Rain event properties and dimensionless rain event hyetographs at the source of the Blue Nile River

Abstract

In the present study, the spatial and temporal patterns of the rain event properties are analysed. The event properties are rain event depth, event duration, mean event intensity, peak intensity and the time span between two consecutive rain events which is referred to as inter-event time (IET). Dimensionless event hyetographs are established by relating fractions of event intensities to the corresponding fractions of event durations. The spatial variation of the characteristics of the hyetographs is also evaluated. A model in the form of the beta distribution function is applied to reproduce the dimensionless hyetographs. Rainfall data is obtained from a field campaign in two wet seasons of June–August (JJA) of 2007 and 2008 in the Gilgel Abbay watershed that is situated at the source basin of the upper Blue Nile River in Ethiopia. The rainfall data was recorded at eight stations. The results reveal that rain event depth is more related to peak intensity than to event duration. At the start and towards the end of the wet season, the rain events have larger depth with longer duration and longer IET than the rain events in the mid-season. Mean event intensity and IET are strongly related to terrain elevation. Sekela which is on a mountain area has the shortest IET while Bahir Dar which is at the south shore of the lake has the longest IET

Analysis of rainfall events over Peninsular Malaysia

“…To separate rainfall events, a guideline value for the minimum dry period length between two wet periods has to be set. Such a guideline is known as the minimum inter‐event time (MIT) (Dunkerley, ; Haile et al ., , ) or inter‐event time definition (IETD) (Palynchuk and Guo, ; Balistrocchi and Bacchi, ). If the dry period between two wet periods is equal to or longer than the minimum inter‐event time, they are considered to be two separate rainfall events; if the dry period is shorter than the minimum inter‐event time, they are considered to be a single rainfall event.…”

Relationship between minimum inter‐event time and the number of rainfall events in Peninsular Malaysia

“…One of the most widely used criteria for the separation of rainfall events is minimum inter‐event time (MIT) (Heneker et al, ; Haile et al, ; ), which is also known as inter‐event time definition (IETD) (Guo and Baetz, ; Branham and Behera, ; Balistrocchi and Bacchi, ). The dry period between two wet periods is known as inter‐event time, and if it is equal to or longer than the desired MIT or IETD, they are considered as two individual events.…”

Rainfall variability and estimation for hydrologic modeling : a remote sensing based study at the source basin of the Upper Blue Nile river

“…With regard to (ii), Haile et al (2009a) showed that both Sekela and Jema have large seasonal rainfall but Jema receives more frequent and high intensity rain events while Sekela receives clustered hourly rainfall with mostly light to moderate rainfall intensities. Haile et al (2009c) showed that rainfall ii the lowland areas of Gilgel Abbay can be characterized by large depth, high intensity, short duration and long inter-event time as compared to the mountain areas. As a result of the differences in rainfall properties, removing Jema and Sekela from the network can result in larger differences in the estimated spatial rainfall as compared to removing any of the other stations.…”