Determining satellite-based evapotranspiration product and identifying relationship with other observed data in Punjab, Pakistan

Evapotranspiration is an important hydrological parameter that takes place due to water bodies and many physical features (plants, soil) on earth. Punjab lies in the zone of Pakistan that is mostly affected by climate change. A decrease in rainfall and an increase in temperature and potential evapotranspiration (PET) tend toward a more disastrous situation particularly in the southern region of Punjab. MODIS satellite imagery (MOD16) and climatic data over the 16 and 23 years' time periods (1993-2016) were utilized in this study. Firstly for the estimation of the average spatial and temporal trend of rainfall patterns. Maximum of 2000 mm annual rainfall was estimated in 1997, while in 2016 about 1300 mm of annual rainfall was estimated. A declining trend of annual rainfall has been observed both in satellite imagery and observed data results from 1993 to 2016. Modified Penman-Monteith equation was used to estimate PET and moisture index. Thornthwaite Moisture Index was applied on different scales for moisture observation. It was estimated that from 1993 to 2016 the trend of PET increased while that of moisture content decreased in the study area. Results obtained from both datasets showed that southern Punjab having less amount of rainfall and a gradually increasing trend in potential evapotranspiration as compared to the northern part of the province Punjab.