Design of deep open drains for sugarcane crop in the Ukai Right Bank canal command area using probability distribution Shrivastava P. K., Patel B. R. NARP, Navsari Agriculture University, Navsari -396 145, Gujarat. Abstract The study area, Ukai Right Bank canal command area is spread over Bharuch and Surat districts of Gujarat. Screening of annual rainfall data of Sisodara meteorological station was performed for absence of trend and stability of variance and mean. The time series revealed no major discrepancies and trend, and variance and mean were stable. Later since the probability of occurrence of 24 h maximum rainfall is of importance in drainage system design, this information was obtained by frequency analysis. The probability of exceedence of maximum rainfall events of each year was found by using Weibull's empirical method and three other analytical methods viz. Gumbel's extreme value distribution, Log Pearson distribution, and Log normal distribution. For testing the agreement between the observed data and estimated data, the Chi -square test for goodness of fit was carried out to select the best fit distribution. Gumbel's extreme value distribution gave the best fit for annual maximum rainfall data. The curve number method was used to estimate the direct runoff from the rainfall data. To cater the agronomic criteria for sugarcane crop and on the basis of general size and shape of land holdings in the area, the suggested spacing between drains and depth should be 45 m and 1.0 m, respectively in heavy black soils for sugarcane crop. The bottom width may be 0.30 m with side slope of 1: 1 and longitudinal slope shpuld follow the ground slope but in lands having flat topography it may be 0.001 m per m. The suggested design has many times more capacity than the theoretical discharges calculated. The estimated cost of the drainage system was worked out to be Rs. 10,000 ha−1. However, on farmers' field it was found reduced to Rs. 5000 ha−1, when the farmer used his own farm labour. Top Keywords Drainage design, Rainfall analysis, Rainfall distribution, Sub-surface drainage. Top |