| Summary: | Abstract
The future water availability could be predicted using data generation analysis. Markov chain model (AR-2) was used to generate data for this research and the sintetic data was applied to plan the cropping pattern of an irrigation scheme.
Before using the data for analysis, it was necessary to test the consistency of the data using RAPS method (Rescaled Adjusted Partial Sums). The predicted rainfall and also runoff were compared to the observed one to validate the model using T test. The predicted runoff was used as the available water, meanwhile the predicted rainfall was used to find out the effective rainfall and these data were used to calculate the irrigation water requirement. The cropping pattern and the accurate planting schedule were based on the appropriate water balance where the available water was enough for the irrigation water requirement.
The results indicated that the runoff and rainfall were consistent and so for predicted data were significant. Based on the water balance, it was known that the appropriate cropping pattern of Papah Irrigation Scheme was by applying the grouping system. For the first growing period, the land cultivation was started at 16 November 1999 for the first group (Kongklangan Manunggal) and 1 December 1999 for the second group (Cangkring Mulyo). For the second growing period, the area of paddy land was decreased by planting the upland crops. The results indicated that for the second growing period at Kongklangan Manunggal the area of paddy was 176 ha, corn 290 ha and sugarcane 10 ha, meanwhile for Cangkring Mulyo it was 159 ha for paddy, 290 ha for corn, and 58 ha for sugarcane. The irrigation channel of Kongklangan Manunggal was better to dry for the first half-monthly of August, meanwhile for Cangkring Mulyo was second half-monthly of August.
Keywords: available runoff- irrigation water requirement - cropping pattern - planting schedule
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