مجله مهندسی و مدیریت آبخیز
سال شانزدهم شماره 2 (تابستان 1403)

The role of water in agricultural development and economic growth is undeniable. The imbalance between water supply and demand in Iran has created a challenge for the management of water resources, especially in agriculture. Paying serious attention to water productivity and improving it through appropriate methods and policies is one of the most effective solutions to address the water crisis and enhance the quantity and quality of agricultural production. The concept of water productivity is to produce the best and most products with the least amount of water. Agricultural water productivity has received serious attention in recent years from scientific societies related to irrigation and agriculture. The variation in water productivity for different crops at the local level and in comparison with other countries with similar climatic conditions indicates the potential for increasing agricultural water productivity. In the present research, the productivity of agricultural and horticultural products was investigated through field surveys, field measurements, and remote sensing analyses.

First, the status of water resources in the aquifer, including changes in groundwater levels and programmable water, was investigated. Then, the water consumption of agricultural plants was calculated using the difference between effective rainfall and plant water requirement (evaporation-transpiration). In the next step, the cultivated area of Basht Aquifer was examined using Sentinel-2 satellite images in Google Earth Engine software. Yield, dates of planting and harvesting, and irrigation times for agricultural products were verified through questionnaires completed by farmers and experts. After that, the water requirement of the current cultivation pattern was calculated using the FAO Penman-Monteith method. Finally, the productivity of different products was determined by evaluating the products in terms of productivity.

The area of the alluvial aquifer was 45.5 km², with an average length of about 25 km and a width of 5 km. The total volume of discharge and extraction from groundwater resources was 39.723 MCM. The infiltration amount of the Basht alluvial aquifer was calculated to be 7.905 MCM. By joining the outflow streams, including transfer streams through different elevations, the aquifer was recharged with a total of 20.377 MCM. Calculations using the FAO Penman-Monteith method showed that the water requirements of the dominant crops in the aquifer, including citrus fruits, wheat, barley, corn, canola, watermelon, rice, legumes, and alfalfa, were 9170, 5630, 4821, 7863, 5411, 9291, 20234, 5225, and 14083 m³, respectively. In total, the amount of water consumed by the agricultural products of Basht Aquifer was nearly 45 MCM, which was approximately equivalent to 1 m³m⁻² of the cultivated area. This is 2.64 times higher than the amount of water that can be programmed for agriculture (17 MCM).

The cultivation pattern will be influenced by parameters such as the climatic compatibility of products, the potentials of water and soil resources, regional needs, customs and interests of local people, and economic evaluation and income from production. Any change in the cultivation pattern should consider all social, economic, and environmental factors. However, given the existing conditions of the water sources, any cultivation pattern (even those considering high income) that increases discharge compared to the aquifer's recharge sources will be dangerous for future sustainability and will cause groundwater salinization and aquifer subsidence. Cultivation of high water-consumption plants such as seed corn should be stopped due to the severe water conditions of the region, and more investment should be made in developing crops such as canola, which are better adapted to the region's climate.

The main purpose of this research is to identify the behavior of rivers in the area of Lashtghan shrimp breeding site and to provide technical solutions to organize and prevent flood risks there.

In this study, HEC-RAS was used to perform hydraulic flow calculations based on unsteady flow. Calculations were done with changes in flood flow with different return periods. To determine the flood zone for the 25-year return period, the water height was transferred to ArcGIS. Using the HEC-Geo-RAS extension, the flood zone was determined in ArcGIS. To present the proposed natural bed line, satellite images at different time intervals were analyzed and the proposed bed line was extracted after verifying the flood zone with these images. The amount of technical protection was calculated using the DLSRS (Discharge Location Stability Regime Social Tension) method. The flood return period for the design was considered to be 100 years, based on economic, social, and climatic conditions. Considering the project's purpose, domain of usage, and technical and economic conditions, an earthen dike was selected for the land protection plan against floods. In Civil 3D software, the protective dike project line was defined and, according to the 100-year flood water level, the protective dike was designed.

The boundary for modeling the flow of rivers and canals leading to the Lashtghan site was established upstream of the hydrograph and downstream of the water level (2.9 meters, or 76% of the duration of the course is less than this value), based on justification studies. The observed minimum height is approximately 0.65 meters, the maximum height is 5.7 meters, and the average height is approximately 1.6 meters; these measurements are insufficient to ascertain the height of the dike. The height reached its highest and lowest values every six hours. In the northern region of the site, the maximum water level, maximum flow depth, and maximum flow speed were more apparent. The water level fluctuated between 1.2 and 35 meters, the maximum flow depth increased from 0.001 to 40 meters, and the maximum flow velocity improved from 0.00033 to 1.8 meters per second.

The model output included characteristics of the maximum flow level, depth of flow, and maximum flow velocity in the study area. It was observed that the built dike has no effect on the surrounding residential areas. Due to the topography, the earthen dike acts like a reservoir in some places, preventing downstream flow and storing water behind the dike. This reservoir has a volume of about 3 million cubic meters for a 100-year return period flood. By constructing a borrow pit near the dike, a significant part of the water can be transferred downstream. Finally, the height of the dike, the slope of the body, and the width of its crown were calculated, with the cost estimated at 72,925,000,000 million Rials.

The degradation of soil structure and reduced water infiltration into the soil are indicators of soil degradation, which lead to decreased stability and production quality, as well as environmental problems. Soil conservation methods are widely used to curb soil degradation processes and improve soil structure and permeability. The effectiveness of these methods in enhancing these indicators and controlling soil degradation requires further study and evaluation. This research aims to investigate the stability of soil structure and soil infiltration rate affected by various soil management and conservation operations, and to compare them in the Razin Watershed area of Kermanshah Province.

For this purpose, eight common reclamation and conservation operations in the study area were selected and evaluated. These operations include pit-seeding and seeding, rangeland audit plan - conversion of dryfarming to rangeland, rangeland audit plan - conversion of dryfarming to forage cultivation, almond tree planting alongside digging holes, land leveling, seedling planting, conversion of dryfarming to rangeland, forage cultivation and orchard, and forest area. For evaluation, random systematic sampling points were selected within the area of each operation and their corresponding control area for study and sampling. After digging profiles and sampling the soil, the laboratory measured and calculated soil aggregate stability indices, including Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD), and the proportion of stable aggregates larger than 0.25 mm (WSA>0.25). The final infiltration rate was also measured in the operation areas and their controls using a disc infiltrometer. Finally, a statistical comparison of the mean values of MWD, GMD, WSA>0.25, and final infiltration rate in soil conservation operations and their control areas was performed using the T-test for independent samples and the Duncan test for comparing the means of these indices in various operations using SPSS software.

The evaluation results showed that the lowest MWD index was related to land leveling and sapling planting at 0.15 and 0.35 mm, respectively, while the highest values at 1.9, 1.8, and 1.6 mm were related to 20-year-old almond planting, 10-year-old almond planting, and forest areas, respectively. Additionally, the highest WSA>0.25 index values were found in fodder cultivation, orchard establishment, and 10-year-old almond planting operations, indicating the formation of large and stable aggregates due to conservation operations. Among the eight operations studied, the 20-year-old almond planting operation showed the greatest improvements in MWD and WSA>0.25 indices. The results for the final infiltration rate indicated that soil conservation operations, particularly converting low-yield rain-fed lands to sapling planting and changing rangeland use to 10-year-old almond planting, led to the highest increases in final infiltration rate, at 21.8% and 16%, respectively, compared to the control.

Overall, soil conservation operations increased the relative share of larger soil aggregates. However, the soil infiltration rate index showed conflicting results, as factors other than the evaluated conservation operations also influenced water infiltration into the soil, necessitating further studies. Consequently, examining the role of management, especially land use management, is essential for sustainable soil resource utilization.

The rapid growth of the global population has led to a significant surge in water consumption across various sectors such as agriculture, industry, and domestic use. This heightened demand for water has profound implications, particularly in ensuring food security, meeting industrial needs, and providing safe drinking water. However, alongside this population growth, climate change has emerged as a critical factor, altering precipitation patterns and exacerbating water scarcity issues. In response to these challenges, there is a growing need to identify and manage accessible water resources effectively. This involves understanding the complex interactions between different components of the hydrological cycle, including surface water, groundwater, soil moisture, and atmospheric water. Hydrological models have emerged as valuable tools in this regard, offering insights into water availability, flow patterns, and quality assessment. These models play a crucial role in various aspects of water resource management, including mitigating environmental impacts, managing floods, and predicting future water stress scenarios. Additionally, they facilitate the analysis of watershed-scale dynamics and provide a basis for informed decision-making. Global Hydrological Models (GHMs) have gained prominence due to their ability to capture the interconnectedness of water systems across different regions. They enable researchers to assess and predict hydrological processes on a large scale, contributing to a more comprehensive understanding of water resource dynamics. Recent studies have focused on evaluating the performance of hydrological models, such as the Variable Infiltration Capacity (VIC) model, in simulating river discharge, soil moisture, and precipitation patterns. These evaluations often utilize various data sources, including satellite imagery, to validate model outputs and improve their accuracy. Moreover, the integration of advanced optimization algorithms, such as NSGA-II, enhances the modeling process by optimizing model parameters and improving simulation results. In light of limited ground station data in extensive watersheds, researchers increasingly rely on long-term weather data and modeling techniques to bridge data gaps and improve the accuracy of hydrological predictions. Overall, ongoing research efforts aim to refine hydrological modeling approaches, integrate diverse data sources, and develop robust strategies for sustainable water resource management in the face of growing population pressures and climate uncertainties.

The Heblehroud Watershed, situated in the southern part of the Central Alborz mountain range, covers approximately 326,991 hectares and lies between coordinates 52° 13' to 53° 13' East longitude and 35° 17' to 35° 58' North latitude. It spans across Tehran, Mazandaran, and Semnan provinces. Mount Sefidab, with an elevation of 4047 meters, marks its highest point. The region features a semi-arid climate, receiving 272 mm of annual rainfall predominantly in winter and spring. The Heblehroud River, originating from the northern mountains, serves as the main drainage outlet. The semi-distributed hydrological model (VIC) was employed in this study to optimize the coefficient of efficiency (KGE) in simulating runoff on daily and monthly scales in the state of water balance. The study validated the VIC model using data from the Bonekooh station and applied the NSGA-II optimization algorithm to calibrate soil parameters from 1992 to 1996, considering the impact of watershed management. Soil data were obtained from the HWSD database available on the FAO website and categorized into 36 classes based on physical and chemical soil properties. Land cover data were sourced from the MODIS satellite database and classified into 17 categories according to the IGBP standard. Elevational bands are crucial in the VIC hydrological model for assessing soil water pressure distribution and surface runoff. In the Heblehroud basin, elevation differences can reach several thousand meters, impacting flow estimation. Therefore, using elevation bands derived from SRTM data is essential for accurate simulation. The accuracy of precipitation data from each database at the cell scale was evaluated using the IDW method.

The results indicated that the APHRODITE database had the highest accuracy, while PERSIANN-CDR had the lowest. Additionally, the runoff simulation results demonstrated that the VIC hydrological model performed well in simulating daily and monthly runoff. The KGE efficiency index for simulated daily runoff was 0.78 during the calibration period and 0.76 during the validation period. Evaluating the simulated runoff using climatic precipitation data revealed that PERSIANN-CDR satellite precipitation data was less accurate in detecting precipitation amounts but performed better in simulating runoff. The KGE for this data on a daily scale was 0.64 during the calibration period and 0.77 during the validation period. The KGE index for APHRODITE precipitation data based on ground stations ranked second, with values of 0.62 and 0.75 during the calibration and validation periods, respectively. ERA5-Land precipitation data, which is reanalyzed data, ranked third with a KGE index of 0.50 during the calibration period and 0.66 during the validation period.

These findings indicate that climatic precipitation data can be effectively utilized in watershed management studies with low cost and appropriate accuracy, particularly in basins lacking a regular network or long-term data availability.

The involvement of people in the implementation of natural resource schemes ensures the success of these initiatives and can be very beneficial for the natural resources available in watersheds and stakeholders. Public participation in the implementation of natural resources operations is crucial for achieving the goals and success of these projects. Emphasizing public participation in the conservation of natural resources is of great importance and credibility. Natural resources are an integral pillar of human life, and plans are developed and implemented to improve the environmental and social conditions of socio-ecological systems. Given that this research is focused on desert watersheds, the unique conditions of these watersheds are considered outstanding features of this study. This emphasis highlights the value and importance of people's organizations in desert areas, which usually have smaller populations compared to other climates. It also underscores the necessity of public participation for the success of natural resource projects across different climates in watersheds nationwide. Without public participation, the success of these projects, despite all environmental conditions, is very low.

In this study, the number of cooperative companies, rural development committees, micro funds, and rural funds in the entire Yazdanabad watershed was obtained. The distribution of different villages in the Yazdanabad watershed was then identified, and the activities implemented in them were investigated. Subsequently, meetings held by the PRA method in the villages of the Yazdanabad watershed were studied, and a comparison of NGOs before and after the implementation of the comprehensive natural resources management plan was carried out and analyzed.

The results showed that there are 3 cooperative companies and 4 rural funds in the Yazdanabad watershed, and 16 development committees are active in this area. Almost every village has a development committee, and there are also 2 micro funds in the Yazdanabad watershed. The implementation of natural resources projects has a significant impact on the stakeholders of the watersheds, especially in desert areas, provided that people are the main basis of the implementation of this plan. By encouraging and modeling, 100% participation can be achieved to ensure the success of such projects. The results of natural resources plans before and after their implementation showed that these plans greatly impact people's livelihoods and the sustainable conservation of natural resources. People who are more aware of their natural resources are better able to protect them in their watershed without government assistance. The wide range of natural areas and the lack of human resources have caused the country's forests, rangelands, and watershed management organizations, as the main authorities and custodians of these fields, to have limited influence in all areas. This has led people to spontaneously meet their needs by forming and joining NGOs.

Moreover, the research results showed that the most common executive activities in all villages located in the Yazdanabad watershed were the formation of rural development committees and holding meetings regarding natural resources laws and regulations.

Due to the heterogeneity in watersheds and the non-linearity of hydrological behaviors, it is very complicated and difficult to fully understand the relationships within watersheds. Therefore, in evaluating these systems, a modeling process is necessary. Over the last few decades, hydrological/hydraulic models have become essential in hydrology studies due to the development of programming languages and the provision of optimal and efficient algorithms for solving differential problems. The application of rainfall-runoff simulation models for flood events has been extensively studied by researchers in the field of water and soil protection, leading to the development of various models to simulate rainfall-runoff processes. One of the successful models in this field is the TOPKAPI-X model. This model was created in the 1990s at the University of Bologna by Professor Todini as a distributed rainfall-runoff model in watersheds. An important feature of distributed models is their ability to simulate components at any point of the watershed, allowing results to be extracted at any required point. Unlike lumped models that consider the entire watershed as a single unit, distributed models allow spatial distribution at any point in the watershed. Therefore, in this research, after calibrating and validating the TOPKAPI-X physical-distributed model in the studied basin, the model was optimized for flood estimation.

The Gamasiab basin is located in the west of Iran, in the northern region of the Zagros mountain ranges, to the north of the Karkheh dam basin, and primarily within the territories of Hamadan and Kermanshah provinces. The mountainous regions of this basin are mainly concentrated in the northern and southern parts, while its lowlands and plains are mostly located in the middle and southeastern parts of the basin (Ministry of Energy, 2014). In this research, the TOPKAPI-X model was used to simulate floods in the Gamasiab watershed. First, the watershed boundary was delineated using a digital elevation model (DEM) with a resolution of 30 meters. Land use maps, soil texture, watershed network, and climatic components were entered into the TOPKAPI-X model. The outlet location of the basin (hydrometric station) was used to simulate the flow using the TOPKAPI-X distributed hydrological model. Continuous time series data on a daily time step were used in this rainfall-runoff model. Specifically, daily rainfall data from 13 rain gauge stations and temperature data from 4 synoptic stations during the statistical period (1999 to 2020) were used to simulate the flow. After running the model several times, the general parameters were manually adjusted each time until the optimal values of the general parameters were obtained by considering the appropriate values of the evaluation criteria (NS and Bias) for the basin.

This research was conducted to analyze the flood discharge of one of the main sub-basins of the Karkheh dam basin using the TOPKAPI-X model on a daily time scale. In the TOPKAPI-X software environment, simulations were performed during the calibration period using input maps and observational rainfall, temperature, and discharge data. A visual comparison of the observed and simulated hydrographs allows for a general and quick evaluation of the model's accuracy. The graphical results of the comparison between the discharge generated by the TOPKAPI-X model with the calibrated parameters and the measured discharge in the Gamasiab basin were presented. The TOPKAPI-X model has the ability to estimate the maximum daily flow rates of the Gamasiab basin; however, some of the simulated flow rates are higher than the observed flow rates. Four criteria—NSE, R, BIAS, and RMSE—were used to evaluate the model. The evaluation results of the TOPKAPI-X model indicate the accuracy of flow simulation, with a Nash-Sutcliffe criterion of 0.697 during the calibration period (1999-2014) and 0.660 during the validation period (2015-2020) for the Gamasiab basin. Therefore, it can be concluded that this model has good performance for flow simulation.

The importance and usefulness of hydrological models for water resources management, understanding hydrological processes, and conducting impact assessment studies is clear. Hydrological models are crucial tools that enable scientists and policymakers to make informed decisions based on simulations of watershed behavior. Considering the increasing demand for water and the impact of climate change, hydrological simulation will be one of the essential methods for future water management. The results of this study showed that the TOPKAPI-X model has potential in simulating runoff in the selected basin. Due to the capabilities of the TOPKAPI-X distributed hydrological model, this software is recommended as a modeling tool for other basins.

Climate is one of the environmental factors whose changes cause extensive alterations in different parts of the ecosystem and pose a significant threat to sustainable development. Temperature, a main element of climate, can affect the climate structure of any region through sudden, short-term, and long-term changes. In recent decades, the Earth has faced global warming, evidenced by climatic changes worldwide. One important consequence of global warming is the increase in extreme weather phenomena, such as sudden temperature changes, excessive heat, abnormal cold, heavy rains and floods, drought, and dust storms caused by the drying of wetlands. Climate extreme indices not only play an important role in investigating climate events on regional and global scales but also assist in climate modeling and decision-making for various sectors.

In this research, temperature data from the MRI-ESM-2 model under three scenarios—optimistic (SSP1-2.6), average (SSP2-4.5), and pessimistic (SSP5-8.5)—for two periods, the near future (2021-2060) and the distant future (2061-2100), were used. First, historical data for the base period and scenario data for the future period (until 2100) for the studied climate model were obtained from the ESGF database. Then, using the R programming language, the time series of historical data and scenarios were extracted from the model for each desired station, and the statistical downscaling of the data was performed using the bilinear interpolation method at the level of the studied stations. The data were grouped based on the three scenarios in all studied stations, and RClimDex software was used to extract indices based on minimum and maximum daily temperatures. In this research, 16 extreme temperature indices for the studied area were calculated on annual and monthly scales, and trends and breakpoints in these indices were investigated using the Mann-Kendall trend detection test, Sen’s Slope test, and Pettitt mutation detection test.

The results show a decrease in extreme hot events based on the SSP1-2.6 scenario, a decrease in indices related to cold and freezing days, and an increase in extreme warm indices based on the SSP5-8.5 scenario, observed in most areas of the province. Generally, the indices for the number of summer days (with a slope of 40-70%), tropical nights (45-65%), the length of the heat period (30-50%), and the length of the growing season (40-60%) showed significant increases. Conversely, the indices for the number of frost days (-20 to -80), ice days (-10 to -40), and the length of the cold period (-10 to -70) significantly decreased. The results of Pettitt's test indicated change points for increasing and decreasing trends in hot and cold extreme indices, respectively, in the 2040s (near future) and 2080s (far future). Therefore, to control extreme temperatures and their adverse effects on various aspects of human life, especially agriculture and water resources, strategies should be developed and implemented according to the needs of each region.

The results indicated more frequent sudden changes in temperature indices under the pessimistic scenario compared to the other two scenarios, affecting broader areas of Mazandaran province. There is a likelihood of sudden increases in hot extreme indices and decreases in cold and freezing days both in the near future (2030s, 2040s, and 2050s) and far future (2070s and 2080s). Overall, significant changes in temperature extreme indices were observed during the future statistical periods studied, with Mazandaran province expected to experience higher air temperatures and more frequent extreme heat events. These findings align with regional and global studies. The rise in temperature, particularly during hot months when precipitation decreases naturally, significantly impacts agriculture in this region, which is a major area for rice production in the country. These changes also affect the hydrological cycle downstream of the Haraz basin. Additionally, temperature fluctuations during winter and cold months can influence the timing of snow melting in the basin, thereby affecting peak flood flows downstream. Given these factors and the necessity of such research in understanding human activities, water resource management, food security, and human health, it is crucial to investigate the impacts of extreme climate events driven by temperature in future policy-making. Human societies must adapt and adjust based on these anticipated conditions. Therefore, studying the intensity, frequency, and timing of extreme events and raising awareness about them can effectively address environmental challenges and enable rational planning to mitigate and reduce these events.

Currently, drought poses a significant threat to food security due to reduced rainfall and increased agricultural demand. Its impact is particularly severe in arid and semi-arid regions, where populations are more vulnerable. Drought affects groundwater systems by initially lowering water supply, followed by a decline in groundwater levels and discharge. Compared to other types of drought, characteristics such as duration, intensity, and frequency alter groundwater systems.

Given the critical need for drought assessment and monitoring, this study investigated drought conditions in 12 areas within the Daranjir Watershed from 2002–2003 to 2017-2018. The watershed spans approximately 50,736.44 km² across Yazd and Kerman provinces, with elevations ranging up to 1,857.90 meters. Highlands cover 58.99% of the area, while plains cover 40.99%. Data on groundwater levels from observation wells were obtained from Iranian Water Resources Research Organization (Tamab) and regional water organizations in Yazd and Kerman provinces. Average monthly groundwater level values were then extracted from maps using inverse distance weighting interpolation in MATLAB. Groundwater drought conditions were subsequently calculated based on the Groundwater Resources Index (GRI) in MATLAB.

The GRI index calculations revealed severe droughts in Daranjir, Bardsir, and Qaryeh al-Arab deserts, with deficits of 81.38, 77.75, and 75.66, respectively. Qaryeh al-Arab experienced the longest drought, spanning 121 months, indicating the area's high intensity and prolonged drought conditions compared to other study areas. Mild droughts were the most frequent after normal drought across all study areas based on GRI index class frequencies.

Due to insufficient and highly variable atmospheric precipitation, drought is inevitable, especially in arid and semi-arid climates. Understanding drought severity and its impact on ecosystems is crucial for effective watershed resource management and optimal resource utilization. Continuous monitoring of groundwater levels due to drought and preparation of a comprehensive atlas for other watersheds in the country are recommended. Additionally, comparing drought conditions using appropriate models is essential. Short and long-term strategies are advised to mitigate this natural phenomenon, such as expanding greenhouse crop cultivation, utilizing drought-resistant crop varieties with high water efficiency, adopting pressurized irrigation systems, and implementing infrastructure projects to enhance groundwater and surface water storage, such as cement dams, reservoirs, and floodwater spreading systems in the study area.