چكيده به لاتين
The streamflow and sediment load to the Anzali wetland, located in the north of Iran, have been influenced by global Climate Change (CC) and Land-use Land-cover Change (LULC). Hence, the CMIP6 data with quantile delta mapping bias-corrected method was used for five models, which perform better than other models to evaluate the CC effects, reducing the uncertainty and increasing the results' reliability. Also, the Land Change Modeler (LCM) was used to predict the future LULC. The precipitation is projected to decrease, especially in the north and northeast of the basin, under different CC scenarios. The maximum and minimum air temperature is projected to increase under the Shared Socio-economic Pathway (SSP) scenarios. Also, LCM predicts an increase in deforestation and urbanization in the Anzali wetland watershed over time. In order to determine the impacts of CC and LUC on the streamflow, sediment load, and total nitrogen load, the Soil and Water Assessment Tool (SWAT) was employed. Therefore, by examining the results, it has been determined that the most increasing/decreasing period, streamflow, sediment load, and total nitrogen load entering Anzali Wetland under the climate change scenarios alter to 3%/-10.5%, 11%/-11%, and 22.7%/-4.2% respectively compared to the base period (1989-2020). It should be noted that the future time step is divided into three periods of the near future (2050-2021), the middle future (2051-2080), and the far future (2081-2100).
Meanwhile, if the LULC changes are considered with climate changes in the simulation process, the mentioned changes for streamflow, sediment load, and total nitrogen load entering the Anzali wetland are equal to 9.2%/-6.5%, 22.2%/-5.2%, and 40.2%/3.8%. These results indicate that surface runoff relative to sediments and total nitrogen is less sensitive to climate changes and changes in LULC. These results prove that, in general, the amount of sediment entering the Anzali wetland will increase compared to the base period, which can cause a decrease in the water volume of the wetland, which can fill only the part of the Anzali wetland that has water with incoming sediments in the future. On the other hand, the total nitrogen load entering Anzali Wetland is also expected to increase. With the increase of the total nitrogen load and the decrease of the water volume of the wetland due to the decrease in discharge and the increase of sediments, it is not far from mind to increase the eutrophication of the wetland, which can have adverse effects on the life of the wetland ecosystem. Therefore, in this research, an attempt has been made to project the future conditions of the basin in terms of streamflow, sediment load, and total nitrogen load entering the Anzali wetland with less uncertainty through the use of several general circulation models that can reduce the uncertainty caused by climate studies. Moreover, based on the historical trend of the LULC degradation, LULC change must consider dynamically in the CC impact assessment study to produce reliable results for decision-makers to adaptation strategies to persevere wetlands from potential threats.
