Hydrological Trend, Variability and Time Series Modeling of Weyib Catc
No Thumbnail Available
Date
2017-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The main goal of this study is to assess trend, spatio- temporal variability of rainfall and runoff,
and time series modeling of major tributaries of Weyib River catchment, which is located in
Genale Dawa basin between 6022’ to 7006’N and 39037’ to 41015’E. Stream flow records from
six flow-gauging stations in four major river catchment of the weyib between (1981- 2008) and
six precipitation stations all over the weyib catchment between (1984-2014) were studied at
monthly, seasonal, and annual scales. In the study, the data were firstly subjected to quality
checks through the cumulative deviations test and the standard normal homogeneity test. To
detect correlation Lag-1 autocorrelation coefficient was used. ArcGIS 10 environment is used to
investigate the spatial variability. The Coefficient of Variation (CV) was used for variability
analysis. Mann-Kendall trend analysis and Sen’s slope estimator in MAKESENSE version 1.0
Excel template are used in determining the changes in the rainfall and runoff. ARIMA model in
Minitab 17 Statistical software was used for time series modeling. By using statistical measure
(R2, AIC and BIC) it was determined that, ARIMA time series model is better appropriate to
stream flow forecasting. The interesting observation is that all sub catchment of the Weyib
catchment for both rainfall and runoff exhibit different behavior as far as trend and variability
analysis is concerned. Trend analyses with Mann-Kendall test show that, there is increase in
significant trend in annual mean runoff at Togona and Tebel station while the other four stations
(Shaya, Agarfa, Alemkerem and Denbel) shows no significant trend. From precipitation stations,
only Ginir station shows significant increasing trend in annual basis. The direction of rainfall and
runoff trend was, in general, upward and statistically significant (upward) trends (95% to 99.9%)
significant levels were observed. Global climate change influence on the changes in rainfall and
runoff characteristics was not conclusive. The key conclusion is that, the results of this study are
expected to assist water resources managers and policy makers in making better planning
decisions in the Weyib River catchment.
Keywords: Weyib River catchment ; Minitab 17 ;Trend analysis ;Precipitation ; Mann-Kendall
Test ; Sen’s Slope Estimator; probability distribution
Description
Keywords
Weyib River Catchment, Minitab 17, Trend Analysis, Precipitation, Mann-Kendall Test, Sen’s Slope Estimator, Probability Distribution