DROUGHTS IN PERUDROUGHTS IN PERU

December 2009

NATIONAL METEOROLOGY AND HYDROLOGY SERVICE

Ing. Constantino Alarcón

Since Peru is a double-nature country, mountanious and tropical, it ischaracterized by the presence ofmultiple micro climates, that are alteredby the occurrence of extreme hydrometeorological events such as heat waves, frosts, cold fronts, heavyrainfall, droughts, floods, causinginnumerable loss.

The presence of the Andes Mountains, together with other climate andoceanographic factors determine theexistence of three natural regions:•The coast that shows desert, arid andsemi-arid characteristics.•The mountain region, that shows a hilly relief with deep and narrow valleys. •The jungle which is mostly covered by tropical forest..

A typical phenomenon of theinterannual climate variability in Peru is the occurrence ofdroughts, that every certainperiods of time occur, mainlyaffecting the mountain region.

The General Directorate of Agrometeorology carries out theagrometeorological monitoring of the hydrographic basins at nationallevel, it is made using agrometeorological indices and parameters, based on meteorological and phenological records. One of the mainactivities of this monitoring is to determine rainfall deficit and droughtsfor 10-day and monthly periods.

The indices used for this monitoring are:

• Humidity index (HI)

• Standardized precipitation index (SPI)

• Palmer drought severity index (PDSI)

AGROMETEOROLOGICAL DROUGHT

Precipitation index (Pi)

It shows the deficit and/or excess of humidity of the crops in theenvironment, place and considered period of time. The Pi is equal to therelation between precipitation and potential evapotranspiration. Pi=Pre/PET

Classification of Precipitation Index (Pi) adapted to rainfall regimen and soil in Peru(SENAMHI- DGA-2002).

DECADAL VARIATION OF HUMIDITY INDEX IN THE MOUNTAIN REGIONAGRICULTURAL CAMPAIGN 2009 – 2010

Decadal variation ofthe humidity index

Hi = p/ETo

SPI Ramis river basinAgricultural campaign 2009-2010

Monthly Behavior of the SPI in the Ramis river basin

Agricultural campaign 2008-2009 Agricultural campaing 2009-2010

Palmer Drought Severity Index (PDSI)

The methodology proposed by the National Agriculture Decision SupportSystem (NADSS) is used . Original and Self-Calibrating Palmer DroughtSeverity Index .

The General Directorate of Hydrology and Water Resources carries out the hydrologicalevaluation at national level, based on information from the hydrometeorological networkinstalled in the Peruvian territory. The analysis made focuses on the evaluation ofprecipitation behavior per pluviometric zone, with and emphasis on hydrological drought.

HYDROLOGICAL DROUGHT

METHOD

• The SPI method is used to define periods of drought and water excess.

• Estimation of the SPI at 3, 6, 12 y 24 month scale, using Fortran Spinderx3 program

• Obtain SPI averages for each time scale, per homogeneous zone

•Determine regional model stations

•Determination of the frequency of dry and humid events

•Identify maximum dry and maximum humid periods per decade

•Identify the intensity of dry and humid events per period.

•Identify maximum values and extreme variability of the SPI at time scales.

Behavior of the SPI per pluviometric region-Southern zone

Fuente: DGH-SENAMHI

Pluviometric regionalization – Southern zone

Spatial behavior of the SPI-1 per pluviometric region –Southern Zone

Severity Index (S.I.)

Defined as the function of the precipitation deficit, expressed in percentage, compared to the mean annual or seasonal long term rainfall and its durationin a determined region.

S.I.= (SUMY-SUMX)/SUMX SUMY<SUMXWhere: Y = monthly registered precipitation X = Normal monthly precipitationSI SUMY - SUMX if less than 0.0, there is meteorological drought

The severity index of meterological drought was classified intoseven classes: Extremely severe (higher than 0.8)Very severe (0.6 to 0.8)Severe (0.5 to 0.6)Very strong (0.4 to 0.5)Strong (0.35 to 0.4)Slight (0.2 to 0.35)

Absence (<0.2).

(Sancho y Cervera, et al., 1980).

METEOROLOGICAL DROUGHTSMETEOROLOGICAL DROUGHTS

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