Investigation of Lag Time Correlation between Agricultural and Meteorological Droughts

The most important natural hazard affecting agriculture in Lorestan province is the occurrence of drought and its consequences. Therefore, the main goal of this research is to investigate and determine the effects of drought on agriculture (irrigated and rainfed) in Lorestan province. To achieve this goal, a combination of field and statistical methods was used. The studied data include characteristics of rainfed and irrigated agriculture, characteristics of water resources, land use map, and drought indicators (meteorological and satellite) of Lorestan province. In order to investigate the relationship between the SPI index and each of the VCI, TCI, and VHI vegetation indices, the correlation coefficient between the indices was calculated and investigated, and a relationship was established between them through single and multiple linear regression. The correlation coefficient between the SPI drought index and TCI and VCI vegetation indices was estimated to be 0.77 and 0.70, respectively. Also, the correspondence between meteorological drought classes and vegetation cover was investigated using a mixed matrix. About the evaluation of the impact of agricultural drought on rainfed and irrigated agriculture, the results indicate that there is a positive and direct relationship between the values of the correlation index between the yield of rainfed and irrigated plants (especially wheat and barley) and the values of various drought indicators during the period of 1991-2017. In terms of time, the highest value of the correlation index between yield and drought index values is observed in the time scale of one to six months, and the correlation value decreases in longer time scales. One of the main reasons for these conditions is the physiological characteristics of different products. Based on the obtained results, in general, it can be said that the increase in drought and heat stress in Lorestan province has caused a decrease in yield and an increase in the water requirement of various aquatic crops.