Land degradation modeling in Taleghan watershed

Land degradation is a negative phenomenon affecting the environment and causes a gradual decrease in ecosystem performance. Considering that more than half of the watersheds of Iran are in arid and semi-arid Mediterranean areas, land degradation is important considering the role of these watersheds in water and food production. In land degradation, types of soil degradation, biodiversity and water scarcity have been mentioned as consequences of land degradation more than other consequences. Land degradation can occur due to various reasons, including poor management of the environmental resources and land uses, climatic conditions and environmental land characteristics. Watersheds are sensitive ecosystems that have faced extensive land degradation in Iran in recent years. The present study was conducted with the aim of modeling land degradation at the Taleghan Dam watershed scale in 2021.

This is a descriptive-applied study. Periodic remote sensing data including aerial photographs and images of LandsatTM and ETM + satellites (1987 and 2002) and IRS 2016, visual and DN methods (for further verification) review and periodic analysis of status and characteristics of land use-related features in the environment were and GIS (IDRIS software) was used in this study. Land use map of the studied watershed in 1970 in accordance with the meteorological and hydrometric data in the research area using aerial photographs with a scale of 1: 20,000 and utilizing the technique and knowledge of interpreting aerial photographs and using a desktop stereoscope, after combining with the area map The research was conducted in a GIS environment. From the method used in the model of the Food and Agriculture Organization for estimating soil erosion (EPM) and decision support systems, a practical model is presented to investigate the current situation of land degradation at the watershed scale. This model has 6 criteria and 43 indicators that the sum of their scores in 6 classes determines the status of land degradation.

The results of the studies indicate that the current land use in the study area includes pastures, rainfed agriculture, irrigated agriculture and orchards and areas without use (rock protrusion). According to the result, the relationship between soil erosion intensity and water erosion intensity coefficient in the model in which the spatial factor of land slope is one of the factors under study. There is% (P-value = 0.005) so that the trend of its changes in the studied time periods is incremental. The results of land degradation using the model in the watershed of Taleghan Dam as a research area showed that the intensity of land degradation in 9.5% of the watershed is low, and in 70, 19 and 0.50% of the watershed are moderate, respectively. "It is relatively high and high. Based on the calculation of land degradation coefficient in Taleghan watershed, index values have decreased from 0.56 to 0.46, which indicates a degradation of 17.86% of the range.

Statistics on population growth in the world show that the highest population growth is in developing countries. Thus, it is important to consider the increased global water and food demand in the issue of population growth. It is predicted to reach twice the global need for water and food by 2030 compared to the current situation. In developing countries, it will increase about 2.5 to 3 times. The results of previous research and the present study show that the environmental consequences of land degradation as a risky phenomenon (mostly under the influence of human actions) despite the lack of full knowledge is so "clear and transparent that if the answer to eliminate Not all the challenges arise from it, but it can be sufficient and justifiable in the necessity and necessity of reducing the risks related to the phenomenon of land degradation, even from a social and economic point of view, in addition to the environment. It is suggested that considering the proposed model dynamically, 6 criteria affecting land degradation in the climatic conditions of watersheds include: water erosion facies, lithological characteristics, soil science and slope of lands with land use and vegetation density It can be used as an efficient model in determining the rate (intensity) and extent of land degradation at the watershed scale to accurately identify degraded sites to combat and manage the phenomenon in question at the national level.