Hydrological Impact Assessment of Climate Change on Lake Tana’s Water Balance, Ethiopia

The aim of this study is to evaluate the hydrological impacts of climate change on the water balance of Lake Tana in Ethiopia. Impact assessments are by downscaled General Circulation Model (GCM) output and hydrological modeling. For A2 and B2 emission scenarios, precipitation, maximum and minimum temperature estimates from the HadCM3 GCM were used. GCM output was downscaled using the Statistical DownScaling Model (SDSM 4.2). Impact analyses were applied for three future time periods: early, mid and late 21st century. Over-lake evaporation is estimated by Hardgrave’s method, and over-lake precipitation is estimated by inverse distance weighing interpolation, whereas inflows from gauged and ungauged catchments are simulated by the HBV hydrological model. Findings indicate increases in maximum and minimum temperature on annual base for both emission scenarios. The projection of mean annual over lake precipitation for both A2 and B2 emission scenarios shows increasing pattern for 21st century in comparison to the baseline period. The increase of mean annual precipitation for A2 emission scenario is 9% (112 mm/year), 10% (125 mm/year) and 11% (137 mm/year) for the three future periods respectively. B2 emission scenario mean annual precipitation shows increase by 9% (111 mm/year), 10% (122 mm/year) and 10% (130 mm/year) respectively for the three future periods. Findings indicate consistent increases of lake storage for all three future periods for both A2 and B2 emission scenarios.

Water Quality Assessment by Measuring and Using Landsat 7 ETM+ Images for the Current and Previous Trend Perspective: Lake Tana Ethiopia

Recently there are signs of water quality impairment in Lake Tana, the largest fresh water in Ethiopia. The lake is the growth corridor of the government and supports millions of livelihood around. In order to sustain the benefit and maintain the ecosystem of the lake, the lake health has to be kept safe. Therefore monitoring and evaluation of the water quality of lake is very vital. This study focuses on current and previous trends water quality of the lake through measurements and Landsat Images near entry of Gumera River. Statistical analysis of the physical (Turbidity and STD and biological (Cha-a,) and chemical (DPC) water quality parameters were done. Linear and non-linear regression models between water quality parameter and reflectance of Landsat 7 ETM+ images were fitted based on band combinations. Pervious trend in turbidity was analyzed based on the regression models. The results showed that reflectance and turbidity satisfactorily result with an R2 ranging from 0.61 - 0.68. Form 1999-2014 the turbidity of the lake has indicated an increasing trend. Delta development near the entry of Gumera River has been enlarged by 48% because of an increase sediment inflow. The sign in the decreasing water quality of the lake was attributed to the non-point source sediment and nutrient inflow to the lake with high erosion rate from the watersheds. Measures to reduce the non-point source sediment and nutrient inflow by targeting the source areas (hot spots) in the agricultural watersheds need to be priority for stakeholders working on the soil and water conservation. Moreover, reducing the recession agriculture around the lake and wetland management could be crucial for improving lake water quality.

Groundwater Quality in an Upland Agricultural Watershed in the Sub-Humid Ethiopian Highlands

Agricultural intensification to meet the food needs of the rapidly growing population in developing countries is negatively affecting the water quality. In most of these countries such as Ethiopia, information on surface and especially groundwater quality is lacking. This limits the measure that can be taken to stop pollution. We, therefore, investigated the spatial and temporal variation of groundwater quality in the upland watershed. Tikur-Wuha watershed was selected because it is located in the Lake Tana watershed, which is seeing the first signs of eutrophication. Groundwater samples were collected from July 2014 to June 2015 from 19 shallow wells located throughout the watershed. Collected water samples were analyzed both in situ and in the laboratory to determine pH, electric conductivity (EC) and total dissolved solid (TDS), concentration of chemicals (nitrate, dissolved phosphorus, calcium, magnesium, aluminum and iron) and Escherichia coli (E. coli). We found that shallow groundwater had greater chemical concentrations and E. coli level in the monsoon rain phase than in the dry phase. Wells located down slope exhibited greater concentrations than mid- and upper-slope positions, with the exception of the nitrate concentration that was less down slope, due to denitrification in the shallow groundwater. Only E. coli level was above the WHO drinking water quality standards. Further studies on groundwater quality should be carried out to understand the extent of groundwater contamination.

Hydrochemistry as Indicator to Select the Suitable Locations for Water Storage in Tharthar Valley, Al-Jazira Area, Iraq

Four locations were chosen according to geomorphologic and engineering criterion to store the water on the midstream of Tharthar valley, water samples were collected from the four locations to evaluate the hydrochemical properties as indicator to select the more suitable location, these locations are Hatra, Abu-Hamam, Tlol Al-Baj and Al-Sukkariah from the north to the south respectively. Also, the groundwater samples were collected from two shallow wells on the banks. The samples were analyzed to determine the concentrations of most common anions and cations in the water Ca2+, Mg2+, Na+, K+, CO32-, HCO3-, Cl–, SO42+. Also, pH, EC and TDS were measured. The results reflect high variations in concentrations of the soluble materials, the concentrations of these components are highly increased in locations of Tlol Al-Baj and Al-Sukkariah in comparison with the locations of Hatra and Abu-Hamam. The variation in geology of the area along the valley was represented a main role on the quality of water. These results can help to select the suitable locations of small dam (dams) to store the water in the valley and prevent the problem of salinity. According to the results, the northern part of midstream (north of Abu-Hamam) is suitable for water storage and the dam construction. While the locations of the downstream enriched by local sources of salts.

Development of Magnesium-Dominant Soils Under Irrigated Agriculture in Southern Kazakhstan

Irrational irrigation practices in the Arys Turkestan Canal command area in the southern part of Kazakhstan have led to the formation of soils with poor physical and chemical properties. To study whether irrigation and leaching practices and/or groundwater rise have contributed to the accumulation of Mg2+ on the cation exchange complex of these soils, historical changes in soil and groundwater quality were used as source data and the Visual MINTEQ model was applied to analyze the chemical composition of water and soils in the study area. The imposed irrigation regime and the leaching of light sierosem soils led to the dissolution and subsequent leaching of inherent gypsum and organic matter from the soil profile. Further, the domination of bicarbonate in the irrigation water promoted weathering of the carbonate minerals present as calcite. The higher concentrations of Mg2+ in comparison to Ca2+ in the irrigation water resulted in the replacement of Na+ by Mg2+ on the cation exchange complex. In the lower part of the command area, shallow groundwater has contributed to the accumulation of Na+ and to a large extent of Mg2+ on the cation exchange sites.

Disposal and Use of Sewage on Agricultural Lands in Pakistan: A Review

Raw sewage is widely used on agricultural soils in urban areas of developing countries to meet water shortages. Although it is a good source of plant nutrients, such sewage also increases the heavy metal load to soils, which may impact the food chain. Management options for sewage contaminated soils includes addition of nontoxic compounds such as lime, calcium sulfate and organic matter, which form insoluble metal complexes, thus reducing metal phytoavailability to plants. In this paper we review the variation in irrigation quality of sewage at different sites and its impact on the quality of soils and vegetables. Although quality of sewage was highly variable at source, yet the effluent from food industries was relatively safe for irrigation. In comparison effluent samples collected from textile, dyeing, calendaring, steel industry, hospitals and clinical laboratories, foundries and tanneries were hazardous with respect to soluble salts, sodium adsorption ratio and heavy metals like zinc, copper, iron, manganese, nickel, cobalt and cadmium. The sewage quality in main drains was better than that at the industry outlet, but was still not safe for irrigation. In general, higher accumulation of metals in fruits and vegetable roots was recorded compared to that in plant leaves. Edible parts of vegetables (fruits and/or leaves) accumulated metals more than the permissible limits despite the soils contained ammonium bicarbonate diethylenetriaminepentaacetic acid extractable metals within a safe range. In either case further scientific investigations are needed to ensure safe management strategies. Cadmium appeared to be the most threatening metal especially in leafy vegetables. It is advisable to avoid leafy vegetables cultivation in sewage irrigated areas everywhere to restrict its entry into food chain.

Impact of exclosures on wood biomass production and fuelwood supply in northern Ethiopia

In the Ethiopian highlands, communal grazing lands are one of the major land uses, and are source of livelihood for the rural people. Free and uncontrolled grazing in the communal grazing lands is the dominant grazing system. The traditional uncontrolled and free grazing system has caused severe degradation of the grazing lands. As a result, communities have started to establish exclosures and support the restoration of degraded communal grazing lands. Studies have shown that exclosures are effective to restoring degraded communal grazing lands and improving ecosystem services. However, studies that investigate the changes in aboveground biomass following the establishment of exclosures and compare it with fuelwood demand of the beneficiaries in our study area is lacking. Therefore, our study aimed at:(1) quantifying yearly biomass accumulation in exclosures and compare it to fuelwood demand of households that manage the exclosures;(2) assessing household energy sources and their consumption levels. To monitor changes in biomass production with over time, replicated(n = 3) 5 and10 year-old exclosures were sampled. To investigate fuelwood sources and consumption patterns, household surveys, key informant interviews and focus group discussion were conducted. Our results demonstrated that total biomass production increased with exclosure age. In both exclosure, biomass production from Vachellia etbaica was significantly(p \ 0.05) greater than that from Euclea.racemosa. Average daily fuelwood consumption per person was(0.63 ± 0.2) kg day^(-1). This means that the total biomass(27.5 Mg year^(-1)) obtained from 114.6 ha of exclosures covers only 9.4% of yearly fuelwood demand of the residents who manage the sampled exclosures. Nearly all respondents(95%) confirmed that they travel more than10 km day^(-1) to gather fuelwood from surrounding degraded forest patches. We recommend plantings of fast growing native tree species within exclosures and around homesteads to provide a sustainable fuelwood supply and using improved stoves to address the problem of fuelwood shortage. District agricultural offices could provide seedlings of native plant species, while communities provide unpaid labour for planting and managing plantations.

Nitrogen fertilization effects on grain quality of durum wheat (<i>Triticum turgidum</i>L. var. durum) varieties in central Ethiopia

Four released durum wheat varieties, two medium tall (Arsi-Robe and Kilinto) and two recently released semidwarfs (Ude and Yerer) were evaluated under five different N rates (0, 60, 120, 180 and 240 kg·ha-1) in 2005/06 growing season at Akaki and Debre Zeit, central Ethiopia. The quality responses of durum wheat varieties to different N-fertilizer rates and the N responses between tall and short durum wheat varieties were assessed. Protein and gluten content, vitreous kernel count, thousand kernel weight, test weight and lodging were considered. Vitreous kernel count, protein and gluten content were higher at Debre Zeit than at Akaki. Unlike Debre Zeit, there were significant relationships between response variables and fertilizer levels at Akaki. Lodging slightly affected the medium tall varieties at Debre Zeit whereas it was not a problem at Akaki. At Akaki, varieties response to each additional N rate was entirely below the quality standard set by ICC, 2000 except for thousandkernel weight. Therefore, it is unwise to promote durum wheat scaling up/out program for quality production at Akaki.

Remote sensing and census based assessment and scope for improvement of rice and wheat water productivity in the Indo-Gangetic Basin

Understanding of crop water productivity (WP) over large scale, e.g., river basin, has significant impli-cations for sustainable basin development planning. This paper presents a simplified approach to combine remote sensing, census and weather data to analyze basin rice and wheat WP in Indo-Gangetic River Basin, South Asia. A crop dominance map is synthesized from ground truth data and three existing LULC maps. National statistics on crop area and production information are collected and the yield is interpolated to pixel level using moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI). Crop evapotranspiration is mapped using simplified surface energy balance (SSEB) model with MODIS land surface temperature products and meteorological data collected from 56 weather stations. The average ET by rice and wheat is 368 mm and 210 mm respectively, accounting for only 69% and 65% of potential ET, and 67% and 338% of rainfall of the crop growth period measured from Tropical Rainfall Measurement Mission (TRMM). Average WP for rice and wheat is 0.84 and 1.36 kg/m3 respectively. WP variability generally follows the same trend as shown by crop yield disregarding climate and topography changes. Sum of rice-wheat water productivity, however, exhibits different variability leading to better understanding of irrigation water management as wheat heavily relies on irrigation. Causes for variations and scope for improvement are also analyzed.

The influence of grazing and cultivation on runoff, soil erosion, and soil nutrient export in the central highlands of Ethiopia

Background:Grazing by livestock and cultivation have been considered as two important causes of soil erosion and nutrient export.However,there has been limited evidence that grazing or cultivation matters to soil erosion and nutrient export in Ethiopia.Hence,this study was conducted in the Galesa watershed in Ethiopia to examine the effects of grazing and cultivation on runoff,soil loss,and nutrient export.Daily values of runoff,soil erosion,and nutrient outflow were measured for three consecutive years following standard procedures.Independent t test was performed to check if the means of runoff,soil loss,and nutrient loss from grazing and cultivated lands were significantly different.Moreover,repeated analysis of variance(ANOVA)was used to test if mean values of runoff,soil loss,and nutrient export varied significantly over the study years.Results:Although the average annual runoff depth was 7.8%higher in grazing land(GL),soil erosion was significantly lower(39%)in GL as compared to cultivated land(CL).Similarly,sediment and runoff-associated annual losses of total nitrogen(N),available phosphorus(P),exchangeable potassium(K),and organic carbon(OC)were low in the GL treatments.Lowest losses of total N(9.30 kg ha^(−1) year^(−1)),available P(0.83 kg ha^(−1) year^(−1)),and exchangeable K(1.84 kg ha^(−1) year^(−1))were recorded in GL treatment.Likewise,lowest losses of sediment-associated total N(32.8 kg ha^(−1) year^(−1)),available P(0.39 kg ha^(−1) year^(−1)),exchangeable K(0.23 kg ha^(−1) year^(−1)),and soil organic carbon(630 kg ha^(−1) year^(−1))were recorded from GL over the 3 years of experimentation.Conclusion:Our results indicate that cultivation increased soil erosion as compared to grazing.Although there were significant reductions in soil erosion and nutrient export from grazing lands compared with cultivated lands,the absolute losses were still high.This implies the need for grazing land management using appropriate physical and biological erosion control measures to increase productivity and reduce soil erosion as well as nutrient export.

Estimating landscape susceptibility to soil erosion using a GIS-based approach in Northern Ethiopia

Soil erosion is a very critical form of land degradation resulting in the loss of soil nutrients and downstream sedimentation of water storages in the highlands of Ethiopia.As it is technically and financially impossible to conserve all landscapes affected by erosion,identification of priority areas of intervention is necessary.Spatially distributed erosion models can help map landscape susceptibility to erosion and identify high erosion risk areas.Integration of erosion models with geographic information systems(GIS)enables assessing evaluate the spatial variability of soil erosion and plan implementing conservation measures at landscape levels.In this study,the Revised Universal Soil Loss Equation adjusted for sediment delivery ratio was used in a GIS system to assess landscape sensitivity to erosion and identify hotspots.The approach was applied in three catchments with size being 10–20 km^(2) and results were compared against quantitative and semi-quantitative data.The model estimated mean soil loss rates of about 45 t ha^(−1) y^(−1) with an average variability of 30%between catchments.The estimated soil loss rate is above the tolerable limit of 10 t ha^(−1) y^(−1).The model predicted high soil loss rates at steep slopes and shoulder positions as well as along gullies.The results of the study demonstrate that knowledge of spatial patterns of high soil loss risk areas can help deploy site-specific conservation measures.