Doubtlessly hydroclimatic models play important role in the management of water resources. The hydroclimatic time series have three principle components (autoregressive, seasonality and stochastic) and the performance of the models are related to these components, In the current research, the wavelet transform was linked to the Holt-Winters (HW) model for prediction of monthly runoff in Lighvanchai (Iran), Trinity, and West Nishnabotna (US) watersheds and minimum temperature of Tabriz. The obtained results were compared with autoregressive and seasonal models such as ARIMA, seasonal ARIMA (SARIMA) and HW. For this purpose, the main time series were decomposed to some multi-frequency time series by wavelet transform. Then due to the univariated nature of the HW model, these subseries were imposed as input data to the HW models for two scenarios. In the first scenario only approximation subseries and one detail subseries (resulting from the accumulation of all details subseries) and in the second scenario all subseries were used as input to HW models. Results showed that the second scenario of hybrid wavelet-holtwinters model (WHW2) could lead to considerably increased accuracy of both runoff and temperature monthly modeling because of the multiscale analysis and considering all multi-frequency subseries.

1. Introduction: In the present paper, the ability of the Artificial Neural Network (ANN) and combined wavelet-neural network (WANN) model were investigated for multistep modeling of hydroclimatic processes with the least input. For this purpose, the ANN model and then the WANN model were used to predict one to twelve steps in advance. Finally, the efficiencies of all models were examined using the evaluation criteria, and all models were compared with each other. . .

Paleoclimatic investigation of the Quaternary period reflects fluctuation in climatic conditions during geological periods. Abrupt climatic changes, viewed as problem causing global incidents bring about adverse side effects in sensitive climatic zones such as Iran. Droughts and unpredictable floods that damage natural resources as well as human life become common yearly occurrences. Apart from influences of natural physical factors, human activities, if not properly controlled, add to the destructive power of the floods too. This happened in the Nekaroud basin mainly due to deforestation and damaging changes in landuse during the last century. The huge magnitude flood of summer 1999 which caused irreparable downstream damage and death of citizens is a sad incident of such environmental changes. The present study is an investigation into some characteristics of Nekaroud basin, an analysis of the reasons behind the occurrence of the catastrophic flood, ways to predict and prevent similar disastrous incidents in other catchments basins in Mazandaran as well as in other regions with similar conditions in Iran.

Extended abstract Introduction In recent decades, droughts have intensified globally, affecting diverse climatic regions with varying characteristics. Rising global temperatures alter climatic components like precipitation, evapotranspiration, and soil moisture, impacting river regimes and exacerbating water scarcity. Droughts are categorized into meteorological, agricultural, hydrological, and socio-economic types, with interconnected impacts on groundwater depletion, agricultural productivity, drinking water access, and socio-political stability. In arid/semi-arid regions like Iran, groundwater is critical for drinking, agriculture, and economic development, necessitating advanced management strategies to address spatial-temporal variability. Studies emphasize analyzing hydrological and climatic trends using parametric/non-parametric methods. The non-parametric Mann-Kendall test is widely used for trend detection in non-normal data, while Discrete Wavelet Transform (DWT) decomposes time-series data to identify non-stationary patterns. Global Land Data Assimilation System (GLDAS) data (25 km resolution), developed by NASA and NOAA, enables large-scale analysis of land surface parameters (e.g., soil moisture, evaporation) using models like CLM and Noah. This study employs GLDAS data, Mann-Kendall tests, and 1D wavelet analysis to assess hydroclimatic trends across Iran’s climates and major basins. By integrating statistical and signal-processing methods, it aims to decode drought frequency oscillations in meteorological, hydrological, and groundwater indices, offering insights for policymakers to optimize water management amid climate change. The research distinguishes itself through national-scale analysis, frequency-domain insights from satellite data (vs. station-based studies), and simultaneous evaluation of broad trends and granular fluctuations, aiding climate adaptation and drought forecasting. Methodology In this study, data were initially obtained from the Google Earth Engine platform. Annual precipitation data for a 20-year period from 2003 to 2022 were extracted using CHIRPS, which offers a temporal resolution of five days. CHIRPS data are specifically designed for climate and drought management studies, covering the period from 1981 to present. Due to the absence of precipitation data before 2003 in GLDAS, CHIRPS was selected. Additionally, GLDAS data for groundwater level, soil moisture, and surface runoff were acquired for the same period at a 25 km spatial resolution. These variables are directly linked to the water cycle and are crucial for water resource planning, drought management, climate change prediction, and policy-making. Daily and five-day data were aggregated into monthly scales using MATLAB and then processed in ENVI software for the entire study period. The Mann-Kendall non-parametric test was employed to detect trends and non-stationarity in the hydroclimatic time series. To analyze the nature and patterns of changes, one-dimensional discrete wavelet transform (DWT) was applied. Wavelets are powerful mathematical tools for decomposing signals and time series, enabling identification of short- and long-term trends and fluctuations. Daubechies wavelet, well-suited for precipitation data, was chosen as the mother wavelet. DWT decomposed the 12-month meteorological, hydrological, and groundwater drought indices of Iran’s climates into eight levels of detail and approximation components. This approach facilitated detailed trend analysis of drought indices over the study period, providing valuable insights into hydroclimatic variability and drought dynamics. Results The trend analysis using the Mann-Kendall test revealed that precipitation exhibited a decreasing, though statistically insignificant, trend across most regions. Similarly, actual evapotranspiration, soil moisture, and groundwater levels showed significant decreasing trends, consistent with the decline in precipitation. Overall, the results indicate that precipitation, or meteorological drought, is the primary hydrometeorological component, acting as the starting point for other types of droughts. Wavelet analysis of drought trends across different climates in Iran showed that the trend of the Approximation frequency, reflecting low-frequency changes in the original signal, was similar across all climates. This suggests a common change pattern nationwide. The Approximation frequency displayed an increasing trend for all drought types, indicating that drought frequency has intensified in recent years and is likely to continue increasing. The Detail frequency analysis revealed that fluctuations in the SPI (Standardized Precipitation Index) and SSI (Standardized Soil Moisture Index) were significantly greater in wetter climates than in drier regions. In dry areas, fewer details were observed in the trends of these indices, likely due to greater rainfall variability, larger water resources, and complex hydrological structures in wetter areas. Changes in groundwater levels were less pronounced compared to other indices, resulting in fewer details in both high- and low-frequency trends. This can be attributed to the delayed response of groundwater to rainfall or meteorological drought. In contrast, hydrological drought, specific to surface water resources, showed substantial fluctuations due to the strong dependence of surface water on precipitation in most regions. Discussion and Conclusion Iran’s climate is influenced by the subtropical high-pressure system, a dynamic warm air system that has intensified in strength and extent due to global warming. This expansion reduces precipitation in affected areas because these high-pressure systems induce descending air currents, which inhibit cloud formation and rainfall while increasing evapotranspiration. Although global warming has raised temperatures in Iran, actual evapotranspiration has decreased over the past 20 years due to declining precipitation. Groundwater levels have also declined, primarily driven by reduced rainfall alongside factors like over-extraction, illegal wells, and industrial use in low-precipitation regions. Overall, precipitation or meteorological drought is the primary hydroclimatic factor influencing other drought types. Wavelet analysis of drought indices (SPI and SSI) revealed that fluctuations are more pronounced in humid climates compared to arid ones, likely due to greater rainfall variability, more abundant water resources, and complex hydrology in wetter regions. In contrast, arid areas show fewer fluctuations and details due to limited water sources. Groundwater changes exhibited minimal variability, reflecting delayed responses to drought and greater stability across climates. Surface water drought showed significant variability, influenced by its strong dependence on rainfall and sensitivity to short-term events like floods or dry spells. This dynamic nature causes surface water to respond rapidly to climatic changes. The study’s findings help identify critical regions vulnerable to reduced rainfall, increased evapotranspiration, groundwater depletion, and surface water fluctuations. Despite the lower resolution of satellite data compared to ground observations, this research provides valuable insights for water resource management, drought and flood risk planning, agricultural development, and land-use planning at a national scale.

Hydro-climactic factors like air temperature, rainfall, rate and its distribution are important indices for anticipating or forecasting the landslide events. Thus, the hydro-climactic thresholds can be used as an empirical basis for issuing warnings, in areas highly susceptible to snow melt-season landslides. Other measures can be the deployment of field instrumentation to monitor hazardous landslides, timing avoidance of mitigation strategies, scheduling construction projects in sensitive areas, and anticipating highway maintenance needs. The purpose of this paper is to present the results of research done in many parts of the world.

Introduction and GoalIn the last three decades, land use in the Minab river basin has undergone significant changes and these changes along with climate change in the basin can affect the trend of hydroclimatic variables. Due to the changes that have occurred in the climate and land use of the Minab River Basin in the past decades until now, the investigation of trends and changes in the threshold indicators of precipitation, temperature and flow rate becomes particularly important. Therefore, the aim of the current research is to investigate the trend of land use changes and hydroclimatic variables in the Minab basin.Materials and MethodsIn the current research, the data of hydrometric, rain gauge and evapotranspiration stations in the Minab watershed were analyzed to extract threshold indices based on the ETCCDI standard including precipitation, temperature and river flow. Trend analysis was done using a non-parametric Mann-Kendall test. Also, land use changes were extracted using TM series Landsat satellite images in 1989, 2004, and 2020 from TM, ETM+, and OLI sensors, respectively, and the accuracy of the extracted images was confirmed with Kappa statistics.Results and DiscussionThe finding showed that all the temperature limit indices, including tropical nights, hot days, hot nights and the range of day and night temperature, have an increasing trend. The extreme precipitation indices, heavy precipitation of 10, 20, and 30 mm in some stations has an increasing trend, but the annual average precipitation has an increasing trend. The number of wet days is decreasing and the number of dry days is increasing. The investigation of the changes in the rainfall regime of the region showed that the intensity of the rainfall is increasing in the duration of 15 and 45 minutes. According to the changes that have occurred, the change in the precipitation situation in the region is inevitable. The survey of land use changes over the past three decades showed that 22% of the pasture land area has decreased, and residential and agricultural land has increased by 280 and 220%, respectively.Conclusion and SuggestionThe findings of this research showed that despite the increase in the average annual rainfall (16 mm per year), and other rainfall indicators that had no significant trend, the trend of 15 and 45 minute rainfall intensity was increasing and significant. Contrary to the trend of precipitation, which cannot be proven with great certainty, the increasing trend of all temperature indices (on average 0.9°C per year) confirmed the climatic changes in the Minab watershed. On the other hand, the trend of minimum and maximum stream flow and maximum discharge was also increasing in the watershed, and it can be one of the reasons for the changes in rainfall, construction of dams, and changes in land use from pasture and war lands to agriculture and residential. Based on the results of this research, it is suggested to investigate the effect of future climate changes on meteorological and hydrological variables and use its findings in natural resources management.

Extended Abstract Introduction: The excessive exploitation of natural resources, driven by the unsustainable practices of human societies to meet growing population needs, has become a critical global issue, threatening the health and sustainability of watersheds. To mitigate these risks, effective management measures are essential to build resilient communities capable of withstanding natural events and disasters. Accurate quantification of ecological changes and the identification of key indicators for watershed management are crucial for promoting resilience and ecological sustainability. In this context, viability—defined as the ability of a watershed system to return to its resilience threshold—is a vital concept for assessing the restoration of health and sustainability. However, analyzing and evaluating viability requires a comprehensive understanding of the complex relationships among various variables. Despite its importance, no prior research has specifically addressed the assessment of watershed viability. Materials and methods: This pioneering study aims to evaluate the viability of the Shazand Watershed in Markazi Province, Iran, based on its hydroclimatic characteristics. The study began by calculating selected hydroclimatic variables, followed by statistical analyses to identify and remove less relevant variables. Resilience and release thresholds were then determined for the remaining variables. The viability index was prioritized by comparing current conditions with these thresholds. Finally, the overall viability of the watershed was assessed by calculating the geometric mean of the hydroclimatic variables. Results and Discussion: The modeling and zoning results revealed that the hydroclimatic viability index of the Shazand Watershed is 0.58, indicating an intermediate state. Notably, the prioritization of sub-watersheds using the viability method differs significantly from conventional estimation methods. While examining current conditions alone provides limited insights, comparing the variability of variables in resilient and release states with current conditions offers a more robust assessment. For instance, instead of taking management measures in sub-watershed 7 with high priority in the current conditions state, it is necessary to pay attention to sub-watershed 21 with viability, hydrological, and hydroclimatic priorities of 1, 4, and 1, respectively. Other high-priority watersheds include sub-watersheds 9, 20, 24, 16, 1, 11, and 15. The aforementioned sub-watersheds, especially 9, 20, and 11, are currently in good condition, but they have very low viability (high variability). Sub-watersheds 22, 5, and 4 are also among the sub-watersheds with high viability (low variability). By focusing on priority sub-watersheds, hydroclimatic conditions can be significantly improved, enhancing the stabilization of these areas. Key variables influencing viability include normal characteristic discharge and erosion rates, with industrial expansion in the region identified as a major driver of variability, particularly in sub-watersheds 3, 6, and 7. Conclusion: This study demonstrates that identifying resilience and release thresholds for variables and comparing them with current conditions can help bring critical sub-watersheds closer to their resilience thresholds, preventing system collapse. Given the complexity of watershed systems and the multitude of factors influencing their performance, a comprehensive assessment of viability, incorporating all relevant variables, is essential for effective watershed management. The integration of modern technologies can further enhance our understanding of resources and environmental dynamics, ultimately improving comprehensive watershed management practices.

Jazmurian basin in the southeast of Iran is one of the most important and vital basins. Due to the lack of surface water resources and placing in the priority of use this basin is faced with a sharp decline in the level of underground aquifers. The aim of this study was to identify the factors affecting groundwater resources and predict the groundwater level and its variation in Jazmourian Basin. In this study by considering the importance of identifying the factors affecting the condition of groundwater resources and the causes of decline, initially, the geological and geomorphological features of the basin and its impacts on the quantity and distribution of the groundwater resources were studied. Then, the effect of hydrological droughts with using two streamflow index (SDI) and the standardized precipitation index (SPI) at hydrometric, pluviometric, and synoptic stations located in the basin aquifers was studied. The portion of perceptions on changes in groundwater resources by wells, spring, and aqueducts, as well as the impact of surface structures and expenditures on land surface level changes were determined. In addition, the average monthly and annual mean of groundwater levels during the years 1370-93 were investigated using time series models to predict groundwater changes by the year 1420. The study results on the effect of different factors on groundwater water changes showed that hydroclimatic droughts, although affecting underground water changes, did not have a significant effect. The dams and deep and semi-deep wells with negative correlations of 0. 83, 0. 75 and 0. 68 had the most negative effects on groundwater drops, respectively, and the average discharge of wells and springs increased significantly with increasing groundwater level. Also, the study of changes in groundwater level in the basin indicates a significant decrease (0. 37 m / year) and predictions show that in the coming years it will face more severe losses. The high level of decline was observed in the summer with a change of 1. 96% and in the autumn it was 1. 78% lower than the other seasons. Overall, the results showed that if the current trend of exploitation of the groundwater resources continues, the region will be facing more challenges.

Changes in land use and climatic variables cause changes in sediment yield, filling of reservoirs in dams, and challenges in the demand of residents of the region for access to fresh water. Therefore, understanding the trend of hydroclimatic indicators to evaluate the impact of climatic and hydrological changes on sediment yield seems very necessary. The purpose of this study is to investigate the effect of land use changes and hydroclimatic indicators on sediment production in the Minab Basin using Mann-Kendall and Pettit trend analysis. The results showed that there is no significant trend in rainfall, but the maximum flood discharge, volume and concentration of sediment have a significant increasing trend that occurred in the 1980s. On the other hand, the investigation of land use changes in the Minab basin during the last three decades, 1990, 2005 and 2021, showed that 11% of the area of pasture lands decreased and agricultural and residential lands increased by 220 and 280%, respectively. Therefore, despite the non-significance of the precipitation trend, due to obvious land use changes that have a controlling role on the flood peak flow and sediment production, an increase in the peak flow and sediment production is evident in the basin.