GIS-BASED SURFACE IRRIGATION POTENTIAL ASSESSMENT: A CASE STUDY OF TEME WATERSHED, EAST GOJAM ZONE, AMHARA REGION, ETHIOPIA

Abstract

Assessment 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.