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The dynamic shifts in precipitation patterns across Punjab: Is it a tale of changing climate?

Punjab State of India, is located in the north-western region of India and renowned for its agricultural productivity, since the green revolution era.

The state heavily relies on water availability for its agricultural output. Nevertheless, in recent times, Punjab has experienced increased fluctuations in precipitation patterns. Several studies have been conducted in Punjab to investigate the fluctuations in precipitation and their impacts. This study provides a quick summary of all the major studies conducted to date, to understand the major reasons behind the dynamic shift in the precipitation pattern across Punjab.

The annual rainfall in Punjab, which used to be approximately 800 mm in the 1980s, has now decreased to around 650 mm (Chaba, 2021). A study conducted by Kumar et al. (2021) noted a significant reduction in rainfall activity over Punjab during the decades of 1991-2000 and 2000-2010. The decade of 2001-2010 was particularly dry, with a Rainfall Variability Index (RVI) of -1.19, while the subsequent decade of 2011-2020 was the wettest, with an RVI index of +1.09.

Punjab has been witnessing differences in rainfall amounts among its districts as well. Krishan et al. (2015) conducted a comprehensive analysis of rainfall trends in Punjab over a period of 102 years (1901-2002) using the modified Mann-Kendall (MK) test and Sen's slope. The results showed that there was an overall increase in annual and seasonal rainfall in most districts of Punjab, except for the winter season in certain districts such as Amritsar, Fatehgarh Sahib, Gurdaspur, Hoshiarpur, Jalandhar, Kapurthala, Ludhiana, Moga, Nawanshahr, Patiala, and Roopnagar.

However, the magnitude of the trend varied across districts, with Amritsar district experiencing the highest increase of 1.459 mm/year and Muktsar district the lowest increase of 0.824 mm/year, averaging at 1.164 mm/year across all districts. Moreover, the increase in rainfall was generally higher in the north-western districts and lower in the south-western districts, indicating that the variability of rainfall in Punjab is likely to increase in the future.

A similar finding was revealed by Punjab Agricultural University (PAU) also. The study analyzed rainfall data spanning 41 years, revealing significant variability in rainfall across different districts. The north-eastern parts of the region received rainfall ranging from 1,000 to 1,100 mm, while the south-western region experienced considerably lower rainfall, with amounts falling below 400 mm.

As time is progressing, an increasing level of unpredictability in climate and weather patterns is being observed. Specifically, during the monsoon season spanning from 1st June to 30th September 2022, Punjab received a total of 413.7 mm of rainfall, which is 6% lower than the average of 438.8 mm. Among the 22 districts in Punjab, 10 districts received average rainfall, 4 districts received above-average rainfall, 1 district received significantly higher than average rainfall, while 7 districts experienced below-average rainfall (Southwest monsoon report, 2022).

Likewise, the projected rainfall for the year 2023 is expected to be around 94% of the long-period average (LPA) of 868.6 mm, with an error margin of +/-5%. This decrease in rainfall is attributed to an increased likelihood of El-Nino, a climatic phenomenon known for bringing dry weather conditions (Hindustan Times 2023).

As Punjab is primarily an agricultural state, farmers are often the first to be affected by natural disasters. Unseasonal rains and hailstorms can cause significant losses for farmers. Recent untimely heavy rainfall in various parts of Punjab during the month of March 2023 has had a severe impact on the standing wheat crop, covering over 15 lakh hectares, which is more than 40% of the total area sown with this winter staple crop (Nibber, 2023).

For instance, the rainfall in March this year was 54.8 millimeters (mm), in contrast to only 0.8 mm during last year as recorded in the primary observatory of Punjab Agricultural University (Mohan, 2023). Over a period of six years (2015-2021), India experienced a loss of 35 million hectares of cropped area which also includes north-western states i.e Punjab and Haryana (Gupta, 2022).

The issues stemming from precipitation variability have far-reaching consequences, with climate change being a major contributing factor, whether through natural or anthropogenic means. Climate change has the potential to alter the frequency and intensity of precipitation events. For instance, as the Himalayas experience warming of 2.5°C, the melting of glaciers and loss of snow cover could pose a threat to the stability and reliability of northern India's glacier-fed rivers, such as the Indus and Brahmaputra, which have direct impacts on Punjab's water supply.

The effects of climate change are particularly evident in the Hindu Kush Himalayan region, including the Indus River basin, where rapid deglaciation is taking place, leading to significant regional impacts on water resources. Deforestation, which reduces evapotranspiration and can disrupt local rainfall patterns, is another factor contributing to precipitation variability.

According to Global Forest Watch (2022), Punjab had 61.2 thousand hectares of natural forest covering 1.4% of its land area in 2010. However, by 2021, it had lost 14.3 thousand hectares of natural forest, resulting in emissions equivalent to 5.48 thousand metric tons of CO₂. Such widespread deforestation could potentially result in a significant reduction in recycled precipitation, which in turn can impact total precipitation patterns (Fernandes, 2016).

Urbanization has also played a role in exacerbating extreme rainfall events in Punjab's cities. The growth of impervious surfaces such as roads and buildings in urban areas can disrupt natural water cycles and result in altered precipitation patterns. In addition, Punjab, known as the breadbasket of the country, is grappling with severe water stress due to intensified agriculture, as documented in numerous studies.

Some villages in central Punjab have already experienced groundwater depletion to alarming levels, with water tables dropping below 100 meters and reaching as low as 150-200 meters (500-600 feet). This depletion of groundwater resources in Punjab has contributed to man-made climate change, further exacerbating the precipitation variability issue (Gupta, 2022).

In conclusion, it is likely that anthropogenic climate change, rather than natural climate change, is the primary cause of precipitation variability in Punjab, India. Understanding changes in precipitation variability is crucial for comprehensively explaining the response of the hydrologic cycle to warming and its impacts. Although there has been extensive research on changes in mean and extreme precipitation, precipitation variability has received less attention, despite its theoretical and practical significance.

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