فصلنامه حفاظت منابع آب و خاک
سال دوازدهم شماره 4 (پیاپی 48، تابستان 1402)

With the increase in the production of greenhouse gases due to the industrialization of the countries of the world, we are witnessing the occurrence of global warming, which has caused climate changes all over the planet in recent years. One of the effects of this phenomenon is the change in the behavior of weather parameters such as temperature and precipitation. The effects of climate change phenomenon on precipitation have led to changes in the intensity of precipitation and finally changes in intensity-duration-frequency (IDF) curves of precipitation for different regions of the world and country. Therefore, updating the intensity-duration-frequency (IDF) curves is necessary because of their importance in the design of hydraulic structures used in urban flood management. One of the problems of producing intensity-duration-frequency (IDF) curves is the lack of access to rainfall data with different continuities. The purpose of this research is to use the fractal method to obtain precipitation with different continuities and then evaluate the effect of climate change on the intensity of precipitation in Rasht City. .

In this research, the accuracy of the fractal method for generating intensity-duration-frequency curves is first evaluated. Then intensity-duration-abundance curves are produced by using fractal theory and by determining the effect of climate change on rainfall intensity by TREND software, two periods before and after climate change are evaluated and compared.

In this research, the validation of the Fractal method shows that the IDF curve production for Rasht city using the Fractal method compared to the IDF curve production using observational data has about a three percent difference. Therefore, this method was used to generate IDF curves for the years when rainfall data with less than three hours of duration was not available. The evaluation of IDF curves with TREND software on the rainfall intensity for different durations demonstrates that the rainfall intensity jump occurred in 2003 towards becoming more intense due to the effect of climate change. For example, for 10 minutes with a return period of 100 years before the effect of climate change, the intensity of rainfall is 158 (mm/h) and after the effect of climate change, the intensity of rainfall is 225 (mm/h). Also, the results showed that the period of short returns has changed more than the period of large returns, that is, the 2-year return period has increased by about 70% and the 100-year return period has increased by about 40%.

In this research, by evaluating the fractal method, it was determined that if there is no access to rainfall data with different durations, the fractal method is a suitable method for generating different rainfall durations and generating IDF curves with acceptable accuracy. be Also, the results showed that the jump of intensity-duration-frequency curves occurred under the effect of climate change in 2003, and in the period of climate change, compared to the period before climate change, the intensity of rainfall moved towards more intense rainfall, and this event occurred in the period Short-term returns show a greater increase.

Water resources management has long been the focus of residents in Iran. Knowing of the time and the amount of rainfall contributes to better planning for water resources management, and this can be examined according to the available statistical data. The need for knowledge about precipitation trends in the study areas facilitates and legalizes water resources management and planning and helps to supply water with a higher reliability factor. The purpose of this research is to estimate and analyze the precipitation trends in Kohgiluyeh and Boyer-Ahmad Province within the  Zohre-Jirahi basin.

This research is carried out in the Zohre-Jirahi basin in Kohgiluyeh and Boyer-Ahmad province based on the data from 1966 to 2018. In this regard, first, meteorological stations related to the studied area were located and their statistics were extracted from the received data. The stations’ data homogeneity is calculated based on the Kolmogorov-Smirnov method, and those without homogeneous data or with limited data are removed and, 30 stations are selected for data rebuilding. Rebuilding of missing data is done with Inverse Distance Weighted methods with the power of two and ordinary linear Kriging and after evaluating the methods by three criteria of Root Mean Square Error, Mean Absolute Error, and Coefficient of Determination, the optimal method is selected to rebuild the missing data in this study area. After rebuilding the data, a multi-dimensional raster containing rainfall information related to the years of the statistical period is produced and the time series of the relevant data is created in an array and per surface unit. In this research, according to the surface of the study area, time series of 8915 points are analyzed, and the trend of changes based on the Mann-Kendall method and Sen's slope on an annual and monthly scale are assessed in these points and, raster maps are produced.

Among the methods used for rebuilding missing data, based on the evaluation of the models, the optimal method for rebuilding missing data in the study area was the Inverse Distance Weighted method with a coefficient of determination of 0.95.The results of calculations on an annual scale show that the average Sen's slope in the study area does not have a significant trend and is equal to 0.0011. The average Sen's slope in the study area on a monthly scale is 0.28 in April and has an upward trend, in May Sen's slope is equal to -0.03 and indicates a downward trend and in June and July, an unobserved trend, and the results of Sen's slope calculations are zero. In August, there is an upward trend, and it’s value is equal to 0.11. In September, there is an upward trend, and it is equal to 0.06. In October, there is no observed trend, and it is equivalent to zero. In November and December, the trend is upward, and the average Sen's slope in the study area is equal to 0.19 and 0.62, respectively, and in January, February and March, the downward trend is equal to -0.48, -0.55, and -0.14.

The results do not demonstrate a significant trend on an annual scale, however on a monthly scale, in December, April, November, August, and September, respectively, the highest upward trend is observed, while in February, December, March, and May, respectively, have the highest downward trend, and June, July, and October lack trends. The maximum average Sen's slope is calculated for December and equal to 0.62, and its minimum is in February and equal to -0.55. The management of water resources, especially in the agricultural sector as the main consumer, has large economic and social dimensions and is inevitable, and due to the great impact of water supply time to optimize and increase productivity, this research can be used to review the pattern and time of cultivation in this area. Groundwater artificial recharge, storage process, and consumption process should adapt to the new changes.

It is possible to identify the areas of plains that are highly vulnerable to contaminating wells by modeling, integrating, and developing indicators. The presence of polluting points in these areas will bring and intensify the risk of contamination of wells. The main goal of this research is to develop and provide a new index to determine the vulnerable levels around the wells that can cause the pollution of drinking and agricultural wells and, consequently, the pollution of the aquifer. In this research, the combination of point pollutant sources density was used as a risk index and well capture zones as a vulnerability index. This method is more accurate than other methods because it takes into account features such as discharge, natural damping, soil, aquifer hydraulic conductivity, land use, landcover, and distribution of wells, and it is a combination of vulnerability index and risk index.

In the present research, the vulnerability of Meshginshahr’s plain’s aquifer with an area of 614 square kilometers is estimated using the combination of two factors of the density of polluting sources in the areas of the rivers and the well capture zones.First, the density of point pollution sources such as industries, villages, gas stations, as an index of potential polluting sources in Mashgin Shahr’s plain’s rivers is determined by Karnal method in GIS environment. Then, numerical modeling is done to determine the well capture zonesusing MODFLOW and MODPATH models.The statistical data of 10 years from 2011 to 2020 is divided into three categories.The first 8 years are used for the calibration, and the last 2 years were used for model validation.Modeling was performed for stable state.Then the parameters of hydraulic conductivity, recharge and anisotropy are subjected to sensitivity analysis.In the next step, using the MODPATH model and based on the results of the MODFLOW model, well capture zonesor areas with high vulnerability are estimated in different periods.By combining the density layer of point pollutants in the rivers’ protection area and well capture zones, the developed pollution index of the plain is obtained.

The density of pollutants in the region varied from zero to 0.998 items per square kilometer, so that the highest density is in the southwest of the plain, around the important cities of the region. In 16% of the total surface of the plain, there is no capture of pollution by wells. The final capture with 25% of the plain has the largest share and the 10-year capture with less than 1% of the plain has the lowest share. The results of the final index shows that the entire level of the plain is in the range of low risk, and about 50% of the level of the Meshgin’s plain is in the range of low vulnerability. The results of this index are validated based on the density of two important pollutants, nitrate and chloride, which have a positive correlation with the vulnerability index. Two potential pollutants are selected as accuracy parameters to confirm the result of the index developed in this research. Nitrate is considered in rural and agricultural areas, which are affected by agricultural fertilizers and sewage. Chloride also indicates pollution in industrial and commercial places. The results show that the relationship between the two parameters of chlorine and nitrate is almost linear, so that the Pearson correlation coefficient for nitrate is 0.58 and for chloride is 0.49.

The results of this research indicated that in the plains’ management in order to protect the wells’ water quality, the combination of the risk index of point pollutants in the rivers and the vulnerability of the well capture zones can play an important role, and in the industrial development of Mashgin Shahr plain, priority should be given to areas with lower risk. Due to the fact that there are no industrial towns or units in Mashgin Plain, it is not possible to evaluate the risk classes of this index with the spatial changes of groundwater pollution, and it is recommended that this index be used and evaluated in industrial plains. The index presented in this research is simpler compared to other developed indices in the field of aquifer pollution, however; for more accuracy, the weight of the effect can be determined for any point or non-point pollutant, or other parameters can be used

Land use change has a direct impact on hydrological components and water resources and plays an important role in aggravating possible risks such as drought and floods. Therefore, it is necessary to investigate the effects of land use on water components such as runoff. Thus, in this study, the runoff condition of the Kiwi Chai Basin, one of the most important basins in Ardabil province, from an environmental point of view in terms of land use change is investigated using the SWAT model.

ArcGIS 10.1, Envi 5.1, and Ecognition software are used for data processing, classification, and analysis. Also, the method based on radiative transfer models, such as FLAASH, is used as the best method for atmospheric correction. Multiresolution algorithm is applied for segmentation and the nearest neighbor algorithm is used for classification. Then, educational samples are collected from the area using field visits and Google Earth satellite images and used to evaluate the accuracy and precision of the classification. At the end, the Thematic change dynamic detection method is applied in Envi5 to identify the changes that have happened over the years. The SWAT hydrological model is additionally used to investigate the effect of land use changes on the basin's runoff. After extracting the effective parameters in the basin’s outlet, the model is calibrated and validated with SWAT-CUP software and SUFI-2 algorithm. Nash-Sutcliffe indices and coefficient of determination are used to evaluate the results of this stage.

In this research, after applying object-oriented land classification, land use map in seven classes of Rainfed agriculture, irrigated agriculture, garden, forest, residential, pasture and water are provided. In the land use map of the basin, pasture cover is the dominant land use class; however, a significant decrease from 1224.18 square kilometers to 1046.59 square kilometers has been observed between 1987 and 2019. The values obtained for R-Factor, P-Factor, R2, NS indicators in the calibration period are, respectively, for Abgarm station (0.53, 0.47,0.71,0.69) and for Firozabad station (0.32,0.3,0.67,0.64) and in the validation period, for Abgram station (0.09,0,0.62,0.56) and for Firozabad station (0.13,0,0.53,0.51), respectively. Based on this, the results obtained in the calibration and validation stage are evaluated as acceptable. The evaluation of the SWAT model's response to land use also shows that, on an annual scale, the amount of flow in Firozabad station has decreases from 3.08 to 2.81 cubic meters per second -8,77percent) and in Abgarm station from 1.11 to 0.96 cubic meters per second (-13.51), which can be attributed to changes in land use, especially the change in the use of pastures and its conversion to rainfed agriculture, gardens, and forests.

The trend of land use changes in the basin between 1987 and 2019 has been accompanied by a decreasing trend in rainfed, pasture and water uses and an increasing trend in irrigated agriculture, garden, forest, and residential uses. The high value of the fit of the indicators used in the evaluation of the model indicates that the model has a good capability in simulating the runoff of the basin. Moreover, the model implemented for different land uses illustrates that the flow of the basin in both hydrometric stations in most of the months increase in the short term and decrease in the long term average with the land use change. Continuous land use change is becoming a serious threat to watersheds. Land use change should be controlled in catchment areas, and measures should be taken to stabilize land use change.

In order to understand the impacts of watershed management (WM) measures and their effect in solving the socio-economic and environmental problems of region, it is necessary to evaluate these measures to improve future activities in watersheds. One of the important aspects in the watershed management decision making (DM) is to consider the stakeholders participation in the planning process. On the other hand, the participation of stakeholders is not same and their opinions on the issue are varied.

Therefore, stakeholders in the mentioned watershed were divided into six main groups, and the values of the social network ratios of stakeholder groups regarding the issues discussed during face-to-face interviews were calculated.In this study, the Social Profile Ratio (SPR) method was used to determine effective stakeholder groups in decision-making and implementation of watershed management activities in the Emamkandi watershed in the northern province of Urmia in 1999. The social profile ratio, as a tool for introducing the characteristics of society and stakeholders, plays an important role in informed decision-making by the Watershed Planning Committee, and is calculated based on the scores of components including the position, power, and salience of stakeholders in relation to the issue. Therefore, stakeholders in the mentioned watershed were divided into six main groups, and the values of the social network ratios of stakeholder groups regarding the issues discussed during face-to-face interviews were calculated.

According to the results, stakeholders placed more importance on the "importance" component compared to the "position" and "power" components. The social network ratios for all stakeholders were calculated to be greater than one, indicating their agreement with the issue.

Overall, based on the results of the study, it can be said that the group of managers and experts from the Agricultural Jihad organization had the highest agreement with the issues raised compared to other groups. The use of local knowledge to create motivation for better participation had the highest social network ratio, and the lowest agreement was related to the issue of the impact of decisions made by institutions and executive organizations on improving the income of watershed residents. The results of the social network ratios for the issue of using local knowledge to create motivation for better participation in watershed management projects showed that three groups of managers, biological experts, and agricultural Jihad experts agreed with the issue raised, and the numerical value of this ratio for managers (equal to 33) indicates the agreement of most managers. In all participating groups except for managers and Agricultural Jihad experts, the social network ratios indicate their disagreement with the issue of involving watershed residents in practical watershed management decisions.

In recent years, due to the repeated emphasis of the country's development programs on food security and promotion of self-sufficiency in the production of basic agricultural crops, many efforts have been made for agricultural development. Ignoring the sustainability of the environment, as one of the fundamental pillars of the sustainability of agricultural production systems, has put a lot of pressure on the fragile environment and especially on the aquatic ecosystems. One of the important aspects for assessing the sustainability of regional water resources is how to determine the long-term satisfaction of the environmental flow requirements (EFR) of the resources. This research investigates the satisfaction trend of quantitative and qualitative EFR of surface and groundwater resources in the area of Tajan Irrigation and Drainage Network (TIDN) in Mazandaran province.

Hydrological and qualitative EFR of surface water (S.EFR) including Tajan River (T.EFR) and Ab-bandans (A.EFR) and groundwater (G.EFR) was determined for pre (1997- 1984) and post (1998-2019) TIDN periods. Hydrological EFR of Tajan River is calculated using four hydrological methods variable monthly flow (VMF), Tennant, Tasman and Smakhtin. The qualitative EFR of this river is determined based on the three main surface water pollutants in the region, including nitrogen, phosphorus and salinity. The minimum volume of water required to sustainably maintain Ab-bandan ecosystems is considered as A.EFR. Due to the fact that until now no specific method has been provided to determine the EFR of groundwater resources; in this research, by combining hydrologic and qualitative parameters such as the depth of groundwater, salinity and, nitrogen concentrations, the EFR of these resources is determined.

The average river flow before and after the operation of TIDN was 14.53 and 8.36 m3 s-1, respectively. Before TIDN, based on MVF, Smakhtin, Tasman, and Tennant methods, the hydrological EFR of the river satisfied in 79.1, 59.2, 69.1, and 90.1% of cases, respectively. The satisfaction was 53.4, 27.1, 41.4, and 73.3% of cases, respectively, during the TIDN operation. From nitrogen and salinity perspectives, the violation rates of the qualitative EFRs of this river during TIDN operation increased by 11.1 and 9.9%, respectively, compared to the pre-TIDN period. EC has the main role in the deficit of qualitative EFR of the river, followed by nitrogen and phosphorus. The operation of TIDN caused an increase in the depth and nitrogen concentration of the groundwater, resulting in an increase in the unstable area regarding these two parameters during the operation period. Before the construction of TIDN, no part of the region had a hydrological EFR deficiency of more than 353 m3, but after that, about 40.6% of the region experienced higher deficiencies than this value. Also, the area with nitrogen related qualitative EFR deficiency rises from 13.4% in pre-TIDN to 35.6% in post-TIDN.

The development of TIDN increases the violation of quantitative and qualitative EFR of surface and groundwater resources in the region. Considering the limitation of EFR satisfaction after TIDN, especially in low rainfall seasons, it seems necessary to revise the cropping pattern and irrigation method. Otherwise, the continuation of the current trend, through completely disrupting the ecological balance, will make agriculture unsustainable.

Due to the occurrence of drought periods and increased exploitation of the plain, alongside of the agriculture expansion and the rise in groundwater extraction, the level of the groundwater table in the Zanjan plain has decreased, which has resulted in a fall in the level of the groundwater table and a decrease in the efficiency of the wells. The purpose of this research is to investigate and Zoning of Temporal and Spatial of the depth, level and changes of the level of groundwater table of Zanjan plain, trends of depletion and annual changes and temporal monitoring of the drought (GRI) of groundwater resource of Zanjan plain based on the representative hydrograph.

In order to carry out this research, the statistics of 69 observation wells are analyzed during 3 time periods (2001-2008, 2008-2013 and 2013-2018). At first, statistical data is collected and after importing the data into the Geographical Information System (GIS), maps of iso-depth, iso-level and zoning changes of the groundwater table are prepared with the interpolation method. The plain hydrograph has been prepared to investigate the long-term changes and fluctuations of groundwater table, as well as to detect the periods of rise and fall of the water level, during the statistical period for the Zanjan plain. Long-term changes and fluctuations of groundwater table are also drawn in the Excel. The phenomenon of drought in the long term causes the reduction of water resources through the drying up of surface and underground streams. For this purpose, the GRI index has been used to temporal monitoring of drought of groundwater resources in Zanjan plain.

The results obtain from the maps of the iso-loss show that the highest level of groundwater in the first time period (2013-2018) in the northern part of the plain is 12.4 m, in the second time period (2008-2013) in the southern part and the eastern part of the plain has dropped by 9.4 m and in the third period (2001-2008) in the northwestern parts, it has dropped by 14.5 m. The hydrographs of the groundwater table illustrate that during the period of 20 years, the depletion of the Zanjan plain table is 12.9 m, which means that the water level has depleted by 0.65 m annually on average. This actually indicates the negative changes in the groundwater level in the studied area. The results of the changes in the volume of the Zanjan plain demonstrate that the volume deficit of the Zanjan plain is 705.8 MCM. Also, temporal monitoring of the drought in groundwater resources of the Zanjan plain with the GRI index shows a very descending trend towards drought during the twenty-year period.

Groundwater is the main source of agricultural needs, especially in arid and semi-arid areas; therefore, having a sustainable agriculture requires careful management and planning on how to use these resources, which itself requires sufficient knowledge about the spatial changes of the groundwater level in a certain period. In the present research, the investigation of the depletion of the groundwater table, especially in the piezometers of the northern and side parts of the Zanjan plain, shows that this water disaster (groundwater level depletion of about 13 m) is mainly due to the improper management of water resources and the increase in the issuance of permits for deep and semi-deep wells with 61% growth in the last two decades. The negative balance of the plain is so severe that even the good rains of the last few years have not been able to stop the process of lowering the groundwater table. It is recommended to prevent the continuation of the Zanjan plain volume decrease, to manage and control the exploitation of the wells and to prevent any over-exploitation, as well as to use the implementation and development of plain projects to supply the shortage of water resources and feed the plain.

The increase in water consumption in agriculture has caused irrigation management to be studied by experts and researchers in recent years. Water is one of the most important factors limiting the production of lentils. Increasing water productivity through the application of deficit irrigation methods is one of the important topics in the production of this crop. One of the important needs in agricultural planning is to identify the plant's nutritional needs. Iron is one of the essential elements of low consumption and low mobility that plants need the most among micronutrients. Therefore, the present study was conducted with the aim of investigating the irrigation management and iron nano-chelate on the yield and yield components of lentils in Guilan province.

The present experiment is conducted as a split-plot in the form of a randomized complete block design in three iterations in the Deylaman region. The main factor includes four levels namely without irrigation (rainfed), irrigation in the flowering stage, irrigation in the pod formation stage, and irrigation in the flowering and pod formation stage (full) and the sub-factor includes fertilizing nano iron chelate solution during flowering, pod formation time, flowering and podding time and, pre-ripening.

The findings of the research demonstrate that the effect of irrigation management and the influence of nano-chelate on grain and biological yields are significant at the level of 1 percent. As a result of irrigation management, the highest grain and biological yields are observed in the flowering and podding stages under irrigation conditions with an average of 1457 and 4380 kg.ha-1, respectively. At different levels of iron nano-chelate fertilizer, in the flowering and podding stage and fertilization in the pre-ripening stage, the highest grain yield is with an average of 834.2 and 861.7 kg.ha-1, respectively, and the maximum biological yield with an average of 3317.4 and 3228.6 kg.ha-1, respectively.

With full irrigation, the number of main branches, the number of full pods per plant, and the biological and grain yields increases, and spraying solution of iron nano chelate fertilizer improves the number of nodes in the stem, and the number of full pods in the plant and rises the biological yield. Therefore, full irrigation and use of iron nano chelate fertilizer during the flowering and podding stages are recommended for the local lentil plant in the study area.

The lack of water resources in arid and semi-arid regions like our country and the high volume of water losses through evaporation have made the importance of appropriate and practical methods to reduce evaporation from water reservoirs to be more and more clear day by day. Water is one of the most essential human needs. Evaporation is one of the climatic phenomenon in lakes and open space water loss. Different types of decreasing evaporation varied according to regional and economic conditions and environmental issues. On the other hand, in Iran the research conducted regarding reducing and controlling evaporation from water reservoirs is limited. Therefore, the current research is carried out with the aim of using new, economic, and appropriate to climatic conditions and accessible methods to reduce evaporation from water reservoirs, especially agricultural water reservoirs, in the Semnan region.

The efficiency of 6 physical covers (white plastic balls, empty bottles, bottles filled with straw and stubble, green canopy net with 50% density, green canopy net with 80% density, and white canopy net with 50% density), after preparation on the sunken Colorado evaporation pans, is evaluated in four periods of about 30 days in fall 2018 and winter of 2019 and spring and summer of 2021. Measuring the amount of evaporation from pans during 4 periods of approximately 30 days in different seasons of the year are done daily at 10:30 in autumn and winter and at 9:30 in spring and summer. It should be noted that the water temperature is also measured using an alcohol thermometer at the same time as the water level reading.

Based on the results of measurements, the rate of evaporation from the treatments of white plastic balls, empty bottles, bottles containing straw and stubble, green canopy net with 50% density, green canopy net with 80% density, canopy net White with a density of 50% and the control is equal to 259, 320, 213, 277, 369, 283 and 754 mm, respectively in four periods, which clearly shows a significant reduction in the evaporation of the applying six covers to the amount of 66, 58, 72, 63, 52 and 61 percent compared to the control treatment.

In general, according to the efficiency of all the treatments in this research and the application of these covers, taking into account the economic, social conditions and the feasibility of implementation, in order to reduce evaporation from open water reservoirs, especially agricultural water storage pools, it is evaluated as efficient and suitable. Generally, among the methods used, the most efficient related to the bottle filled with straw and stubble, followed by plastic ball treatments and green canopy netting with a density of 80 are evaluated as the most appropriate methods.

Most of the studies that have been conducted in order to investigate the pattern of temporal and spatial changes of rainfall in rainfed areas have finally resulted in determining the trend of total annual, seasonal, and monthly rainfall in the target areas. However, changes in the frequency and intensity of rainfall are among the important parameters that have a great impact on the trend of rainfall and the planning of rainfed areas. The purpose of this study is to investigate the effect of changes in the frequency and intensity of daily rainfall on the trend of annual and seasonal rainfall in Kurdistan province.

For this purpose, the rainfall data of 30 years (1988 to 2017) of four synoptic stations of Sanandaj, Bijar, Qorveh, and Saqez, located in Kurdistan province, were used. After the data homogeneity test, the trend of changes in time series of frequency and amount of rainfall was calculated through the non-parametric Mann-Kendall test and Sen's slope estimator.

 The obtained results indicated a decreasing trend between 25 and 31% of total annual rainfall compared to the average of the studied period in four stations and this decrease was related to spring, summer, and winter seasons in most cases. The rainfall trend did not change significantly in the autumn season. Even though the trend of the rainy days in Sanandaj and Qorveh stations had a significant increase of 0.54 and 0.63 days per year, respectively, the results showed that this increase was related to spring rains which have had less intensity than five millimeters per day and cannot be very effective in providing water requirement. The noteworthy point was that the intensity of rainfall has decreased in all stations which is the main reason for the more than 40% decrease in the amount of rainfall during the spring and winter seasons of Sanandaj, Qorveh, and Saqez stations.

In general, increasing the frequency of low-intensity rains and decreasing the intensity of rains in rainfed areas can be a serious threat to reducing yield. Therefore, it is necessary to investigate the changes in the frequency and intensity of rainfall, along with its values, in order to determine the distribution pattern of annual and seasonal rainfall in rainfed areas.