Moving towards development and increasing water demands are aligned and they are in conflict with the water that ecosystems need to survive. This problem is growing not only in Iran but also in many parts of the world. Although it shows up faster and more intensely in developing countries. It seems necessary to determining and assigning “Environmental Flow Requirement” as the most effective approach to prevent negative effects of building hydraulic structures on river ecosystems. Environmental flows provide terms of a series of aquatic habitats protection. There are different methods for calculating environmental flow. In this case study, environmental flow requirements of Dez river have been calculated and evaluated using hydrologic methods of Tenant, Flow Duration Curve and hydraulic method of wetted perimeter (slope value and maximum curvature) from Dez check dam to Bandeghir. In order to compare these methods, drought frequency analysis was carried out for the minimum annual discharge of Dez River. The maximum curvature method was selected as the appropriate method for obtaining the environmental flow requirement of Dez river and the amount obtained from this method was proposed 100 cubic meters per second as the minimum environmental discharge of Dez river. According to the results and comparing it with the average annual flow of the studied stations, the flow of the river has not been able to provide the required ecosystem discharge since 2008 and the environment of the region is in a critical condition.

 Gotvand Oli Dam is one of the largest dams in Iran, built on the Karun River in southwestern Iran. This dam is the last dam built on Karun River before entering Khuzestan plain in Gotvand area. The Gachsaran Formation is one of the reservoirs in which the Karun River passes through the Godarlandar Dam to the Gotvand Regulatory Dam. Water contact with Gachsaran Formation has affected the water quality of the river and the reservoir. The role of agricultural land development and the construction of the Gotvand dam is unclear on Karun water salinity (Gotvand to Farsiat). The purpose of the This research is to determine the role of the pollutants in these two parts of the pollutants. In this study, we studied the changes in Q, EC and TDS in 9 hydrometric stations of the study area using non-parametric tests of Mann-Kendall and Pettit test during the statistical period of 2001-2016. According to the results of the Pettitt test, the 16 year interval was divided into two sub-periods between 2001-2007 and 2008-2016. The results indicate that failure has occurred since 2007 in all of the parameters. Increasing the EC and TDS and reducing the Q after the breakage point are the results of the Pettit test in this study. Using the SDI index, a hydrological drought survey was conducted in the region. The results showed that the increase of electrical conductivity in the Karun River in recent years is undeniable, however, the main reason for this is the occurrence of artificial hydrological droughts in the region since the Water year of 2007 - 2008. This drought can be due to reasons such as the occurrence of meteorological droughts, the drainage of upstream dams and, finally, the transfer of water between basins and harvesting of shoots. In the years after the Gotvand Upay dam (2011-2016), the electrical conductivity of water in all stations was lower than the average period of drought before it (2008-2010).

 At the beginning of the industrial revolution, increasing emissions of carbon dioxide, methane and other greenhouse gases causing climate confusion is average global and local levels. In studies of climate change, predictions of future climate by General Circulation Models (GCMs) and is performed under scenarios of greenhouse gas emissions, but the output parameters of the large-scale atmospheric circulation and the dimensions are tens of thousands of square kilometers, lack of spatial and temporal accuracy are suitable for use in the study area. For this purpose, the downscaling models can be used for practical studies of climate change. In this study, In addition, according to the high uncertainty statistical downscaling cannot be ignored uncertainty and For this purpose, it is recommended to apply several downscaling methods. In order to achieve this purpose, in this study used data of General Circulation Models (GCMs) and two scenarios A2 and B1 related to them. The data have been downscaling by a statistical model (LARS-WG), a downscaling multivariable regression model (SDSM) and change factor model. The results indicate that in order to compare the three models, generally, a model can not be given preference over another because the functions of a model for various climatic parameters, the differences in results and performance. If necessary need to choose the superiority of one model to the rest, it can be said that for temperature parameters, SDSM have been better results. In the case of rainfall data, LARS has been better performance.

Iran, due to locating at the dry and semi-dry climate condition, copes with the shortage of water resources in many of its regions with average annual precipitation less than one-third of the global annual average. Therefore, optimal operation of water resources is significantly important. In this study, simulation-optimization technique by integrating WEAP simulator model and Multi-Objective Particle Swarm Optimization (MOPSO) PSO algorithm were used in order to operate optimally water resources systems from Maroon basin to Shadeghan wetland. Maroon Dam is used for water supply to four plains of Behbahan, Jayzan-Fajr, Ramshir and Shadegan which two latter ones situate at the downstream crossing with Allah River. That is why, in addition to the Maroon Dam, Jarreh Dam was modeled, as well. After entering information into the simulator model, model calibration was conducted in Maroon Dam area for a 13-year period from 2001 to 2013 water years and for Jarreh Dam of a 4-year period from 2010 to 2013. After calibrating and ensuring the accuracy of the model, four scenarios were defined for the next 20 years that included optimization scenario, too. In the reference scenario, the continuation of existing conditions in the coming years was assumed. In the second scenario called the land development, conditions of the region were modeled in the presence of land development in the next 20 years. Accordingly, the model for development scenario was coupled with optimizer model. In the optimizer model, two objective functions were considered so that the first one indicated the maximization of demand site coverage related to all consumptions in different months contrasting the second one which was to minimize the amount of violation from storage capacity operation. Given the population size of 240 and MOPSO run for 400 iterations within 14 days and 10 hours and 47 minutes, near-optimal results were achieved. Finally, another scenario assuming increase of the efficiency with the existance of the considtions derived from optimization scenario was defined. The results of the model run for each scenario were extracted and compared. Results shows that with land development, the pressure on water resources will increase in the future that it will be further increased with land development and rise in the amount of needs . In land development scenario, in most of dry years and in the last six years of planning in most consumptions, demand site coverage in three to eight consecutive dry months was equal to zero, and in the rest of low-water years, it was lower than 5% in these months. Subsequently, by running the model for optimization, there was seen that demand site coverage reach from 28% to 60% in these months. In general, the average of demand site coverage will increase compared to land development scenario so that there was observed 16% increase in demand site coverage in some months and for some needs, on average. Reliability in some of water rights and agricultural needs in this scenario was somewhat decreased that this was due to the policies considered in the optimization in order to supply all needs in different months and no need to be remained without supply. İn addition, the reliability related to environmental needs of Jarrahi river and Maroon hydropower increased in this scenario 3% and 6% compared to land development, respectively. As well as, results revealed that by increasing efficiency in the fourth scenario in terms of optimal operation, demand sites coverage and thier reliability will be increased, so that demand sites coverage on average will reach 90% in excess in more than six months of the year and it will on average inccrease 12% compared to optimization scenario for some months and some needs so that consumption of current resources will be saved. This study shows that using the research strategy will result in better reservoir management and reducing the severity of the failure in supplying different usages in low-water months.

 Developing of techniques for regional flood frequency estimation in ungauged sites is one of the main purposes in contemporary hydrology. The flood frequency evaluation for ungauged catchments is usually calculated using appropriate statistical relationships (models) between flood statistics and basins characteristics. Already, several equations have been presented to estimate the flood frequency in different areas such as Karkheh basin. However, due to the complexity of this phenomenon, the relationships have not been capable to simulate the flood frequency with desired accuracy. Accordingly, in this study, in addition to the regression method frequently used in the previous studies, the Artificial neural network and Tree Classification Algorithm models are applied. In fact, these are a type of Artificial intelligence models in which inputs data are directly converted into outputs data. This similarity indicates that this type of the new models is actually similar to the regression relations, however, with further flexibility to adjust the weights and to use as a multiple regressions. The study area, including 32 hydrometry stations, is located in the west of Iran; 27 of the stations for calibration along with 5 of the stations for validation. To approach a unique model, return period was taken into account as the independent factor.
To achieve the best Artificial Neural Network, Tree Classification Algorithm models and regression model, different combinations of physiographic with return periods, as input data, has been used. Accordingly, the best structure of the each models was obtained and‌ following that the evaluation criteria were compared. The results indicated that the Artificial Intelligence (M5 algorithm and Artificial neural network), in comparison to the regression method, has a better performance to estimate flood in all return periods and also any flood.,because the Decision Tree is able to predict in the formula so that is better than artificial neural network. With imposing of physiographic characteristics and the return period, the flood were estimated for any ungauged catchments.

  Due to large extent of watersheds, and economic and administrative constraints, reclamation of watersheds not only isn't possible from point of view flood control in a individual project, but may have inverse effects. As regards that flooding and its damages is increasing in often watersheds of Iran, determining flood productive areas and prioritize sub-watersheds for comprehensive management of watersheds and flood control projects is very important. In this research, by combining ArcGIS and HEC-HMS model, the contribution rate of different sub-watersheds in outlet flood of Amameh watershed has been determined based on different return periods. The study area is located in northeast of Tehran City and southern flanks of Central Alborz Mountains, and among six main basins of Iran sit in The Central Basin. To achieve the objectives of this study, the Single Successive Sub-watershed Elimination (SSSE) method from rainfall-runoff model has been used. The results of this study show that the contribution rate of sub-watersheds in total outlet of watershed not only affected by area and peak flow of sub-watersheds, but interaction of factors such as location of sub-watersheds, distance from output, CN, and flood routing role in main river also have significant impact on the sub-watersheds flooding. Accordingly, upstream and intermediate sub-watersheds are more important in the outlet peak flow. So, is recommended that corrective operations and flood controls concentrate on these regions and should be avoided these activities in downstream regions. Sub-watersheds flooding priority also is changed in different retune periods.

Iran is one of arid and semi-arid countries. This dryness has clearly affected living conditions of the people, especially in the Southwest, South and East of the country. In these areas precipitation is low and has short and moderate winters and summers are long and hot. In such circumstances, it is not unlikely that every few years the phenomenon of drought and water scarcity happened therefore, investigation to resolve this shortcoming is important. Physical-hydrological model structure is based on solar still which can work with both solar and electrical energy to Process evaporation and distillation. The way it works is, first fill basin to the desired volume then water is starting to boil because of sun’s energy or an electrical source. When reach to the boiling point of water, droplets separated and hit to the roof then enter to the collector because of gradient effect. The collected water is transferred by a tube to a container outside the model. The results showed that most of the water product, in solar experiments in six hours, was 1,000 ml, which occurred when the water level in the basin 6 cm. Also in experiments were conducted with the help of electric energy maximum product relate to 100 ° C as we expected which was 3430 ml. But the highest efficiency was 90% which recorded at 85 ° C

 Soil and water are the most important natural resources and basic needs of life in each country So that the development of cities and cultures depends on them. Soil erosion and sediment production are factors that make these valuable resources at risk. The lack of sufficient data in field of soil erosion and sediment yield in many watersheds, make experimental methods necessary for appropriate erosion and sediment estimation. In this study, experimental models MPSIAC, FSM, EPM and FSO were used to estimate the amount of sediment and erosion to find out which one has better results. Also 15 consecutive mortar- rocky dams located in the region to measure and compare with an estimated rate of erosion area was used by models. The results indicate the superiority of MPSIAC model than other models in the estimation of erosion. Also, all models predicted erosion intense in the region, compared to the amount of sediments behind the dams to assess the value is measured. In this study, the total sediment estimation by the model MPSIAC is 2439.81, the amount of sediment by EPM model 1016.891 and the amount of sediment in the FSM model is 2855 m3/year. Significantly MPSIAC model has a closer estimation than the other two models according to the amount of sediment behind dams. MPSIAC relative error rate was 17% and lower than other models.

Volume and maximum discharge of runoff are the main design criteria in most hydrologic and hydraulic projects. In some cases, especially in flood control projects, runoff hydrograph is required to design water systems. To generalize available data of gauged basins to ungauged ones, the spatial changes of these factors and their relationship with constant properties of basins should be studied. Accordingly, evaluations can be made for ungauged basins in which it not possible to access these parameters.Karst basins have an important effect on surface water infilteration and groundwater recharge. Thus, it is more difficult to estimate the flood hydrograph in such basins. To examine the accuracy of rainfall-runoff theories, geomorphological artificial neural network (GANN) and geomorphological instantaneous unit hydrograph (GIUH) were used. Environmental conditions of the basin and groundwater-river interaction play an important role in the selection of appropriate methods for separation of the base flow. Assessing the straight-line method and recursive digital filter using stable isotopes (filter-isotope) is an important step in identification of interactions between groundwater and surface water in the Abolabbas basin.Abolabbasbasin was studied by filter-isotope method to adapt the models with the karst basin. Moreover, initial–continuing lossand initial-proportional loss methods were used to estimate excess rainfall. In total, each model was used in 4 different modes. According to the results of GIUH model, GIUH-D1C (in which excess rainfall is estimated by initial-proportional loss method and the base flow is separated by filter-isotope method) outperformed the rest of modes. In all events, GANN model showed a significant correlation with a small root mean square error. In addition, GANN outperformed GIUH model in flood hydrograph simulation.

 Climate change, as one of the pervasive and important component of the ecosystems can influence other components such as water resources, agriculture, etc. to varying degrees even to a limited extent. While the climate change shows it's most negative effects in underdeveloped and developing countries. Since these countries are highly influenced by climate compared to the other ones and their life depends on natural resources and agriculture. The first step in detecting the climate change is to investigate the abnormalities and oscillations created in the climatic parameters in the study area. Given the importance of the issue, the present study examines the trend of changes in climatic parameters such as temperature, precipitation and relative humidity percent in seasonal and annual scales in 37 synoptic stations in Iran using Mann-Kendall nonparametric test, Sen's slope estimator test and Pettit test during the statistical period 1961-2010. According to the Pettit test results and closer scrutiny of changes, the 50-year period was divided into two sub-intervals: 1985-1961 and 2010-1986. Finally, results of the test statistics were prepared as zoning maps regarding the different time scales at 95% confidence level using inverse distance weighted (IDW) method. Generally, in 50-years interval, results show the increasing trends in temperature and decreasing trend in precipitation and relative humidity in most parts of the country. In the entire country apart from the high and mountainous stations including Shahrekord, Khoramabad and Saghez, the increasing trend of temperature was observed that the most significant increasing temperature at confidence level 95% has occurred in Mashhad, Zahedan, Zabol, Bam, Yazd, Babolsar, Kermanshah, Abadan, Tabriz and Khoy stations to a rate of 0.03 °C. Decreasing precipitation trend was observed in the East, West, and Northwest of country that the most significant precipitation reduction at the confidence level 95% is in Northwest and about 2.3 mm. Relative humidity reduction trend is observed in the most areas except a part of the Northwest and South of the Caspian Sea that the most significant relative humidity reduction at the confidence level 95% is in Abadan, Zahedan and Kermanshah stations and about 0.09 percent

Because the amount of evaporation in arid and semi-arid countries is very high, Estimating and predicting the rate of evaporation from large water reservoirs in the management of this resource is helpful. On the other hand, global warming due to increasing greenhouse gases could cause increased evaporation water resources. Therefore, in this study the effects of climate change on evaporation from the Dez dam reservoir is discussed. First by using meteorological and hydrological information and take advantage of the energy balance method, Rate of reference evaporation was calculated Then, by using the evaluation indexes, By comparing the Rate of evaporation obtained from empirical formulas And the Rate of evaporation obtained by the energy balance method, The best formula for estimating evaporation in the region were identified. Using the outputs of the AOGCMs models, the evaporation of the Dez dam region, Were examined for the years 2020-2044. Also, in order to consider the uncertainty of the models of atmospheric general circulation models, ten outputs under three emissions scenarios (B1, A2, A1B) were used. Finally the uncertainty of these models using the kernel estimator for the results of the evaporation from the reservoir the future at three levels of 10%, 50% and 90% was developed. . Because the output of AOGCMs models are large-scale, To use for regional scale, LARS-WG model, was used. The results show that between the methods investigated, Priestley-Taylor method provides the best estimate of evaporation, And also determined the effects of climate change in different months, are different, but, the overall rate of evaporation in all months except the months of October, November and December will increase. Also maximum evaporation rate increased is in May with a probability of 90% for A1B emissions scenario and maximum rate of decline evaporation is in March with a probability of 10% under the B1 emissions scenario.
 

Amendment and design of the rain gage network to increase accuracy in prediction of precipitation value needs to find optimum location of the rain gage station. Most of the precipitation prediction error is due to location of the rain gage station that optimum design of the rain gage stations can reduce precipitation prediction error. In this study used geostatic methods named Kriging and cokriging to optimization of the Bakhtegan- Maharlu rain gage stations network. After determination of the best model of semivariogram and the best geostatic method, in the first step, the rain gage which precipitation prediction in them has appropriate accuracy determined with the help of other rain gage network. In the next step, using assessment of network prediction error value which remain from first step, the points that needs new rain gage determined. Finally 7 unnecessary rain gages stations determined and 5 new rain gages added to the network.

Runoff from urban areas and consequently flooded pathways and flood inundation, one of the major problems of these communities. Expanding of urban areas and conversion of perviouse land to imperviouse has caused an increase in volume and intensity of urban stormwater. Due to high volume of urban flooding, it can be as a source of water for various uses. The estimation of urban stormwater and flooding volume is importance in design and optimization Sewer and surface water collection networks and reuse of urban floods. Despite Ahvaz sewer system is separated, due to the lack of surface water collection system in this area, most of the rainwater influence to sewerage network and this system is considered as the main transmitter of runoff. This study has performed with aims to estimate runoff from rainfall for different return periods in Zeytoon karmandy of Ahwaz, assessment of performance Sewer collection system in transport of runoff generated and determining the critical points of rejection. In order to simulate the rainfall-runoff process and evaluation of Sewer collection system, SWMM model used. According to the characteristics of the study area and based on existing bylaws, return periods of 2, 5 and 10 years were chosen. Sensitivity analysis of parameters affecting the peak runoff discharge was done. Despite the lack of hydrometric stations in the study area, there has been effort that required information to verify the model results, as far as possible be extracted based on actual measurements and observations. Results show entrance rain flow into the study sewer collection system significantly (between 5 to 13-folds wastewater flow in different return periods). This network only can pass less than 50 percent of runoff in all of return periods and durations that was studied. The situation of sewerage network and surface waters disposal facilities in Zeytoon karmandy, evaluated critical and require to urgent improvement and reconstruction. The results of this study can be used for designe of surface water disposal systems, optimization of sewer collection systems taking entry of runoff and urban runoff management in Zeytoon karmandy are.

 Abstract :
Regarding the limited sources of freshwater in the world and infinite needs of human for the freshwater, and on the other hand the natural and human factors in the recent decades in most of this country’s plains including Lorestan Province specifically the fertile plain of Alashtar have encountered the water level decreasing. The aim of this study is to determine the changes of water level of Alashtar aquifer in the period of 10 years (2003-2013), using Thissen, Koriging, and cokriging methods. The results show that the regular cokriging method, (exponential model) is the most accurate and best method. Also results shows that during the hydrologic years of (2003-2004), (2005-2006), (2007, 2008), and (2009, 2010) the plain’s balance is positive and during the years of (2004, 2005), (2007-2008), (2008-2009), (2010-2011), (2011-2012), and (2012-2013) the water balance is negative and the amount of aquifer deficit is 15.6 million cubic meters. The hydrologic year of (2006-2007) has the most deficit of the aquifer. The reasons of the negative balance of ground water in Alashtar plain include 61% inappropriate management of ground water dedication, 20.5 % removing more than usual from the agricultural wells, and 18.5% inappropriate distribution and dispersion of temporal and the spatial of precipitation. A solution to make this deficit up is that it should be 2% from the average discharge of the plain or the annual performance hour of the wells should be removed. In case of continuing this trend the Alashtar plain balance will get its balance after a while.

Ahwaz is one of the polluted cities of Iran and world, has always been in the spotlight. This city that is also the capital of Khuzestan province, in recent decades has been witnessed the expansion of the industry, without regard to principles of sustainable development. The Karun River, the main vital artery of the region, has great importance to the city of Ahwaz. Not long ago this river has been the passage of ships. Causes such as constructing several dams in the upstream river, withdraw water from the upstream to the needs of other regions of Iran, exposure of various industries along the river and discharge of industrial and urban sewage into the river, seen that today is deteriorating rapidly, qua today is the depth of river reach to 1 m with a high concentration of pollutants. This study is a methodology for quality management of surface water resources, which subject to various industrial effluents, municipal and etc. In this study, considering the quality parameters, by using the QUAL2K model and with regard to water quality standards and defined classification of water, we assess the assimilative capacity of the river. Then four parameters, BOD, DO, Nitrate and total coliform were chosen as indicator parameters for assessing the assimilative capacity of the river. Then model was calibrated to data from April to September 2012, verification was performed by winter 2013 and finally validation performed by spring 2013. Then the model was used to take management decisions for critical situation. Fortunately the two parameters DO and NO3 are in good conditions. For BOD, river water condition is not in proper quality but by using the management scenarios this problem has been resolved. But unfortunately the situation is so dire for coliform bacteria, qua by eliminating all pollution entering the river in two first reaches, and reducing coliform load in reach 3, we reaches the water quality goal. Eight scenarios are defined for water quality management which two scenarios were described as dysfunctional. Six remained scenario was evaluated and finally fifth scenario defined as the best scenario.

Groundwater is the 2nd largest available reservoir of fresh water in the world. Hence the protection and management of these resources is vital. Also awareness of the impact of climate change on groundwater resources is necessary. According to importance of Dezful-Andimeshk plain (composed of five smaller plains) as the agricultural hub of Khuzestan province, the aim of this research was to investigate the effect of climate change on groundwater resources. At the first groundwater model is created and after ensuring the validity of the model, the status of groundwater in future periods (2044-2020) was investigated using Atmosphere-Ocean General Circulation Models output (AOGCM). In order to consider the uncertainty of the AOGCM models, the output of the 15 general circulation models of the atmosphere under three different scenarios of greenhouse gas emissions (A2, A1B and B1) was used. Finely the uncertainty of the models was determine using a kernel estimator. It is notable that the LARS-WG model was used for downscaling of AOGCMs. Results showed that the effect of water balance components vary in different parts of the plain. Due to lack of irrigation network in the Lore plain, the effect of climate change on recharge is more than other plains. Also Results indicated that rainfall in future will shift from summer to fall and recharge will increase in August. Considering the uncertainty of the AOGCMs model at all risk levels, recharge will reduce in spring and October.