مجله تحقیقات منابع آب ایران
سال هجدهم شماره 3 (پیاپی 62، پاییز 1401)

Investigation of future drought trends and variations under climate change scenarios plays a key role in developing management strategies for minimizing drought's negative societal and economic impacts. Therefore, this study aimed to assess changes in drought characteristics such as the frequency of dry and wet periods, and the trend of drought index based on fuzzy drought index (at time scales of 3, 6, and 12 months) under SSP3 and SSP5 scenarios of CMIP6 during the 21st century. The data of 6 synoptic stations in Karoon River Basin during 1991-2014 have been used in this study. Assessing the reliability of climate models for drought monitoring with fuzzy drought index in the base period showed that the highest correlation coefficient (CC>0.90) and the lowest root mean square error (RMSE<0.14) are found at 3 and 6 month time-scales. In addition, monitoring the drought conditions of the basin under climatic scenarios in future periods revealed an increasing trend (at the 95% confidence level) and the wetness frequency in the northern, northwestern, and western of the basin is more likely to decrease. Over the periods 2046–2072 and 2073-2099 the result of the non-parametric Mann-Kendall test for the scenarios of SSP3_7.0 and SSP5_8.5 was 1.64. Therefore, due to the increasing trend of fuzzy drought index changes to dry conditions in Boroujerd, Safiabad, and Kuhrang stations, the risk of drought during the periods 2073-2099 and 2046-2072 are higher. Accordingly, water managers and farmers should adopt strategies in order to reduce the damages. The results of this research can be valuable in adopting policies and planning for sustainable management of water resources affected by climate change.

Determining flood generation processes and incorporating them in hydrological studies can help make more reliable estimates. Focusing merely on mathematical computations in flood studies sometimes lead to paying less attention to the basic physical processes. Therefore, this research aims to present a process-based flood separation study for 20 hydrometric stations in the Gorganrood River Basin attributed as a flood prone area in the northern part of Iran. For this purpose, partial series of flood events at each station were extracted using the Peak-Over-Threshold (POT) approach selecting an optimal threshold value to determine flood events and considering the independence of the series values. Subsequent to characterizing flood events using some separation indicators including time of occurrence, rainfall duration, flood duration, air temperature, and antecedent soil moisture condition, different types of floods (i.e., floods caused by frontal precipitation, convective precipitation, snowmelt and rain on snow) were identified for each station. The results showed that floods caused by frontal precipitation and rain on snow have the highest and lowest frequencies in the basin, respectively. The research findings indicated that using POT approach and the indicators for classifying the different flood types can lead to a more accurate statistical analysis in flood studies and management.

Arsenic is a toxic and dangerous pollution in groundwaters. A new, efficient and low-cost method for in-situ removal of the arsenic from aquifers is by using zero-valent iron nanoparticles which has been investigated in this research by three types of laboratory experiments including batch, homogenies soil column, and heterogeneous soil column tests. Batch tests have been mainly performed to investigate the effects of temperature and pH on the reaction process between the iron nanoparticles and arsenic. Then, the effect of soil grain sizes and flow velocity in the arsenic remediation by iron nanoparticles have been investigated in homogeneous and heterogeneous soil columns. Based on the experimental results useful graphs are presented to estimate the arsenic concentration for different time and different locations on the soil columns. The results showed the high capability of the zero-valent iron nanoparticles as a useful tool for removing the arsenic pollution from the groundwater. Injected nanoparticles in the soil column, especially in the lower flow velocities and fine-grained soils have been reduced hydraulic conductivity. Also, the results showed that as the flow velocity increases the remediation rate of arsenic pollution with iron nano particles decreases.

Since the water resources systems are most affected by the climate change phenomenon, the organizations which manage the social and ecological demands of water can greatly impact the adaptation to this phenomenon. The adaptive capacity of a water resources system is influenced by various factors and the improvement of each of these factors would lead to an increase in the adaptation capacity of the entire system against the climate change and accordingly less vulnerability against it. In this article, the barriers to the adaptation of the water resources system of the Qarrangu basin against climate change have been identified from the perspective of administrative institutions related to water resources management and the causal relationships between these institutions have been investigated. The study was carried out in the framework of qualitative research strategy and based on thematic analysis method and interviewing the key people in the organizations in charge of the water management in the watershed. Using purposeful sampling under the snowball method and conducting 20 interviews, the theoretical saturation was achieved. Aiming at more reliability 2 more interviews were also conducted but no extra information was acquired. The results show that adaptation barriers in the studied basin can be categorized in three main groups; barriers caused by the attributes of actors, by the characteristics of the water resources system structure, and by the environmental characteristics. Finally, using the system dynamic analysis approach, the causal relationships between the barriers have been identified and solutions have been proposed to overcome such.

In the set of laws and regulations regarding Iran's water resources, the legal relationship of individuals with these resources is referred to as the right of exploitation. This is based on jurisprudence and legal principles that recognize water as a common trust and in other words, a public trust, and negate any right to ownership for the user. However, due to the ambiguity in the legal nature of this exploitation right, we continue to witness the possessive behavior of the exploiters and the conflicting opinions of the administrative and legal authorities in this regard. Therefore, in this analytical and descriptive study, we examined the jurisprudential and legal foundations of the subject and then put forward the theories that have been established in the relevant laws based on the shared and trust nature of this public wealth. Then, referring to Article 29 of the Civil Law, which is in the position of expressing the various rights that individuals have in relation to property and in which the right to ownership, including the object and benefit, the right to usufruct and easement, the characteristics of the right of exploitation, we observed an affinity for usufruct rights in the Iranian right of water exploitation. Therefore, under this legal nature, we came to the conclusion that the water users are not entitled to any kind of proprietary policy, including the right to transfer and waste this right, and the government that has this public trust supervises water sources and uses by prescribing and adjusting exploitation licenses according to public interests and regardless of the proprietary behaviors.

Climate change and its intensifying impact on the hydrological cycle have been acknowledged in recent years. Considering the importance of available snow to the water resources recharge, especially in semiarid regions, evaluating climate change impacts on snow cover area (SCA) has gained significant attention. In this study, a methodology is presented which is capable of evaluating the impact of climate change on SCA. To collect historical data, MODIS snow products are used. To evaluate the impact of climate change on SCA, the turning points of SCA time series are detected using the Standard Normal Homogeneity Test; and the trend of historical data is analyzed using Mann-Kendall and Sen’s slope tests. To project the future SCA (2021-2099) under climate change considering precipitation and temperature as inputs an Artificial Neural Network-based model is developed. The proposed methodology is tested in sub-basins in Iran. Analyzing the present SCA (2000-2020) the results showed that the SCA’s turning points are only detected in two sub-basins of Tashk-Bakhtegan-Maharloo in 2007 and Gavkhooni in 2008, respectively. Moreover, a significant decreasing trend of SCA is detected during winter in the majority of sub-basins. According to the results, most sub-basins will experience a significant reduction in their future SCA under all climate change scenarios. In other words, compared to the historical SCA, the average future SCA will increase by 100 percent in RCP 4.5 scenario while decreasing by 20 percent in RCP 8.5 scenario.

Human interventions, including land-use change and encroachment on river boundaries along with the impacts of the climate change have resulted in an increase in flood damages. This study aimed to identify and analyze the factors intensifying the floods of April 2019 in the Khuzestan province. To this end, we determined the return period of large floods in the region in April 2019; investigated land-use changes between 2000 and 2018 by using the random forest classifier; explored the changes in the soil moisture using remote sensing data; and analyzed the rule curve of the Karkheh and Dez dams. The results showed that the discharge observed at the Jelogir station, as the nearest station upstream of Karkheh Dam had a return period of 262 years, which is far greater than the return period of historical floods in the study area. The weak correlation between runoff intensity and antecedent soil moisture at 5% confidence level during 30, 45, 60 and 120 days before the flood indicated that beside the antecedent soil moisture other factors such as rainfall intensity and snowmelt were contributing to the intensified flood. We further concluded that the change in the land-use between 2000 and 2018 in the study area cannot be considered as a strong factor in the intensification of floods. Finally, the operation of Dez Dam in the water year of 2018-2019 had a much more effectiver impact on the flood control of April 2019 compared to the operation of Karkheh Dam.

The correct application of deficit irrigation requires thorough understanding of the yield response to water (crop sensitivity to drought stress) and the economic impact of reductions in yield of products. In regions where water resources are restrictive, it can be more profitable for farmers to maximize crop water productivity instead of maximizing the harvest per unit land. Therefore, in the present study the effect of adoption of Clarke's deficit irrigation was evaluated in farms-level in Ardalan plain with emphasis on water resources management. This case were applied using a spatial-aggregation positive mathematical programming (SA-PMP) model and the questionnaire data related to year 2019-2020. After calibration of proposed modeling system in GAMS software, the effects of Clarke deficit irrigation in 5 and 10 percent levels on optimum cropping pattern, consumable water resources and farmers' gross margin were evaluated. The results showed that there is a significant difference between farmers' paid water charges (547 Rials) and economic value of irrigation water (1348 Rials) in Ardalan plain which leads farmers to consider water as a free input and its over-consumption in crop lands. Also, applying the deficit irrigation method leads to a saving of 5.01 to 9.78 percent in irrigation water for only a slight decrease in yield of selected products (from 0.88 to 5.72 percent) and in farmers’ gross margin (from 3.15 to 7.07 percent). More stretchability of water demand in small farm (ewater= 0.573) and increasing the economic value of water from 3.9 to 8.9 percent compared to the base year condition are another consequence of application of deficit irrigation in representative farms pattern. Finally, for a sustainable management of water resources in Ardalan plain it is recommended to use deficit irrigation method at low levels (5 and 10 percent) especially in large farms, to apply the policy program of equality consideration (in order to reduce the gap between the water price and the economic value of water), to modify the pricing system to differentiate the price of water for small, medium and large farms.

Global warming changes precipitation and temperature patterns. In this study, the linear scaling post-processing method was used to correct the biases of seven climate models (GCMs) under the Coupled Model Intercomparison Project Phase 6 (CMIP6). Also, the performance of these models was evaluated for simulating temperature and precipitation in the Hamedan-Bahar plain in the baseline period of 1990 to 2014. Three performance indicators (mean square root error, Nash-Sutcliffe, coefficient of correlation) were used to quantify the models᾽ reproducibility to climatic parameters for the historical period (1990–2014). Based on the results, CMCC-ESM2, MIROC 6, and NorESM2-MM models were selected and their ensemble were used to project temperature and precipitation in near (2026–2050), mid (2051-2075) and far futures (2076-2100) under three socioeconomic shared pathway (SSP) 1–2.6, 2–4.5 and 5–8.5. Based on the obtained results, in all three periods, the average precipitation decrease in summer is higher than the other seasons, and the highest amount of decrease will occur in the mid future period under the SSP5-8.5 scenario (67%). Moreover, the minimum and maximum temperatures increased in all three future periods and under all three scenarios. The highest increase of temperature occurred in January and February. Predicting climate parameters using selected models in this study can be a basis for planning and managing water resources and developing the necessary measures to climate change adaptation in Hamadan-Bahar region.

Urban management, with the aim of thinking and planning on how to improve the current situation of a city and its citizens, tries to represent a good perspective for the future development and progress. Traditional urban water management in the Qajar period, despite its gradual awareness of modern management models on an international scale, was inefficient in developing the water supply networks in Tehran and unable to equip the city's water structures with modern systems. There are fundamental ambiguities about the underdevelopment and the roots of this inefficiency. This article employs an analytical approach and an explanatory-interpretive method in order to pathology the roots of the underdevelopment of urban water management and water structures in Tehran in the Qajar period. The authors tried to answer this question that why the water supply network of Tehran during the Qajar period was not adjusted despite the growing awareness of the government officials about the modern urban water management in other countries. The results showed that the lack of clear laws and structural and administrative interference, as well as the preference of personal interests over public interests, parasitism and "crisis escape" policy when Tehran water problems occured, were serious and fundamental harms that hinder the efficiency of urban water management and development of sustainable water supply networks.

The trend of the sea level changes is seriously challenging the coastal cities around the globe. Changes are various in different geographical conditions. The semi-enclosed sea of the Persian Gulf experiences the anaomalies with a higher rate in camparison to the world average. Therefore, it is quite imporatant to investigate the degree of influence and correlation of governing parameters including, sea surface temperature (SST), air temperature at 2 meters above the surface, sea surface salinity (SSS), and horizontal wind speed in both east and north directions using a set of remote sensing data, hybrid (HYCOM), and reanalysis product data (ERA5) from 1993 to 2020 in the Persian Gulf. The long-term annual trend in the Persian Gulf shows the following changes; 3.9 mm/yr in the sea level, 0.02 °C/yr in SST, 0.024 °C/yr in air temperature at 2 m above the surface, -0.03 psu/yr in SSS, and -0.01 ms-1/yr and 0.01 ms-1/yr in horizontal speed of air moving respectively towards the East direction and the north direction. Also, according to the results of the monthly and annual correlation between these parameters with the sea level changes only correlation with SST  with R2=0.6 (p-value=0.04) and with SSS R2=-0.4 (p-value=0.03) were significant. The comparison of the results in monthly and annual scales shows that the sea level changes in the Persian Gulf do not show the same patterns. Rather, these changes are affected by different parameters in different time of the year.

Nowadays, issues related to soil erosion are one of the most critical issues and one of the major concerns in watershed management. Accordingly, knowledge on soil erosion process at watershed scale needs proper, suitable, accurate, and desirable temporal resolution data collection using appropriate device. An innovative device is designed and manufactured through this research for automatic sampling and measuring suspended sediment concentration. This aimed at a better understanding of the processes of soil erosion and sediment yield through better time-distributed measurements. The background of studies and research related to the project has been reviewed worldwide and based on previous experiences, manufacturing the mechanical part of the system was carried out and completed. Also, the necessary laboratory practices for designing, formulating, and simulating the electronic parts were performed. Numerous tests and attempts were made to optimize the mechanical and opto-electronic parts based on determining different arrangements and sources of light. The field test of the device in several rivers in the northern Iran indicated a high agreement of more than 93.25% between the observed and estimated suspended sediment concentrations. The designed sampler is expected to provide suitable estimates on concentration of suspended sediment in the dominant range in watercourses with acceptable, affordable cost and energy, particularly in special conditions such as floods, in the entire day and night hours, and even for remote areas.