The Clark method is one of the most applicable techniques for development of instantaneous UNIT HYDROGRAPH whose efficacy depends upon the accuracy in estimating storage coefficient. The present study was conducted in Kasilian watershed in Mazandaran Province to determine the efficiency of developed HYDROGRAPH using Clark's method and to compare the Muskingum storage coefficients obtained through graphical, Clark, Linsley, Mitchell, Johnstone-Cross and Eaton methods. To this aim, the time-area histogram of the study watershed was initially developed. The 3h-UNIT HYDROGRAPH was then derived using the data collected in Sangedeh climatological and Valikbon hydrometric stations. The efficiency of Clark’s instantaneous UNIT HYDROGRAPH developed based on 6 methods for calculation of Muskingum storage coefficient was ultimately compared with the observed average 3h-UNIT HYDROGRAPH of the study area. The results of the study revealed that the Clark’s instantaneous UNIT HYDROGRAPH obtained from graphical method for estimation of storage coefficient with estimation error of less than 33.33% and efficiency coefficient of 83% could suitably simulate different components of the observed average UNIT HYDROGRAPH for the study watershed.

Groundwater modeling is widely used as a management tool to understand the behavior of aquifer systems under different hydrological stresses. Eyvanekey alluvial aquifer, which is 126 square kilometers flow budget boundaries, is one of the main aquifer in Semnan province. Indiscriminate exploitation of groundwater in recent years led to a water table shortage in this aquifer. In this study to acquire the aquifer hydraulic parameters, prediction the water table and the flow budget of the aquifer, the modeling approach was used by GMS interface. Model calibrated for steady state in a period of one month (Sep. 2008), and for a period of 12 months (2008-2009 water year) for the transient state, using a hydraulic load for the existing wells in plain view, and calibrating in this way, S, and K values were optimized. The verification process, confirms the validity of the results for unsteady conditions. After the model calibration and verification, water table of the pizometers to September 2013 was predicted. The results show that the current trend of declining aquifer will be continued and at the end of the forecast (Sep. 2013), the water level of the HYDROGRAPH represents nearly 898.5 m and in proportion to September 2008 will be decrease 8.3 m. The flow budget result shows that most with drawal is done by extraction wells in spring and summer. The aquifer reservoir deficit is about five million cubic meters during SIMULATION period (87-88).

Among the main objectives in hydrology are to forecast quantitatively the process of rainfall-runoff, and to determine flood discharge at the outlet of a watershed. Flood discharge can be estimated using rainfall-runoff models which explain hydrological phenomena for unmeasured watersheds. Relationship between hydrology and geomorphologic parameters can lead to the estimate of hydrologic response of a basin. The purpose of this study is to investigate the consistency, accuracy and reliability of geomorphologic model (GIUH) in estimating the shape and discharge of flood resulting from a rainfall with certain intensity and duration. The results of this model were compared with SCS (Soil Conservation Service), Snyder, triangular, Rosso and Geomorphoclimatic (GCIUH) UNIT HYDROGRAPHs. The results showed that in Kasilian basin with the area of 67/78 km2, GIUH model had the least amounts of main relativity (MRE) and square error (MSE). Furthermore the result showed that the efficiency of geomorphologic model ratio to Snyder, SCS, Triangle, Rosso and GCIUH in Kasilian Basin are 91.06, 99.11, 88.642, 48.19 and 4.94 respectively. Therefore the result of Geomorphologic model compared to other models (based on this study) is the most efficient model to estimate flood discharge.

The present study has been conducted to evaluate the efficiency of Clark Instantaneous UNIT HYDROGRAPH Model in regenerating flood UNIT HYDROGRAPH in Bazoft watershed in Chaharmahal and Bakhtiari Province. The comparative evaluation is conducted between the 2h-UNIT hydographs simulated using Clark model and the one obtained from averaging the observed ones. This comparison is made with the help of statistical criteria viz. relative error, root mean square of error, coefficient of efficiency and bias. It verified high level of compatibility between two UNIT HYDROGRAPHs using the dark model and the HYDROGRAPH obtained by averaging the observed data.

Efficacy in estimation of storage coefficient in Clark method, as one of the applicable techniques for development of instantaneous UNIT HYDROGRAPH, may have great effect on ultimate UNIT HYDROGRAPH. The present study was therefore conducted in Bazoft watershed in Chaharmahal and Bakhtiari Province to determine the efficiency of developed HYDROGRAPH using Clark method and to compare the Muskingum storage coefficient obtained through graphical, Clark and Linsley methods. Firstly, the time-area histogram of the watershed was developed. The 2h-UNIT HYDROGRAPH was then derived using the data collected in Chelgerd climatological and Morghak hydrometric stations. The efficiency of Clark's instantaneous UNIT HYDROGRAPH developed based on graphical, Clark and Linsley methods for calculation of Muskingum storage coefficient was ultimately evaluated. The results of the study revealed that the Clark's instantaneous UNIT HYDROGRAPH resulted from graphical method for estimation of storage coefficient is more compatible with average UNIT HYDROGRAPH existed for the watershed than other two methods.

The usage of geomorphologic parameters for estimating of UNIT HYDROGRAPH are a basic role in hyrological science. Due to lack of observed data in basins. Relationship between hydrology and geomorphologic parameters can lead to estimate hydrologic response of a basin. Dynamics and static parameters such as velocity and rainfall intensity plus bifraction ratio length ratio, area ratio length and slope of the main stream affect on response of basin. To make relation between these two elements can estimate the output HYDROGRAPH of a basin. In this research project by this method for representative basin of Kasilian in north Iran hydro graph were estimated and then by other synthetic methods such as Snayder, SCS and triangular SCS were compared. It is mentioned that the giuh by ROSSO method also acquised. After then these methods compared by observed HYDROGRAPH, the result was satisfied and they have no significant differences.

Sediment graph is an important tool for soil and water resources management of watersheds. It is therefore important to find an appropriate procedure to simulate sediment graph data in different watersheds with inadequate and unreliable suspended sediment data. However, achieving simple procedures based on easily accessible data has been less considered. Hence, the present study was conducted in Galazchai Watershed in West-Azerbaijan Province, Iran, with an area of some 103 km2 to investigate the ability of synthetic sediment graph development by using HYDROGRAPH. Towards this attempt, a databank of 18 storm events occurred during autumn 2011 and spring 2014 was developed and corresponding total and direct HYDROGRAPHs and sediment graphs were prepared. All total and direct sediment graph components were simulated using corresponding HYDROGRAPH components with the help of different bivariate regression models and the best performed model was ultimately determined by applying different criteria. The results showed that the SIMULATION of different total sediment graph components was possible using HYDROGRAPH components except for base time and ordinates of 50 and 75 percent of peak. Direct sediment graph SIMULATION results also verified the SIMULATION ability of all components except for ordinates of 75 percent of peak. According to the results, SIMULATION of temporal components with the lower relative errors had better performance than the other components. So that, for total sediment graph, the lowest relative estimation and validation errors for time to peak were 48. 86% and 45. 65%, respectively. Also, the best performed model developed for the direct sediment graph base time had the lowest relative estimation and validation errors of 23. 03% and 21. 75% and the highest coefficient of efficiency of 0. 93.

Forecasting the probable maximum flood in a watershed is of vital importance in designing the spillways of the dams and estimating the volume of the reservoirs to be constructed on its respective river. As numerous watersheds are un gauged or lack reliable long-time data, many hydrologists have tried to develop theories based on the geomorphology of such basins. We simulated the direct surface run-off (DSRO) HYDROGRAPHs for 4 rainfall events for the Shoor Indica Catchment (SIC) in the Khuzestan Province, Iran using the GIUH-based Clark-Nash models and compared them statistically with the instantaneous UNIT HYDROGRAPH (IUH) model option of the HEC-HMS package and the Nash IUH model using some commonly used objective functions. The geomorphological parameters of the SIC were evaluated as the Horton’s ratio from the topographic and HYDROGRAPHic maps using the GIS package. Individual dynamic velocity parameter was estimated for each event using the regional relationships developed between the flow velocity and the excess mean rainfall intensity based on the river cross sectional geometry. Statistical comparison of the developed and the recorded HYDROGRAPHs indicated that the GIUH-based estimations more precisely predicted the events than the IUH routine.

Given the increasing trend of application of Geographic Information System (GIS) for natural resources study in one hand and complication of biological, geomorphological, hydrological and ecosystem mechanisms on the other hand, scale is an overlooked but very impressive and flourishing concept. As for any natural resources study consistent with its phase, various maps are used and produced so in order to make the achieved results usable for planning as well as management of resources, determination of scale of the study and application domain for the results is very significant. Since using GIUH model in the basins without hydrological data have been widely recommended by hydrologist and this model developed in accordance to the relationship between geomorphological properties of basins and their effects on hydrological responses, so before using that it is essential to determine the optimal scale (in view points of accuracy, time and cost) which in this paper will be selected from 1: 50000 and 1: 25000 scales, inclusively used in topographic maps in Iran, using multi-scale analysis. Of course, it should be mentioned that giving a comparison between the results of GIUH and the recorded data as well as the model’ s effectiveness in our research basin has not been the purpose.

Time of concentration is one of the main topics of physiographic and hydrology studies in watersheds, and it has relatively large impact in calculation of other hydrology parameters, especially flood peak discharge. Moreover, it is used to derive the UNIT HYDROGRAPH of watershed. Fractal geometry can be used as a qualitative tool in order to examine the geomorphology of rivers and also modeling of complex natural phenomena. The most important feature which is analyzed about the phenomena is the fractal dimension that has a great importance to understand and predict the behavior of river changes. This article is aimed to find relationships for time of concentration based on fractal dimension using the production of fractal triangular UNIT HYDROGRAPH of Walnut Gulch watershed. Accordingly, all sub-watersheds and waterways of Walnut Gulch watershed were separated using the GIS software, image of sub-watersheds were digital image processed and the fractal dimension of waterways were calculated using box counting method. Then, by fitting the curve of watershed fractal dimension with the concentration time, which had been calculated by the Kirpich method, a new time of concentration relation was obtained based on the fractal dimension. Finally, fractal triangular UNIT HYDROGRAPH was developed using the new time of concentration. Results showed that the developed triangular UNIT HYDROGRAPHs had a relatively appropriate match with NRCS triangular UNIT HYDROGRAPH.