Institute of Technology
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Item GIS-BASED SURFACE IRRIGATION POTENTIAL ASSESSMENT: A CASE STUDY OF TEME WATERSHED, EAST GOJAM ZONE, AMHARA REGION, ETHIOPIA(Hawassa University, 2022-03-28) GETNET GUADIEAssessment of available land and water resources for surface irrigation development within watershed level using Geographic Information System (GIS) is important for planning its use. Due to the development of irrigated agriculture is less regardless of its important to alleviate food insecurity and food production problem in the study area, improving of agricultural productivity within the study are needs a quantified irrigable land and potential of water resources through in a systematic and scientific way. Identification of suitable land and mapping to it for surface irrigation, estimation of available flow, determination of irrigation water requirement and Comparing the Gross irrigation water requirement of the selected crops for the identified suitable land with simulated river flow were the main steps that were followed. To identify suitable land, the land suitability parameters like slope, soil (texture, depth and drainage), river proximity, and LULC of the study area were used. Application of weighted overlay tool was used for analysis of these factors to give a suitable land among river sub watershed of Tejatil, G/Teme, Tige Bahar and Tiwa as 578ha, 735ha, 234ha and 955ha respectively, which accounts 13.7% of the total study area. Simulated flow of the four manually added outlets and one linking stream added outlet in the watershed after calibration and validation by considering 12 sensitivity parameters and observed flow of gauged river were conducted. The mean monthly flow of 4.34m3 /s was determined at the outlet of the watershed. Three crops (Tomato, Maize and Potato) were selected to grow on the identified irrigable areas and its irrigation water requirement of these crops were estimating by implementing CROPWAT8.0 model as an input of climatic, crop and soil data .By comparing gross irrigation water requirement of the selected crops for identified irrigable land and simulated river flow at the area of selected site, the total irrigation potential site of the study area for surface irrigation was found to be 555ha, which accounts 3.04% of the total study area. In conclusion, the potential irrigable land is very small due to the scarcity of water. Therefore, the irrigation potential of the area could be increased either by harvesting rainwater and using ground water or by analysis a suitability of other method of irrigation such as trickle/drip and sprinkler irrigation method.Item ASSESSMENT OF SURFACE IRRIGATION POTENTIAL: THE CASE OF GIDABO WATERSHED, RIFT VALLEY LAKES BASIN, ETHIOPIA(Hawassa University, 2019-03-07) AZEMERAW ALEMUEthiopia has immense potential in expanding irrigated agriculture. Irrigable land assessment is essential for the development of irrigated agriculture. The study was aimed at assessing land potential of Gidado watershed. Land suitable for irrigation development was determined with a GIS-based multi-criteria evaluation, which considers the interaction of various factors such as slope, soil, LULC, proximity to river and road. The Analytical Hierarchal Process (AHP) and ArcSWAT were used for analyzing the different factors by assigning weights and mapping of suitable potential irrigable areas and surface water potential of the study area was estimated using SWAT model respectively. The model was calibrated and validated from observed stream flow data at three monitoring sites within the watershed using the periods of 1993-2004 and 2005-2012 respectively by using SWAT-CUP program and Global Sensitivity Analysis (GSA) was used for identifying important model parameters. The irrigable land of the area was identified using weighted overlay analysis of the suitability parameters, thus the result indicated that 1138.31 km2 areas was classified suitable and 2042.19 km2 area was classified as not suitable for surface irrigation. During calibration and validation, the results of model performance indicators were in the acceptable range (R 2= 0.68, 0.73, 0.72), (NSE = 0.60, 0.63, 0.71) and (PBIAS=12.2, -9.0 and -14.0) for Gidabo, Kola and Bedessa rivers respectively which indicated that a good to very good agreement between observed and simulated values. And average surface water resource potential of the catchment estimated to be 86.36m3 /s or 223.86 MCM. However after analyzing 25 years river discharge and determined the water demand of the crop, 74390.89ha (23.39%) of the potential irrigable area was estimated and could be irrigated consistently with runoff from the river systems. For sustainable irrigation development, other suitability factors such as soil chemical properties, socio-economic, environmental issues, and distance from markets and town should be consideredItem Assessment of Climate Change Impact on Surface Water Availability: Gerhu-Sirnay Catchment, Mereb Sub- Basin,(Hawassa University, 2024-07-12) ZEGEYE TAMIRU HAMESSOInvestigating surface water availability under climate change impact is vital to ensure water resource sustainability. The general objective of this thesis was to assess the impact of climate change over surface water availability of Gerhu-Sirnay catchment using CORDEX-RCA4 with soil and water assessment tool (SWAT). To achieve this, quality of observed data was accepted for outlier, adequacy and consistency tests, and CORDEX-RCA4 datasets were passed the Power transformation and variance scaling bias correction and square root normalization. The baseline monthly stream flow (1990-2003) was modeled using SWAT, calibrated (1992-1999) and validated (2000-2003) in SWAT-CUP under SUFI2 tool. The CORDEX-RCA4 models were compared their performance at the baseline period (1990 to 2001) using volumetric metrics and Taylor diagram to predict future precipitation and stream flow variability by the best fit RCA4 model under RCP4.5 and 8.5 emission scenarios for 2050s and 2080s periods. The results showed that SWAT was very good at modeling baseline stream flow indicated by R 2 , NSE, PBIAS and RSR as 0.93, 0.94, 6.3% and 0.13 for calibration, and 0.82, 0.89, 10.4% and 0.07 for validation respectively. ICHEC-EC-EARTH-RCA4 was best fitted by scoring 0.9838, 0.0000, 0.9838 and 0.0162 for VHI, VFAR, VCSI and VMI respectively for volumetric, and 0.749, little less than 75 and little less than 100 for CC, NRMSE and δN respectively and better at annual scale at Taylor diagram. The baseline variability of seasonal rainfall indicated that an increments on the winter and autumn and decrease on the spring season. In the 2050s and 2080s of both emission scenarios significant increase and decrease was projected than the baseline periods at seasonal and annual scales. The mean annual rainfall was decreased by; 7.58% and 9.82% at 2050s and 2080s, and 4.92% and 9.28% during 2050s and 2080s under RCP4.5 and RCP8.5 respectively. The total change of rainfall was; 9.89% for 2050s and 13.52% for 2080s, and 8.79% at 2050s and 13.31% at 2080s for RCP4.5 and RCP8.5 scenarios respectively. Future annual stream flow will be decreased by; 8.84% in 2050s and 10.59% in 2080s, and 6.32% in 2050s and 9.88% at 2080s under RCP4.5 and RCP8.5 respectively. The total annual stream flow change will be; 9.88% during 2050s and 13.67% at 2080s, and 9.96% at 2050s and 13.86% at 2080s for the RCP4.5 and RCP8.5 scenarios respectively. Findings of this study indicated that climate change has significant impact over surface water availability of Gerhu-Sirnay catchment. To conduct policy oriented climate change impact over surface water availability, future researchers should consider multiple; climate variables, dynamic drivers and uncertainty analysis, and improve CORDEX inputs