Abstract
The impact of climate change and global warming on Earth's climate and other systems such as water sources, agriculture, environment, industry, health and the economy as a known the threats to sustainable development. So the effects of climate change on different systems and adaptive solutions to deal with the negative consequences of this phenomenon in future periods is essential. So according to importance of the issue, the purpose of this study was to evaluate the effects of climate change on temperature, precipitation, runoff and finally hydrological drought in the “Roude Zard” watershed in the future. For this purpose, data from the years 2000-1971 as a base data to small-scale model of LARS-WG introduction and calibration data for the years 1997-1990 and 1989-1974 years data were used to validate models of rainfall-runoff IHACRES. In order to evaluate hydrologic drought index SDI was used. Results show that increase in mean annual temperature in the study area 1.02 degrees Celsius as well as the expected changes in mean annual precipitation to the study area 11/91 percent and 73/78 millimeters. Results IHACRES model to simulate rainfall-runoff study area show that this model is suitable. The simulation results runoff also indicated an increase in the average runoff affected by climate change in some of the months of January, February and March and a decrease in average monthly runoff out of the area in September, October. Also results of the SDI index show increase in intensity of drought in the future compared to the base period. The results of this study will be to adapt to climate change studies in order to provide suitable management strategies used in the study area.
Introduction
Climate change, a global phenomenon driven by the relentless accumulation of greenhouse gases in the Earth's atmosphere, has emerged as a paramount threat to sustainable development. Its far-reaching consequences extend to various interconnected systems, including water resources, agriculture, the environment, industry, health, and the economy. Understanding the intricate interplay between climate change and these systems is crucial for devising effective adaptive strategies to mitigate and manage its adverse impacts.
In this context, the Roude Zard watershed, a vital water resource region in Iran, serves as a compelling case study for scrutinizing the projected effects of climate change. The watershed's susceptibility to hydrological drought, a prolonged period of insufficient rainfall leading to water scarcity, underscores the urgency of assessing potential climate-driven changes in this crucial water resource.
The primary objective of this study is to delve into the projected effects of climate change on temperature, precipitation, runoff, and ultimately, hydrological drought in the Roude Zard watershed. By employing a comprehensive methodology encompassing historical data analysis, climate modeling, rainfall-runoff modeling, and drought index assessment, we aim to unravel the intricate relationship between climate change and the watershed's water resources.
To evaluate the intensity of hydrological drought, we employ the Standardized Precipitation Index (SPI), a drought index that quantifies the deviation of precipitation from its long-term average. By comparing SPI values to standardized drought thresholds, we can assess the severity of drought episodes and their potential impact on water resources availability.

Methodology
To achieve the study's objectives, a comprehensive methodology was employed, incorporating historical data analysis, climate modeling, rainfall-runoff modeling, and drought index assessment. Historical data from 1971 to 2000 served as a baseline for assessing future climate conditions under three representative concentration pathways (RCPs) – RCP2.6, RCP4.5, and RCP8.5 – which represent different greenhouse gas emission scenarios.
The Local Adaptive Regional Climate Model (LARS-WG) was employed to project future temperature and precipitation changes in the Roude Zard watershed. LARS-WG is a state-of-the-art regional climate model that effectively simulates climate variables at a finer spatial scale than global climate models. The simulations were conducted using historical and projected emission scenarios to generate future climate projections for the study area.
The IHACRES model, a well-established rainfall-runoff model, was utilized to simulate runoff under the projected climate conditions. IHACRES incorporates various factors, including topography, land use, and soil characteristics, to accurately predict runoff patterns. The model was calibrated using historical data from 1997 to 1990 and 1989 to 1974 to ensure its reliability for future projections.
To assess the intensity of hydrological drought, the Standardized Precipitation Index (SPI) was employed. SPI is a drought index that quantifies the deviation of precipitation from its long-term average, providing a standardized measure of drought severity.
Conclusion
The study's findings reveal significant changes in temperature and precipitation patterns under the projected climate scenarios. Mean annual temperature is expected to increase by approximately 1.02 degrees Celsius, while precipitation patterns are projected to shift towards a more distinct seasonal distribution. The months of January, February, and March are anticipated to experience an increase in precipitation, while September and October are projected to experience a decline.
Simulations using the IHACRES model indicate alterations in runoff patterns under climate change. Runoff is projected to increase during the months of January, February, and March, while a decrease is expected in September and October. These changes in runoff patterns are attributed to the anticipated temperature and precipitation shifts.
The SPI index, used to evaluate drought intensity, revealed a projected increase in drought frequency and severity in the future compared to the baseline period. This suggests that hydrological drought is likely to become a more prevalent and impactful phenomenon in the Roude Zard watershed under climate change.
The study's findings underscore the profound impact of climate change on the Roude Zard watershed. Projected increases in temperature, changes in precipitation patterns, and a rise in drought intensity pose significant challenges to water resource management, agriculture, and the environment in the region. These findings emphasize the need for adaptation strategies to mitigate the negative consequences of climate change and promote sustainable development in the Roude Zard watershed.
The study's findings contribute to the body of knowledge on climate change impacts and provide valuable insights for water resource management and adaptation planning in the Roude Zard watershed. The results can inform decision-making processes aimed at enhancing water security, promoting sustainable water use practices, and developing effective drought mitigation strategies in the region. In addition, the study's methodology and modeling approaches can serve as a foundation for similar studies in other watersheds facing similar climate change threats.
Overall, the study highlights the urgency of addressing climate change and its implications for water resources management and sustainable development in the Roude Zard watershed. By understanding the projected impacts and developing adaptation strategies, stakeholders can effectively manage water resources, minimize the risk of drought, and promote sustainable practices for the future.