CS(AR)-12/98-99 : Drought studies for Kalahandi Dist. In Orissa

Abstract

Agriculture is the main source of people's livelihood in Kalahandi district . Most of the crops are grown there under rainfed condition. The normal rainfall of the district is about 1378.2 mm, out of this about 90% is received during monsoon season. The long breaks of monsoon (dry spells) during the crop growing season and wide variations in the quantum of rainfall from year to year result in frequent failure of crops and consequently the entire district is drought prone.

The hydrological and agricultural aspects of drought have been studied for all the thirteen blocks in Kalahandi district. The 31 years rainfall data for all the blocks has been analysed in order to portend the drought frequency, duration, dates of onset and withdrawal of monsoon and critical dry spells. According to rainfall departure analysis the different parts of the district had experienced drought with an average frequency of 4-8 years. It was observed that the Koksara and Kalampur blocks were least affected. The probability distribution of annual rainfall revealed that the probability of occurrence of 75% of normal rainfall varies from 0. 72 to 0. 88. Also, the ranges of annual rainfall at 75% probability level varies from 800-900 at Langigarh to 2000-2100 at Th. Rampur. The period between 13th June to 19th September is found as the average length of monsoon in Kalahandi. On an average, the monsoon period incorporates two-to-three intervening critical dry spells per year. Rainfall records witnessed that the distribution of rainfall in time and space, and critical dry spells play major role in crop loss rather than the grass annual amount of rainfall. The crop evapotranspiration (ETcrop) has been computed using reference-crop evapotranspiration (ETp) and crop coefficients ( (kc) values. The water requirement for different crops namely paddy, maize, greengram (kharif), greengram (pre-rabi), blackgram, sesamum and minor millet have been estimated as 587 mm, 551 mm, 297 mm, 268 mm, 358 mm, 413 mm and 283 mm respectively. The irrigation requirement for the critical dry spells have been worked out to plan for alternate supplemental irrigation.

The district Kalahandi needs appropriate focus on alternative provisions for supplementary irrigation to the Kharif crop as well as for providing assured water supply at least for one irrigation to Rabi crop. This leads to the need for extending irrigation facilities by conserving the monsoon runoff in tanks/ponds/reservoirs to take care of the requirements in deficit-rainfall months.

The area has vast scope for development and exploitation of ground water. The ground water table records of pre & post monsoon season for a period of last 9 years indicate that the ground water table is almost static (i.e neither rising nor lowering). A planned development and exploitation of available ground water may not only contribute as a sustainable source of water for supplemental irrigation but also for tackling the situation during drought.