Contrasting Climate Induced Variability of the Upper Citarum River Baseflow and Eventflow during Early 20th Century and Recent Decades

摘要

Recorded daily flow data of the upper Citarum River from 24 October 1918 through 23 October 1935 and from 24 October 1976 through 23 October 2015 from the Nanjung Station, located near the river’s outlet, is investigated for its baseflow and eventflow variabilities. Statistical analysis detects no trend in daily flow and baseflow during the study periods. However, baseflow variability during the latter period is higher than during the former period and is found to be related with the El Ni?o/Southern Oscillation (ENSO) events. By applying a novel approach of analysing decadal values of separated eventflow, an increasing value of the upper Citarum River basin runoff coefficient from 34 % to 41 % (up to a 20 % increase from the initial value) during a period between 1980 and 2009 (especially after 1990) is overlapping with massive land use and land cover changes during the period. Analysis on rainfall–baseflow variability shows that, after 1990, computed baseflow variability is increasingly more sensitive to rainfall variability.