مجله اکو هیدرولوژی
سال چهارم شماره 3 (پاییز 1396)

In a recent decades to increase human knowledge on the Earth's climate and concern for people from climate change in the future, thereby has been identified the precise factors influencing Earth's climate. One of the climate phenomena that changes them cause great anomalies of climate, particularly on temperature and precipitation patterns in many parts of the world that are teleconnection. The reveal relationships between climatic parameters and they towards a better understanding of the volatility and climate variability is very important in every area. In this study, the relationship between large-scale and well-known patterns such as the Southern Oscillation Index (SOI), North Atlantic oscillation (NAO), Pacific North America (PNA), Multivariate ENSO Index (MEI) and (PDO) with 9 temperature and precipitation variables in the Karaj synoptic station as monthly were analyzed over a 26 year period (2010-1985). At first, the normality of the data series based on the Kolmogorov - Smirnov was confirmed. In order to examine the relationship between large-scale patterns with temperature and precipitation variables, was used the Pearson correlation coefficient. Correlations on a monthly were assessed basis without delay and a delay of one month. The results showed that the relationship between the NAO index and the temperature and precipitation variables is observed in autumn and winter months and the impact on the autumn months is higher than the winter months. SOI index further communication with the precipitation variables is paramount; the role of this index is more obvious the autumn and winter months, while the MEI index shows a higher correlation with the temperature variables and was not observed particular relevance with precipitation variables. Role and impact in particular on temperature parameters months of spring, April and May and December in late autumn is stronger. PDO index on the temperature and precipitation variables in May is observed more in the middle of spring. PNA index only, is effective on the temperature variables and in December and February, higher communication is paramount. Results are important for greater understanding of the temperature and precipitation variability.

The governing factors of drought are non-linearly correlated. Therefore, researcher needs to apply nonlinear methods such as CA to model and predict the drought. CA and its derivatives are among novel methods of drought simulation that rarely used for predicting the drought. While such methods have simple structures; they provide high visual capabilities for drought monitoring. This paper investigates drought in Najaf Abad plain using Markov, CA Markov and Landsat satellite images. At first, satellite image time series of transpiration were classified for 1995, 2008, 2015, and the land zonation of drought condition were estimated. Then, the drought in 2020 was predicted using CA Markov. The Kappa index is 0.63 and the agreement between actual and predicted map (M (m)) is 0.85. Our findings showed that our proposed model can suitably predict the drought. In addition, the drought distribution map showing the possibility of changes in 2020, suggests that if the situation continues and no changes in the type of cultivation and cropping pattern happen, all areas in danger of drought in 2015, will face drought more intensely and more widely, in 2020.

Exploitation of underground water resources is a way to modulate the shortage of seasonal water. In this regard, proper site selection for constructing underground dam to reserve waters is a challenging issue. Thus, using an approach with minimum error is essential. The purpose of this paper was optimum selection of potential sites for constructing underground dam in Hamedan-Bahar catchment basin using a new GIS-based approach to reduce the error. For this, the efficient criteria of a proper site to make underground dam were first recognized. These criteria include density of drainages, separation of the aqueducts, spring and wells, geological appropriate, slope, fault density, proximity to roads and villages and special conditions of land use. Then, different evidence layers were weighted in [0, 1] range using logistic function in geographic information system. Finally, the weighted evidence layers were integrated using geometric average function. Thus, a model representing favorable areas for making underground dam was generated. The results obtained introduced less than 10% of the streams (respecting the whole streams in the study area) as suitable, and demonstrated that the method applied can be used efficiently to delimit the study area and to recognize suitable streams for construction of underground dam.

Obtaining necessary data including snow depth, snow density and snow water equivalent (SWE) in order to manage water resources in mountains areas is inevitable. On the other hand, due to financial constraints, unfair weather and impassability of mountainous areas, measurement is limited to the points, and its generalization to larger areas is associated with large errors. A method for predicting the SWE is investigation on relationship between the SWE and effective factors. Therefore, in this research, mountainous Sohravard watershed located in Zanjan Province was selected as the case study.The required data and maps including Digital Elevation Model (DEM), slope, aspect, northern, eastern, profile curvature, plan curvature, topography position index and solar radiation maps were extracted. Then, during the peak of snowfall in the area, snow depth of 150 points and snow density of 18 points were measured using Latin Hypercube and random sampling methods, respectively. The calculation of upwind slope was carried out for the measured snow points. In the next step, the quantitative relation between the SWE and effective factors was determined by fitting a regression relationship. The efficiency of the created models was evaluated by statistical criteria including mean bias error, mean absolute error, root mean square error and correlation coefficient(R). The results showed that SWE in the studied watershed could be estimated by using stepwise regression. Also based on the results, although climate factor of upwind slope requires high computing, but its incorporation in the model can lead to increase the model efficiency in the SWE estimation. The SWE had the highest significant correlation equal to 0.607 with the elevation, and the lowest significant correlation equal to 0.204 to the northern the study area. Correlation coefficient between the dependent variable SWE and independent variable upwind slope shows that 300 meters distance is the most effective distance the interaction of wind and terrain in creation of wind sheltering and wind deflation. Coefficient of variation snow depth and snow density measurement is 54.14 and 7.89 percent respectively.

Drought is one of the natural disasters which is strongly influenced by climatic fluctuations and makes a set of complex problems in various parts. The aim of this study is investigation of time relationship between meteorological and hydrological drought in Karkhe catchment. To achieve the goal, 26 rain gauge stations and 8 gauging stations were used. In part of research for understanding delay trends in compare with precipitation in real mood, Pearson correlation coefficient between precipitation and discharge was calculated with different time delays. Two indices (SPI and SDI index) were selected for examining Meteorological drought and hydrological drought. Index values in short term step (1 to 3 months), medium-term (6 months) and long term (12 months) was calculated by DrinC software. The results showed that there is 99% direct significant correlation between precipitation-discharge and two SPI-SDI indices in four steps of time. However the correlation coefficient is significant for any four time steps, but the value of correlation coefficient is containing more delay time in a mood that there is not delay time in compare with other cases. Therefore, we can conclude that drought occurs simultaneously in the catchment Karkhe meteorological and hydrological. Also, due to the lack of consistent correlation coefficients and delay time in both cases, two aforementioned indices properly show drought conditions.

Surface water and groundwater interactions can be occurred between surface water bodies (such as rivers, lakes, and wetlands) and groundwater resources. Quantifying water exchange between a wetland and an underlying aquifer is an important task for studies in the field of e.g. water budgets and environmental water requirements. In this study, the groundwater component from controlling factors on wetland water level is considered to determine the water requirements of Kaniborazan wetland, located at the southern part of Urmia Lake. The results of the present study indicate that during the assessment period of 1998-2015, Kaniborazan wetland has been always recharged from underlying groundwater resources considering the hydraulic gradient threshold of this wetland. These recharge values have been maximum for 1998, 2002, and 2015 with the annual value of 4.11, 5.09, and 3.78 MCM, respectively. The mean annual value of this wetland depth has been estimated to be less than 16 cm. The impacts of drainage system, channels, and traditional streams have been investigated on this wetland during the assessment period. The obtained results show that these sources have a significant effect on the water supply of the wetland. Based on the available data and information, for example for 2006 and 2015, ignoring the impacts of drainage system, channels, and traditional streams on this wetland causes the wetland water volume reduction of about 15% and 30%, respectively.

In the present study first the behavioral patterns of precipitation climatic variable in period 1985-2014 in Kharrood watershed was investigated. Then, to analysis effects of climate change resulting from reduced rainfall under different scenarios mild, moderate and severe on hydrological (available water resources and economic value of irrigation water) and economic (agricultural products and farmers’ gross profit) variables from a biophysical- economic modeling system was used. Above modeling system includes the products yield function based on rainfall (biophysical part of model) and positive mathematical programming approach (economic part of model) that was solved in consecutive three stages and in the GAMS 24.1 software. The required data by the rain gauge stations and the relevant agencies in Qazvin province were collected. Behavioral pattern of precipitation showed that this climate variable was reduced in Kharrood watershed after year 2001. The results of proposed model showed that climate change resulting from reduced rainfall under mild to severe scenarios decreases the available water resources 11/3 to 23/0 %, increases the economic value of irrigation water 7/08 to 15/22 %, decreases the total acreage of water crops 5/14 to 16/39 % and decreases the farmers’ gross profit 6/58 to 13/41 % compared to the base year. The highest decrease of the available water resources in Kharrod watershed under severe scenarios and at a rate of 15/29 million cubic meters was obtained. Finally, use of deficit irrigation techniques, determination the rate of water charge to farmers on the basis of equality consideration, fallow-lands and providing financing convenience to farmers for farms outfit to new irrigation system to contrast with the effects of climate change and protection of water resources in this watershed were proposed.

Groundwater is considered one of the most valuable fresh water resources. The rapid increase in human population has increased the demand for groundwater supplies for drinking, agricultural, and industrial purposes. Produce groundwater spring potential maps an essential tool for implementing a successful groundwater determination, protection, and management program. The main objective of this study was to produce groundwater spring potential maps in the jahrom region, using frequency ratio, statistic index and entropy methods. Twelve hydrological-geological-physiographical (HGP) factors that influence locations of springs were considered in this research and processing in ArcGIS environment. These factors include slope degree, slope aspect, altitude, topographic wetness index (TWI), slope length (LS), distance to roads, distance to rivers, distance to faults, lithology, land use and fault density. The predicted results from the three models were validated using the receiver operating characteristics curve (ROC). From 103 springs identified, 70 (≈70 %) locations were used for the spring potential mapping, while the remaining 33 (≈30 %) springs were used for the model validation. The area under the curve (AUC) for the statistic index model was calculated as %91 and for frequency ratio and entropy the AUC were %92 and %92.7, respectively.

Drought has major negative effects on water resources and its related environments. Sometimes the drought damages are irreparable. Groundwater drought is one of the most important droughts that caused by insufficient groundwater recharge. This study aims to evaluate the effect of drought on groundwater resources of Dayyer- Abdan district, south of Boushehr province. Data and information such as rainfall, groundwater level, well discharge rates and groundwater quality data were used to this purpose. The Standardized Precipitation Index (SPI) and Groundwater Resource Index (GRI) were used to assess the drought situation. A new index called Hydrogeological Drought Management Index (HDMI) is introduced in this research. The HDMI index is a combination of Groundwater Resource Index (GRI), the Modified Standardized Electrical Conductivity Index (MSECI) and Standardized Well Discharge Index (SWDI). According to the achieved results, the average of GRI index is less than -1, that indicates a moderate groundwater drought. Groundwater drought also has destroyed the groundwater quality. From the groundwater quality view point (MSECI index), the most critical zone of the aquifer is located in the southern part of the study area. From the aquifer potential view point (SWDI index), the most suitable groundwater zone is the northern parts of the study area. The southern parts of the Dayyer-Abdan district (adjacent to the Persian Gulf) have the lowest amounts of HDMI index (less than -4). So the exploitation of groundwater is not recommended in these areas.

Despite the arid and semi-arid climate of Iran, a considerable volume of water is out of the reach by annual flash flood events. Therefore, for solving the problem, Floodwater Spreading Systems have been implemented approximately since three decades ago. The aim of this study was to evaluate quantitative changes of the groundwater affected by the Sarcahan floodwater spreading which was implemented in Hormozgarn Province by using Control Volume technique. Sarcahan floodwater spreading project has been implemented in an area of 2000 hectares. The well-hydrographs, rainfall histographs, and the fluctuation of groundwater at observation wells in synchronizing with the frequency of flooding were used to evaluate the effect of the project on the groundwater. Examined observation wells showed a relative increase in the level of groundwater after the primarily flood controlling so that the hydrograph of observation well located in the area of flooding has considerably risen about 1.34 meters. Groundwater levels changes recorded at the observation wells are quite similar to the feeding/withdrawing ratio whereas in 2008 groundwater level increased about 4.43 meters. Furthermore, in the Gahkom-Saadatabad the amount of rain more than 60 mm or continuous rainfall in large quantities can artificially recharge the aquifer. The results indicated that the

In this research, clustering of a hydrochemical data set from Sarab plain aquifer using Fuzzy C-Means (FCM) and Hierarchical Cluster Analysis (HCA) techniques have carried out and its application in delineation of hydrochemical facies has studied. The statistical clusters are analyzed for spatial coherence and confirming that the clusters have a hydrogeological corresponding to aquifer hydrochemical facies. Groundwater samples using the optimizing the number of the classes and fuzziness exponent using the fuzzy c-mean were grouped into four classes. The data set including 49 water samples and 12 hydrochemical variables form the study area have used. Results from both approach produced cluster centers that can be used in order to identify the physical and chemical processes creating the variations in the hydrochemistry variation of study area. The FCM method is potentially useful in establishing hydrochemical facies distribution. The results showed that the clustering scheme for partitioning water chemistry samples into homogeneous groups produced by FCM method is an important tool for the determination of aquifer hydrochemical facies and the FCM method is more capable to investigate threshold data rather than HCA method that variation is sharp and abruptly.

Providing effective solutions to prevent and reduce the damage caused by landslides is inevitable. Predicting and zoning landslides are among these solutions. Accordingly, the present study was conducted to compare and assess the accuracy of two Analytical Hierarchy Process (AHP) and Multivariate Regression (MR) methods in landslide hazard zoning in Valiasr Watershed with an area of 198 km-2 located in western Ardebil Province. Six factors of aspect, slope, elevation, lithology, land use and distance from the river were known as the most effective factors in landslide occurrence in the study area. Landslide zones were then obtained in five classes using two AHP and MR methods. Finally, landslide zoning maps were compared and evaluated by Density ratio index (Dr) and Quality sum index (Qs) to assess the accuracy of two studied methods. The results showed that distance from river, slope, land use, lithology and height were weighting in 0.426, 0.173, 0.145, 0.134, 0.089, and 0.033 in the AHP methods and 0.531, 0.109, 0.344, 0.273, 0.123 and 0.061 in the MR method, respectively. The amount of two Dr and Qs indices were calculated 5.51 and 0.44 respectively in the AHP method and 6.45 and 0.72 respectively in MR method which indicated that MR method having 28% disagreement with reality were more accurate than AHP method having 56% disagreement with reality for landslide hazard in the study area.

Solution of stream-wise flow velocity on two dimensions (in width and depth directions) in rivers is essential for many hydraulic features such as stage-discharge rating curve development, suspended sediment transport estimation and boundary shear stress calculation. In this paper based on Chiu's entropy theory, a simple method has been proposed for simulation of vertical and transverse profiles of flow velocity in the straight rivers. For calibration and validation of the proposed method, a new idea based on the optimum estimation of entropy parameter in rivers was used. The results of this study at Aghghalla hydrometric station located on Gorganrood River showed that velocity flow field obtained by the Chiu's theory has suitable accuracy compared to the field data. Further, statistical analysis of the results revealed that the mean absolute errors of this method for solution of flow velocities in calibration and validation stages are 5.2% and 3.5%, respectively. These errors are 5.9% and 6.04% respectively for the total river flow discharge prediction. According to the few required input data, the proposed method has more advantage than other existing methods.

Evapotranspiration is one of the important components of basin water balance which cannot be measured directly at the basin scale. Therefore, it is inevitably estimates through indirect methods. In this regard, the Advection Aridity model, one of the widely used models of complementary relationship has attracted a lot of attentions. Due to the existence of Priestley-Taylor equation in the Advection Aridity model, it is required to calibrate Priestley-Taylor coefficient to increase the accuracy of the model. The current research aims at calibrating Priestley-Taylor coefficient in estimation of potential evaporation through Penman method to apply it in the Advection Aridity model in the studied area of Mahabad dam reservoir, Iran. The required data were collected for a period of 26 years (1986-2012) from Mahabad 1st order meteorological station which is located at short distance from Mahabad reservoir. The results showed that Priestley-Taylor coefficient undergoes monthly changes during a year and decrease during the warm months of the year. Therefore, it is better to use its monthly values in calculations, its minimum and maximum averages were 1.01 and 1.68, respectively. Moreover, the long term average of this coefficient during a period of 26 years has been calculated 1.25.

Organic (wild) Pistacia vera is a species of broadleaf forest. One of the most important natural forest habitatsin the world is located at northwest and southwest of the city of Sarakhs, Khorasan Razavi Province, Iran.In addition, the unique ecological features of this habitant and the economic value of organic pistachio greatly impact on the lives of people residing in this region and the country.Unfortunately, continuous over harvesting and drought-stricken development endanger natural life, regrowth and cultivation of this unique species.Understanding spatial distribution of this species plays a significant role for assessing regional protection and development; on the other hand, it can be helpful to recognize effective ecological factors on its habitat.Ttherefore, modeling this distribution is very important.In this paper, habitat modeling of this species is studied by method of maximum entropy according to edaphic, climatic and physiographic data in the city of Sarakhs (under district of Gonbadli). results of Jackknife test for surveying significance of variables shows that changes in soil properties such as gravel percentage, exchangeable sodium adsorption ratio, sodium content soil, gypsum, climatic factors (temperature and precipitation)and height above sea level are most important factors affecting the distribution of habitats.The accuracy of model is assessed by kappa coefficient for 0.72 and AUC 0.92 as well as result sreveals that maximum entropy method is an appropriate method for habitat modeling.

Given the vital importance of water in human life, recognizing the effective use of rainfall and crop water requirement and economic planning are very important. Identifying and applying appropriate method for estimating effective rainfall, especially in rainfed has importance. In this study to determine the most suitable experimental method for estimating effective rainfall in rainfed Wheat, Barley, Peas and Lentils for high rainfall areas (Rasht in Gilan) as compared to areas of low rainfall (Daran in Isfahan) are discussed. In this study, five different experimental methods to determine the effective rainfall, including: methods of the Soil Conservation Service (SCS), reliable method, empirical, United States Department of Agriculture (USDA), and percentage method. The results shown that all methods used in effective rainfall in Rasht is useful. But if in Daran that a low rainfall area want determine the effective rainfall, it need to be pre-calibrated. Results have shown that the use of methods to prioritize the review in these two areas, methods for Rasht are SCS and the percentage and USDA were recommended in Daran. Since the amount and duration of rainfall is not controllable can be effective strategies to increase performance of precipitation and consequently precipitation. Including the reduction of surface runoff, water storage for times of low rainfall and reduced water depth plan for the cultivation of plants used in accordance with the precipitation regime.

This is obvious that no erosion occurs unless detachment takes place first either by raindrop or runoff. The Raindrop-Impact-Induced Erosion (RIIE) occurs when detachment results by raindrop energy. Towards this attempt, a set of laboratorial experiments were scheduled for effects of consecutive storms on RIIE components (i.e. upward splash, downward splash, net splash, total splash and upward splash/downward splash). The experiments were conducted for two different rainfall intensities of 30 and 90 mm h−1 at slope of 5% under rainfall simulation and soil erosion for a soil collected from Kojour rangeland watershed in the Alborz Mountains, northern of Iran. The comparative analysis of the results showed that upward with downward splash under rainfall intensity of 30 as well as under rainfall intensity of 90 mm h−1 in consecutive storms were not significant difference (p ≤ 0.05) by One-Way ANOVA in SPSS Statistics 22 software In addition, results indicated that RIIE components viz. total and upward and downward splash were significant difference (p ≤ 0.01) under rainfall intensities of 30 and 90 mm h−1 in consecutive storms of third, fourth and fifth. While, net splash and upward/downward splash proportion was not significant difference (p > 0.05) under rainfall intensities of 30 and 90 mm h−1 in different consecutive storms. The results also indicated a 2.5-fold increase in coefficient of variation of net splash and total splash under rainfall intensity of 30 mm h-1 then the rainfall intensity of 90 mm h-1.

In this paper climate change impact on annual precipitation and temperature series for Zanjan province was assessed and uncertainties were investigated. Spatial average of annual time series of precipitation and temperature for Zanjan province were calculated and then were modelled using ARMA model and 100 annual precipitation and temperature series of length 30 years were generated for spatial average of Zanjan province. Using the models, future scenarios of 6 GCMs under 3 emission scenarios were downscaled and 100 annual precipitation and temperature series of length 30 years were generated for each of the scenarios. 90% bounds of the variable statistics for the current condition were compared with the 90% bounds of the corresponding values for the all of the future scenarios and the uncertainties were investigated in the results. Model validation showed that the models are adequate for generation of the annual temperature and precipitation series. In confidence level of 90%, it is expected that average temperature of Zanjan province will increase from 0.6 to 3.2 ºC and average precipitation change from -25% to % in 2035-64 period. So, the uncertainty due to the GCMs Structure and the emission scenarios are considerable and should be considered.

In recent years, paying attention to groundwater and management, It's extraction due to lack of surface water and population growth, agricultural development has increased.This source is considered as one of the valuable resources of freshwater so that this source has become one of the most valuable vital resources. Groundwater extraction in recent years caused to down the level of this water. So that is reached to amount of 19.9m in the plain of qorveh since 1986,1987 until 2015.so that the plain has become one of the forbidden plains of 625 plain country. In recent years, integrating data of remote sensing (RS) and geographic information system(GIS) has increased for exploration this valuable material. So that the combination of these two has become a point in the field related to the issue of water. In this study with help of (RS) and (GIS) data potential areas of groundwater were identified. Layers that were created for site selection of aquifer in this study are as follows: geology, topography, slope, lineament, density of lineament, drainage, density of drainage, land use and vegetation of cover. At last the final map with help respective layers obtained with method of fuzzy in gis. The resulting map was divided to five groups very good, good, average, weak and very weak. The results showed the areas with good and very good potential with an area of 136461 hectare which about half the area of plains in more northern parts and accordance with alluvial lands with vegetation of cover and down slope and regions with lower potential more in southern parts and matches the slope area covered with rock solid.

One of the problems in wells after long term use is creation of deposits on well screen or gravel packs. The deposits, despite the presence of water in the context of the aquifer, prevent the penetration of water into the well. As a result, it greatly reduces the amount of water production of the well. Rehabilitation of wells is removing the deposits from the front and back of the well screen. There have been some methods of well rehabilitation before, but today, with the development of technology, more efficient methods have been developed which cause less damage to the aquifer and the environment. In this study, new methods of well rehabilitation is investigated for implementation in Iran. A criteria for determining the efficiency of the methods is proposed. The method of air shock in combination to water jet is estimated to be more efficient with less time and cost consumption for implementing in Iran.

Soil erosion is the most serious and irreversible threat to sustainable development. According to the increasing rate of soil erosion and sediment yield, the objective of this study was to determine relative contribution of sediment sources in Ziarat catchment in fall, winter and spring seasons by using of sediment fingerprinting technique. In view of this, 43 samples from sediment sources including rangeland and cultivated land as surface erosion and stream bank and road verges as sub-surface erosion as well as 14 samples of suspended sediment at outlet of catchment were collected and concentration of geochemical tracers, organic carbon and 137Cs were measured. The optimum set of tracers was selected by using the Kruskal-Wallis H test and discriminant function analysis. Finally, the relative contribution of sediment sources was determined using mixing model in different seasons. The results showed that the maximum relative contribution was related to surface erosion in winter and spring seasons. Sub-surface erosion in spring season with 60.4% was also contributed a large amount of sediment yield. The results of this study can be used to select the management strategies in soil erosion and sediment control of Ziarat catchment in different seasons.

Optimization the number of synoptic stations in the estimation of rainfall is an important step in terms of reducing the maintenance cost and saving in the data collection. The main objective of this study was to determine the optimal number of synoptic stations to estimate the amount of rainfall in Iran country. Accordingly, the amount of rainfall of synoptic stations related to a common 14-year period was received from the National Weather Service and the performances of five different interpolation methods were evaluated. Based on the results of radial basis function (RBF), with a margin of error of 0.63, this method was selected as the most appropriate method in fitting the data. Studies show by eliminating the synoptic stations in PCA method the estimation error of RMSE increases from 0.48 to 0.52 related to the case that all synoptic stations were used and in the radial basis function interpolation method decreases from 0.63 to 0.55 which indicates the suitability of this method in the optimization of synoptic stations. The results indicate that removing 34 and 22 points from the network of synoptic stations in Iran respectively in the PCA method and interpolation method of radial basis, the resulting error is acceptable.

In hydrology studies, natural river regimes are considered while this assumption is not correct because the water of the river is using for developing agriculture, industry, and other needs, particularly in the middle basins. The requirement for river base flow separation is having access to natural river regime on a daily scale, which regarding the limitations of naturalization, natural river regime can be calculated in the annual or monthly scale. Because of this issue, the estimation of base flow has been faced with some difficulties. On the other side, due to the complex relation of surface water with groundwater, the estimation of base flow is too hard. Therefore, in this study, the removal process method was used for naturalizing monthly discharge of Belbar basin, and Eckhart RDF algorithm, because of considering aquifer characteristics for calculating base flow and ability to optimizing its parameters, was used. The parameters of return constant and the maximum base flow index for monthly natural river discharge in hydrometric stations of Belbar dam was optimized. Then, the monthly base flow was calculated and the results showed that the monthly natural river discharge can be used like the daily natural river discharge with the same accuracy.

Number and frequency of drought are more than other natural disasters that have influenced human societies in recent decades. Drought is a kind of natural disaster which is formed and extended smoothly and in a crawling way in comparison with natural hazards like heavy precipitations and floodwaters. There are different and numerous indicators for quantitative expression of drought. Percentage Indicators of normal precipitation (PNPI) and precipitation abnormality (RAI) status and continuation of drought in 8 stations of Abadan, Ahvaz, Bandar-e Mahshahr, Bostan, Masjed Soleyman, Omidieh, Ramhormoz and Safi Abad in Khuzestan province during the statistical period (1990-2014) have been considered in this research. Results represented that based on PNPI indicator, the most severe drought happened during period 1990-2014 in Bandar- e Mahshahr station with the amount of 20.39 in 2010. Also, the most severe wet period happened in Ahvaz station with the amount of 216.33 in 1997, based on PNPI indicator. Also, based on RAI indicator, the most severe drought happened in Bandar- e Mahshahr with the amount of 6.26 in 2010 during the period 1990-2014. Based on RAI indicator, the most amount of wet period occurred in Ahvaz station with the amount of 8.6 in 1997.

Since Iranians introduced Qanat to the world, it has been widely spread around the world due to its usefulness and it has provided people with groundwater. According to studies conducted in Iran, there are 300 thousand wells for accessing Qanats and these structures have the total length of 10000 kilometers. In order to utilize these water resources, sustainable development should be considered as an important issue which means exploitation of these resources with responsibility, reasonable and proper planning. Tourism has many advantages like a cultural exchange, flourishing native businesses, increasing the rate of employment and familiarizing communities. Studying the history and structure of Qanats in Iran and other regions, reveals the high technical knowledge of our ancestors. Due to many reasons such as new methods of irrigation, climate changes and inappropriate management knowledge have caused drought in many Qanats. Successful experiences in reviving Qanats in order to use them as tourist attractions in different regions, has illustrated the high potential of Tehran to attract a huge number of tourists by reviving and improving these structures in historical parts of this city.