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With climate change prevailing around the world, understanding the changes in long-term annual and seasonal rainfall at local scales is very important in planning for required adaptation measures. This is especially true for areas such as the Awash River basin where there is very high dependence on rain- fed agriculture characterized by frequent droughts and subsequent famines. The aim of the study is to analyze long-term trends of annual and seasonal rainfall in the Awash River Basin, Ethiopia. Monthly rainfall data extracted from Climatic Research Unit (CRU 4.01) dataset for 54 grid points representing the entire basin were aggregated to find the respective areal annual and seasonal rainfall time series for the entire basin and its seven sub-basins. The Mann-Kendall (MK) test and Sen Slope estimator were applied to the time series for detecting the trends and for estimating the rate of change, respectively. The Statistical software package R version 3.5.2 was used for data extraction, data analyses, and plotting. Geographic information system (GIS) package was also used for grid making, site selection, and mapping. The results showed that no significant trend (at α = 0.05) was identified in annual rainfall in all sub-basins and over the entire basin in the period (1902 to 2016). However, the results for seasonal rainfall are mixed across the study areas. The summer rainfall (June through September) showed significant decreasing trend (at α ≤ 0.1) over five of the seven sub-basins at a rate varying from 4 to 7.4 mm per decade but it showed no trend over the two sub-basins. The autumn rainfall (October through January) showed no significant trends over four of the seven sub-basins but showed increasing trends over three sub-basins at a rate varying from 2 to 5 mm per decade. The winter rainfall (February through May) showed no significant trends over four sub-basins but showed significant increasing trends (at α ≤ 0.1) over three sub-basins at a rate varying from 0.6 to 2.7 mm per decade. At the basin level, the summer rainfall showed a significant decreasing trend (at α = 0.05) while the autumn and winter rainfall showed no significant trends. In addition, shift in some amount of summer rainfall to winter and autumn season was noticed. It is evident that climate change has shown pronounced effects on the trends and patterns of seasonal rainfall. Thus, the study contribute to better understanding of climate change in the basin and the information from the study can be used in planning for adaptation measures against a changing climate.

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Over the last 40 years a great deal of research has been published on the use of duckweed to treat wastewater both from point sources (feedlots, food processing plants) and from non-point sources. These plants can recover nutrients such as nitrogen and phosphorus from contaminated waters in those agricultural practices. They can also remove or accumulate metals, radionuclides, and other pollutants in their tissues. In addition, the duckweed can be used as a feed source for livestock and poultry as well as an energy source for biofuel production. A summary of some of the published work done using duckweed species to phytoremediate natural, domestic, industrial, and agricultural wastewaters is presented.

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Potential contamination of groundwater because of nitrogen leaching has been an important concern in municipal wastewater land application systems; however, few efforts have made to measure nitrogen leaching (total N, NO3−‐N, and NH4+‐N) under field conditions. This research successfully developed a conceptual nitrogen mass balance model and quantified its components at a wastewater land application system located at the City of Littlefield, Texas, from October 2005 to September 2007. The concentrations of total nitrogen and nitrate‐nitrogen in the leachate were significantly less than 10 mg/L, therefore, there was no potential nitrogen contamination to groundwater found at this site during the research period. Linear regression models were analyzed and resulted in R2 values of 0.918, 0.966, and 0.833 between cumulative applied total nitrogen mass and cumulative leached total nitrogen mass, cumulative applied nitrate‐nitrogen mass and cumulative leached nitrate‐nitrogen mass, and cumulative applied ammonia‐nitrogen mass and cumulative leached ammonia‐nitrogen mass, respectively.
The nitrogen mass balance design approach for this site resulted in significant nitrogen removal. Organic nitrogen may leach with other forms of nitrogen, and denitrification plays an important role in nitrogen removal during the winter and spring seasons when the grass is dry.