Investigation of intensity, duration and spatial distribution of drought in Semnan province

Subject Areas : forest

Mohammad Reza  Zandmoghadam ¹ (Faculty Member of Department of Geography and Urban Planning, Semnan Branch, Islamic Azad University, Semnan, Iran)
Behrooz  Arastoo ² (Researcher of Agriculture and Natural Resources Research and Education Center of Semnan province.)
Askari  Mojtahedzadeh ³ (Department of Geography, Faculty of Humanities, Semnan Branch, Islamic Azad University, Semnan, Iran)

Received: 2022-10-23 Accepted : 2023-03-02 Published : 2023-03-17

Keywords: SPI, Semnan Province, spatial distribution, drought,

Abstract :

Drought is an environmental event and an integral part of climatic fluctuations and is a periodic and normal weather feature. Unlike dry land, which is a permanent feature of the climate, drought is a temporary occurrence that results directly in a decrease in the amount of rain over a long period of time, usually in one season or more, and results in water shortages for some activities, groups or sections Is environmental. The greatest concentration of references in the assessment of droughts is on climate drought, which is due to the presence of more extensive and more comprehensive information, as well as the factor of rainfall in the factors causing drought. Due to the impact of drought in different sectors, different approaches to this phenomenon are considered, which requires space and time attention and its expansion to manage it. Currently, drought analysis is based on rainfall data as the most important factor for all types of drought. In this research, firstly, the annual precipitation index (SPI) values were calculated by selecting the default distribution (gamma) and then the frequency of different classes of drought for each period of 1,3,6,12, 24 months ending April 2016 was extracted for the settlements of the province. For the spatial-temporal distribution of drought-affected areas, the inverted interpolation method of IDW distance was used. Based on the frequency of drought classes, a single layer of variables was prepared and the range of each of the classes was determined in the province, the output of which is the spatial-temporal distribution maps of drought and the area of each of the different classes of drought were calculated in GIS software. By analyzing the course status, in the 1 month period ending April 2016, the highest spatio-temporal distribution with about 68.13 Percent of the province's settlements was related to the indicator In the normal period, in the 3 months period, with about 50.64 Percent, the average drought and in the 6,12and 24 months periods were 38.72, 41.76 and 36.98 Percent, respectively, with droughts, and any amount of time period to time It goes on for a long time, the effects of drought become more pronounced.