The trend of rainfall, discharge, and land cover of Kaligarang Watershed, Central Java, Indonesia

Abstract

Rainfall is one of the factors affecting stream water discharge and flooding. The high amount and intensity of rainfall frequently cause downstream flooding. In this regard, a study with the purpose to know the trend of rainfall, discharge, and land cover of Kaligarang or Garang Watershed was conducted. Kaligarang Watershed is located in Central Java, Indonesia. Secondary data were collected from published papers and related institutions. Land cover data were derived from Landsat images. A regression analysis was conducted to observe the trend of maximum rainfall and peak discharge. The simple regression was conducted between the time and maximum rainfall or peak discharge within the corresponding year. The results showed that maximum daily rainfall 1972-1980 tended to increase. Maximum daily rainfall from 1981 to 1990 slightly decrease, however, extreme rainfall occurred in 1990. Compared to the data 1972-1980, the maximum rainfall in the period of 1991-2010 was lower. The peak discharge of the period 1961-1970 tended to decrease, conversely, starting 1971 to 2017, the peak discharge tended to increase. The reduction of the dryland forest and plantation forest were observed from every decade starting from 1990, in contrast, the settlement increased 138% from 1990 to 2020.