Effect of Vegetation Cover on Pre-Monsoonal Rainfall Trend over Ranchi Region, Jharkhand, India

Abstract

In the present study, trend of changing rainfall pattern and its correlation with vegetation cover during premonsoonal season were determined for Ranchi district of Jharkhand for the last 20 years. In the year 1998 the western side of the district received a good amount of rainfall but the scenario after that was observed quite alarming. In the next 20 years the western region received very low rainfall except in the year of 2005 and 2014. While year 2005 received a good rainfall in south-western region of the district. Eastern region having a good amount of green cover received plenty of rainfall consistently in last two decade. The central part is the most urbanized zone of the study area having least green cover. This zone has never received good rainfall in last two decade. On the contrary despite of having good vegetation over the north-western side; the region never received good rainfall. The NonParametric trend analysis for last 20 years shows an overall increase in rainfall with 0.141625 mm . While the analysis for last 117 years showed a significant positive trend in pre-monsoonal month of February, March, and April while a negative trend was observed in May. The maximum decrease in rainfall was found in the month of February (-0.1804803 mm ) and minimum (-0.0007663818 mm ) during the month of April. The trend of rainfall during month of May was found increasing (0.1296284 mm ).While the overall trend of rainfall during pre-monsoonal season (MarchMay) was found increasing (0.02156622 mm ). Rainfall variability pattern showed the maximum value of CV as 105.7%, whereas pre-monsoonal rainfall showed the minimum value of CV as 60.52%. High variation of CV indicated that the study are is vulnerable to droughts and floods. Disturbance in uniformity of distribution in rainfall pattern and extreme event cases over the district during the pre-monsoonal season in last two decade was observed.