GIS- BASED SURFACE IRRIGATION POTENTIAL ASSESSMENT IN THE CASE STUDY OF TEMICHA WATERSHED EAST GOJAM ZONE OF AMHARA REGION

Abstract

Irrigation is an important investment for improving rural income through increased agricultural production. The development of irrigation and agricultural water management holds significant potential to enhance productivity and reduce vulnerability to the clim actic volatility in any country. The major consequence of irrigation development are fluctuations of basic climatic elements such as rainfall, temperature, humidity , and other atmospheric conditions. This study was concerned with assessment of surface irrigation potential in the Temicha watershed by implementing Arc GIS 10.1. The study identifies suitable land, crop water demand and supply for dominant crops grown in the catchment, and also providing suitability maps for surface irrigation development. To identify suitable land the land suitability parameters were used such as land slope, soil type and land cove r land uses. The suitability of each parameters analyze individually and then application of the weighted overlay tool was provided to get the overall suitability factors and suitability was conducted by considering FAO criteria for surface irrigation deve lopment. The crop water requirement of major growing crops of the study area were identified based on some earlier studies and agro climatic condition of the study area i.e. Wheat and Maize and its demand of water was estimated by implementing CROPWAT-8 model as an input of climatic data’s. The stream flow data in the watershed were assessed by implementing the SWAT model with an interface Arc GIS 10.1 software. The model was calibrated and validated from observed stream flow of the watershed. The calibration and validation result showed that model performance evaluation statistics coefficient of determination (R 2 ), Nash-Sutcliffe model efficiency (ENS) and Relative Volume Error (RVE) were in the acceptable range (R 2 > 0.8, ENS > 0.8 and RVE < -10 % ). This shows that a good agreement between the simulated and observed values. The result of the weight overlay analysis revealed that 45.5% (49629.2 ha) of lands in the watershed were in the range of highly sui table for marginally suitable class due to the combined effect of slope, soil and land use land cover suitability and 54.5% (59445.9 ha) of the area were unsuitable for surface irrigation. So that, the current study considered only slope, land use land cov er and soil physical properties but other suitability factors like, socioeconomic, environmental issues, soil chemical properties, method of irrigation system and other relevant parameters should be studied for detail assessment of irrigation development in the study area