Time Step Issue in Unit Hydrograph for Improving Runoff Prediction in Small Catchments

Dyah Indriana Kusumastuti, Dwi Jokowinarno

University of Lampung.

DOI: 10.4236/jwarp.2012.48079                

Abstract

Unit hydrograph is a very practical tool in runoff prediction which has been used since decades ago and to date it remains useful. Unit hydrograph method is applied in Way Kuala Garuntang, an ungauged catchment in Lampung Province, Indonesia. To derive an observed unit hydrograph it requires rainfall and water level data with fine time scale which are obtained from automatic gauges. Observed unit hydrograph has an advantage that it is possible to derive it for various time steps including those with time step less than an hour. In order to get a more accurate unit hydrograph, it is necessary to derive a unit hydrograph with small time step for a small catchment such as those used in this study. The study area includes Way Kuala Garuntang and its tributaries, i.e. Way Simpur, Way Awi with areas are 60.52 km², 3.691 km², and 9.846 km² respectively. The results of this study highlight the importance of time step selection on unit hydrograph, which are shown to have a significant impact on the resulting unit hydrograph’s variables such as peak discharge and time to peak.

Keywords

Unit Hydrograph; Time Step; Peak Discharge; Time to Peak

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	M. Sivapalan, J. Schaake and J. Sapporo, “PUB Science and Implementation Plan V5,” 2003. http://pub.iwmi.org/UI/Images/PUB_Science_Plan_V_5.pdf
[2]	M. Sivapalan, K. Takeuchi, S. Franks, V. K. Gupta, H. Karambiri, V. Lakshmi, X. Liang, J. McDonnell, E. Mendiondo, E. P. O’Connell, T. Oki, J. W. Pomeroy, D. Schertzer, S. Uhlenbrook and E. Zehe, “IAHS Decade on Predictions in Ungauged Basins (PUB), 2003-2012: Shaping an Exciting Future for the Hydrologic Sciences,” Hydrological Sciences Journal, Vol. 48, No. 6, 2003, pp. 857-880. doi:10.1623/hysj.48.6.857.51421
[3]	D. I. Kusumastuti, “The Impact of Rainfall Variability and Hydrological Regimes on Flood Frequency,” Proceedings International Seminar on Water Related Risk Management, Jakarta, 15-17 July 2011, pp. 131-136.
[4]	J. Seibert and K. Beven, “Gauging the Ungauged Basin: How Many Discharge Measurements are Needed?” Hydrology and Earth System Sciences, Vol. 13, 2009, pp. 883-892. doi:10.5194/hess-13-883-2009
[5]	D. Duband, Ch. Oblend and J. Y. Rodriguez, “Unit Hydrograph Revisited: An Alternate Iterative Approach to UH and Effective Precipitation Identification,” Journal of Hydrology, Vol. 150, No. 1, 1993, pp. 115-149. doi:10.1016/0022-1694(93)90158-6
[6]	D. K. Natakusumah, D. Harlan and W. Hatmoko, “A General Procedure for Development of ITB-1 and ITB-2 Synthetic Unit Hydrograph Based on Mass Conservative Principle,” Proceedings International Seminar on Water Related Risk Management, Jakarta, 15-17 July 2011, pp. 114-122.
[7]	B. Sri Harto, “Study of the Unit Hydrograph Basic Characteristics of Rivers on the Island of Jawa for Flood Estimation,” Doctoral Thesis, Gadjah Mada University, Jakarta, 1985.
[8]	A. B. Safarina, “Reliability of Nakayasu Synthetic Unit Hydrograph in Various Watershed Area,” Proceedings International Seminar on Water Related Risk Management, Jakarta, 15-17 July 2011, pp. 123-130.
[9]	S. K. Jena and K. N. Tiwari, “Modeling Synthetic Unit Hydrograph Parameters with Geomorphologic Parameters of Watersheds,” Journal of Hydrology, Vol. 319, No. 1-4, 2006, pp. 1-14. doi:10.1016/j.jhydrol.2005.03.025