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Showing 43 results for Land Use
Effect of Land Use Change on Some Fertility and Biological Properties of the Soils of Yasouj Forest Region
H.r. Owliaie, E. Adhami, M. Najafi Ghiri,
Volume 27, Issue 3 (12-2023)
Abstract
Soil resources are important components of the ecosystem, and therefore, their quality should be considered. One of the important factors affecting the quality of soils is land use change. The present study was conducted to investigate the effects of land use change and deforestation on some soil fertility and biological characteristics in the forest area of the Yasouj region. In this area, four land uses of dense forest, sparse forest, deforested (degraded) lands, and rainfed agriculture were randomly sampled from two slope classes. In each land use 10 soil surface samples were taken. Fifteen soil fertility and biological characteristics were measured using routine methods. The results showed that dense forest and deforested (degraded) lands had the best and worst conditions, respectively, in terms of the measured parameters. Among the measured characteristics, the values of alkaline phosphate, exhaled respiration, nitrogen, basal respiration, acid phosphatase, manganese, and zinc showed the greatest decrease respectively, and the values of phosphorus and potassium exhibited the least decrease, as a result of land use change from dense forest to degraded lands. The findings showed that the conversion of ecosystems such as forests to agricultural lands or deforestation has led to a severe decrease in the fertility and biological indicators of soil quality. Therefore, the protection programs of these areas should be more considered.

The Estimation of Land Use Changes under Irrigation Water of Traditional Streams of Khansar City
B. Ebrahimi, M. Pasandi, H. Nilforoushan,
Volume 27, Issue 4 (12-2023)
Abstract
The different land uses in the irrigation water area of the eleven streams of Khansar city during 1969, 1995, 2014, and 2019 have been identified and their area has been determined by analysis of the aerial photos as well as the satellite images of QuickBird, and Landsat in the Google Earth Engine (GEE) environment. Then, the net and gross areas of land under irrigation water, area of non-agricultural land uses, location and area of agricultural land uses under irrigation of the streams are separated according to the type of agricultural activity (orchard or farmland) for each stream. Aerial photos of the study area dated 1969 are the basis for the assessment of agricultural conditions before the law of Fair Water Allocation. The results showed that non-agricultural and particularly urban and residential land uses have increased since 1969. In other words, land use of part of the agricultural lands has been changed to residential and urban land uses. Despite the decreasing trend of agricultural land uses in the last 50 years, these changes have not been the same between the farm and orchard land uses and the area under orchard plantation showed an increasing trend. These changes have dramatically influenced on water demand of the streams. Land use has not significantly changed from 2014 to 2019 and no noticeable change was observed in the area of the agricultural and green agricultural lands as well as the percentage of the orchard and farming lands during these years. The results of this study confirmed the significant changes in agricultural land use and consequently water consumption in the district of the eleven streams of Khansar in recent decades. This study also highlighted the high efficiency of the combined use of aerial photos, spectral satellite images with medium spatial resolution, and visible spectral satellite data with high spectral resolution, as well as using cloud system capabilities of the Google Earth Engine to study changes in agricultural land uses during last decades.

Evaluation of the Effect of Land Use Change on Runoff Using the Markov Chain in Shiraz Nahre Azam Basin
A. Mahdavi, S. Soltani Koopaei, R. Modares, M. Samiei,
Volume 27, Issue 4 (12-2023)
Abstract
Land use changes are one of the main factors in the amount of surface runoff changes in watersheds. Therefore, it is necessary to investigate it to reduce the damages (human and financial) caused by floods and to modify watershed management. The watershed of Nahre Azam is located in the north of Shiraz city and a lot of loss of life and money to the residents of Shiraz due to floods has occurred in previous years. The present research was conducted to investigate the relationship between land use change and runoff in the Nahre Azam watershed in Shiraz using the SWAT model in the period of 2004-2020. The model was calibrated using data from 2004 to 2014 and validated for 2015 to 2020. These images were classified into 6 main land uses using the supervised classification method after performing necessary pre-processing, and a land use map was prepared for 2040 using the Markov chain method. Then, the effect of the land use change in 2003 and 2040 on the amount of simulated runoff was evaluated with the recalibrated model. The calibration results of Nahre Azam watershed for the values of statistical parameters in the calibration step for the coefficient of determination, P-Facor and R-Facor are 0.77, 0.72, and 2.43, respectively, and for the validation step we obtained 0.69, 0.65, and 2.3 respectively. The analysis of the land use map showed that the main land use change in the region related to the conversion of pastures to agricultural land and urban land, which caused a decrease in pastures. Also, the results of the model simulation using the land use maps of 2003 and 2040 indicated that the amount of runoff decreased. The results revealed that if all the uncertainties are minimized, the calibrated SWAT model can produce acceptable hydrological simulation results for the user, which is useful for water resource and environmental managers and politicians as well as city managers of Shiraz.

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