Water quality impairment, due to anthropogenic activities and limited enforcement capacity, is a rapidly growing threat to water security as well as public health in developing countries. Cumulative effects of deteriorating water quality undoubtedly put pressure on public health and socio-economic developments. For example, most industries in Ethiopia discharge their effluent directly into freshwater systems without any treatment process. The problem is severe for rivers such as the Awash that pass through major cities. Although there were a few studies that looked into the issue, there is a lack of comprehensive water quality impact assessment on agriculture, health, and socio-economics. This article systematically summarizes current research on water quality issues in the Awash River Basin to generate comprehensive information that captures the water quality status of the river and impacts of water contamination, and identify information and management gaps. Results showed that water quality degradation along the river course and in selected tributaries exceeds water quality standards by the WHO and national guidelines. For example, E-coli bacteria concentration in two tributaries, Tinishu and Tiliku Akaki, reach up to 6.68 and 6.61 billion CFU 100 ml/L. Virological profile of creeks receiving wastewater from hospitals in the City of Addis Ababa contains coliphages levels reaching as high as 5.2 × 10³ pfu/100 ml for urban rivers and up to 4.92 × 10³ pfu/100 ml. Heavy metals that far exceed the tolerable levels for humans were also detected in vegetables produced using impaired water. Heavy metals such as Cd, Cr, Cu, Hg, Ni, and Zn were detected in potato, Zn and Hg in Cabbage, and Cr in onion and red beet. Lettuce irrigated with Akaki river water found to contain 0.263 (Cd), 420 (Fe), 13.44 (Zn), 7.87 (Cr), 7.49 (Cu), and 6.55 (Pb) in mg/kg both in excess of WHO guideline. In addition, a high concentration of Cr has been also found in fish tissues. There has never been a systematic evaluation of the impact of contaminated water in the Awash Basin. Comprehensive impact of water quality investigation that takes into account the different pollutants dynamic needs to be made to protect the well being of downstream beneficiaries including the aquatic ecosystem. In conclusion the systematic review has shown that for a river that cross-through emerging mega-city like Addis Ababa, the human and ecosystem health impact of aquatic ecosystems pollution should not afterthought action

Grasslands occupy almost half of the world's land area. Soil organic carbon (SOC) is a key indicator of soil fertility and grassland productivity. Increasing SOC stocks (so‐called SOC sequestration) improves soil fertility and contributes to climate change mitigation by binding atmospheric carbon dioxide (CO₂). Grasslands constitute about 70% of all agricultural land, but their potential for SOC sequestration is largely unknown. This review paper quantitatively summarizes observation‐based studies on the SOC sequestration potential of grasslands in six East African countries (Burundi, Ethiopia, Kenya, Rwanda, Tanzania and Uganda) and seeks to identify knowledge gaps related to SOC sequestration potential in the region. In the studies reviewed, SOC stocks in grasslands range from 3 to 93 Mg C/ha in the upper 0.3 m of the soil profile, while SOC sequestration rate ranges from 0.1 to 3.1 Mg C ha^‐1 year^‐1 under different management strategies. Grazing management is reported to have a considerable impact on SOC sequestration rates, and grassland regeneration and protection are recommended as options to stimulate SOC sequestration. However, a very limited number of relevant studies are available (n = 23) and there is a need for fundamental information on SOC sequestration potential in the region. The effectiveness of potential incentive mechanisms, such as payments for environmental services, to foster uptake of SOC‐enhancing practices should also be assessed.

The recent expansion of industries in Addis Ababa is causing additional environmental pollution through wastewater discharges; this is becoming a critical concern. Addis Ababa is located in the upper Awash River basin, and is the main source of industrial pollutants to the river. In this study, physicochemical parameters, nutrients and heavy metal content of wastewaters released from 16 factories, 6 tanneries, 6 beverages and 4 diverse factories, and the Akaki-Kality central wastewater treatment plant in Addis Ababa, were sampled to assess the level of pollutants. Heavy metals were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). Analysis of nutrients were conducted using Palintest Photometer. Physicochemical characteristics were measured either in situ using a portable micro meter or in the laboratory. Among the measured physicochemical properties, critical issues were observed with electrical conductivity, total dissolved solids and total hardness. Effluents from all of the tanneries, and a number of other factories, were found at levels higher than the maximum limits of various guideline standards. In addition, samples from two of the tanneries (T1 and T5), two beverage factories (B3 and B6) and the central wastewater treatment plant showed elevated concentrations of PO₄^3-, which violated the limit (10 mg/l) set by Environmental Protection Agency of Ethiopia (ETHEPA). The two tanneries (T1 and T5) also contained higher SO₄^2- than the guideline limit of 1000 mg/l. On the other hand, only one factory, one brewery (B3), exhibited NO₃^- above the standard limit of 20 mg/l. Whereas NH₃, NH₄⁺, Cl^-, S^2- and NO₂^- were within the limits in all of the samples. Severe pollution was found in wastewaters from tanneries, where half of them (T1, T5 and T6) contained Cr beyond the maximum limit of 2000 µg/l. Furthermore, a third of the tanneries (T1 and T5) and a beverage factory (B5) contained Fe, Mn, Zn and Cu, higher than the ETHEPA limits of 10000, 5000, 5000 and 2000 µg/l, respectively. Waste disposal from factories without proper treatment can cause great harm to the local people and the environment. Hence, the results of this study call for regulatory bodies to pay close attention to factories, particularly tanneries, in Addis Ababa in implementing adequate treatments of their wastewater discharges

Developing countries like Ethiopia are grabbling with rapid population growth, urbanization, agricultural intensification, and climate change which put intense pressure on the availability and quality of water resources. The surface water quality degradation is exacerbating due to increasing urbanization and agricultural activities. The average annual fertilizer use in Ethiopia increased from 132,522 metric tons (mt) in 1996 to 858,825 mt in 2015. Pesticide use also increases significantly from 3,327.7 mt/y in 2006 to 4,211.5 mt/y in 2010. The Awash river is one of the most affected rivers by intensified irrigation schemes, industrial, and urbanization pollution. The Awash river and its tributaries are used for domestic, irrigation, industrial, and recreational purposes. However, as per Canadian water quality indices for the drinking and irrigation water quality, the upper Awash basin scored 34.79, and 46.39, respectively, in the poor and marginal categories; whereas the middle/lower basin indicated 32.25 and 62.78 in poor and marginal ranges, respectively. Dissolved phosphorous in the headwater tributaries is about 0.51 mg/l which is beyond the threshold (0.15 mg/l). The surface water quality impairment is severe in the upper Awash basin where more than 90% of Addis Ababa's industries discharge their waste into nearby waterways without treatment; about 30% of the population lacks access to a liquid waste disposal and treatment facility; only 16% of the population is connected to sewage system, and 25% of the total waste generated enters freshwater systems without treatment. Many studies on surface water quality are reviewed and many of them are inconclusive for a number of reasons. For example, no comprehensive surface water quality research, lack of detailed combined spatial and temporal surface water quality data, and analysis to show the overall picture of the basin are a few of them. Despite the existence of the policy and legal tools, enforcement is lacking. Improving the ecological health of rivers necessitates policy revision as well as increased knowledge and engagement among implementers.

Cropland soils are considered to have the potential to sequester atmospheric CO₂ through agronomic best management practices (BMPs). To estimate this potential in East Africa, the authors reviewed 69 published studies from Ethiopia, Kenya, Rwanda, Tanzania, Uganda, and Burundi assessing the effect of land use conversion from native vegetation to cropland on soil organic carbon (SOC) and the extent to which carbon sequestration is feasible through BMPs. Reported losses of SOC in the top 30 cm of the soil profile in short (25 years) term were 6.7 ± 6.0, 13.0 ± 9.2, and 2.8 ± 1.0 t C ha^–1 year^–1, respectively, for forest-to-cropland; and 16.0, 2.1 ± 2.2 and 0.3 ± 0.8 t C ha^–1 year^–1 respectively, for woodland-to-cropland conversion. Duration to steady-state SOC was 21–38 years for forest-to-cropland conversion. Short-term SOC sequestration (t C ha^–1 year^–1) in the 0–30 cm layer as a result of BMPs was 19.7 ± 3.9 from crop residues, 14.8 ± 8.7 from farmyard manure, 3.5 ± 4.5 from inorganic fertilizers, 2.7 from agroforestry, and 2.5 from improved fallow. However, the studies reviewed were mostly short-term and concentrated to a few locations. Future research should address these gaps.

Plant roots are primary factors to contribute to surface and deep soil carbon sequestration (SCS). Perennial grasses like vetiver produce large and deep root system and are likely to contribute significantly to soil carbon. However, we have limited knowledge on how root and shoot decomposition differ and their contribution to SCS. This study examined biomass production and relative decomposition of vetiver which was grown under glasshouse conditions. Subsequently the biomass incubated for 206 days, and the gas analysed using ANCA-GSL. The results confirmed large shoot and root production potential of 161 and 107 Mg ha⁻¹ (fresh) and 67.7 and 52.5 Mg ha⁻¹ (dry) biomass, respectively with 1:1.43 (fresh) and 1:1.25 (dry) production ratio. Vetiver roots decomposed more rapidly in the clay soil (p < 0.001) compared with the shoots, which could be attributed to the lower C:N ratio of roots than the shoots. The large root biomass produced does indeed contribute more to the soil carbon accumulation and the faster root decomposition is crucial in releasing the carbon in the root exudates and would also speed up its contribution to stable SOM. Hence, planting vetiver and similar tropical perennial grasses on degraded and less fertile soils could be a good strategy to rehabilitate degraded soils and for SCS.