Water Resource
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Item SURFACE ENERGY BALANCE ALGORITHM FOR LAND (SEBAL) BASED EVAPOTRANSPIRATION ESTIMATION IN LOWER GILGEL ABAY CATCHMENT TANA SUB-BASIN, ETHIOPIA(Hawassa University, 2018-07-25) TEWODROS KASSAYE SEMAWOn land, Evapotranspiration (ET) is a combination of evaporation from the soil surface and transpiration from vegetation and it is one of the climate elements that plays an important role in water cycle and an important parameter in water resources management. As a result, many mathematical equations and algorithms have been developed and designed to compute evapotranspiration by different authors. Estimating from conventional methods of ET, which uses meteorological data, cannot estimate at a larger scale rather at certain location. To overcome this problem, remote sensing are one of the important sources of data and techniques to estimate many climate elements including evapotranspiration. The study area was located in Gilgel Abay catchment Tana sub basin in North West part of Ethiopia. The main objective of this study was estimation of evapotranspiration using SEBAL algorism and Landsat 8 imagery with climate data. In this study, SEBAL based remote sensing technique was applied to estimate spatially as well as temporal distributed evapotranspiration. For this analysis, ASTER GDEM, GRASS-python file & reference weather parameters from Bahir Dar weather station was used. The SEBAL python file was used to calculate the values of all parameters including surface radiance, surface reflectance, surface albedo, NDVI, LAI, surface emissivity, surface temperature, net radiation, soil heat flux, sensible heat flux, latent heat flux, which are consequently used to calculate the hourly and daily evapotranspiration in study area. Based on the analysis the results obtained from pixel wise calculation shows the values of the spatial variation of mean ET for different land cover ranged from 4.42 mm/day for closed grassland to 6.25 mm/day for dense forest areas. While the daily ET varied from 0 mm/day to 7.39 mm/day for the study area and its mean, value was 4.78 mm/day for 23 December 2016. For monthly ET calculation selected months were used and results show the maximum estimated actual evapotranspiration over the whole catchment ranged from 6.51 mm/day (Jan) to 7.82 mm/day (Mar). The mean actual evapotranspiration ranged from 4.37 mm/day (Feb) to 4.78 mm/day (Dec). The seasonal ET also was analyzed using the same approach as daily from Landsat 8 data for selected months and results showed with the mean value of 539.92 mm in 2016.Item EFFECT OF DEFICIT IRRIGATION ON WATER PRODUCTIVITY AND YIELD OF COMMON BEAN (PHASEOLUS VULGARIS L.) AT MELKASSA, CENTERAL RIFT VALLEY, ETHIOPIA(Hawassa University, 2020-10-13) ABERA TESFAYE TEFERAThe experiment was conducted at Melkassa Agricultural Research Center during off season under semi-arid climatic condition where moisture stress is higher. The study was under taken to evaluate effect of deficit irrigation on water productivity and yield of common bean (Phaseolus vulgaris L.).The experiment was split plot design with three common bean varieties as main plots and four deficit irrigation levels as sub plots all of which replicated three times. Four deficit irrigation levels 100%ETc, 85%ETc, 70%ETc, 55%ETc and three varieties SER-119, Bio fortified small seed-5, Awash-2 were used for treatment combination. The combined result indicates that there was a significant variation among treatments for yield, above ground biomass and water productivity. All common bean varieties were significantly affected under deficit irrigation levels. Consequently, highest yield (3.4 ton/ha) was obtained from irrigating 100%ETc followed by (3.2 ton/ha) with 85%ETc less yield reduction. In contrast the intermediate (2.8 ton/ha) and smallest yield (2.4 ton/ha) was obtained from irrigating 70ETc and 55%ETc.Water productivity was ranged from (0.83 kg/m3 ) at full irrigation to (1.33 kg/m3 ) at higher deficit irrigation. Based on obtained yield and water productivity, under a limited water supply situation where the goal was to gain highest possible yield of common bean and water productivity utilizing application of water from 70%ETC to 85%ETC at each irrigation event offers opportunities for water saving with yield reduction which was compensated by irrigating other area by saved water. The result of economic analysis shown that the highest net benefit obtained from irrigating full 100%ETc of the three common bean varieties. Based on obtained data the MRR was greater than 50% irrigating common bean with deficit irrigation 85%, 70% and 55% is economically feasible depending on accessibility of water