Effect Of Climate Change On Crop Water Requirement Using CMIP6 Data Over Pakistan

Abstract

In recent years, there has been an increased focus on studying the impact of climate change on crop water requirements (ETc), specifically evapotranspiration, due to the effects of temperature and precipitation variability. While many studies have projected long-term scenarios, there has been a lack of short-term predictions, particularly for a 10-year period, in the existing literature, specifically for assessing crop water requirement (ETc) in Pakistan. This thesis aims to address this gap by utilizing short-duration projected data from the Decadal Climate Prediction Project (DCPP) obtained from the Coupled Model Intercomparison Project Phase 6 (CMIP6) repositories. The objective is to assess the impact of climate change on crop water requirements across the provinces of Pakistan, focusing on the cotton and wheat seasons. To analyze ETc variations attributed to climate change, the study employed the CROPWAT 8.0 software, based on the guidelines provided by the Food and Agriculture Organization (FAO). Results revealed that IQ Range of ETc for the cotton season in Sindh and Balochistan exhibits higher scattering and more erratic behavior compared to Punjab and Khyber Pakhtunkhwa (KPK). The higher IQ Range values in Sindh (8.3 mm/Dm) and Balochistan (3.6 mm/Dm) contribute to this pattern, while Punjab and Khyber Pakhtunkhwa show a more consistent behavior with lower IQ Range values (1.65 mm/Dm and 0.9 mm/Dm) respectively. For the wheat season, the IQ Range analysis of ETc indicates that Sindh displays a higher scattering of anomaly data compared to Punjab, Khyber Pakhtunkhwa, and Balochistan. The higher IQ Range value in Sindh (0.9 mm/Dm) suggests significant variations and erratic behavior of ETc anomalies. In contrast, Punjab, Khyber Pakhtunkhwa, and Balochistan exhibit a more consistent pattern, with their ETc anomalies closer to the median values and lower IQ Range values (0.2 mm/Dm, 0.3 mm/Dm, and 0.3 mm/Dm) respectively, indicating a more stable ETc pattern. The study revealed significant findings regarding the projected changes in crop water requirement (ETc) in different provinces of Pakistan during the cotton and wheat seasons. Sindh exhibited the highest increase in ETc during the cotton season, with a mean anomaly of 1.8 mm/Dm and a standard deviation (StDev) anomaly of 4.6 mm/Dm. Punjab displayed high variability in ETc anomalies during the cotton season, with the highest StDev observed. Balochistan showed an increase of more than 0.4 mm/Dm in evapotranspiration rate for the cotton season, with a StDev of 2 mm/Dm. In contrast, Khyber Pakhtunkhwa experienced a decrease in ETc anomalies for both seasons. These findings have significant implications for water management strategies in the respective regions.