Trend and change-point detection analyses of rainfall and temperature over the Awash River basin of Ethiopia

Abstract

Awash River basin (ARB) as a system is in a state of continuous change that requires successive studies to discern the changes or trends of climatic elements through time due to climate change/variability, and other socio-economical developmental activities in the basin. The livelihood of communities in the ARB is primarily based on rainfall-dependent agriculture. Effects of rainfall anomalies such as reduction of agricultural productivity, water scarcity, and food insecurity are becoming more prevalent in this area. In recent years, ARB has been experiencing more frequent rainfall anomalies that change-point detection test and trend analyses of basin rainfall associated with sea surface temperature is crucial in providing guidance to improve agricultural productivity in ARB. Change-point detection tests such as Pettit's, the von Neumann ratio (VNR), Buishand's range (BR) and standard normal homogeneity (SNH) plus trend analysis Mann-Kendall (MK) test of rainfall and temperature data from 29 meteorological stations in the ARB were carried out from 1986 to 2016. A significant increasing trend of annual and seasonal temperature was found. The temperature change-points for the annual and major rainy season (MRS) were detected in 2001, while for the minor rainy season (mRS) in 1997. A significant decreasing trend, shift, and high variability of rainfall were detected in the downstream part of the ARB. The BR and SNH results showed that the mRS rainfall change-point was in 1998, with a subsequent mean annual decrease of 52.5 mm. The increase (decrease) of rainfall in the annual and MRS was attributable to La Niña (El Niño) events. The significant decreasing trend and change-point of rainfall in the mRS was attributable to the steady warming of the Indian and Atlantic Oceans, local warming, and La Niña events. With this knowledge of the current trends and change-point for rainfall and temperature in the ARB, it is therefore essential that appropriate integrated water management and water-harvesting technologies are established, especially in the downstream areas. Moreover, early detection of El Niño episodes would provide invaluable warning of impending rainfall anomalies in the ARB and would enable better preparations to mitigate its negative effects.

Assessment of upbasin dam impacts on streamflow at Chiang Saen gauging station during the period 1960–2020 in the context of statistical studies

“…The test statistic T k is used to compare the mean of the first n observations with the mean of the remaining n ‐ k observations with n data points (Alexandersson, 1986; Getahun, Li, & Pun, 2021; Jaiswal et al, 2015): where and σx are the mean and SD of the time series. The year k can be considered as the change point and consists of a break where the value of T k attains the maximum value.…”

Spatiotemporal Rainfall Variability and Trend Analysis of Shimsha River Basin, India

“…Severe weather events such as floods and droughts affect the country's food security and gross domestic product (GDP). They also negatively affect the country's development (Wang et al 2020;Getahun et al 2021;Sathish et al 2022). Climate change hazards can be minimized or mitigated from best management techniques in natural resource management/strategies.…”

“…Predicting precipitation trends accurately can aid in sustainable watershed management. For example, developing sustainable agrotechnological solutions for the nation's food security, as well as other types of impact on social and economic development activities, precise trend identification, and future forecast are critical in protecting lives and property (Rahman et al 2017;Asfaw et al 2018a;Getahun et al 2021).…”

Long-Term Evolution of Rainfall and Its Consequences on Water Resources: Application to the Watershed of the Kara River (Northern Togo)

“…The concept of tendency within a hydrometeorological series corresponds to the evolution of its parameters throughout time, independent of seasonal fluctuations [14]. Break tests coupled with tendency tests have often been reported in the literature for the characterization of tendencies within chronological series of climatic data [15][16][17][18][19]. Analyzing past tendencies became an efficient tool for planning, conception and management of water resources, providing valuable information for predictive approaches to evaluate future changes in hydroclimatic parameters [20,21].…”

“…On the contrary, the examination of precipitation and temperature at the watershed of the Mono River, which is located both in Benin and Togo, revealed a tendency of increasing rainfall and temperature by 2050 [17]. This illustrates the spatial variability of rainfall indices [19]. Thus, the watershed's scale seems the one most adapted to comprehend the hydroclimatic function and tendency within chronological rainfall series.…”