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| Titel |
Impacts of climate and land-use changes on the hydrological dynamics in the upper Citarum River basin based on the J2000 hydrological model |
| VerfasserIn |
Miga Magenika Julian, Manfred Fink, Christian Fischer, Peter Krause, Wolfgang-Albert Flügel |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101268
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| Publikation (Nr.) |
 EGU/EGU2015-380.pdf |
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| Zusammenfassung |
| Changes of land-use and climate will most likely result in changes of the hydrological
dynamics in river basins. Such changes can be noticed in the upper Citarum River basin
(UCB), Java Island, Indonesia. This basin covers 1821km2 and is located in a hilly area of the
backcountry of Jakarta. Between 2005 and 2009, the basin’s forest cover has been reduced by
5.0%, residential areas grew around 8.2% expanding around the existing residential areas,
and 3.9% of shrubland was converted into agricultural areas. From 1985 through 2009, the
mean annual air temperature increased by 0.01Ë C/year; whereas, precipitation slightly
decreased by 6.8mm/year.
The process-oriented hydrological model JAMS/J2000 was adapted and implemented to
assess the impact of land-use change and climate variability on the hydrological dynamics of
this basin, including consideration of the temporal and spatial distributions. For this
assessment, three scenarios based on realistic events were investigated; these consisted of the
following (i) land-use changes in 2005 versus 2009; (ii) temperature increase from 1984 to
2009, while keeping a precipitation constant from year 1984; and (iii) variability of
precipitation from 1984 to 2009, while keeping temperature constant from year 1984. The
model-input conditions of land-use, precipitation, and temperature changes where applied
individually, holding the other factors constant. Model simulations were conducted for the
UCB. The J2000 model for the UCB was calibrated and validated using a split-sample
approach. For model calibration and validation, fairly good objective functions were
achieved: i.e. Nash-Sutcliffe efficiencies (E) by 0.79 and 0.76, log E of 0.89 and
0.84, coefficient of determination of 0.79 and 0.77, and a percent bias of -1.4% and
-1.1%.
From the model-simulation results, it was concluded that the land-use changes resulted in
a slight increase in stream discharge (4.6%) and a decrease of evaporation of 3.7%. The
analysis of the different runoff components indicated that, in particular, the amount of
overland flow was estimated to increase 7.9%, primarily because of the significant expansion
of residential areas. The individual effects of precipitation and temperature changes on the
hydrological dynamics was evaluated for four five-year periods (1989-1993, 1994-1998,
1999-2003, and 2004-2009) for comparison with conditions for the first five-year
period (1984-1988). The effect of a temperature increase from 1989 to 2009 on
stream discharge was small, resulting in a reduction of about 1%. The increase of
precipitation from 1985 to 1999 was affecting stream discharge by a small increase
(2%).
Through this application of the J2000, which proved to be an appropriate tool to assess
environmental (land-use and climate) changes on the basin’s hydrological dynamics, we
could show that in the Indonesian test basin the observed change in land-use change might
have a greater impact on hydrological dynamics than the impact of climate change. For future
study, it is recommended to assess hydrological changes under the projected future climate
and land-use conditions. Coupling effects of climate and land-use changes should be
considered and assessed individually when quantifying the resultant hydrological changes
estimated by the model. |
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