Characterization of climatic parameters in the perspective of irrigated agriculture in Uttar Kannada district of Karnataka, India

Yallurkar Shridhar,Nandagiri Lakshman,Nayak Sandeep

doi:10.54302/mausam.v71i2.28

Abstract

A rainfall and potential evapotranspiration characteristics together determine the agro-meteorological regime of a region and influences decision concerning the magnitudes and timing of irrigation application. In the present study, historical rainfall and climate data pertaining to the study area, Uttar Kannada district, Karnataka, was analyzed with a view to characterizing irrigation water requirements. In addition to rainfall input, an important aspect of the water balance model is the crop evapotranspiration (ETcrop), which is the main factor in determining the irrigation schedule. ETcrop could be estimated by reference evapotranspiration (ET0) and crop coefficient. Atmospheric demand for water is represented by ‘potential evapotranspiration’ (PET) and calculated from climatic variables which is crucial for irrigation planning. It has been reported that the Penman-Monteith method gives more consistently correct ET0 estimates to other ET0 methods. While recognizing the importance of both rainfall and PET, an effective measure is known as the ‘Moisture Availability Index’ (MAI), which is computed as the ratio of 75% dependable rainfall and potential evapotranspiration. An MAI value of 1.00 indicates that dependable precipitation is equal to potential evapotranspiration. An MAI value of 0.33 or less for one month during the crop growing season is considered to be a signal of water deficit resulting reduction in crop yield. The findings of this study on MAI are used to decide the selection of the sowing period of crops so as to avoid water stress during the critical harvesting period.

Highlights

Climate is the long-term average of weather in a given location, fairly a long-time period of at least 10 years (Krishnaiah, 1998)
An IMD climate station located at Brahmavar (12° 59' N and 74° 54' E) provided historical records of daily average climatic variables required for estimation of daily mean Food and Agriculture Organization (FAO)-56 Penman-Monteith reference crop evapotranspiration (ET0)
The values of ETcrop selected for the design can be based on a probability of 75 or 80% or the highest ETcrop value out of 4 or 5-years. 50% ET0 values match with average ET0 values (Table 3)

Summary

Introduction

Climate is the long-term average of weather in a given location, fairly a long-time period of at least 10 years (Krishnaiah, 1998) It consists of average values of meteorological or oceanographic variables, such as air temperatures, precipitation, humidity, wind speed or ocean temperature, etc. If the climate changes over time, it can directly affect human activities by the impact on the crops that are grown, the supply of freshwater, or the mean sea level. It can affect natural ecosystems, causing deserts to expand, wildfires to become more prevalent, or (299). It has been reported that the Penman-Monteith method gives more consistently correct ET0 estimates compared to other ET0 methods (Nayak and Nandagiri, 2009)

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