Investigating the effects of drought on the water use efficiency in different climates and land uses (Case study: Tehran province)

In this study, drought was investigated on water use efficiency (WUE) in different climates and uses of Tehran province. To calculate the efficiency of water consumption, the products of Gross primary production (GPP), Evapotranspiration (ET) and Palmer drought severity index (PDSI) obtained from the MODIS meter are used. Then the trend of changes in the index of primary gross production, evaporation and transpiration, water consumption efficiency and drought in the period of 2001-2021 using linearity and Mann-Kendall and slope tests, and then the response of water consumption efficiency to drought in different climates and consumptions with Use. It was evaluated from correlation analysis. By dividing annual rainfall into potential evapotranspiration (PET), the Aridity index (AI) was calculated and climate classification was done with the help of this index. The results showed that the indices of evapotranspiration, primary gross production and drought increased by 81.15, 86.86, and 99.99% respectively, and the water consumption efficiency index decreased by 76.24% in this 20-year period. Is. These results were confirmed by the slope test. Examining the relationship between the efficiency of water consumption and drought in different climates and applications showed that in dry climates, agricultural land and bushland had a negative ratio of 91.86 and 78.93, respectively, and pasture consumption had a positive ratio of 51.96. Agricultural lands, pastures and bushland related to semi-arid climate have increased by 85.38, 66.22, and 64.27 percent, respectively, and forest use has decreased by 84.87 percent. In semi-humid climate, respectively, 47.53, 60.48, 73.41% of the study area has a positive relationship in the use of agriculture, pasture and shrub land, and 91.30% of the use of forests has a negative relationship. In the climate, the negative impact of drought has been in 66.04, 61.15 and 50.56 percent of agricultural, pasture and forestry lands. In general, according to the mentioned results, drought has had a negative effect on water consumption in Tehran province, and it can be said that the resistance of the ecosystem against drought is determined by our correlation between drought index and water consumption efficiency.