Most of the rivers which originate from Zagros Mountains are considered as the permanent rivers of the country. This permanence has caused the growth of some river basins during the Fourth Period being considered as normal and natural (oberlander, 1965). Something which should be remembered about the domestic base surfaces in the Middle Zagros is the ever present changes which have happened in the Quaternary Period. Most of the domestic base surfaces in this area have embedded hydrologic changes in the form of river-terraces during the Fourth period (Eivazi, 1997). Considering the level changes in the domestic rivers of the country as an evidence of climatic changes of the Fourth Period, lack of those evidences in Task river which is the base surface of Kour river, should be considered as unnatural.  

Hydraulic bridges are critical components in infrastructure network. One of the major causes of its collapse is due to local scouring of its foundations. Hence in this study, the mechanism and various factors affecting local scour around bridge piers was analyzed. For this, a software platform Hydrologic Engineering Center River Analysis System (HEC-RAS) was used to evaluate local scouring around piers of spillway bridge with radial gates of Telengiri Irrigation Project located in Koraput district of Odisha, India. Soil samples were collected at the site and tested in the laboratory to determine various properties required for model inputs and assess the vulnerability of soil for scouring. Geometric data and design specifications of radial-gated bridge structure along with soil properties of the case study were used to build HEC-RAS model and then steady-state flow profiles were given to calculate local scour depth. Analytical methods such as Kothyari, Richardson, and IRC equations were used to corroborate local scour depth values with the model. The model predicted scouring of 8.29m which is close enough to values predicted by Richardson equation (8.95 m). This small discrepancy was due to not accounting for bed conditions and armoring of bed material. Parameters were varied in the model such as discharge, width and geometry of piers, skew angle of bridge and piers, angle of attack, and different bed configurations to simulate their effect on local scour depth. The soil was found to be highly erodible as per the soil erodibility factor obtained from the Wischmeier equation.

Flooding is one of the most devastating natural disasters occurring annually in the Philippines. A call for a solution for this malady is very challenging as well as crucial to be addressed. Mapping flood hazard is an effective tool in determining the extent and depth of floods associated with hazard level in specified areas that need to be prioritized during flood occurrences. Precedent to the production of maps is the utilization of reliable and accurate topographic data. In the present study, the performance of 3 digital elevation models having different resolution was evaluated with the aid of flood modeling software such as hydrologic engineering centre-hydrologic modeling system and hydrologic engineering centre-river analysis system. The two-dimensional models were processed using three different digital elevation models, captured through light detection and ranging, interferometric synthetic aperture radar, and synthetic aperture radar technologies, to simulate and compare the flood inundation of 5-, 25-100-year return periods. The accuracy of the generated flood maps was carried out using statistical analysis tools-Overall accuracy, F-measure and root-mean-squareerror. Results reveal that using light detection and ranging– digital elevation model, the overall accuracy of the flood map is 82. 5% with a fitness of 0. 5333 to ground-truth data and an error of 0. 32 meter in simulating flood depth which implies a promising performance of the model compared to other data sources. Thus, higher resolution digital elevation model generates more accurate flood hazard maps while coarser resolution over-predicts the flood extent.

Dam reservoirs supply potable, agricultural, and industrial water in most cities of Iran. Due to lack of proper operational rules or unbalanced demand versus water resources volume, (along operating time) correction in operational rules is required to fulfill current situations. Hence the goal of this study is to optimize the Qeshlaq Dam reservoir operation rules to maximize the water release for agricultural demand with considering maintaining reservoir capacity to allocate 100% of potable water demand. For this purpose a linear optimization program was developed in MATLAB. Herbst method was used to assess drought intensities and periods. Based on Herbst method, a critical period of 51 month (October 1987 – Septamber2012) was determined and an optimal release of 1. 334 MCM was estimated for agricultural use. Based on downstream potential agricultural demand, this released water is supplied only 60% of the agricultural demands. So there will be shortage in supplying agricultural demands for months July (2. 2 MCM), August (2. 47 MCM) and September (2. 29 MCM). The correlation coefficient of R2 = 0. 84 was obtained between modelled and actual monthly reservoir storage. Results showed that the probability of the maximum long term storage of 162 MCM (equal to 0. 75 of reservoir capacity) is 50%. Also statistical distribution analysis revealed that spillway discharge data are agreed with Gumbel distribution more accurately than other distributions. In general, the results of the optimization showed that linear programming can be used for optimal water resources allocation for agriculture and industry use.

Rainfall-runoff hydrological models are important tools in water resources projects. Generally, performance of this group of models is dependent on the proper selection of parameters. Accordingly, several methods have been developed to estimate hydrological parameters. The present study aimed to compare the performance of conceptual hydrologic models such as TANK, SIMHYD and AWBM which benefit from the indirect model parameters estimation approach in discharge simulation of Babolroud watershed, Mazandaran province, Iran. The automatic calibration process of these models was designed using genetic evolutionary search algorithm and objective functions (NSE and RMSE) as error thresholds determinants. Hence, meteorological and hydrological data consist of temperature, evapotranspiration, precipitation and discharge (in daily scale) were gathered from authorities. Input data was also divided into warm-up, train and test steps after preliminary validation and recovery. Based on the results, NSE metric introduced TANK model as the best simulator respectively for train and test step (0. 59 to 0. 72). Depends on RMSE metric, SIMHYD (0. 83) and TANK (0. 15) models were introduced as the best simulator respectively for train and test step either. According to the catchment flow signatures, general simulation of low-flow (excluding the Model TANK), mean-flow and high-flow were conducted with acceptable agreement. While simulation of the flow duration curve slope which represents an intensity of changes (excluding TANK model in train step), did not provide acceptable results. Given the weaknesses and strengths of the proposed models, they can be used as an acceptable simulator in water resources management especially in terms of ungauged basins, after preliminary verification in different climatic conditions.

Introduction Hydrological regimes play a major role in changing the structure and function of ecological processes and river ecosystems. Significant changes in the hydrological regimes of river flow cause the spatial and temporal heterogeneity of river systems and the degradation of natural ecosystem services and threaten biodiversity. Trend analysis and change point detection are important topics in the analysis of hydrological time series. The study area in this research includes the upstream part of the Hablehroud river basin draining to the Bonekoh hydrometry station, located within the jurisdiction of the Tehran province. The Habaleroud river as the main drain of this watershed has recently encountered the pressures induced by human interventions and climate change, resulting in significant changes in its hydrological status. Materials and Methods In this research, using the sequential Mann-Kendall, Pettitt, Buishand Range, Buishand U, Standard Normal Homogeneity, and double mass curve tests, the significant change point in the annual discharge time series (1980–2017) of the Bonekoh hydrometry station at the outlet of the Hableroud watershed was detected. Then, using the Indicators of Hydrologic Alteration (IHA), the alterations in the hydrological condition in the period after the change point (Altered flow regime) compared to the period before the change point (the natural flow regime) were analyzed using the daily observed discharge data of the Hableroud watershed. Results and Discussion According to the research results, in the mid-1990s, a statistically significant change point in the annual discharge time series of the Bonekoh hydrometry station occurred, and most of the hydrological indicators show a deterioration in the condition of the Habaleroud watershed flow regime. Whereas for most of the hydrological indicators, after the change point, the frequency of the low values category has increased and the frequencies of the middle and high values categories, have decreased. These reductions have not only occurred for high extreme values, but also for low extreme values. In addition, the mean monthly discharge for all months of the year and the base flow of the basin have decreased. Both the frequency and duration of low-flow pulses have increased. On the contrary, both the frequency and duration of the high-flow pulses have decreased. For this reason, the frequency and magnitude of high extreme events such as medium and large floods have decreased. The long-term trend analysis indicated that 25 out of the 33 IHA have experienced a statistically significant decreasing trend. Therefore, the mean annual discharge of the watershed at the Bonekoh station has declined from 8.43 m3/s during the pre-impact period to 5.43 m3/s during the post-impact period, which is equivalent to about 35 % decline in the watershed outflow. While the watershed’s mean annual precipitation shows a negligible long-term increasing trend. Therefore, it seems that human interventions across the watershed play a major role in the hydrologic regime alteration of the watershed. Conclusion In the Benkoh hydrometric station in the mid-1990s, the hydrological regime of the basin has changed significantly. Then, using special software, the hydrological change indicators and key environmental flow indicators were analyzed in the periods before and after the change point. Unfortunately, most of the hydrological indicators show a downward trend in the Habaleroud river flow. So that the average discharge has decreased in all months of the year. Base current values are reduced. Both the frequency and duration of minimum current pulses are increased. On the contrary, both the frequency and duration of maximum current pulses are reduced. For this reason, the frequency and magnitude of extreme events such as medium and large floods have decreased. The results of the analysis of the trend of several indicators of the environmental flow also indicate the regressive course in the ecohydrological conditions of the Hableroud watershed. So that the minimum monthly flows for all months of the year show a downward trend. On the one hand, the continuity and frequency of periods of water shortage has increased, and on the other hand, the frequency of high flow pulses has decreased. The consequence of these changes will be creating tension and threatening riverside plant and animal communities that live in the flood plains of rivers and provide many ecological services. On the other hand, with the destruction of these riverside communities, the hydraulic conditions of the floodplains have changed and the vulnerability of river ecosystems and infrastructure facilities around the river increases against possible floods and causes a lot of damage. With the continuation of the existing process of managing water resources of the basin, stakeholders and beneficiaries of the basin will face many challenges in the future. Due to the fact that the average annual rainfall of Hableroud basin does not show a decreasing trend, it seems that human interventions are one of the main factors affecting the hydrological changes of this basin. Therefore, it is suggested that the main focus of management policies and measures should be focused on the management and optimization of human interventions in Hableroud watershed. In other words, instead of focusing on the top-down management approach and (hard) structural engineering measures, the focus should be on the participatory management approach and (soft) management engineering measures, and the water and soil resources of this basin should be used optimally and in accordance with the principles of sustainable development, so that at the same time Reducing the conflicts between the beneficiaries and the stakeholders upstream and downstream of the watershed (social challenges and threats) which currently occurred on a larger scale between the two provinces of Tehran and Semnan, and also preventing these conflicts from occurring on a smaller scale between the smaller communities upstream and downstream in The extension of waterways and rivers in the basin prevented the occurrence and spread of diverse environmental challenges and threats and vulnerability to natural hazards such as sudden floods and droughts. Also, it is suggested that the future changes in discharge of the studied watershed should be predicted according to the results of climate change models and land use changes, and suitable solutions should be formulated and implemented in order to deal with or adapt to these changes.

Hydrologists have always tried to classify atmospheric and hydrologic events in order to simplify the hydrologic convolutions and the observations or to save the time and the budget. Most of these methods are used for the regionalization of hydrologic phenomena like rainfall, streamflow and other components of water cycle. Multivariate techniques have been underlined as suitableand powerful tools for classifying the meteorological data such as rainfall. The karoon river, especially in mountains, is faced big floods, great economic and enviromental damages during recent years. Its hydrologic processes were examined to offer a suitable analysis of its changes trends. In this research, we tried to recognize the data trends and the suitable model of estimating in the future by using Box-cox convert, time series model and helping AIC and BIC indexes. So, we recognize the following models for estimating and suitable trend: ARIMA (4&1) in Shaloo station, ARIMA (2,1,1) * (3,0,3) in Armand station, ARIMA (,0,1) * (3,0,0) * 3 in Barz station and ARIMA ( ,0,0) * (3,1,1) * 4 in Marghak station. Then, we chose statistic period of 2000-2004 as an evidence and recomparing, and we compared data recorded (evidence) and model estimating. However, there was a positive correlatin between data recorded and estimating, we confirmed an upward in the river discharge.

Harirud river with an international nature is shared between Afghanistan, Iran and Turkmenistan and currently there is no treaty among these states regarding the division of its water resources. In recent years, after the construction of the Doosti Dam by Iran and Turkmenistan, Afghanistan, as an upstream state is moving towards hydro-hegemonic policy in the region by building various dams which restrain and divert the water flow of this river in order to decrease the downstream countries’ water rights. On the other hand, due to the high importance of Harirud water resources for Iran, continuing this type of behavior by Afghanistan might cause conflicts and create security risks among these countries in the near future. Therefore, employing a descriptive-analytical approach, the study aims at examining the issue according to international legal documents in the field of sharing common water resources. Finally, the findings indicate that the best and most practical method for exploitation of Harirud water resources is based on the theory of limited territorial sovereignty and implementation of the principle of equitable and reasonable utilization of common water resources by Afghanistan, without causing significant harm to downstream states.

Identification of the existence or non-existence of trends in streamflow and floods by the statistical analysis for water resources management and infrastructure designing is an inevitable issue. Thus, in this study, three hydrologic variables of mean daily discharge, maximum daily discharge and peak discharge were analyzed for detection of any probable trend. Using three non-parametric tests including Mann-Kendall, Spearman’s Rho and Thiel-Sen estimators, the trend of hydrologic variables in the Atrak River basin in northeast of Iran was studied for 10 discharge gauging stations during the 1972-2003 period. The results indicated that the three tests proved the same conclusion about trend existence. Except one station, all other stations within the study area show increasing trend for the peak discharge but for the mean daily discharge show opposite trends. For 70 percents of stations, the observed downward trends in the mean daily discharge are significant at 0.05 or lower levels whereas 30 percents of stations exhibit significant upward trend in the annual peak discharge at 0.05 or lower significance levels. None of the stations present a significant downward or upward trend for the maximum daily discharge. Based on the results it can be concluded that the hydrological regime of the Atrak River basin has undergone considerable changes which is indicated by decrease in annual discharge and increase in magnitude of floods. Therefore, water resources management and planning authorities should consider these changes in the assessment, designing and planning processes. The changes in hydrologic regime of the Atrak River basin is either related to climate or land use changes.

Assessment of river health can be used as a tool for environmental flow estimation and quantification of the amount, timing and required water flow quality for permanence of river ecosystems. The current study aims to determine the spatial and temporal changes of rivers health with an emphasis on hydrologic indicators by using statistical tests in Ardabil province. For this purpose, the daily discharge data of 24 hydrometric stations with the period of 1367-1390 was used for river health analysis. In addition, the non-parametric Mann-Kendall test and Sen's estimator method were performed to determine the presence or absence of positive and negative trends at different statistical levels. Also, after dividing the existed study span into four periods, the Kruskal– Wallis test was applied for the investigation of temporal variations and the existence of differences between short-term periods. Results showed a significant decreasing trend of river health in studied stations (13 stations from 24 stations). Sula and Firuzabad stations had significant increasing trend and in other remained stations, no significant trend was identified. According to the results obtained from the maps of spatial variability of river health, maximum and minimum change of river health indicators were observed in the central part, and northern and southern parts of the province, respectively. Generally, it can be said that, recently, the overall changes as well as reduction in hydrologic flow health have been more compared to the past which can be associated with increase of exploitation intensity from surface water resources as well as reduction in the water yield due to climate change.