ارزیابی اثرات تغییر اقلیم بر فرسایش و هدررفت خاک حوضه آبخیز میناب

تغییرات اقلیمی بر ویژگی‌های حوضه‌های آبخیز تاثیراتی به‌جا می‌گذارد که به‌نوبه خود به تغییر در  فرسایش و رسوب حوضه منجر می‌شود. این پژوهش با تاکید بر نقش عامل فرسایندگی باران، با استفاده از داده‌های ایستگاهی بارش، داده‌های خروجی دو مدل bcc-csm2-mr و canesm5، گزارش پنجم، سناریوهای 2.6، 4.5، 8.5 و مدل rusle به برآورد و پیش‌یابی تغییرات فرسایش خاک در حوضه آبخیز میناب پرداخته شد. عوامل مدل rusle محاسبه و مدل برای سال‌های 2010 و 2019 اجرا شد. در مرحله بعد برای تعیین اثر تغییر اقلیم بر فرسایندگی بارش، از مدل‌های اقلیمی استفاده شد. برای ارزیابی مدل‌های اقلیمی نیز نتایج پیش‌یابی مدل‌ها در سال 2010 و 2019 استخراج شد، سپس با استفاده از داده‌های واقعی و معیارهای rmse و mae به ارزیابی خطای مدل‌ها و سناریوها پرداخته شد. نتایج نشان داد که میانگین لایه فرسایندگی باران از 41.57 در سال 2010 به 52.01 در سال 2020 افزایش داشت. خروجی دو مدل bcc-csm2-mr و canesm5 نیز از افزایش میزان فرسایندگی بارش در سال 2040 حکایت داشت. میانگین فرسایش در سال 2010، 13.8 تن بر هکتار در سال بود که در سال 2020 با 23 درصد افزایش به 17.0 تن بر هکتار در سال افزایش یافت و پیش‌یابی شد که در سال 2040 با 25 درصد افزایش نسبت به 2010، به 17.3 تن بر هکتار در سال افزایش خواهد یافت. بر طبق نتایج، در آینده نزدیک (2040) فرسایش در بخش‌های شمالی و کوهستانی حوضه آبخیز میناب افزایش می‌یابد. به نظر می‌رسد دو عامل ls و r، مهم‌ترین عوامل مدل rusle است که بر تغییرات مکانی ‌‌ زمانی فرسایش در این حوضه موثر می باشد. ls متاثر از ویژگی‌های شیب حوضه از جنوب به شمال افزایش خواهد یافت، ولی فاقد تغییرات زمانی خواهد بود. r نیز متاثر از تغییر اقلیم، در سال 2040 نسبت به دوره قبل افزایش خواهد داشت و به افزایش فرسایش در سال 2040 منجر خواهد شد.

assessing climate change impact on soil erosion in minab watershed, iran

1- introductionthe increase in greenhouse gases in the last few decades has caused a disturbance in the global climate balance and climate changes (aalst, 2006). climate change and the increase in extreme conditions have caused disasters (helmer & hilhorst, 2006), increasing floods, and tropical storms (haqtalab et al., 2012). other consequences of climate change are changes in erosion and soil loss (akbarian & khoorani, 2022). soil loss and sediment transport have always been one of the most critical problems of land management. climate change and, consequently, changes in precipitation affect soil erosion and loss from various aspects such as the amount, intensity-duration, and distribution of rainfall (gabris et al., 2003). as a result of climate change, the erosive power of rain is expected to increase (sun et al., 2002). in order to predict the effects of climate change on the erosivity of rainfall, it is necessary to predict rainfall with climate models and then estimate the erosive power of rainfall with suitable erosion estimation models. rainfall is the most crucial active driver of soil loss that displaces soil particles (talchabhadel, 2020). it is difficult to accurately evaluate raindrops’ characteristics with soil displacement and detachment. therefore, the empirical methods are used based on rainfall. some of these empirical models can be used with future climate data. the revised universal soil loss equation (rusle) is one of the models used to predict soil erosion. since precipitation is one of the main factors in this model, many researchers have used it to reflect upon the role of climate change on erosion changes. according to goldies et al. (2022), using the rusle-gis approach can estimate the current and future annual soil erosion rates in watersheds by reflecting climate change to the r factor based on the latest cmip6 phase 6 climate forecasts.soil loss and sediment transport have always been one of the most critical problems of land management. according to the mentioned materials, the use of different models to estimate erosion is essential in the basins that are faced with a lack of data and statistics. the area studied in this research is the minab watershed, which is vital from various economic and social aspects, especially the drinking water supply of bandar abbas in hormozgan province. accordingly, this research tried to determine the changes of erosion in these periods by examining the climate condition in the past, present, and future periods so that this information becomes available to decision-makers and managers for better planning. the minab watershed is located in the range of 48°56° to 57°59° east and 27° to 28°32° north latitude. this basin is one of the sub-basins of bandar abbas-sedich, located in the northeast of hormozgan province and the south of kerman province. the area of the basin is 10613 square kilometers. the minab river, which is the result of the connection of the jaghin and rodan rivers, is considered the most important river in this basin. with the construction of the minab dam, its water resources are used to provide drinking water to bandar abbas.2- methodologythis research used monthly data from meteorological stations, precipitation data extracted from different climate models and scenarios, soil data, and satellite images. the climate data are in different periods (base period 2020-2002 and future period 2020-2050). the rusle model was used to study erosion changes due to climate change. first, by preparing the rusle model invoices, the model was implemented for the 2010 and 2020 time periods. next, two climate models, bcc-csm2-mr and canesm5, based on the sixth report and under scenarios 2.6, 4.5, and 8.5, were used to predict precipitation. after evaluating the models, the precipitation erosion layer in 2040 was prepared by the two models.3- results the results showed that the average rain erosivity layer has increased from 41.57 in 2010 to 52.01 in 2020. there is not much difference between the prediction results of the bcc-csm2-mr model and the observed value, so it can be said that the model performed well in different scenarios. among the used scenarios, the 8.5 scenario has the slightest error, and the 4.5 scenario is placed at the end. in the case of the canesm5 model, there is no significant difference between the observed and the predicted values. although the difference increases for more distant years, such as 2040, the results of different scenarios are similar. the output of the two bcc-csm2-mr and canesm5 models also indicate an increase in the rate of precipitation erosion in 2040. the average erosion in 2010 was 13.8 t/ha/y, which increased to 17 t/ha/y in 2020 and was predicted to increase to 17.3 t/ha/y in 2040.4- discussion & conclusionsthe average rain erosion layer in 2010 was 41.57; in 2019, this value reached 52.01. according to the results, the analysis of precipitation data obtained from climate scenarios and models shows an increase in the erosivity factor of rain in the near future (2040). considering the importance of the rainfall erosivity layer in water erosion, if other factors affecting erosion remain constant, in the near future, we will see an increase in erosion and soil loss in the minab basin. the results of the rusle model in the three periods also indicate an increase in erosion over time. the spatial changes of basin erosion are a function of ls (topographic factor), and the rainfall erosivity factor (p) causing temporal changes in erosion.