Low Flow Analysis And Regionalization For Gheba River, Ethiopia

Abstract

Analyze the low flow in Gheba river and identify their low flow characteristic for better management and operation of reservoir & water resource as general were estimated by low flow frequency analysis and flow duration curve approaches to the selected 7 days annual minimum flow observed at four stations with an average of 17 years record length. Goodness-of-fit tests, including L-moment methods for regional data, were used to determine the best distributions. Gheba river watershed is the sub-basin of the Tekeze river basin and situated in the northern part of Ethiopia, Tigray Regional State. The total drainage area of Gheba up to the junction to Tekeze is about 5163 km2 and it is characterized by a minimum elevation of 1311 m, with a maximum of 3065m a.s.l. The main problem in the Gheba river basin is that the watershed is ungauged and also water resources in the basin are scarce due to continuously climate change and deforestation. The aim of this study was to estimate the low flow quantile and the low flow frequency growth curve using the statistical parameters were computed using EASY FIT computer program. Accordingly Gheba river sub basin has been divided in to two homogeneous regions. The region one of the basin includes the stations Gheba and Suluh and region two encloses the stations of Agulae and Ilala. The Generalized Logic distribution provides a good fit to low flows in the region one, while the generalized extreme value distribution fitted well in the region two. And the frequency curve for a return period of T was developed for both regions of low flow. On the basis of flow duration curve the flow duration curve indices for low flow of the basin Q60, Q70, Q80, Q90, Q95 and Q100, were quantified. For more certain on the results of this study, further studies are required on the points which are not assessed due to scarce of data, like effect of regionalization by topographic and climatic parameters and the ground water contributions of the regions. Generally this study contains the information required for the development of water resource projects on the sub basin.