TIME SERIES CHARACTERISTIC ANALYSIS OF RAINFALL, LAND USE AND FLOOD DISCHARGE BASED ON ARIMA BOX-JENKINS MODEL
Abstract: Indonesia located in
tropic area consists of wet season and dry season. However, in last few years,
in river discharge in dry season is very little, but in contrary, in wet
season, frequency of flood increases with sharp peak and increasingly great
water elevation. The increased flood discharge may occur due to change in land
use or change in rainfall characteristic. Both matters should get clarity.
Therefore, a research should be done to analyze rainfall characteristic, land
use and flood discharge in some watershed area (DAS) quantitatively from time
series data.
The research was conducted in DAS Gintung in Parakankidang, DAS Gung in
Danawarih, DAS Rambut in Cipero, DAS Kemiri in Sidapurna and DAS Comal in
Nambo, located in Tegal Regency and Pemalang Regency in Central Java Province.
This research activity consisted of three main steps: input, DAS system and
output. Input is DAS determination and selection and searching secondary data.
DAS system is early secondary data processing consisting of rainfall analysis,
HSS GAMA I parameter, land type analysis and DAS land use. Output is final
processing step that consisting of calculation of Tadashi Tanimoto, USSCS
effective rainfall, flood discharge, ARIMA analysis, result analysis and
conclusion. Analytical calculation of ARIMA Box-Jenkins time series used
software Number Cruncher Statistical Systems and Power Analysis Sample Size
(NCSS-PASS) version 2000, which result in time series characteristic in form of
time series pattern, mean square errors (MSE), root mean square ( RMS),
autocorrelation of residual and trend.
Result of this research indicates that composite CN and flood discharge
is proportional that means when composite CN trend increase then flood
discharge trend also increase and vice versa. Meanwhile, decrease of rainfall
trend is not always followed with decrease in flood discharge trend. The main
cause of flood discharge characteristic is DAS management characteristic, not
change in rainfall characteristic.
Author: Abror
Journal Code: jptsipilgg140038
