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[PANEL] 0608 WATER RESOURCES, IRRIGATION AND RAINFALL
Organizers:
SOLOMON Hishe, Mekelle University, Ethiopia; University of Dar es Salaam, Tanzania
TESFAALEM G. Asfaha, Department of Geography and Environmental Studies, Mekelle University, Ethiopia
Paper presenters:
MULATU Kassa Gedamu; SOLOMON Hishe; WOLDEAMLAK Bewket; KIDANE Welde Reda;
HINTSA Libsekal Gebremariam; TESFA Worku; ALEMNEH Teshale Habebo
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ASSESSMENT OF BACTERIOLOGICAL AND PHYSIO CHEMICAL QUALITY OF DRINKING WATER IN CASE OF SHAMBU TOWN, OROMIA,ETHIOPIA [Abstract ID: 0608-05]
Water quality is a critical factor affecting human health and welfare. Ethiopia is one of the worst countries in the world for health status and water quality problems, with only 52% of its population having access to safe water. As a result, 60-80% of the population suffers from water-borne and water-related diseases. Shambu Town is not free of this problem, since people are still using unprotected wells and springs for their domestic water supply. The aim of this research is therefore to evaluate the bacteriological and physio-chemical quality of water in Shambu Town. Two rounds of water samples were taken from each site with a total of 44 water samples. Water sources (n=4), tap water (n=4), and household containers (n=15) were considered for the determination of physio-chemical and bacteriological drinking water quality. The samples were analyzed for physio-chemical parameters like temperature, turbidity, PH, TDS, EC, and the presence of indicator bacteria such as total coliforms (TC) and fecal coliforms (FC).The method of sample collection at each sampling point was according to the WHO Guidelines for drinking water quality assessment. Water samples were collected using a systematic random sampling method. The result showed that the highest counts of TC and FC were detected in the household water containers, followed by unprotected wells, unprotected springs, protected wells, and protected springs. All raw water samples were positive for TC and FC. High bacteriological load was found in the household water containers. This research concluded that the water quality of Shambu Town at household storage is very poor and is not free from contaminants. Thus, deliberate community awareness raising about sanitation and hygienic practices is crucial. The water sources should be protected from contamination by animals and human excreta, and should be treated before being used for drinking.
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EFFECTS OF SOIL AND WATER CONSERVATION ON VEGETATION COVER: A REMOTE SENSING BASED STUDY IN THE MIDDLE SILLUH VALLEY, NORTHERN ETHIOPIA [Abstract ID: 0608-02]
Soil and water conservation (SWC) has been implemented in the Tigray region of Ethiopia since 1985. This has led to noticeable increases in vegetation cover. The objective of this study was to quantify vegetation cover as an effect of SWC activities by analyzing associations between the Soil Adjusted Vegetation Index (SAVI), Land Surface Temperature (LST) and Average Annual Precipitation (AAP) between 1985 and 2015. Multi-temporal remote sensing data from Landsat imagery were used to estimate SAVI and LST for the years 1985, 2000, and 2015. Long-term station-based data on daily precipitation from 1973 were aggregated to annual average in three sections to correspond with the image data and then converted into raster format using the Inverse Distance Weight (IDW) technique. Vegetation cover dynamics were quantified by correlations of SAVI with LST, and SAVI with AAP. The results show that there was a statistically significant inverse relationship between SAVI and LST in all the study periods. These improvements in vegetation cover improvements are attributable to the implementation of integrated soil and water conservation measures, particularly in areas where exclosure areas are defined. This paper concludes by providing a theoretical basis and indicator data support for further research on vegetation restoration for the entire region.
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IDENTIFICATION AND PRIORITIZATION OF SUBWATERSHEDS FOR LAND AND WATER MANAGEMENT IN TEKEZE DAM WATERSHED, NORTHERN ETHIOPIA [Abstract ID: 0608-07]
Sedimentation and/or soil erosion are huge problems that have threatened many reservoirs in the Northern Ethiopian highlands, particularly in the Tekeze dam watershed. This study was done to identify and prioritize the most sensitive subwatersheds with the help of a semi-distributed watershed model (SWAT 2009) for improved management of reservoir sedimentation mitigating strategies at watershed scale. SWAT 2009 was chosen for this study because of its ability to produce routed sediment yield and identify principal sediment source areas at the selected point of interest. On the basis of a digital elevation model (DEM), the catchment was divided into 47 subwatersheds using the dam axis as the main outlet. By overlaying land use, soil, and slope of the study area, the subwatersheds were further divided into 690 hydrological response units (HRUs). Model calibration (for the period January 1996 to December 2002) and validation (for the period January 2003 to December 2006) were carried out for stream flow rate and sediment yield data observed at Emba Madre gage station. The results of model performance evaluation statistics for both stream flow and sediment yield shows that the model has a high potential in estimation of stream flow and sediment yield. Tekeze dam watershed has a mean annual stream flow of 137.74 m3/s and annual sediment yield of 15.17 ton/ha/year. Out of the 47 subwatersheds, 13 subwatersheds (mostly located in the northeastern and northwestern part of the catchment) were prioritized. The maximum sediment outflow of these 13 subwatersheds ranges from 18.49 - 32.57 ton/ha/year and is predominantly characterized by cultivated land, shrub land, and bare land, with an average land slope ranging from 7.9 to 15.2% and with the dominant soil type of eutric cambisols. These results can help to formulate and implement effective, appropriate, and sustainable watershed management which in turn can help in sustaining the reservoir storage capacity of the dam.
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OPTIMIZING IRRIGATION WATER LEVELS TO IMPROVE YIELD AND WATER USE EFFICIENCY OF VEGETABLES: CASE STUDY OF TOMATO [Abstract ID: 0608-08]
The irrigation water requirement needs to be optimized in order to improve the productivity of irrigated agriculture. Hence, adapting the knowledge of irrigation scheduling for a specific crop and location is important. A field experiment was conducted in the Raya Alamata district of Tigray, Ethiopia to investigate the impact of different irrigation water levels on the yield and irrigation water use efficiency (IWUE) of the tomato. Eight treatments (50%, 35%, 25% above estimated crop water requirement (CWR), estimated CWR, 25%, 35%, 50% below the estimated CWR), and farmers’ practices were arranged in randomized complete block design (RCBD) under three replications. Tomato water requirement was estimated using CROPWAT 8 software and it was estimated to be 500 mm in depth. Results showed significant differences in marketable yield (MY), total yield (TY) and irrigation water use efficiency (IWUE) of the tomato according to levels of irrigation. The application of the estimated CWR of the tomato gave higher MY (36.37 ton/ha) and TY (38.58 ton/ha). Unmarketable fruit yield (UY) of the tomato was unaffected by the level of irrigation. Farmers’ practice gave considerable MY (36.32 ton/ha). But the depth of water applied by farmers throughout the growing season was 561mm, which was 12.2% above the estimated CWR. The IWUE ranged from 0.357 kg/m3 to 0.876 kg/m3 for the different irrigation water levels. This shows increasing IWUE with decreasing amounts of water application. In conclusion, deficit irrigation practice could be successful in saving irrigation water up to 35% of tomato CWR without significant reduction in the fruit yield of the tomato in regions where water is a limiting factor for vegetable production.
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OPTIMIZING YIELD AND WATER USE EFFICIENCY OF FURROW IRRIGATED POTATO UNDER DIFFERENT DEPTH OF IRRIGATION WATER LEVELS [Abstract ID: 0608-06]
In Ethiopia, the development of irrigated agriculture plays a key role in improving productivity and food security, but further intensive effort is needed to enhance irrigation water management systems. It is therefore crucial to introduce and adapt the knowledge of irrigation scheduling for each specific crop and location to the beneficiaries. This study aims to improve irrigation water management through the improvement of crop water requirement and irrigation scheduling. This study was conducted in the southern zone of Tigray regional state, Emba Alaje District. The crop water requirement of potato (jalleni variety) was estimated using the CROPWAT 8 software model and determined as 604 mm for the entire growing period. Potatoes (jalleni) were grown under seven treatments of irrigation water application in a complete randomized blocks design with three replications each. Potato yield and water use efficiency was significantly affected (p
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SPATE FLOW AND SEDIMENT OPTIMIZATION IN SPATE IRRIGATION DIVERSION STRUCTURES [Abstract ID: 0608-03]
The aim of this study was to evaluate alternatives in the main intake designs of spate irrigation structures. Relevant data were collected from the field and respective offices. Four scenarios were developed, based on the current problems. The Delft3D model was employed to simulate the hydrodynamic and morpho-dynamic characteristics of the flow around the main intake. The study showed that adjusting the intake deflection angle from 120 to 150 degrees for a 3-meter wide intake could increase irrigation water abstraction by 21%. Changing the intake width from 3 to 5 meters at a 120 degree deflection angle could increase total irrigation water abstraction by 81%. Adjusting the intake width from 3 to 5 meters and the deflection angle from 120 to 150 degrees could improve spate irrigation water abstraction by 101%. These interventions did not result in any significant reduction in sediment deposition at the intake. However, the enhanced supply of water through the main spate flow gates may convince farmers not to block the scour sluice gates. From a purely design point of view, an intake width of 5 meters and 150 degree deflection angle are to be recommended.
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SPATIO-TEMPORAL TREND ANALYSIS OF RAINFALL AND TEMPERATURE USING STATISTICAL APPROACH AND ITS IMPLICATION ON CROP PRODUCTION IN BERESSA WATERSHED, ETHIOPIA [Abstract ID: 0608-04]
Global warming and climatic variability are significant environmental problems in the 21st century. The problems are greatest in developing countries, particularly sub-Saharan countries in which the majority of the population live by rain-fed agriculture. The present study undertakes a spatiotemporal analysis of climatic variability and its impact on crop production. It employs the Mann-Kendall trend test and Sens’s slope estimator. The Precipitation Concentration Index (PCI) has been applied over the period 1980–2014 on an annual and seasonal basis. Pearson correlation analysis between climatic variables and crop production has been carried out. Finally, moving average and Inverse Distance Weighted (IDW) techniques have been used. Based on the MK test and Sen’s slope, upward and downward trends have been observed in rainfall and temperature in the Beressa watershed. A significantly rising trend of 0.28mm/year and 1.07% on mean annual rainfall was recorded at the DB station whereas a significantly decreasing trend of 8.62mm/year and -27.88% was observed at the HG station. An increasing trend in seasonal kiremit rainfall was observed at the DB station (1.623mm/year) and a significantly falling trend at the SD station (-0.9mm/year and -16.2%). A significantly rising trend in the belg season rainfall was observed at the DB station (0.4mm/year) and a significantly decreasing trend at the GIN station (-0.12mm/year). At all stations, a decreasing trend was observed in bega season rainfall, ranging from -0.061mm/year at the GIN station to -0.19mm/year and -56.4% at the DB station. The results obtained from the PCI show that the distribution of rainfall during the kiremit and belg seasons is moderate compared with annual and bega rainfall, in which the rainfall distribution is highly concentrated. From this observation, the rainfall distribution could be classified as irregular to erratic, hence affecting crop production. With some crops, there is significant correlation with rainfall and temperature, but this does not mean that one can conclude that the effect of climate variables on productivity are beyond seasonal influence. The growing periods of some crops run from one season to the next, which means that it cannot be said that a single season has not significantly influenced productivity. The mean annual, minimum and maximum temperatures increased by about 0.95°C/35 years, 0.7°C/35 years and 1.1°C/35 years respectively. In view of this, the incidence of food shortages, famine, and population migration out of the area is high. Therefore, depending on the historical trend in rainfall variability and prolonged temperature increase, appropriate coping and adaptation strategies need to be encouraged.
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TRADITIONAL METHOD OF FERMENTED KOCHO WASHING FORTIFYING ANTHROPOGENIC STRESS ON WATER RESOURCE AND ENSET PLANT IN HADIYA ZONE,ETHIOPIA [Abstract ID: 0608-01]
Traditional methods of producing fermented enset (Ensete ventricosum welw.cheesman) for food – known as kocho – by washing, risks damaging the enset plant and the availability of potable water. The demand for potable water to wash fermented kocho in areas of water scarcity, the need for a large washing area, the drawback of grey water management after washing, are all issues when extracting large amounts of kocho dough (KD) from fibrous pit fermented enset. Unsustainable use of the natural resources, including potable water and enset plants, without replenishing and failing to manage organic waste from fermented kocho washing (FKW) process are all ecosystem hazards and contributors to poverty. The main aim of this research is therefore to assess the impact of traditional methods of processing kocho by FKW on enset plant loss, water demand and the annual amount of discarded fibrous bi-product per hectare, in line with the future market potential of value added kocho flour for prolonged shelf life. A test with a ratio of 1kg of fermented kocho to 4 litres of potable water was conducted accordingbased on the recommendations of women experienced in the process. The result shows that to achieve an annual production of 5,600kg of KD (3,500 kg of sun dried kocho flour) the following natural resources are needed per hectare: 40,000 litres of potable water drained as grey water and 144 mature enset plants, which take 8 years to grow to maturity and are destroyed, leaving 4,400 kg of discarded fibres.