Developing the swamp planting calendar based on the hydrological model application

Abstract

Determining the beginning of rice planting period is an important cultivation strategy in Indonesia, influenced by climate anomalies. On swamps, the beginning of planting period depends on local rainfall patterns, upstream rainfall, discharge, and water level dynamics. This article presents hydrological model application in developing planting calendar for non-tidal swamp agricultural land. The research location was in Tanjung Alai Village, Padang, Ogan Komering Ilir, South Sumatra. This research analyzed multi-variable hydrological data during 1999-2000 period. River discharge was simulated using GR2M model, while land surface elevation dynamic was analyzed using water balance approach. Model parameters included rainfall, evapotranspiration, percolation, river water level, outflow, and inundation level. Results of this study showed the GR2M model calibration between the measured and the Ogan River discharge data had 65% similarity level. The water balance analysis result showed the flooded lands to occur during the decade periods of Jan I to May II, when Ogan River water elevation was between 6.21 and 10.43 m asl. Water balance simulation identified the optimum planting periods were between the decade of May III to July III, when Ogan River water elevation was between 6.73 and 8.83 m, and land water level ranged from 14.96 to 29.56 cm.