Environment and Ecology Research 6(3): 178-186, 2018 http://www.hrpub.org DOI: 10.13189/eer.2018.060305 Probability Distribution Fitting of Rainfall Patterns in Philippine Regions for Effective Risk Management Ma. Dely P. Esberto Doctor of Engineering (Civil Engineering) Program, School of Graduate Studies, College of Engineering, Mindanao State University, Iligan Institute of Technology, Iligan, Philippines Copyright©2018 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract This study aims to determine the best fit frequency distribution of rainfall patterns for event forecasting in order to address potential disasters. The monthly rainfall data were taken from the PAGASA which are analyzed using Chi-Square and K-S goodness-of-fit tests. Rainfall data for the past 26-30 years was used to determine the distribution pattern fitted into more than 60 Probability Distribution Functions (PDF). The best fitted PDF both in Kolmogorov-Smirnov and in Chi-square tests were used in statistical inferences. Findings showed that each site has specific theoretical probability distribution functions to infer rainfall events. Varying levels of rainfall events were measured using the CDF. Consequently, the statistical inferences found in this study are important for designing optimum flood control facilities. Moreover, it is also contributory for the effective management of irrigation system of the National Irrigation Administration for a more efficient water supply to the agricultural sector. Keywords Distribution Fitting, Rainfall 1. Introduction Rainfall is the most important environmental factor contributory to agricultural activities of the Filipino people across regions in the country. Irrigation supply depends much on the availability of water where the volume distribution is based on the available water resources such as spring, river, and rainfall. Water supply through irrigation is an important strategy in alleviating the current food crisis. However, rain-fed agriculture is still the domi- nant practice in most upland areas. Soil moisture manage- ment in some areas of the country is faced with limited and unreliable rainfall and high variability in rainfall pattern. Collection and measurement of hydrological data proved difficult on the part of hydrologists due to limited data with some gaps in the series. It is vital to study the variability of rainfall pattern to address climate changes which resulted to occurrences of floods and droughts in several regions. Dry and wet seasons can be felt simultaneously in the country. When parts in Luzon have been flooded, most areas in Mindanao were experiencing dry season and vice versa as claimed by South Travels [1]. It can be observed that the Philippines have been devastated by these famines for quite a time now. We have been receiving news of flash flood events in various parts of the country, the latest of which occurred in Northern Mindanao, while other areas (Luzon for instance) are experiencing limited rainfall. Similar variations can also be noted in other parts of the globe as reported by JPL TRMM Team [2] and Melville [3]. Such variation can also be noted within adjacent regions or provinces where dry season is widespread in most regions, but some geographical areas are severely hit by excessive monsoon rain leading to flash floods. One example of the incident earlier cited was the December 2010 storm that swept the cities of Iligan and Cagayan de Oro into a severe state of calamity. In contrast, most areas in other regions such as Region XII did not experience heavy rainfall during the time that the storm smashed the two cities. Other related studies which conducted rainfall observations in their areas of jurisdiction showed similar disparity in the occurrences of rainfall distribution. Precipitation anomalies were also described in the articles of Hillis [4], the Bureau of Meteorology [5] and Kumar [6]. However, most of those researches used tabular and graph presentations to describe the rainfall intensities and distribution frequencies. Such information does not tell us the extent of erratic rainfall, when extreme seasonal anomalies are apparent not only in the Philippines but in the entire globe. A review on the published papers of Tilahun [7] and Persson [8] revealed that a specific probability distribution can best describe the rainfall patterns for prediction purposes. It is in this light that the researcher conducted a study of rainfall patterns in some selected regions in Mindanao with the anticipation that the rainfall variability of the selected study sites will fit to a