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EXPLORING CLIMATE CHANGE EFFECTS ON WATERSHED SEDIMENT YIELD 
AND LAND COVER-BASED MITIGATION MEASURES USING SWAT MODEL, RS 
AND GIS: CASE OF CAGAYAN RIVER BASIN, PHILIPPINES 
Jeark A. Principe 
Graduate student, Department of Geodetic Engineering, University of the Philippines Diliman, 
Melchor Hall, College of Engineering, U.P. Diliman, Quezon City, Philippines; 
Tel: +63-02-9818500 loc. 3124; E-mail: jeark principe@yahoo.com 
KEY WORDS: Climate Change, Land Cover Change, SWAT model, RS, GIS 
ABSTRACT: 
The impact of climate change in the Philippines was examined in the country's largest basin—the Cagayan River Basin—by 
predicting its sediment yield for a long period of time. This was done by integrating the Soil and Water Assessment Tool (SWAT) 
model, Remote Sensing (RS) and Geographic Information System (GIS). A set of Landsat imageries were processed to include an 
atmospheric correction and a filling procedure for cloud and cloud-shadow infested pixels was used to maximize each downloaded 
scene for a subsequent land cover classification using Maximum Likelihood classifier. The Shuttle Radar Topography Mission 
(SRTM)-DEM was used for the digital elevation model (DEM) requirement of the model while ArcGISTM provided the platform for 
the ArcSWAT extension, for storing data and displaying spatial data. The impact of climate change was assessed by varying air 
surface temperature and amount of precipitation as predicted in the Intergovernmental Panel on Climate Change (IPCC) scenarios. 
A Nash-Sutcliff efficiency (NSE) > 0.4 and coefficient of determination (R2) > 0.5 for both the calibration and validation of the 
model showed that SWAT model can realistically simulate the hydrological processes in the study area. The model was then utilized 
for land cover change and climate change analyses and their influence on sediment yield. Results showed a significant relationship 
exists among the changes in the climate regime, land cover distributions and sediment yield. Finally, the study suggested land cover 
distribution that can potentially mitigate the serious negative effects of climate change to a regional watershed's sediment yield. 
1. INTRODUCTION 
The Philippines cannot escape the negative impacts of climate 
change. The country was tagged as a climate hotspot and 
vulnerable to some of the worst manifestations of climate 
change (Jabines & Inventor, 2007). As with other developing 
countries in Asia, the Philippines is highly subject to natural 
hazards as exemplified by the 2006 landslide and the havoc 
wreaked by typhoons Frank, Ondoy and Pedring in 2008, 2009 
and 2011 respectively. The country is also prone to various 
hydro-meteorological and geological hazards because of its 
geographic and geologic setting, threatening the country by the 
passage of tropical cyclones and occurrences of extreme or 
prolonged rainfall, strong earthquakes, volcanic eruptions and 
tsunamis and these hazards will be aggravated and the impact 
of geological events can be worsened by global warming 
(Solidum, 2011). Furthermore, climate change threatens the 
country by increasing the intensity and frequency of storms and 
droughts. CAD-PAGASA (2004) reported that the country is 
likely to be adversely affected by climate change since its 
economy is heavily dependent on agriculture and natural 
resources. Given these scenarios, it is timely that research 
pertaining to the impact of climate change to the country be 
quantitatively assessed. 
The study particularly explored the influence of land cover on 
sediment yield and suggested land cover conversions that can 
potentially mitigate the serious negative effects of climate 
change to the sediment yield of a large basin. The study is 
significant for a proposed watershed management in the 
country that will incorporate the possible impacts of climate 
change on sediment yield. 
2. STUDY AREA 
2.1. Geographical and Political boundaries 
The Cagayan River Basin (CRB) is the largest river basin in the 
Philippines. It is located in the northeastern portion of the 
island of Luzon and between 15°52’N-18%23°N latitudes and 
120°51°E-122°19’E longitudes (Figure 1). CRB has a drainage 
area of approximately 27,700 km’ covering the provinces of 
Regions 2, Cordillera Autonomous Region (CAR) and small 
parts of Region 3 (RBCO, 2007). 
2.2. Climate, Topography and Physiography 
CRB falls under Type III climate zone which is characterized 
by no pronounced maximum rain period and a short dry period 
(BRS-DPWH, 2002). According to PAGASA (2009), the 
northern part of the basin has an average annual rainfall of 
1,000 mm and 3,000 mm in the southern mountains. The mean 
annual temperature and average relative humidity are 23.6- 
26.0°C and 75-85%, respectively (DPWH & JICA, 2001). 
The area is relatively flat plain but is broken by low rising 
ridges and hummocks in some places (BRS-DPWH, 2002). 
Approximately 50% of the area is relatively flat with slope that 
varies from 0-17%. About 33% of the area has slopes between 
17-42% while the rest are with slopes greater than 42% based 
on a slope map derived from the SRTM-DEM. It is also 
surrounded by three mountain ranges: Sierra Madre, Cordillera 
Central and Caraballo-Maparang in the east, west and south. 
respectively (DPWH & JICA, 2001).