
1970 2.13 June 16 2.96 July 11 1.60 1980 1971 1.11 May 4 2.77 May 11 6.35 6250 Jan 28 1972 1.97 May 25 3.18 May 12 3.96 3610 June 17 1973 2.09 June 19 4.86 Dec 31 3.33 3120 Jan 8 1974 5.46 June 5 6.87 Aug 15 4.98 4550 Feb 8 1975 4.33 June 16 4.98 Aug 13 4.20 3810 Dec 14 1976 4.95 June 22 5.59 May 29 3.65 3360 June 10 1977 5.52 April 20 6.97 July 29 4.74 4300 Jan 31 1979 5.36 May 2 6.41 July 20 3.75 3440 May 31 1979 6.25 April 1 9.15 June 6 7.17 7580 June 14
1980 6.14 April 18 8.54 July 1 6.53 6520 July 10 1981 5.46 May 19 6.64 July 16 4.40 3980 Jan 1 1982 6.52 April 21 9.71 June 29 7.76 8730 July 29 1983 5.36 May 10 9.08 May 29 9.01 11740 May 29 1994 5.07 June 1 5.95 July 20 5.55 5180 May 12 1985 9.20 June 7 6.95 7200 June 7 1986 4.69 4260 June 10 1997 5.90 5620 June 6 1988 7.65 8500 June 10 1989 6.42 6350 Sept 25
1990 5.75 5430 June 22 1991 5.49 6.64 June 31 4.73 4290 July 8 1992 5.38 7.90 8.55 10530 June 1
Page 3 I Table C.7 Monthly Precipitation in the ParanafParaguayBasin (mm)
Year Jan Feb Mar Apr May Jun JuL Aug Sep Oct Nov Dec
1901 151.33 118.33 91.33 131.33 90.00 54.33 52.00 105.67 73.00 99.67 137.33 67.33 1902 198.67 66.67 116.33 100.33 81.00 53.00 37.33 72.33 81.33 137.00 212.33 240.67 1903 117.00 211.25 195.25 92.75 49.75 90.25 64.75 127.00 45.75 194.00 84.75 280.25 1904 120.50 90.25 99.00 97.00 108.50 69.50 135.00 85.75 141.75 204.25 119.25 147.75 1905 96.75 129.00 118.75 175.25 263.50 65.50 95.75 104.00 108.00 274.50 151.00 148.00 1906 25.25 49.00 74.50 109.25 62.75 103.75 56.00 64.00 71.75 75.25 76.50 115.00 1907 183.50 86.25 111.00 129.00 57.50 44.00 69.75 103.50 104.75 112.00 129.75 231.00 1908 122.75 84.00 86.50 79.75 119.00 70.75 130.75 65.75 76.25 198.50 119.00 228.25 1909 75.75 213.25 115.25 88.00 67.25 69.75 50.00 34.50 97.25 80.75 68.75 109.00 1910 160.25 191.25 121.50 215.00 94.50 66.75 68.50 31.50 103.33 61.00 104.00 69.67 1911 156.00 101.25 105.50 133.00 113.67 63.67 83.67 77.33 141.00 108.33 213.33 230.67 1912 112.67 196.00 51.00 136.33 115.33 125.33 36.67 52.00 65.67 76.67 159.33 154.00 1913 97.67 104.00 171.25 146.67 61.75 51.25 30.75 36.67 103.50 166.25 133.25 68.50 1914 142.50 182.00 203.00 201.33 127.00 114.00 111.75 93.75 77.75 224.50 189.50 133.50 1915 154.50 92.25 172.00 281.00 170.25 60.25 47.50 90.75 73.25 137.00 69.25 143.75 1916 117.50 144.00 46.75 69.00 220.25 102.75 82.50 68.00 66.25 59.50 72.50 139.50 1917 8.00 139.75 83.25 123.75 36.25 28.25 80.25 28.25 127.00 104.00 44.75 94.00 1918 162.50 134.25 217.00 122.75 206.00 153.50 68.75 23.25 71.75 124.25 216.00 197.50 1919 98.75 143.25 107.00 89.33 142.50 146.00 61.33 41.00 37.00 176.00 205.00 134.00 1920 214.50 157.50 125.25 104.00 104.75 128.75 95.75 41.00 140.00 118.25 136.67 186.50 1921 155.45 194.35 185.40 105.75 51.10 104.68 41.00 56.25 189.05 153.80 49.75 105.85 1922 251.15 117.55 109.45 133.45 168.52 93.82 76.68 74.03 89.03 108.00 97.57 100.78 1923 160.50 86.57 78.57 146.93 146.77 162.05 54.25 53.33 80.40 171.80 102.43 228.35 1924 65.97 132.90 85.88 104.30 93.25 80.80 14.67 21.55 75.47 33.53 119.35 71.25 1925 143.12 83.10 39.33 263.80 184.15 33.35 29.12 33.12 140.80 182.30 196.43 112.65 1926 223.68 51.92 78.57 104.50 129.10 76.25 85.95 40.28 99.90 99.12 185.10 148.50 1927 179.82 108.28 188.57 101.25 28.20 97.38 22.50 27.88 95.22 109.70 215.45 111.32 1928 116.60 142.05 129.68 270.15 175.62 75.15 66.38 56.00 219.90 211.25 97.40 104.75 1929 185.55 50.05 119.97 27.73 71.68 73.70 68.12 96.72 163.75 183.32 102.22 131.25 1930 155.77 150.82 155.88 93.22 114.40 30.40 51.12 118.05 50.88 124.68 106.20 178.15 1931 206.22 126.98 96.24 213.36 143.34 62.40 26.36 33.52 52.80 187.54 79.12 166.56 1932 133.86 164.52 176.16 187.20 103.22 72.28 59.24 59.46 98.46 149.42 167.88 124.66 1933 86.32 142.12 39.72 73.26 56.62 15.28 8.74 26.66 60.60 164.02 63.16 143.54 1934 83.80 165.12 107.40 66.04 77.88 60.98 15.08 48.48 74.56 81.86 119.58 137.98 1935 118.68 99.96 80.56 59.40 33.16 99.40 108.08 122.22 117.16 165.82 172.56 226.50 1936 142.68 71.90 90.40 146.34 96.28 130.32 87.08 73.10 83.76 108.16 66.20 125.58 1937 80.38 102.48 168.02 95.12 54.54 45.86 54.38 52.80 93.02 87.40 176.98 81.62 1938 218.00 152.76 107.20 125.70 128.22 66.48 33.92 24.24 66.32 116.40 103.76 93.92 1939 109.08 182.68 180.40 89.94 125.86 79.70 43.62 74.46 143.72 202.48 193.78 175.00 1940 152.68 141.68 178.68 140.34 160.62 74.52 225.00 99.40 66.98 98.02 147.80 152.74 1941 150.66 168.34 213.62 241.56 135.10 49.72 58.34 90.72 120.10 51.22 197.16 141.90 1942 203.16 118.40 181.66 104.26 127.36 129.22 47.58 66.04 83.16 88.70 59.98 84.36 1943 104.10 121.56 111.94 39.06 101.20 108.92 53.40 24.82 54.46 112.06 142.12 110.48 1944 101.22 122.58 102.86 56.26 29.06 70.14 18.50 33.56 49.52 116.84 102.28 64.84 1945 134.74 154.46 143.30 64.58 62.76 42.02 89.94 23.78 95.54 108.76 125.32 132.20 1946 238.32 202.00 207.30 98.62 165.60 36.72 79.60 42.46 86.88 176.30 161.36 180.52 1947 177.22 166.10 90.12 146.56 176.08 114.68 85.52 54.80 132.64 95.32 41.06 66.18 1948 135.56 209.86 174.38 163.42 68.78 40.10 103.50 41.00 101.30 123.18 162.66 52.06 1949 168.36 94.12 212.76 74.66 43.68 112.64 37.78 30.10 75.38 88.04 121.26 196.54 1950 216.90 155.54 186.82 82.52 116.14 132.52 45.22 15.70 85.64 116.92 145.06 179.28 1951 170.57 182.86 220.86 45.14 57.29 30.00 10.86 21.29 49.14 160.86 132.43 131.14 1952 130.86 238.00 142.00 62.71 119.29 83.57 43.29 33.29 92.14 143.43 157.00 67.17 1953 175.67 81.67 96.17 150.50 229.33 95.33 26.67 29.83 136.83 201.00 140.83 116.83 1954 238.33 171.17 106.00 168.67 157.67 101.00 90.83 30.50 121.00 237.17 32.67 133.83 1955 107.43 103.86 216.29 116.71 85.43 143.86 57.00 36.43 21.86 104.71 68.57 152.14 1956 253.86 117.14 166.14 196.Q0 81.00 80.00 137.57 50.57 57.86 197.71 42.00 96.57 1957 227.29 170.43 70.00 163.14 72.S7 92.29 98.57 79.71 163.29 144.14 116.00 169.00 1958 87.71 201.71 121.29 108.43 110.29 34.14 67.14 35.71 119.71 103.14 238.71 271.14 1959 165.00 202.25 122.38 180.50 106.75 69.12 66.88 62.50 75.62 147.25 119.00 172.75 1960 161.00 150.75 69.12 137.62 74.00 79.25 45.12 92.75 72.00 206.62 174.00 135.75 1961 119.94 168.84 200.06 187.41 97.54 92.20 42.90 33.26 104.53 158.90 223.21 136.17 1962 151.93 88.69 123.94 138.60 69.46 27.61 24.24 35.56 94.62 134.09 96.11 116.72 1963 190.62 142.11 144.19 100.90 74.45 69.43 28.49 20.49 89.21 95.40 182.79 125.65 1964 90.21 169.30 179.17 158.90 34.20 64.63 37.08 8.86 88.13 70.30 119.46 177.30 1965 168.50 203.S2 87.28 176.50 127.87 89.26 86.37 65.61 94.13 230.91 133.69 281.30 1966 190.33 167.94 202.56 124.82 70.97 85.63 41.43 40.38 49.02 160.73 107.02 158.90 1967 222.46 218.92 154.96 33.31 30.97 86.12 74.32 39.70 40.76 97.90 100.08 99.59 1968 213.94 105.80 75.46 72.35 46.92 43.U 46.58 87.56 72.12 164.73 82.72 165.61 1969 204.63 129.00 105.08 131.97 144.36 54.31 26.93 12.93 93.21 200.61 212.14 73.99 1970 143.73 138.04 148.81 71.71 95.28 99.08 39.77 48.63 159.74 130.76 93.90 162.02 1971 204.70 143.73 200.82 119.17 113.36 72.00 91.62 39.00 50.92 96.83 78.75 99.64 1972 155.91 185.27 128.45 128.17 80.77 98.54 57.08 106.38 87.58 138.33 257.40 145.25 1973 212.77 114.85 191.08 125.09 116.50 118.78 65.67 88.82 64.42 169.00 125.73 247.45 1974 183.45 166.18 143.17 71.83 131.00 51.67 33.91 86.10 32.27 148.18 119.73 155.Q0
1 1975 95.50 111.69 194.54 184.15 32.42 84.38 69.62 61.54 84.85 145.36 202.00 175.54 1976 202.21 109.54 128.20 131.73 119.27 35.87 26.14 64.29 101.00 178.23 107.75 1K4.29 1977 255.80 89.60 137.47 68.80 81.29 64.64 42.29 50.36 51.21 67.23 234.58 138.50 1978 127.00 103.80 73.43 32.67 67.91 33.21 63.50 50.50 99.50 140.00 158.29 144.67 1979 123.93 136.71 78.00 139.14 129.85 23.92 57.00 90.29 125.64 152.36 155.93 252.77 1980 149.57 122.00 126.00 95.23 134.36 58.14 33.60 68.73 117.40 134.00 179.07 154.27 1981 180.64 155.40 117.47 109.33 60.08 73.47 13.71 43.40 40.86 105.27 164.14 186.29 1982 72.29 195.50 145.83 80.13 79.33 165.21 57.62 94.00 99.79 151.29 340.93 209.29 1983 252.64 178.80 189.20 225.13 268.20 72.29 94.27 10.27 98.87 144.67 162.07 110.80 1984 203.33 100.27 196.20 110.53 104.20 52.71 11.93 60.13 92.27 103.93 222.4 182.53 1985 66.29 148.54 163.36 137.10 115.53 30.57 89.64 57.86 71.67 63.31 78.60 86.50 1986 141.23 151.08 237.69 193.62 174.07 44.09 37.92 61.00 88.93 125.21 175.07 170.82 1987 195.86 179.00 96.86 162.92 135.86 85.00 82.15 39.77 38.00 129.83 149.00 164.92 1988 139.54 104.17 128.38 145.92 84.50 28.42 8.83 12.23 54.50 119.15 97.83 163.55 1989 227.50 139.69 178.92 142.08 34.69 80.85 53.25 106.70 86.42 130.93 102.71 147.31 1990 220.21 111.50 163.00 256.08 138.43 87.31 72.82 84.64 142.17 142.85 136.69 153.31 1991 157.18 109.89 138.00 144.15 122.83 99.71 26.22 19.17 94.10 98.00 129.82 250.00 1992 118.78 279.00 186.83 207.00 174.80 54.12 42.00 100.38 -1.00 -1.00 -1.00 -1.00
2