جستجوی مقالات مرتبط با کلیدواژه « Instantaneous unit hydrograph » در نشریات گروه « مهندسی آب »

The GIUH method is one method which deals with prediction of the catchment’s runoff based on the stream-order-ratios (SOR) data and the geomorphologic data of the catchments lacking statistics. Many of the catchments, lack digital DEM map and need GIS to provide them which requires GIS expertise and spending extra time in which may of the hydrologists are not interested and are looking for simpler runoff-rainfall models. In this study, based on the stream ordering data of nine different stream catchments in the world some equations have been provided to determine stream-orderratios. Five regression equations have been presented to measure the geomorphologic of the streams including bifurcation ratio (RB), length ratio, area ration(Ra), (RL), stream slope ratio (RS) and overland slope ratio (RSO). The results of SOR for three other catchments have been evaluated. Based on the regression equations, the surface runoff of the other catchments of Heng-Chi and Kasilian using the GIUH method were estimated. Based on the results, the peak error of the calculated runoff using GIUH model based on the regression equations was 10% more than the model’s measurements based on the real data obtained from GIS. The errors of the model in the estimation of RB, RL, RA, RS, and RSO in the three case study catchments were 4.7%, 23.5%, 7.1%. 41.3%, and 22.9%, respectively. The relative sensitivities of the ratios RB, RL, RA, RS, and RSO are shown to be 0.56, 0.01, 0.92, 0.042, and 1.33, respectively.

The present study was conducted to study the effect of storage coefficient on estimating the output hydrograph in a watershed which lacks basic data, using time- area method and Clark’s model. To this end, the time area histogram was determined by ArcGIS and the topographic map of the area. Then, using rain gauge data and time-area method, the output hydrograph was estimated. In the next step, the obtained results were compared with the observed output hydrograph. The Clark instantaneous unit hydrograph was also estimated by using storage coefficient in order to simulate the hydrograph in Kasilian watershed. As for the unit hydrograph, the statistical values of root mean square of error, bias in peak discharge, coefficient of efficiency, and relative errors in peak discharge, time to peak and base time were 1.64, 0.90, 0.76, 11.38, 33.33 and 15.38%, respectively. The results showed that Clark’s model was more efficient compared to time area method which is indicative of the effect of storage coefficient on flood routing in Kasilian forest watershed. Therefore, this method can be used to accurately estimate the output hydrograph in forest watershed when there is a lack of basic data.

This paper applies the discrete wavelet transform to decompose the instantaneous unit hydrograph (IUH) into low and high frequency bands. The fast Fourier transform exploits to extract IUH from observed rainfall – runoff data. It is estimated the oscillations of IUH by wavelet coefficients and coefficients that are close to zero are set to zero. The obtained result is a hydrograph with the information of low frequency that approximates the real IUH. Calibration criteria between observed and calculated hydrographs are used to select the best filter length in wavelet. In this research, it is demonstrated that wavelets introduced by Daubechies (1992) with filter length 6 is the best alternative in this study. The results have shown that the methodology is acceptable for the system identification of rainfall – runoff for small catchments.