مجله علوم و مهندسی آبخیزداری ایران
پیاپی 46 (پاییز 1398)

In this study, to analyze the pattern of soil temperature changes in the depths of  5, 10, 20, 30, 50 and 100 cm under the influence of temperature (minimum, average and maximum) and humidity (minimum, average and maximum) the Pearson and regression methods were used for Taleghaan synoptic station during the period of 2008 to 2016 . The results showed that soil temperature had the highest correlation coefficient with air temperature while the lowest correlation was found with air humidity time series. So that the maximum coefficient of determination of air temperature and humidity was in a depth of 5 cm whereas the lowest was found in a depth of 100 cm. In order to estimate the deep soil temperature using temperature and humidity variables, the regression models were fitted by 70% to 30% of data for calibration and validation stages, respectively. So to evaluate the accuracy of the calibration and validation stages the NSE and RMSE error criteria were used. In general, the results indicated that the presented regression models had very good and acceptable performance to estimate soil temperature and also with increasing soil depths, correlation coefficient has decreased while error evaluation criteria has increased.

Reducing or increasing the climate parameters such as temperature and rainfall as a result of the climate change process, causes a variety of droughts. In this study, the effect of climate change on meteorological drought in Yazd province is investigated. For this purpose, the drought time series were determined in two historical periods (1961-2005) and the future (2017-2100) by SPI and SPEI. Historical data from Yazd's synoptic station and future data were generated by the CanESM2 model under RCP scenarios. Drought characteristics such as severity, duration and frequency were extracted based on run theory in order to compare and evaluate the trend of drought changes. The results showed case study experiences more sever droughts in the future than historical period based on SPI under 3 RCP scenarios while based on SPEI index under RCP2.6 and RCP4.5, the drought characteristics will decrease in the future compared with historical period and under RCP8.5, the severity and duration of the drought will increase. The severity-frequency and duration-frequency curve showed that increasing the return period increases the severity and duration of drought.

Any changes in the climate system affect on the access and management of natural resources such as water and soil. Temperature and precipitation are the key elements of climate for studying their trend can be important for atmospheric scientists, environmental managers and planners in the field of hydrology, agriculture, environment and so on. In this study, the trend of climate fluctuations was investigated using the ERA-Interim data. In the first step, calculating RMSE, MAE and Pearson correlation coefficient, the accuracy monthly data of ERA-Interim was studied using synoptic data of Yazd city. The monthly data with the least error and the highest correlation were selected to analyze the changes trend. Then, the selected data including the temperature of two meters above ground level, the soil surface temperature in depth of 1-7 cm, soil temperature in depth of 7-28 cm and synoptic monthly means precipitation were modified by the TerrSet software using the test Mann Kendall. The results showed that the northern and central western parts of the study area had a decreasing trend of precipitation variation at a level of 5% and in the rest of the areas changes are not significant. Also, studying the trend of temperature variables showed that soil temperature changes in two meters above ground level, in depths of 1-7 and 8-28 cm was significant at 1% level in all of study area. The change in the Z test of Mann Kendall was greater than 4.8 everywhere.

Soil erosion is one of the major environmental problems worldwide. Morphometric and landcover  analysis provides a platform for quick and efficient watershed management In the present study, morphometric parameters have been coupled with land cover classes to assess soil erosion susceptibility of sub-watersheds of  lavasanat watershed. The data used in this study included Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) data, with 30 m spatial resolution for drainage generation; and Landsat8  (OLI/TIRS) data with 30 m spatial resolution (band 1 to 11 expect band 3) to generate land cover information of the study area. we estimated 15 morphometric parameters using ASTER DEM  with Arc Hydro package. At first, for proper determination of flow direction and flow accumulation, DEM sinks identified and filled. We used a critical threshold 100 for defining streams. Strahler’s scheme for stream ordering has been used.The sub-watershed erosion prioritization by using morphometric parameters and COPRAS method showed that sub-watersheds 12, 2 and 1 have the highest sensitivity to erosion with the lowest scores (0.098, 0.095, 0.088). In order to prioritize sub-watersheds based on surface coverage, the percentage of each surface coverage class in each sub-watershed was calculated. Based on the results of sub-watershed prioritization based on surface coverage, sub-watersheds3, 2 and 1 with the lowest scores (0.234, 0.221, and 0.164) have the most sensitivity to soil erosion and must be taken up for implementation of soil and water conservation measures.

Results of assessment of the future climate change impacts is associated with some uncertainties. Considering the range of uncertainties increases reliability of the results. In this study, climate change impacts on daily precipitation, maximum and minimum temperature of Sira basin are assessed using LARS-WG model, for 2036-65 period. Accordingly, uncertainty of new emissions scenarios (RCP2.6، RCP4.5، RCP6 و RCP8.5) of HadGEM2 and climatic variability are investigated. Climate variability is a major source of uncertainty which is ignored in most previous studies. Based on the results, for precipitation, the range of the future scenarios have considerable overlaps with the historical ranges. So, it cannot certainly be concluded that whether precipitation increase or decrease in the future. But in the mean of the possible scenarios, it is expected that annual precipitation will change between -9% to +1% in the future. About temperature, the range of the future temperature scenarios have no overlaps with the corresponding historical ranges, and there is a grate certainty for temperature increasing in most of the months, and change in the seasonal cycle of temperature. In the mean of the possible scenarios, it is expected that average temperature will rise between 2.1 to 3 ºC in the future.

Ground waters are considered as substantial water resources in many parts of the world especially in arid and semi-arid area such as Iran. The population growth, the intensive use ofsurface water and groundwater resources has often affected ground water levels. To meeting water management objectives it is essential to have a comprehensive study on the aquifer recharge and ground water withdrawal. In this paper 3-D analysis MODFLOW model served to simulate Abarkuh aquifer for a three year period (2013-2015) with 36 time steps. Modflow model was calibrated in two steady and Transient states. The model validation was measured using 36 month time steps (October 2009 to September 2012). Root Mean square (RMS) error was used to evaluated the accuracy of the calibrated and validated models. RMS error of the calibrated and validated models were 1.046 and 1.10, respectively.. The results showed that continuing current policies for managing water will only widen and deepen water crisis, this condition will reduce aquifer storage and result in decreasing hydraulic head by -1.5 m year-. To control this crisis different scenarios were simulated to represent the effects of ground water management on the aquifer. These scenarios including changes in irrigation methods, using of evaporation reduction methods and changes in cropping patterns. Results showed that all scenarios are capable to restore and protect the groundwater resources in Abarkuh aquifer. Therefore, adjusting crop farming structures and improving irrigation system have been important means of protecting groundwater resources in this region.

The lack of a comprehensive system for identifying the role and understanding of the structural relationships of local water users in the local stakeholder’s network is one of the most important challenges for the integrated management of water resources and the governance perspective. Thus, identifying and analyzing canyons, as the most important element of planning and implementing activities related to water resources management, is one of the requirements for integrated management and the establishment of optimal water resources management. In this research, in order to understand this complexity in the field of water management, social network analysis method was used to measure the cooperation relation of local users as the executive arm of the water resources management plans in the top of Taleghan watershed. Based on the analysis of the micro indicators of the network, local leaders have been identified in water resources management and the modularity in the macro level of the network has been considered as an effective size in increasing social capital and in line with the success of participatory management plane. The results indicate a moderate separation of the local stakeholder’s network, which indicates a moderate fragility in the relationship of cooperation among the local stakeholders. So that the most internal ties of stakeholders is the Gatedeh Village with about 380 transplants and the lowest with 283 transplants in the village of Mehran. Also, according to the results of the analysis of the middle and middle level index of some water resource users, they have been placed in a key position. These are known local leaders who, based on their authority and social influence, can play a significant role in establishing water governance and establishing links with other operators at the local level, above all other actors based on cooperation ties.

By understanding the temporal and spatial variations of water resources in a region, the better management and planning of water resources and water consumptions can be done. Time series modeling, if used correctly, will lead to acceptable results in this regard. For this purpose, the monthly runoff time series for 28 years was prepared at the hydrometric stations of Mehregerd region and the presence of trend was studied using the Mann-Kendall method. Then, different patterns of ARIMA were fitted to the data using the univariate Box-Jenkins method, and the most suitable pattern for predicting the future years was chosen. The results indicated that runoff had a decreasing trend in all months and seasons. The role of increased water consumption in the process of decreased water resources of the area was investigated and it was observed that the water consumption in the region has significantly increased since 2006. The consumption level in this basin is estimated about 46 Mm3/year. The forecast of runoff by 2023 using ARIMA (0, 1, 0) * (0, 1, 1) was performed as the most suitable model and it was found that the surface water resources in the upcoming years would experience a significant decrease if the current trend of exploitation is continued.

Gully erosion is one of the important forms of soil degradation especially in semi-arid areas. Gullies are occupying 13 percent of Ilam Province area. This research focused on studying the, topographic threshold of gullies, dominant process of gully initiation and development as well, in agricultural and rangeland land uses. Ilam province with 2 million hac area is located in western Iran. Ilam has 3 climatic zones with 425 mm annual average precipitation. Dominant land use in Ilam is dried forest with 640000 hac area. Topographic characteristics of 120 gullies including initiation and development slopes, initiation and development contributing areas and surface characteristics of gullies contributing area including vegetation, rock fragment and bare soil by 1 m2 plot and soil samples from top soil and gullies wall were collected, as well, in semi-arid part of Ilam province.Results show that Initiation and development topographic threshold value in croplands are 0.02 and 0.04 and increase to 0.1 and 0.2 in rangelands. Topographic threshold in rangelands is more 5 times than croplands. Dominant process in gully initiation and development is surface runoff. Effective factors on gully topographic threshold are organic matter, vegetation cover, rock fragments and bare soil that describe 31 percent of topographic threshold; also, organic matter with beta coefficient of 62 percent has the most contribution in topographic threshold variation. Gully frequency has negative exponential relationship with rock fragment and vegetation cover and decay rate for rock fragment and vegetation cover are 60 and 35 percent respectively.Topographic thresholds showed that topography has important role in gully format5ion but environmental characteristics as vegetation cover, rock fragment and land management are more important

Due to the increasing need for water and the lack of access to its sources, it is essential to maintain and use groundwater resources. So, identifying and exploiting these resources has particular importance. Investigating interflows requires geo-electric and geotechnical studies, both of which require a lot of time and cost. Therefore, it is necessary to provide a method or model that can minimize the cost of investigating interflows as much as possible. In this research, two types of artificial neural networks- multi-layer perceptron (MLP) and radial base function (RBF) were used to study the relationship between hydro-geomorphological characteristics of the watershed basin and interflows in seven watershed sub-basins in Kerman province. Hydro-geomorphological characteristics of subsurface dams were considered as input independent variables, and the discharge of interflow in the watershed basin outlet was considered as dependent variable. The results of this study show that radial base function (RBF) with determination coefficient of 0.9182 and mean squares error of 0.0289, has more accurate results in estimating the discharge of interflow, compared to artificial neural network method of multilayer perceptron (MLP) with determination coefficient of 0.5288  and mean squares error of 0.725. Regarding the determination coefficient in the used methods, it can be concluded that the model of the neural network is the appropriate solution and low cost to check this connection in the watershed.

Broujen township is located at an area of ​​2755 square kilometers(16 percent of the area of ​​Chaharmahal and Bakhtiari province) 65 kilometers from the province center(Shahrekord). In 2016, this township had 122483 inhabitants in the form of 36,238 households. In recent years, various watershed management activities have been implemented at the provincial level or planned for implementation in order to control and maintain surface water and optimize their use. This research was conducted with the aim of analyzing the factors affecting the participation of rurals in watershed management in Cheshmeh Zainal watershed of Broujen township in Chaharmahal and Bakhtiari province. The data collection tool was a questionnaire and the collected data were analyzed using descriptive statistics and inferential statistics and analyzed by SPSS software. The results show that there is a negative and non-significant relationship between age (r = -0.136) and the experience of people in agriculture(r = -0.032) with their participation in watershed activities. Also, there was a positive and significant relationship between social versatility(r = 0.43), socioeconomic status(r = 0.57), membership in rural public institutions(r = 0.36) and use of information resources(r = 0.37) with respondents' participation in watershed activities at one percent. The results of multi regression analysis in stepwise method indicate that the level of awareness of the goals and characteristics of watershed projects has the highest role(0.53) in the participation rate of the respondents in the watershed management activities.

Gully erosion is known as one of the most important and destructive forms of land degradation, and the loss of soil throughout the world. As estimation of soil volume loss and understanding the economic costs of soil erosion are of great importance; this study has been carried out to calculate the amount of soil volume loss due to gully erosion and estimate its economic cost in Ghazeian watershed located in north of Fars province. To do so, the volume of gullies was calculated and thereafter, the mass of soil loss was determined using soil bulk density. Then, total amount of soil loss mass was determined by summation of the mass of soil loss from gullies. The results showed that an average of 201.10 m3 (263.43 ton) soil eroded and loss each year due to gullies erosion in this region, and it damaged the soil resources by an average of 7376.25 dollars (295050000 Rials) per annum. These results indicate the destructive effect of gully erosion on soil loss, and therefore, more attention is required to control this type of erosion by establishing native and consistent vegetation, increasing the roughness coefficient, diverting runoff path, and performing precise research in different regions of the country.

Deficiency of water with suitable quality is a vital challenge in urban and specially in arid and semiarid regions. The aim of this study is to assess temporal and spatial variation of drinking groundwater quality and quantity in County of Mallard in Tehran province. Mallard is a County at margin of Central Iran Plateau. The data used in this research comprises of 14 parameters in 31 drinking water wells that obtained during a 6-year interval. Spatiotemporal variation in these wells were analyzed by applying Parametric and nonparametric statistical techniques including one-way ANOVA, Kruskal-Wallis, independent-samples T-test, Mann-Whitney. The results reveals that concentration of sulfate, chlorine, bicarbonate, electrical conductivity, TDS, sodium and fluorine in dry and wet periods have significant difference. Effects of space on quality of groundwater in Mallard suggest that boring wells in pyroclastic, tuff and sandy lime (E2) Formations meaningfully and at level of Percent 95 have the most impact on mineral concentration of water quality parameters. Furthermore, concentration of nitrate has increased in cultivation and urban-rural land use and the level of pH in cultivating and urban-rural use has decreased significant and at level of Percent 95 in comparison to other lands.