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Spatio-temporal impacts of climate change over Cagayan River Basin, Philippines〇 Khagendra P. BHARAMBE, Sameh A. KANTOUSH, Tetsuya SUMI, Mohamed SABER, Orlando
BALDERAMA

Introduction

potential impacts to understand the spatio-temporal

Severe droughts and frequent heavy precipitation

changes. Hence, this research has been conceptualized

events are likely to increase because of climate change

to explore the spatial and temporal changes in climate

and a higher degree of fluctuation in precipitation andvariability

temperature (IPCC, 2007; Carter et al., 2007). Thelong-term historical and future climate data to identify

most critical impacts are affecting water resources,

the present and future potential climate change risk

which directly affect agricultural systems and foodover Cagayan River Basin in the Philippines.

andextreme

climateindicesusingsecurity. And the Cagayan River Basin (CRB) in thePhilippines (Figure 1) is the largest, covering a total

Methodology

land area of 27,493.49 km2, currently facing critical

The Spatio-temporal modeling by Sen's slope

issues of rapid climate variability and frequentestimation using Mann Kendall's (MK) test was used

occurrences of hydroclimatic extremes events liketo analyze the magnitude of change and variability inflood, drought, etc. These are the most significant

climate variables and extreme climate indices, using

constraints that somehow prevent further development

thein CRB, and the situation may worsen in thehigh-resolution CMIP6 simulation data produced byupcoming period due to the rapid climate variability

MRI-AGCM3.2S over historical (1951-2014) andand changes over CRB.

future (2015-2099) period (Mizuta et al., 2019). Thismeteorologicalvariables

obtainedfromstudy estimated the relative changes for extreme
climate indices like CDD, CWD, R95p, TX90p, andTN90p (Table 1) to determine the magnitude ofchange and level of climate risk over each sub-basin
and time, considering the most relevant for agriculture
and water resource protection point of view.
Table 1: Indices for characterizing temperature andrainfall extremes (Source: ETCCDI)
Precipitation Indices
IndicesFigure 1: Location map of study area.

Definition

UnitIndices Definition

Unit

PRCPTOT Total Annual Precipitation

mm/yrTXMean daily max.
temperature
Mean daily min.
temperature

0C0C

Amount of hot days:
Percentage of days
when TX>90th
percentile
Amount of warm
nights: Percentage ofdays when TN>90th
percentile

%

CDD

CWD

Therefore, there is a strong need for an integrated
approach to study climate change, by combining
aspects of climate projections and prediction of future

Temperature Indices

R95p

Consecutive Dry Days: Numberof Spell of five consecutive days
with rainfall <1mm per year
Consecutive Wet Days: Numberof Spell of five consecutive wet
per year with rainfall <1mmdaysTNdays

TX90p

Very wet days rainfall: Annual
total rainfall when daily rainfall
exceeds the 95th percentile ofwet days

Mm/yr TN90p%

Results

guidance to the disaster risk reduction authority for

The estimated relative changes of climate variables,

taking an appropriate decision for executing theand extreme climate indices over space and time werefeasible adaptation strategies.

illustrated in Figure 2 and Figure 3.
ConclusionA

consistentincrease

intemperature

andprecipitation is likely to bring prolonged dry spells
leading to droughts and wet spells leading to intensive
floods at the Cagayan River Basin. However, theclimate change risk will not be uniform; somesub-basins will experience higher vulnerability thanthe other sub-basins, significantly accelerating thedifferentchangesofhydroclimatic

extremes.

In the future, the intra-annual rainfall trend has been

Therefore, spatiotemporal modeling is crucial toincreasing with a higher fluctuation rate in minimum

determine the changes over space and time acrossand maximum annual rainfall. This will result inriver

droughts in the sub-basins of Chico, Magat, andimplementation of adaptation strategies.

basinsandisusefulfor

theeffective

Cagayan Segment1 where precipitation has been
observed to decrease in the future, whereas floods are

Acknowledgment

expected in the sub-basins of Siffu-Mallig, Ganano,This research is funded by "Asia-Pacific Network for

and Addalam where precipitation has shown an

Global Change Research" (APN) under projectincreasing trend in future (Figure 2). Findings also

reference

revealed that the Addalam sub-basin would experience(Funder ID: https://doi.org/10.13039/100005536).

numberCRRP2020-09MYKantoushan increase in average annual rainfall and percentage
of consecutive dry days (CDD) in the future, which

Referencesindicates an increased risk of intense dry spells andCarter, T. R., et al. 2007. General guidelines on the use ofheavy precipitation events resulting in severe drought

scenario data for climate impact and adaptationand flood events (Figure 3).

assessment. Geneva: IPCCI, Task Group on Data andScenario Support for Impact and Climate Assessment.
Expert Team on Climate Change Detection and Indices(ETCCDI), https://www.wcrp-climate.org/etccdi
IPCC, 2007: Climate Change 2007: Synthesis Report.
Contribution of Working Groups I, II and III to the FourthAssessment Report of the IPCC
Mizuta, Ryo; Yoshimura, Hiromasa; Ose, Tomoaki;Hosaka, Masahiro; Yukimoto, Seiji (2019). MRI
MRI-AGCM3-2-S model output prepared for CMIP6Hence, these results would be an easy-to-use resource

HighResMIP-Version1. Earth System Grid Federation.

to tackle the higher-risk zone and able to provide

https://doi.org/10.22033/ESGF/CMIP6.1625