Watershed conservation prioritization using morphometric parameters applied with principal component analysis approach | JBES 2021
The present study analyzed and quantified the different morphometric aspects of the Upper Pulangi Watershed in Bukidnon, the Philippines using a 10-m spatial resolution digital elevation model. The study was carried out using geospatial techniques to quantify morphometric parameters relative to the tendency of the watershed to erosion threat to provide a basis and guidelines in prioritizing watersheds that need an immediate rehabilitation and conservation. The morphometric analysis applied with Principal Component Analysis was used in prioritizing watersheds. Principal Component Analysis is a dimension-reduction tool that can be used to reduce a large set of variables to a small set that still contains most of the information in the large set. It also decreases the dimensionality of the data set and identifies a new meaningful underlying variable. Results showed that the Nabalintungan sub-watershed with a compound ranking value (Cp = 4.17) was classified under very high priority followed by the Maapag sub-watershed with (Cp = 4.25) thus, implying more attention for conservation measures. The upper puling sub-watershed with (Cp = 6.75) was classified under very low priority followed by the Sawaga sub-watershed with (Cp = 6.00), signifying promising environmental conditions among the nine sub-watershed areas. The study provides significant information that is helpful to watershed managers and planners in coming up with an informed decisions and actions in relation to planning for watershed management, for soil and water conservation programs, and project implementation under limited resources.
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Materials and methods Watershed study Pulangi River is the longest river in Bukidnon, Philippines. It lies within the geographic coordinates of 7°01'60.00"N latitude and 124°29'59.99"E longitude as shown in Fig. 1. It has one reservoir type power plant, the Pulangi IV Hydroelectric Plant and watershed which provides for 25% of Mindanao's power needs. The reservoir and dam are also the main water source for the province of Bukidnon, both for drinking water and for irrigation through the National Irrigation Administration (Bukidnon, 2012). Pulangi River has a length of 320 kilometers and traverses through most of the cities and municipalities of Bukidnon from its source in Barangay Kalabugao, Impasugong, Bukidnon. Records from the Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) shows that rainy season in the province of Bukidnon where most of the watershed area is located occurs in June to November with mean annual precipitation of 1,703mm for the period 1981-2011 (INREMP, 2018). Watershed Delineation and Morphometric Analysis A 10-meter resolution DEM Synthetic Aperture Radar (SAR) digital elevation data of the National Mapping and Resource Information Authority (NAMRIA) of DENR acquired through the Geo-informatics for the Systematic Assessment of Flood Effects and Risk for Resilient Mindanao (Geo-SAFER Mindanao) was used to outline watershed boundary and stream network using Arc Hydro Tool of ArcGIS version 10.2.2. A threshold of 10, 60, 150, 50, 20, 20, 5, 30, and 10 hectares for Taganibong, Sawaga, Upper Pulangi, Manupali, Nabalintungan, Maapag, Panlibatuhan, Tigwa, and Malingun, respectively, were arbitrarily chosen in delineating perimeter and channels of the watersheds that are representative to the actual configuration on the ground. An open-source of Map Window GIS software was used to automatically delineate stream orders which follow the technique commonly applied in previous studies.