Change point of river streamow in Turkey

The present study aims to determine the hydrological change-year by evaluating the homogeneity of average annual streamow data in Turkey. Pertaining to the years 1936-2005, change-year streamow data from 74 streamow gauging stations, which have no regulatory structure on the source side, and possessing a minimum of 39 years of data, from streamow gauging stations located on 26 streamow basins in Turkey, have been collected. By using the employed homogeneity tests, it has been attempted to detect the change year. Employed methods are the Buishand test, the Pettitt test, the Standard Normal Homogeneity test and the Von Neumann test. By comparing the results obtained from tests, it is aimed to detect the consistency of the change years in gauging stations. The change year could be detected in 16 gauging stations using three tests each every year, and 18 stations using 2 tests in the same year. It has also been ascertained that change years of streamow are geographically closer to each other in western Turkey in comparison to the east. The reason for values in the west to be closer, with respect to both location and time, might be attributed to the precipitation characteristics and uniformity of measured data. ©2014 Sharif University of Technology. All rights reserved

Investigation of manning coefficient caused by rigid body plants [Rijit gövdeli bitkilerin neden oldu?u manning katsayisinin araştirilmasi]

To study flows in man-made or natural channels, the identification of the roughness caused by vegetation is important. The roughness parameters used in several equations such as Manning, Chezy, and Darcy-Weisbach are the experimental coefficients that represent mostly sidewall characteristics. In open channel flows having natural or man-made vegetation to control the flow sections, the knowledge of flow velocities, flow depths and/or flow rates are crucial for planning and management studies. For such studies, the quantification of the roughness caused by the vegetation becomes vital. In this study, roughness caused by vegetation in open channel flows is investigated experimentally and a non-linear regression equation relating Manning roughness coefficient to flow and vegetation characteristics is proposed

ENSO modulations on streamflow characteristics

El Niño Southern Oscillation (ENSO) has been linked to climate and hydrologic anomalies throughout the world. This paper presents how ENSO modulates the basic statistical characteristics of streamflow time series that is assumed to be affected by ENSO. For this we first considered hypothetical series that can be obtained from the original series at each station by assuming non-occurrence of El Niño events in the past. Instead those data belonging to El Niño years were simulated by the Radial Based Artificial Neural Network (RBANN) method. Then we compared these data to the original series to see a significant difference with respect to their basic statistical characteristics (i.e., variance, mean and autocorrelation parameters). Various statistical hypothesis testing methods were used for four different scenarios. Consequently if there exist a significant difference, then it can be inferred that the ENSO events modulate the major statistical characteristics of streamflow series concerned. The results of this research were in good agreement with those of the previous studies

Frequency analysis of mean monthly streamflow in Çoruh basin, Turkey

This paper analyzes mean monthly stream-flow data recorded from 29 stream-flow gauging sites in Çoruh basin, Turkey. In regional mean monthly stream-flow analysis based on L-moments, at first, discordancy measures have been used to screen data on each of the 29 gauging sites. Homogeneity of the basin has been tested using L-momentbased heterogeneity measure. We divided Çoruh basin into 5 subregions and single sites. A number of L-momentsbased frequency distributions (i.e., generalized logistic (GLO), generalized extreme value (GEV), generalized Pareto (GPA), generalized normal (GNO), Pearson type III (PE3), and 5-parameter Wakeby (WAK) distribution) have been used in order to find a suitable distribution for quantile estimates. We determined that the GNO, GPA, and WAK distributions appeared to be a robust distribution in Çoruh basin. Finally, we carried out the Monte Carlo simulations for the quantile estimation accuracy. As a result, the GPA, GNO and WAK distributions generated similar quantiles. © by PSP