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Predicting the Impacts of Land Use/Land Cover Change on Water and Sediment Yields : A Case of Marikina Sub-watershed, Philippines 원문보기

  • 저자

    ABINO AZYLEAH C

  • 학위수여기관

    공주대학교 대학원

  • 학위구분

    국내석사

  • 학과

    산림자원학과

  • 지도교수

    이영진

  • 발행년도

    2014

  • 총페이지

    ix, 127 p.

  • 키워드

    "Land Use/Land Cover" "Water Yield" "Sediment Yield" "Philippines" "Marikina";

  • 언어

    eng

  • 원문 URL

    http://www.riss.kr/link?id=T13532663&outLink=K  

  • 초록

    Over recent decades, the Laguna de Bay watershed has been subjected to environmental pressures which resulted in massive changes in the watershed and the lake itself, threatening both water quality and ecology. Its geographical location in the midst of the Philippines' center of urban and industrial development makes it vulnerable to degradation mainly due to anthropogenic interventions. In order to grasp the influence of man's utilization of the natural resource, which is often undocumented on the ground, the integrated remote sensing (RS) and geographic information system (GIS) approach was utilized in this study to classify land use/land cover (LULC), detect the changes based over time, and identify transition trends in the Marikina sub-watershed, Laguna de Bay watershed, Philippines. Landsat 5 Thematic Mapper (TM) imageries, acquired in 1999 and 2006, were pre-processed and classified using the supervised classification technique with maximum likelihood classifier (MLC) algorithm in RS and were used to develop maps of the sub-watershed and sub-subwatershed levels in a GIS platform. Analysis of LULC changes revealed that significant changes occurred in the sub-watershed between 1999 and 2006. Particularly, there was an increase of agricultural (11.76%) and orchard (4.52%) areas at the expense of brushland (16.56%) areas. Other LULCs such as water bodies, built-up, forest, and grassland remained almost unchanged. In the sub-subwatershed level, Tayabasan experienced minimal changes, whilst Tanay had major transitions. The overall accuracy and Kappa statistics were derived using the confusion matrix, which resulted in 96.15% and 95.49% for the 1999 image, and 93.82% and 92.73% for the 2006 image, respectively. LULC persistence and transition trends were analyzed using the Land Change Modeler, while Markov chain model was utilized to predict the LULC distribution in 2020 pertinent to the rates of change from 1999 to 2006. The understanding of LULC changes in relation to the driving factors provides essential information for LULC planning to allow sustainable management of the watershed. With this motivation, the RS and GIS were further integrated with the hydrological model, Soil and Water Assessment Tool (SWAT), to quantitatively predict the impacts of the LULC changes on water and sediment yields in the Wawa sub-subwatershed situated at the center of the Marikina sub-watershed. The simulation was based on the existing LULC, soil type, slope, time series of meteorological data (1991-2011), and hydrological data (1991-2002) recorded from monitoring stations located in close proximity to and within the study site. Relative to the scarcity of observed data, particularly on sediment accumulation, only the hydrological component recorded at the Wawa gauging station was calibrated (1994-1998) and validated (1999-2002) in this study. Based on the simulation, the SWAT model demonstrated satisfactory prediction of the water yield with Nash-Sutcliffe Efficiency (ENS) values of 0.54 and 0.81, coefficient of determination (R2) values of 0.74 and 0.88, percent bias (PBIAS) of 23.17 and 23.04, and root mean square observations standard deviation ration (RSR) of 0.64 and 0.41 during the model calibration and validation, respectively. The calibrated model was used to estimate the sediment yield, which provided an indicative result since the main driving force (i.e. streamflow) was calibrated. Simulation of the LULC scenarios using the SWAT model indicated a minimal increase of 0.15% in the water yield, and a decrease of 55.53% in the sediment yield if 50% of the brushland was to be converted to forest. Consequently, an increase of 0.26% in the water yield and a much significant decrease of 82.36% in the sediment yield could be obtained if the entire area covered with brushland was to be converted to forest. Furthermore, simulation of a 50% conversion of the brushland to agricultural land resulted in an increase in both water yield (0.59%) and sediment yield (109.39%). Likewise, a 100% conversion of brushland to agricultural land resulted in a greater increase in both water yield (0.98%) and sediment yield (174.50%). The simulation demonstrated acceptable results, thus, the model adequately predicted the streamflow and sediment coming from the Wawa sub-subwatershed which will eventually find its way to the lake. The establishment of a state-of-the-art mathematical modeling system, particularly in data-scarce watershed like that of Laguna de Bay, will assist watershed decision-makers and local government units in the development of efficient integrated watershed management interventions that will eventually pave the way for replication and scale up in the management of other watersheds in the Philippines and other countries worldwide.


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