Model hidrologi terdistribusi hujan – limpasan berbasis integrasi data radar cuaca dan observasi hujan permukaan di Das Ciliwung

Abstract

Rainfall data from C-Band Doppler Radar (CDR), surface rainfall station (AWS), and water level station (AWLR) from 14 Januari to 15 Februari 2010, were used in this research to obtain the relationship between radar reflectivity and rainfall intensity (rain rate) and to simulate the rainfall - runoff in Ciliwung River basin using distributed hydrologic simulation model. Data processing were focussed on observation data during the Intensive Observational Period (IOP) at the five sites, namely: Citeko, Bogor, Serpong, Serang, and Pramuka Island. The relationship between radar reflectivity and rainfall intensity establish the empirical constants a and b which was derived from Marshall – Palmer formula, the most suitable Z – R relation from the five rainfall stations is from Bogor site. The relationship obtained for Bogor site: Z = 0.046175 R2.814297 with correlation determination is 24,19%. River flow simulations were exercised based on Bogor site relationship for three rainfall intensity levels: light rainfall (1 – 5 mm/hour), heavy rainfall (10 – 20 mm/hour), and very heavy rainfall/extreme (>20 mm/hour), while flow simulation for medium rainfall (5 – 10 mm/jam) was not done because the results showed no much difference with light and heavy rainfall. River flow simulations during the period of 22 to 24 January 2010 for light rainfall condition (1 – 5 mm/hour) indicate the flow rate has no response because rainfall use almost all for evaporation, during 4 to 6 February 2010 for heavy rainfall condition (10 – 20 mm/hour) the highest flow rate is 844,002 m3/s, and the highest flow rate of 887,66 m3/s and 760,852 m3/s occurred on 9 to 11 February 2010, with two peak flows on February 10, 2010, for very heavy rainfall condition (> 20 mm/hour). Therefore the radar technology has good potential for near real time monitoring of extreme weather in Indonesia and prediction of related floods.