No abstract

Accurate assessment of the rainfall characteristics of a river basin is essential for its proper management. In this study, we examine long-term trends in annual rainfall, the regional climate cycle and the frequency and magnitude of extreme rainfall events in the Bumbu watershed of Morobe Province, Papua New Guinea. Data for the study are derived from 36 years of rainfall measurement from the rain gauge station at the Papua New Guinea University of Technology (PNGUOT), located in the municipality of Lae within the Bumbu watershed. The overall trend of the rainfall is studied using multiple analytical techniques, linear regression, Mann-Kendall rank statistics, Sen's Slope and Innovative Trend Analysis. Given the large amount of variance in the raw data attributable to cyclic phenomena, raw data are prepared for trend analysis using spectral analysis to remove cyclic components. The spectral analysis also assists assessment of the regional climatic cycles. Changes in the frequency and magnitude of extreme rainfall events over the last 50 years are tested using Chi-Square analysis. The four analyses of trend revealed that there had been a statistically significant decrease in annual rainfall (20 to 24%) in the study area over the years 1972-2007. Spectral analysis of regional climatic variation established that the area exhibits a unique climatic cycle compared to its regional neighbors. The study also concluded that there has been a significant increase in the frequency of extreme rainfall events in the region, providing valuable information for flood emergency response planning. KeywordsRainfall • Papua New Guinea • ENSO cycles • Spectral analysis • Trend analysis • Extreme rainfall events Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.