Authors: Yizhe Xu (Data Analyst) & Drew Marticorena (Agronomic Modeling Scientist)
Assam tea growers are hoping the weather returns to normal in time for harvesting the region’s second flush of tea - which is considered to be the region's most distinctive tea and commands a premium price. Uncharacteristic rains have left the region moister than growers would like; they are hoping there won’t be any more rain (http://goo.gl/P1Y60w) before late May or early June.
The weather conditions for tea growers in Assam, the capital of India’s tea production, have been tough in recent years. This has been especially pronounced across the Brahmaputra valley where most of the productive tea gardens are located. According to a study by the Indian Institute of Technology (IIT) in Guwahati, over this time period rainstorms at this critical time of the year have become more common, sporadic, and intense contributing to problems in tea gardens such as waterlogging and soil erosion. This year, the first flush of tea, which generally occurs between April to mid-May, is likely to be only 34 million kg. For comparison, the harvest in 2015 was 44 million kg (http://goo.gl/xvQXZi).
For reference, this image shows where the Assam tea garden’s are primarily located (http://goo.gl/1zM0jp). This area corresponds to the upper right quadrant of the maps below
Figure 2 (below) shows how the rains over the past 2 months have far exceeded what would be expected based on historical norms. The areas where most Assam tea gardens are located, received on average in excess of 100-350 mm of more rain compared to what they historically have at this same time of the year.
Figure 2. Precipitation Difference from 10 Year Long Term Normal March - May, 2016 in India
Figure 3 below shows aWhere’s derived P/PET values for the same time period. P/PET is a measurement of of whether water is accumulating/departing the region more so than has occured historically (https://goo.gl/sq9Ocm). The figure below clearly shows that there has been a buildup of moisture in the region over the last two months, indicating that the excess rains have not been balanced by warmer weather thus likely causing saturated soil conditions and related problems. Tea farmers across the region are hoping this trend will reverse itself in time for them to capitalize on a prime second flush harvest.
Figure 3. Precipitation over Potential Evapotranspiration Difference from 10 Year Long Term Normal March - May, 2016 in India