Abstract
Today environmental issue becomes the biggest concern of humankind because of scientific evidence about the increasing concentration of greenhouse gases in the atmosphere and the changing climate of the Earth. This study was conducted in eastern Ethiopia specifically at <i>Chiro</i> and <i>Hurso</i> stations. The study assessed quantitatively the rainfall Intensity Duration Frequency (IDF) relationships under changing climate condition and compare with the existing rainfall- Intensity Duration- Frequency (IDF) relationships. Rainfall intensity duration and frequency curves were developed using historical rainfall time series data under the assumption that climate is stationary. This assumption is not valid under changing climatic conditions that may shifts in the magnitude and frequency of extreme rainfall. Such shifts in extreme rainfall at the local level demand new regulations for any intervention management as well as changes in design practices. In order to estimate the level of climate change impact on the rainfall Intensity Duration Frequency (IDF) relationships, these changes of the climate variables were applied to Hyetos Temporal Rainfall Disaggregation model to simulate future IDF relationships. From the results can see graphical presentation of IDF curves for return periods of 2, 5, 10, 25, 50 and 100 years for durations of 1, 2, 3, 6, 12 and 24 hours. The comparison results indicate that, difference between rainfall intensities (percentage) of climate change scenario and historic rainfall for 2020s ranges between 1.58% and 10.92% for 2050s, ranges between 0.07% and 20.22% and for 2080s, ranges between 0.71% and 55.93% in <i>Chiro</i> station, respectively. Similarly, in the case of <i>Hurso</i> station, the difference between climate change scenario and historic rainfall for 2020s ranges between1.10% and 27.83% for 2050s ranges between 110.5% and 40.21% and for 2080s that ranges between 19.44% and 67.75%, respectively. Therefore, the outputs of the study indicates that the rainfall magnitude will be different in the future and thereby the decrease and increase in rainfall intensity and magnitude may have major implications on ways in which current and future intervention is designed, operated, and maintained. Therefore, design standards and guidelines currently employed in the study area should be revised with the confirmation of the impacts of climate change.
Highlights
Nowadays, environmental issue becomes the biggest concern of humankind because of scientific evidence about the increasing concentration of greenhouse gases in the atmosphere and the changing climate of the Earth
The data source were the automatically recorded rainfall charts collected in National Meteorological Service Agency (NMSA) and the climatic data used for SDSM were collected from the Canadian Institute for climate studies Website for model output of HadCM3.Global circulation data for the selectedmodelsfromwww.pcmdi.llnl.gov/ipcc/about_ipcc.php website
The computed extreme rainfall values for the durations of interest; 1, 2, 3, 6, 12 and 24 hours and return periods of 2, 5, 10, 25, 50 and 100 years computed for Chiro station is presented in Table 2(a, b and c).Calculated extreme rainfall events (XT) was directly related to both return period and duration of rainfall event; i.e. for each return period the values of extreme rainfall events increases with increasing the rainfall durations and for each duration it increase with increasing of return period as shown in the table 2 below
Summary
Environmental issue becomes the biggest concern of humankind because of scientific evidence about the increasing concentration of greenhouse gases in the atmosphere and the changing climate of the Earth. According to the International Panel on Climate Change [2] Scientific Assessment Report, global average temperature would rise between 1.4 and 5.8°C by 2100 with the doubling of the CO2 concentration in the atmosphere. Extreme high precipitation amounts are among environmental events with the most disastrous consequences for society. Estimates of their return periods and design values are of great importance in hydrologic modeling, engineering practice for water resource systems and reservoirs design and management, planning for weather-
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