Analyses of Rainfall and Soil Characteristics of Kuanria Canal Command for Water Resources Management

Abstract

Rainfall analyses are essential for proper management of water resources and crop planning even in canal command areas, especially under changing climate. Attempts have been made to collection of rainfall data and analyzing this for Daspalla region in Odisha, eastern India for prediction of monsoon and post-monsoon rainfall by using six different probability distribution functions, forecasting the probable date of onset and withdrawal of monsoon, occurrence of dry spells by using Markov chain model and finally crop planning for the region. Soil parameters viz. particle size distribution, soil pH, bulk density (BD), soil moisture content at field capacity and permanent wilting point, available water capacity (AWC), soil organic carbon storage were assessed; and pedotransfer functions (PTFs) were developed for saturated hydraulic conductivity (Ks), water retention at field capacity (FC, -33 kPa) and permanent wilting point (PWP, -1500 kPa) for different sites under major cropping system in the Kuanria canal command. It is revealed from this analysis that, for prediction of monsoon and post-monsoon rainfall, Log Pearson Type-III and Gumbel distribution, respectively have been found as the best fit probability distribution function. The earliest and delayed most week of onset of rainy season was 20th standard meteorological week (SMW) (14-20th May) and 25th SMW (18-24th June), respectively. Similarly, the earliest and delayed most week of withdrawal of rainy season is 39th SMW (24-30th September) and 47th SMW (19-25th November), respectively. The longest and shortest length of rainy season was 26 and 17 weeks, respectively. The chances of occurrence of dry spells are high from 1st – 22nd SMW and again 42nd SMW to the end of the year. The probability of weeks (23rd-40th SMW) remain wet (PW) varies between 62 to 100% for the region. The study on soil characteristics reveals that the soils are mainly composed of sand and clay with the clay contents ranging from 29.6 to 48.8% depending on the soil depth and cropping system.The BD, which increased with increase in soil depth, ranged from 1.44 to 1.72 Mg/m3 irrespective of different sites under rice-based cropping. The Ks decreased significantly with soil depth due to greater clay contents in lower layers; whereas water retention at FC, PWP, and AWC increased significantly with increase in soil depths and was higher under rice-sugarcane crop rotation compared to other cropping systems. Soil organic carbon (SOC) varied from 0.34 to 0.95%; it was the highest in the surface (0-15 cm) layer and then decreased down to the soil profile. SOC storage in the surface layer was higher in rice-sugarcane crop rotation systems (18.90-20.53 Mg/ha ) than other sites. The soil enzymes viz. dehydrogenase for surface soil (0-15 cm) for different cropping systems showed a range of 283.52 to 313.31 μg TPF/g soil per 24h with the coefficient of variation (CV) ranged from 8.36 to 9.22%. Soil phosphatase activity ranged from 280.58 to 480.28 μg phenol/g soil/h with the CV of 9.24 to 11.93% and soil urease activity ranged from 38.36 to 67.75 μg NH4+ -N/g soil/2h with CV of 9.73 to 11.08% irrespective of different sites and cropping systems. The PTFs were best represented as the power functions for prediction of Ks with clay content (%) as a predictor variable; whereas the PTFs for water retention at FC and PWP were better represented as the exponential functions using clay content. These are valid with significant values of R2 for every study site. The developed PTFs for different sites under major cropping systems would be very useful in soil and water management strategies for the study area or elsewhere having similar soil and cropping practices.