Istiarto Istiarto
Department of Civil and Environmental Engineering, Universitas Gadjah Mada, Yogyakarta, INDONESIA

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Cost Comparison of Drainage Channel Construction Considering Uncertainty of Rainfall Distribution Intan Supraba; Istiarto Istiarto; Radianta Triatmadja
Journal of the Civil Engineering Forum Vol. 5 No. 1 (January 2019)
Publisher : Department of Civil and Environmental Engineering, Faculty of Engineering, UGM

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1061.969 KB) | DOI: 10.22146/jcef.39121

Abstract

Rainfall data is the main parameter to design drainage channel. The accuracy of rainfall data determines the accuracy of peak discharge estimation that is used for designing the drainage channel for flood mitigation purpose. The previous study presented that uncertainty of peak discharge is associated with the uncertainty of rainfall distribution and uncertainty of water holding capacity. The main purpose of this study is for understanding the sensitivity of rainfall data by comparing the estimated cost to construct drainage channel based on different values of peak discharges using two different rainfall data set which one rainfall data is created by considering 10% uncertainty of rainfall distribution. This study area is located on Plampang, Sumbawa Besar, West Nusa Tenggara. Results showed that the total cost to construct drainage channel increased by 15% if considering 10% uncertainty of rainfall.
Acceptance Analysis of PDAM Sleman’s Water Tariff, Based on Revenue and Willingness to Pay Projection Made Widiadnyana Wardiha; Istiarto Istiarto; Fatchan Nurrochmad
Journal of the Civil Engineering Forum Vol. 7 No. 2 (May 2021)
Publisher : Department of Civil and Environmental Engineering, Faculty of Engineering, UGM

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jcef.60536

Abstract

In Sleman, the Regional Water Company (PDAM) provides clean water to the community and charges a tariff for each cubic meter of water sold to customers. According to the Minister of Home Affairs Regulation No. 71 of 2016 states, PDAM tariffs requiring an annual review in November. The most recent tariff was set by PDAM Sleman in 2016, therefore, a recalculation is required. In addition, there is a need to analyze the tariff acceptance from the service provider, and service recipient’s point of view. In this study, the calculation tariff method utilized a formula based on the Minister of Home Affairs Regulation No. 71 of 2016. Meanwhile, the acceptance analysis from profit point of view conducted by calculating the projection of water sales revenue, profit to earning assets ratio, and customer willingness to pay (WTP). Furthermore, revenue projections were obtained by multiplying tariffs with the water sold volume, while the WTP projection is obtained using the inflation method, based on the PDAM Sleman customers’ wTP, from the 2007’s research. PDAM Sleman tariffs based on calculations resulted in low tariffs of IDR3727.48, basic tariffs of IDR4659.36, and full rate of IDR9460.17. Based on the WTP analysis, the tariffs are feasible from the service recipient’s (PDAM customers) point of view, because this is affordable by customers, for the average water consumption. However, from the service provider’s (PDAM Sleman) point of view, the tariffs are not feasible a 0.31% profit ratio is much lower, compared to the 10% profit ratio. Therefore, tariff adjustments are required to increase profits. These strategies include determining tariffs based on consumption blocks alone, without breaking down based on customer group categories and adjusting the second and third consumption blocks’ rate.