Andean snowpack and streamflow variations in recent and Andean snowpack and streamflow variations in recent and historic times in central Chile and central-western Argentinahistoric times in central Chile and central-western Argentina

Mariano MasiokasMariano MasiokasRicardo VillalbaRicardo VillalbaBrian LuckmanBrian LuckmanElma MontañaElma MontañaDuncan ChristieDuncan ChristieCarlos Le QuesneCarlos Le QuesneErnesto BetmanErnesto BetmanSteven MaugetSteven Mauget

Santiago, Chile

Mendoza, Argentina

• The winter snowpack in the Andes between 30° and 37°S is arguably the single most important natural resource in semi-arid central Chile and central-western Argentina

• Andean snowpack is the primary water supply and main source of surface runoff

• Over 10 million people depend on the mountain meltwater for domestic consumption, irrigation, industries, hydroelectric generation and aquifer recharge

IntroductionIntroduction

We developed regional We developed regional snowpack and streamflow snowpack and streamflow records using the longest records using the longest and most complete seriesand most complete series

Comparison between regional snowpack and streamflow seriesComparison between regional snowpack and streamflow series

Correlation of snowpack vs. discharges Jul-Jun = Correlation of snowpack vs. discharges Jul-Jun = 0.9330.933; discharges Nov-Feb = ; discharges Nov-Feb = 0.9490.949

Wettest

1982 246.6%

1987 225.1%

1972 199.6%

1953 194.2%

2005 189.3%

Driest

1968 5.4%

1998 24.3%

2004 25.8%

1985 28.1%

1996 29.0%

List of extreme years (5 driest and wettest years) in List of extreme years (5 driest and wettest years) in the central Andes of Chile and Argentina, 1951-2009the central Andes of Chile and Argentina, 1951-2009

Ranking

1

2

3

4

5

(all expressed as percentages of the 1961-2004 mean)

Records from both sides Records from both sides of the Andes show of the Andes show striking similaritiesstriking similarities

El Niño events are El Niño events are generally associated with generally associated with wet years; La Niña years wet years; La Niña years usually result in dry yearsusually result in dry years

Correlations between regional snowpack record and mid-winter (Jun-Sep) Sea Surface Temperatures and Sea Level Pressures

Field correlation maps corroborate the strong ENSO-related Field correlation maps corroborate the strong ENSO-related influence on the inter-annual hydrologic variability of this regioninfluence on the inter-annual hydrologic variability of this region

SST SLP

Average 500-hPa geopotential height anomalies for the 10 snowiest and driest years (1951-2005)

10 snowiest10 snowiestyearsyears

10 driest10 driestyearsyears

Snowpack variations are also influenced by conditions in the Snowpack variations are also influenced by conditions in the Amundsen-Bellingshausen SeasAmundsen-Bellingshausen Seas

Analyses of the main temporal features in the regional Jul-Analyses of the main temporal features in the regional Jul-Jun streamflow record showed:Jun streamflow record showed:

1.1. Non-significant linear trend, strong year-to-year fluctuationsNon-significant linear trend, strong year-to-year fluctuations

2.2. Two significant regime shifts in 1945 (-31%) and in 1977 (+28%)Two significant regime shifts in 1945 (-31%) and in 1977 (+28%)

Relative magnitude and statistical significance of 5-20 yr moving Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow recordwindows in the regional mean annual streamflow record

5-year moving windows

Relative magnitude and statistical significance of 5-20 yr moving Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow recordwindows in the regional mean annual streamflow record

10-year moving windows

Relative magnitude and statistical significance of 5-20 yr moving Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow recordwindows in the regional mean annual streamflow record

15-year moving windows

Relative magnitude and statistical significance of 5-20 yr moving Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow recordwindows in the regional mean annual streamflow record

20-year moving windows

Driest and wettest periods on recordDriest and wettest periods on record

1.1. Driest period on record: 1954-71 (p<0.01); 2Driest period on record: 1954-71 (p<0.01); 2ndnd driest: 1945-52 driest: 1945-52

2.2. Wettest period on record: 1977-87 (p<0.05); 2Wettest period on record: 1977-87 (p<0.05); 2ndnd wettest: 1914-22 wettest: 1914-22

Statistically significant Statistically significant regime shifts in 1945 and regime shifts in 1945 and 1977 coincide almost 1977 coincide almost exactly with well-known exactly with well-known shifts in the Pacific shifts in the Pacific Decadal Oscillation (PDO)Decadal Oscillation (PDO)

PDO influencing the low PDO influencing the low frequency modes of frequency modes of hydroclimatic variability hydroclimatic variability in the study area?in the study area?

Extended wet periods Extended wet periods coincide with “warm” coincide with “warm” phases of the PDO, dry phases of the PDO, dry period coincide with “cool” period coincide with “cool” phase of PDOphase of PDO

It is possible to reconstruct winter snow accumulation using It is possible to reconstruct winter snow accumulation using complementary information from different “proxies”complementary information from different “proxies”

Central Chile rainfall and precipitation-Central Chile rainfall and precipitation-sensitive tree-ring width series show strong sensitive tree-ring width series show strong similarities with the regional snowpack seriessimilarities with the regional snowpack series

These proxy series allow inferring snowpack changes over These proxy series allow inferring snowpack changes over the past two to eight centuriesthe past two to eight centuries

Reconstructing Andean snowpack offers the opportunity of Reconstructing Andean snowpack offers the opportunity of assessing the patterns of recent decades in a long term contextassessing the patterns of recent decades in a long term context

since AD 1866since AD 1866

since AD 1150since AD 1150

• Integration of Chilean and Argentinean hydrological data provided reliable, regionally representative records

• Regional snowpack and annual streamflow records show striking similarities that highlight the strong common hydrologic signal in this region and the good quality of the original data

• Two significant regime shifts in 1945 (-) and 1977 (+) were identified that mark the transition between three well defined low frequency modes of variability.

• In addition to ENSO, PDO may be influencing decadal hydrological patterns in this region

Conclusions IConclusions I

- Good quality, multi-centennial, annually-resolved snowpack reconstructions are possible at these latitudes

- These quantitative reconstructions provide important information on past hydroclimatic variations in the southern Andes

- Paleoclimate research- Water management- Climate modeling

- Extended hydrologic information also help to understand current conditions in a long term context and provide a range of possible scenarios for the future

- This type of hydro-climatic information may help understand the functioning of the coupled natural and social systems modulating the the majority of socio-economic activities of the oases in this region

Conclusions IIConclusions II

THANK YOU!THANK YOU!