Determination of Agricultural land drainage coefficient using rainfall probability analysis for Osmanabad district

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Date
2017-11-01
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Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani
Abstract
The present study was planned to evaluate drainage needs for the soils of Osmanabad region by determining the drainage coefficient of agricultural lands and development of spatial maps of drainage coefficient using GIS. For this investigation taluka-wise daily rainfall data of eight stations of district viz., Bhoom, Kallamb, Lohara, Omerga, Osmanabad, Paranda, Tuljapur and Washi of Osmanabad district for the period of 31 years (January 1986 to December 2016) were collected from Maharashtra Engineering Research Institute (MERI), Nashik. The rainfall data was arranged year wise in descending order. The observed values of maximum 1 to 5 consecutive maximum rainfall were computed by Weibull’s method. The expected values of maximum 1 to 5 consecutive maximum rainfall were estimated using various probability distributions such as Gumbel, Lognormal, Log Pearson Type III and Normal. Using the standard equations and adopting the prescribed procedure, 1 to 5 consecutive day’s maximum rainfall values were estimated. The observed and expected values of 1 to 5 consecutive maximum rainfalls were compared using Chi-square test and the best fit probability distribution was determined. Based on the expected consecutive day’s maximum rainfall estimated by the best fit probability distribution, basic infiltration rate of soil, recurrence period the drainage coefficients were estimated. In order to avoid tedious calculations and time the VNMKV_DCS software developed by VNMKV Parbhani was used for determination of drainage coefficient. The maps showing spatial distribution of drainage coefficient for Osmanabad were developed using Inverse Distance Weighing Technique of GIS It is observed that Gumbel, Normal and Log Pearson Type III distributions were best fitted to almost all stations of Osmanabad district whereas Log normal distribution was fitted best only for Osmanabad station for 5 consecutive day’s maximum rainfall values. Results showed that there are more chances of occurrence 1 day or 2 consecutive days maximum rainfall at all the stations except Bhoom where consecutive day’s maximum rainfall can be expected till 4 days. The estimated drainage coefficient for various stations in Osmanabad district indicated that the soils of Kallamb, Bhoom, Omerga, Osmanabad and Tuljapur talukas having basic infiltration rate between 1 to 4 mm h-1 necessarily have to be provided with agricultural land drainage system based on tolerance of different crops to water logging. On the other hand Lohara, Paranda and Washi talukas need land drainage for soils having basic infiltration rate of 1 to 3 mm hr-1. Kallamb, Bhoom, Tuljapur, Osmanabad and Omerga talukas have higher values of drainage coefficient whereas Lohara, Paranda and Washi have lesser chances of water stagnation. The maximum drainage coefficient is for Kallamb taluka at basic infiltration rate of 1 to 5 mm/hr with recurrence interval of 2, 5, 10 years and minimum drainage coefficient is for Lohara taluka for basic infiltration rate 1 to 3 mm/hr with recurrence interval of 2 and 5 years. The GIS maps showing spatial distribution of drainage coefficient for Osmanabad district can be used by the farmers or development agencies for planning and designing surface drainage systems in the regions based on the prevailing cropping pattern and the recurrence interval.
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