Analysis of Local Rainfall Characteristics as a Mitigation Strategy for Hydrometeorology Disaster in Rain-fed Reservoirs Area

摘要

The Gembong reservoir in Pati Regency, Java, Indonesia is a rain-fed reservoir, which experiences a depletion of it carrying capacity. The characteristic of local rainfall is one of the important factors in assessing the potential of hydrometeorology disasters in its area. Sedimentation in watersheds and reservoirs has covered water sources, so local rainfall determines the dynamics of water availability. This research is needed in the development of mitigation strategies. This article contains an analysis of the characteristics of local rainfall, and forecasting based on local daily rainfall data. This data was obtained from the rainfall gauge station in the Gembong reservoir area in 2007-2019. Variation coefficient, anomaly index, rainfall concentration index, and Mann-Kendall test were used to identify its characteristics. The time series model is used as modeling for forecasting. The results of empirical analysis show that rainfall volatility with irregular changes in high variability, meteorological drought in moderate category, rainfall trends follow fluctuating patterns and do not follow monotonic trend patterns but high concentrations of rainfall. Forecasting results with the Autoregressive Integrated Moving Average model for the wet months show an increasing in total rainfall by 17% in the next year. So, the potential for flooding is greater than the potential for drought. Based on the analysis of the local rainfall characteristics, then mitigation on flood is preferred.