Effects of Climatic Factors and Land Use on Runoff, Sediment Load, and Pesticide Loading in Upland Microcatchments in Bukidnon, Philippines
Edward R. Lapong1, Victor B. Ella2, Manolo G. Villano2, Pepito M. Bato3
A study on the relationship and effects of different land use patterns on runoff (average, peak and volume), sediment yield, and pesticide loading on a watershed-scale was conducted on four selected upland microcatchments in Manupali Watershed at Lantapan, Bukidnon.
Results showed that the weekly average runoff (Qave), peak runoff (Qpeak), and runoff volume (Vq) per unit area of the catchments ranged from 0.0407 to 0.0512 lps/ha, 0.2531 to 0.3520 lps/ha, and 27.69 to 35.41 m3/ha, respectively. The ranged of mean weekly sediment yield was from 0.0089 to 0.0466 ton/ha while weekly pesticide loading ranged from 0.0031 to 0.0959 µg/s/ha. On the other hand, statistical analyses showed that on a per unit basis, runoff variables (Qave, Qpeak and Vq) were not significantly different among the catchments while sediment yield and pesticide loading were significantly different. Runoff, sediment yield, and pesticide loading were also directly proportional to the percentage cultivated area and inversely proportional to the percentage conserved area. This indicates that an increase in land use leads to the increase in runoff, soil erosion, and pesticide transport while increase in percentage conserved area lessens the detrimental effect of such variables.
Among the independent variables, rainfall was found to have the greatest contribution in runoff with partial R2 ranging from 0.206 (in Kiluya 2) to 0.830 (in Kalainigon 1); while average runoff had the greatest contribution on sediment yield with partial R2 ranging from 0.334 (in Kalainigon 1) to 0.692 (in Kalainigon 2). Moreover, the percentage cultivated area exhibited greater contribution on runoff, sediment yield, and pesticide loading than percentage conserved area. The prediction equations for the runoff, sediment yield, and pesticide loading were found highly acceptable with model R2 ranging from 0.818 to 0.964.
Keywords: land use pattern, sediment load, pesticide load, upland microcatchment
1Assistant Professor, Mindanao State University, General Santos City, Philippines; 2Associate Professors, Land and Water Resources Division, Institute of Agricultural Engineering, College of Engineering and Agro-industrial Technology, University of the Philippines Los Baños, 4031 College, Laguna, Philippines; 3Assistant Professor, Agricultural Machinery Division, Institute of Agricultural Engineering, College of Engineering and Agro-industrial Technology, University of the Philippines Los Baños, 4031 College, Laguna, Philippines.