Header

UZH-Logo

Maintenance Infos

The long-term hydrology of East Africa’s water tower: statistical change detection in the watersheds of the Abbay Basin


Gebreyohannis Gebrehiwot, Solomon; Gärdenäs, Annemieke I; Bewket, Woldeamlak; Seibert, Jan; Ilstedt, Ulrik; Bishop, Kevin H (2014). The long-term hydrology of East Africa’s water tower: statistical change detection in the watersheds of the Abbay Basin. Regional Environmental Change, 14(1):321-331.

Abstract

Forty-five years (1960–2004) of hydrological data from 12 watersheds in the Abbay Basin, Ethiopia, were tested for possible trends over the entire time series and differences in medians (step-wise changes) between three sub-periods. The classification of the sub-periods was based on the major political changes in 1975 and 1991. Variables investigated were rainfall (P), total flow (Qt), high flow (Qh), low flow (Ql), low flow index (LFI) and run-off coefficient (C). Data were checked for outliers, errors and homogeneity. Trend was tested after serial and cross-correlation tests. The data for each variable were serially uncorrelated from 1 to 10 lag years. There were five globally significant trends out of 50 test cases and 36 significant step-wise changes out of 180 tests. The majority of the significant changes were watershed specific. Run-off coefficient was the single variable showing a consistently increasing trend and stood for ca. 25 % of the total significant trends and step-wise changes. Half of these changes occurred after 1991. We concluded that despite the land use policy changes in 1975 and 1991, as well as the long-term soil degradation, the hydrological regime was quite stable over the 45-year period, with the exception of an increase in the run-off coefficient in the latter part of the run-off record in some watersheds.

Abstract

Forty-five years (1960–2004) of hydrological data from 12 watersheds in the Abbay Basin, Ethiopia, were tested for possible trends over the entire time series and differences in medians (step-wise changes) between three sub-periods. The classification of the sub-periods was based on the major political changes in 1975 and 1991. Variables investigated were rainfall (P), total flow (Qt), high flow (Qh), low flow (Ql), low flow index (LFI) and run-off coefficient (C). Data were checked for outliers, errors and homogeneity. Trend was tested after serial and cross-correlation tests. The data for each variable were serially uncorrelated from 1 to 10 lag years. There were five globally significant trends out of 50 test cases and 36 significant step-wise changes out of 180 tests. The majority of the significant changes were watershed specific. Run-off coefficient was the single variable showing a consistently increasing trend and stood for ca. 25 % of the total significant trends and step-wise changes. Half of these changes occurred after 1991. We concluded that despite the land use policy changes in 1975 and 1991, as well as the long-term soil degradation, the hydrological regime was quite stable over the 45-year period, with the exception of an increase in the run-off coefficient in the latter part of the run-off record in some watersheds.

Statistics

Citations

3 citations in Web of Science®
4 citations in Scopus®
Google Scholar™

Altmetrics

Downloads

2 downloads since deposited on 16 Dec 2013
0 downloads since 12 months
Detailed statistics

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:2014
Deposited On:16 Dec 2013 13:27
Last Modified:05 Apr 2016 17:14
Publisher:Springer
ISSN:1436-3798
Publisher DOI:https://doi.org/10.1007/s10113-013-0491-x

Download

Preview Icon on Download
Content: Published Version
Language: English
Filetype: PDF - Registered users only
Size: 933kB
View at publisher

TrendTerms

TrendTerms displays relevant terms of the abstract of this publication and related documents on a map. The terms and their relations were extracted from ZORA using word statistics. Their timelines are taken from ZORA as well. The bubble size of a term is proportional to the number of documents where the term occurs. Red, orange, yellow and green colors are used for terms that occur in the current document; red indicates high interlinkedness of a term with other terms, orange, yellow and green decreasing interlinkedness. Blue is used for terms that have a relation with the terms in this document, but occur in other documents.
You can navigate and zoom the map. Mouse-hovering a term displays its timeline, clicking it yields the associated documents.

Author Collaborations