Predicting the Effect of Climate Change on Rainfall Erosivity in the Talar Watershed of Mazandaran Province, Iran

Introduction and Goal 
Climate change is one of the major environmental challenges, with extensive impacts on both natural and human processes. These changes can affect hydrological cycles, leading to alterations in rainfall patterns and soil erosion. Rising temperatures and variations in the amount and intensity of precipitation may have detrimental effects on the stability of water and soil resources. Decrease in precipitation in some areas and an increase in others will alter the spatial and temporal distribution of runoff, which can impact the storage capacity of surface and groundwater resources. Given the importance of natural resource management and the need to predict the consequences of climate change, This study investigates the effects of climate change on precipitation and rainfall erosivity in the Talar watershed. The main objective of the present research is to evaluate the effects of three climate scenarios SSP1-2.6, SSP2-4.5, and SSP5-8.5 on precipitation and rainfall erosivity in the near future year 2046. By forecasting climate change in the near future 2046, we can prepare for its short-term impacts, such as water scarcity, droughts, and floods, and to carry out necessary planning in this areas of water and soil resource management, agriculture, and infrastructure development of appropriate measures for adapting to climate change. Additionally, the analysis of climatic changes will assist policymakers in making more effective decisions when designing and implementing long-term sustainable development programs.
Materials and Methods
The methodology of this research includes using precipitation data from five stations (Qharakhil, Sang Deh, Shirgah, Pol Sefid, and Alasht) in the study area for the period 1985–2014.Subsequently, near-future precipitation was simulated using climate model data from CMIP6, including MIROC6, ACCESS_CM2, CAN5, and CNRM_CM6, along with the CMHYD downscaling software. The selection of the best model for downscaling precipitation was based on a comparison of the results from various models with observational data. Metrics such as Root Mean Square Error (RMSE), coefficient of determination (R²), Nash-Sutcliffe efficiency (NSE), Pearson correlation coefficient (R), and Taylor diagram were used to evaluate and compare the simulation models. The results indicate that the MIROC6 model with the LI method has the best performance in simulating precipitation and rainfall erosivity in the Talar watershed. The Rain Erosivity Index (R) was calculated for both the baseline and future periods, and its variations under different scenarios were examined. Additionally, Geographic Information Systems (GIS) were utilized to analyze the spatial and temporal changes in rainfall and rainfall erosivity. These analyses helped identify vulnerable regions, which were subsequently considered in management planning.
Results and Discussion
The results indicated that rainfall variations under the influence of climate change differ across various scenarios. The research findings suggest that in the future, under the optimistic SSP1-2.6 scenario, a 43% increase in precipitation leads to a 16.89% increase in rainfall erosivity. This increase could have different effects on soil erosion during dry and wet periods. Specifically, in wet periods, it leads to increased soil erosion, while in dry periods, it alters the runoff pattern. In the moderate SSP2-4.5 and pessimistic SSP5-8.5 scenarios, precipitation decreases by 38.6% and 1.28%, respectively, resulting in corresponding reductions of 37.9% and 10.8% in rainfall erosivity. The results of spatial analysis reveals that reduced precipitation and rainfall erosivity in forested and rangeland areas. Additionally, in residential areas like Pol Sefid, increased construction and the creation of impervious surfaces lead to reduced vegetation cover and increased vulnerability to intense rainfall. In  areas like Shirgah, increased precipitation and rainfall erosivity could elevate the risk of landslides and erosion in road trenches. These changes can have significant impacts on soil erosion and water resource management in the region. In this regard, the necessity of adopting protective measures and continuously monitoring climate variations in the area is emphasized.
Conclusion and Suggestions
Overall, the findings highlight that climate change can significantly impact natural resources and livelihoods in the Talar watershed. Urgent actions, including the sustainable management of water and soil resources, are necessary for adaptation to these changes. Such actions involve monitoring livestock grazing in pastures, protecting vegetation cover, and cultivating erosion-resistant plants and developing watershed management techniques. It is also recommended to mitigate the damages caused by intense rainfall by employing appropriate vegetation cover in erosion-prone areas, monitoring vegetation cover changes, and implementing erosion control measures in watersheds. The outcomes of this research can assist policymakers and natural resource managers in making informed decisions to mitigate the adverse effects of climate change and improve the management of water and soil resources. Additionally, projected data on the future erosion by rainfall can be used for the further research development and strategic planning in watershed management. Furthermore, it is recommended that future research examine changes in rainfall intensity and their impact on soil erosion. Additionally, conducting field studies and utilizing advanced numerical models can enhance the accuracy of predictions and contribute to the development of effective strategies for climate change management.