Temesgen Enku

The technical performance evaluation of Koga Irrigation Scheme was made in order to identify management practices for implementation to improve the system operation and the performance of the irrigation system. The evaluation was made based on the selected performance indicators such as water application efficiency, dependability of irrigation interval and sustainability of irrigated command area. The results obtained showed that Application efficiency monitored on three farmers’ farm located on different ends of the command ranges from 52.2 to 61.8% at irrigation scheme. Dependability of the schemes evaluated in terms of irrigation interval shows that the schemes irrigate more frequently than was intended. The sustainability of the irrigated area initially planned for development or the actual irrigated area during the design period was 7,004 ha. However currently it is irrigating about 6,200 ha. This shows that the sustainability of the scheme is 0.86 ~ 86%. In conclusion, on farm...

This research document was the result of a project of Learning and Communication of Water supply, Sanitation and Hygiene (WaSH) of Amhara region which was financed by Water Aid Ethiopia. The following people were the research team members from the school of Civil &

The effect of land cover and landscape on runoff and sediment yield was evaluated in the Ethiopian highlands. We selected three small catchments: agriculture dominated watershed, bush & agriculture dominated watershed and agriculture dominated but with higher coverage of bush & grass watershed compared to the other two watersheds with in 399 ha Ene-chilala watershed. Hydrometric, sediment concentration and rill erosion data were measured for two years (2015 and 2016). The result showed that; sediment yield were statistically significant different between watershed one and watershed two. Moreover, the sediment concentration in watershed three varies statistically when compared with watershed one and watershed two. The greater runoff, suspended sediment concentration and yield in the agriculture dominated but with higher coverage of bush & grass catchment (WS3) results from saturated areas and gully erosion in the bottomlands. Since the agricultural land is highly degraded no more soi...

The Ethiopian government has declared the Lake Tana Beles region as a growth corridor. Irrigation development is one of the priorities. Groundwater has the greatest potential for increasing irrigation. However there is lack of information on ground water availability and rates of recharge and thus rates of sustainable withdrawals. Therefore the objective of this research is to determine the groundwater recharge. The study was conducted in Robit-Bata, an experimental watershed of 911 ha, located at the south-eastern edge of Lake Tana. More than 300 hand dug wells are used for domestic use and irrigation of Chat mainly in the watershed. Fifty wells were selected for water table observations starting from April, 2014. Daily Precipitation was recorded for the same period. The annual recharge was estimated using the water – level fluctuation method. Specific yield was defined as the difference of porosity and field capacity of the subsurface formation. We found that annual average areal ...

Abstract Groundwater (GW), which contributes to the quality of life, economic development, improved food security, and rural society stability, is essential to improving rural water supply access and quality. Given its multi-purpose uses, GW quality has been degraded and polluted by global climate change, population growth, human activities, land use land cover (LULC) transition. GW quality, therefore, should be evaluated and tracked continuously to secure its multi-purpose uses. Herein, this study aims to assess the shallow GW standard using water quality indices (WQI) and GIS techniques in the northwestern boundary of Lake Tana, Upper Blue Nile (UBN) of the Amhara Region, Ethiopia. The water samples were collected from 30 sites, and physico-chemical parameters such as pH, electrical conductivity (EC) were measured in situ. Calcium (Ca +), magnesium (Mg+), sodium (Na+), potassium (K+), chlorine (Cl− ), sulphate (SO 4−2), nitrate (NO−3), bicarbonate (HCO3−), carbonate (CO3−2) concentraions were determined. Irrigation water quality indices, including sodium adsorption ratio (SAR), sodium soluble percentage (SSP), residual sodium carbonate (RSC), permeability index (PI), magnesium adsorption ratio (MAR), Kelley's ratio (KR), and Na% were calculated. The results show that EC (46.7%), SAR (97%), KR (53%), SSP (53.3%) MH (100%) and Na+ (50%) are suitable for irrigation. The overall WQI for drinking purposes ranges from 46 to 67.5, which confirms that 22%, 38.8%, and 39.2% of samples fall under very good, good, and poor quality, respectively. The hydrochemical facies indicated that, the dominant water type (43% of samples) is type-III (Na-K-Cl-SO4) and mixed type. Most shallow wells near Lake Tana are unsuitable for drinking purpose. Further, the government should monitor contamination sources, including agricultural activities, domestic wastes and landfills for sustainable GW quality.

The Ethiopian government has declared the Lake Tana Beles region a growth corridor Irrigation development is one of the priority. Since baseflow is limited, groundwater has the greatest potential for increasing irrigation in the near future. The main drawback is a lack of information on sustainable groundwater use and specifically the ground water recharge. Therefore the objective of this research is to calculate the annual recharge to the ground water. The study is conducted in Robit-Bata, an experimental watershed of 911 ha, located at the south-eastern edge of Lake Tana. Farmers have excavated more than 300 hand dug wells for irrigation and we used 50 shallow groundwater wells and observed water table fluctuation and precipitation for the past one year. The annual recharge was estimated using water – level fluctuation method. Specific yield was taken to be the difference of porosity and field capacity of the subsurface formation. The annual average areal groundwater recharge of t...

Understanding functions of a watershed is important for implementing appropriate soil and water conservation measures and for planning and development of sustainable water resources use. Watershed storage is a significant part of a catchment water budget and its quantification provides a clue to understand the fundamental catchment hydrological processes. This study is aimed to investigate the dynamics of watershed storage of the Anjeni experimental watershed in the Upper Blue Nile basin for which a long series of rainfall and runoff data is available for this study. A daily water balance equation was used to quantify the watershed storage over the distinct rainy season. On average, 86 % of the annual rainfall occurs during distinct rainy season. The study showed that the watershed storage increases with the increase of cumulative rainfall till the watershed stores its maximum capacity. After this maximum capacity, the watershed storage remains constant, even if rainfall continuous. The Anjeni watershed stores an average of 380 mm of water after a cumulative effective rainfall of 625 mm. Before the maximum storage was reached, about 60 % of the effective rainfall is used to wet up the watershed. Then, the remainder becomes surface runoff and interflow, during which about 40 % of the flow appeared at the outlet.

The Koga irrigation scheme is the first attempt of eleven major proposed large-scale irrigation schemes in Lake Tana sub-basin in the Upper Blue Nile Basin. The schemes are to provide water for small holder farmers. The completion of Koga scheme poses various challenges and provides important lessons in implementing and operating large-scale irrigation projects. With anticipated increased agricultural productivity, one of the foreseeable challenges will be the continuous assessment of the water quality. This study assesses the quality status of Koga River by analysing samples collected from planned sampling locations. Two sampling campaigns were undertaken, and 23 physical and chemical water quality parameters were measured using standard methods. On the basis of FAO irrigation water quality guideline, Koga irrigation water is well within limits of salinity, sodicity and toxicity hazard except above the threshold value of boron. Among the dominant crops cultivated potato, barley and wheat production are susceptible to yield reduction. A detailed investigation is required to quantify the extent of yield reduction incurred due to higher level of boron. Multivariate statistical technique is applied for the evaluation of relationship between streamflow and various water quality parameters.

ABSTRACT AbstractConventional methods and remote sensing were applied for the estimation of reference evapotranspiration and actual evapotranspiration over the Fogera floodplain. Reference evapotranspiration (ET0) by Modified Makkink (MM), Priestly-Taylor (PT) and Abtew (A) simple equations was compared to the PenmanMonteith (PM) estimations, in order to decide which method for ET0 is the most suitable alternative to PM in data scarce conditions. A comparison was also made to a satellite based energy balance approach that estimated actual evapotranspiration. For the remote sensing approach, images from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor were selected. For the study, data has been used from Bahir Dar meteorological station at a distance of 50 km from the floodplain and from Woreta weather station that is located in the floodplain. The comparison of results from the conventional methods indicated that the MM method performed best over the floodplain as compared to the PM approach while the PT and Abtew (A) simple equations only produced fair results. The latter two approaches required calibration of site specific coefficients that may have affected the estimation results. Accumulated actual evapotranspiration from the satellite based approach for the year 2008 was about 1,519 mm for rice, while the reference evapotranspiration by the PM approach was 1,498 mm. A comparison of these results with literature values of the crop coefficient of rice indicated that rice transpired at a potential rate. KeywordsEvapotranspiration · MODIS· SEBS · Remote sensing · Penman-Monteith·Makkink·Priestley-Taylor·Abtew model·Fogera

Accurate estimation of evapotranspiration (ET) is vital for water resource management. The FAO-56 Penman–Monteith (FAO-56 PM) is a standard method, but it requires numerous weather data. This challenges water resource managers to estimate ET in areas where there are no adequate meteorological data. Hence, simplified approaches that are less data intensive are the right alternatives. Here, ET was estimated using different approaches and their performances were evaluated in different ecosystems of Ethiopia. Surface Energy Balance Systems (SEBS) model was also used for spatio-temporal mapping of ET in the Fogera floodplain, Lake Tana Basin. The spatial average of actual ET (ETa) from remote-sensing (RS) data over the floodplain was less than the Penman–Monteith (PM) reference ET (ETo) in drier periods and larger in wet seasons. A sensitivity analysis of PM input variables at the Bahir Dar station showed that the incoming solar radiation and air temperature are most sensitive, and wind speed was found to be the least sensitive. The comparison of simple Enku (E) temperature method, Abtew (A) equation, modified Makkink (MM) method, and Priestley–Taylor (PT) method with the PM ETo in the different ecosystems of Ethiopia showed the MM method performed best in all the stations except Dire Dawa stations with coefficient of determination (R 2) of 0.94, Nash–Sutcliffe efficiency (NSE) of 0.88, root mean square error (RMSE) of 0.26 mm, and absolute mean error (AME) of 0.21 mm at Addis Ababa and Awassa stations. The performance of MM and PT methods in the dry and hot climate was poor. The E method performed consistently well in all the stations considered. While ET estimation from remotely sensed inputs has generally been improved, selection of the method of estimation is very important and should always be tested with observational data.

In Ethiopia the population is rapidly expanding. As a consequence the landscape is rapidly changing. Eucalyptus plantations are increasing and irrigation projects are implemented. The hydrological effects of the changing landscape on river (low) flows have not been well documented and therefore the amount of water available in the future might be over optimistic. The objective of this paper is to establish how low flows have been impacted by new developments in irrigation and by landscape change. For this paper, we choose the Gilgel Abay in the headwaters of the upper Blue Nile basin, since it has both good quality discharge data and it is located in the Tana Beles growth corridor. Numerical and statistical means were used to analyze the 25 years of available low flow data. We found a statistically significant decreasing trend (P < 0.00001) of low flow in the Gilgel Abay. From 1980’s to 1990’s the low flow decreased by 25% and from 1990’s to 2000’s the low flow was reduced by 46%...

First results are shown of a project aiming to estimate daily values of reference crop evapotranspiration ET0 from geo-stationary satellite imagery. In particular, for Woreta, a site in the Ethiopian highland at an elevation of about 1800 m, we tested a radiation-temperature based approximate formula proposed by Makkink (MAK), adopting ET0 evaluated with the version of the Penman-Monteith equation described in the FAO Irrigation and Drainage paper 56 as the most accurate estimate. More precisely we used the latter with measured daily solar radiation as input (denoted by PMFAO-Rs). Our data set for Woreta concerns a period where the surface was fully covered with short green non-stressed vegetation. Our project was carried out in the context of the Satellite Application Facility on Land Surface Analysis (LANDSAF) facility. Among others, the scope of LANDSAF is to increase benefit from the EUMETSAT Satellite Meteosat Second Generation (MSG). In this study we applied daily values of downward solar radiation at the surface obtained from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) radiometer. In addition, air temperature at 2 m was obtained from 3-hourly forecasts provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Both MAK and PMFAO-Rs contain the psychrometric "constant", which is proportional to air pressure, which, in turn, decreases with elevation. In order to test elevation effects we tested MAK and its LANDSAF input data for 2 sites in the Jordan Valley located about 250 m b.s.l. Except for a small underestimation of air temperature at the Ethiopian site at 1800 m, the first results of our LANDSAF-ET0 project are promising. If our approach to derive ET0 proves successfully, then the LANDSAF will be able to initiate nearly real time free distribution of ET0 for the full MSG disk.

First results are shown of a project aiming to estimate daily values of reference crop evapotranspiration ET0 from geo-stationary satellite imagery. In particular, for Woreta, a site in the Ethiopian highland at an elevation of about 1800 m, we tested a radiation-temperature based approximate formula proposed by Makkink (MAK) adopting ET0 evaluated with the version of the Penman-Monteith equation described in the FAO Irrigation and Drainage paper 56 as the most accurate estimate. More precisely we used the latter with measured daily solar radiation as input (denoted by PMFAO-Rs). Our data set for Woreta concerns a period where the surface was fully covered with short green non-stressed vegetation. Our project was carried out in the context of the Satellite Application Facility on Land Surface Analysis (LANDSAF) facility. Among others, the scope of LANDSAF is to increase benefit from the EUMETSAT Satellite Meteosat Second Generation (MSG). In this study we applied daily values of downward solar radiation at the surface obtained from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) radiometer. In addition, air temperature at 2 m was obtained from 3-hourly forecasts provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Both MAK and PMFAO-Rs contain the psychrometric "constant", which is proportional to air pressure, which, in turn, decreases with elevation. In order to test elevation effects we tested MAK and its LANDSAF input data for 2 sites in the Jordan Valley located about 250 m b.s.l. Except for a small underestimation of air temperature at the Ethiopian site at 1800 m, the first results of our LANDSAF-ET0 project are promising. If our approach to derive ET0 proves successfully, then the LANDSAF will be able to initiate nearly real time free distribution of ET0 for the full MSG disk.