Abstract:
The fundamental and essential issues for a country's sustainable development is land and water
resource development. It is vital to comprehend the quantity or the distribution in place and time
through various studies in order to use land and water resources in the most efficient and effective
manner. Hence, this study was carried out on the hydrological process and evaluate the physical
the suitability of land for irrigation in the Zala watershed of the Omo gibe basin using the SWAT
model which is integrated with GIS based multi criteria decision making of AHP. The processes
included defining the boundaries of watersheds, determining what area could be used for
irrigation, and estimating the amount of surface runoff for irrigation. In this study calibration and
validation of simulated versus measured flows of Zenti river and estimation of surface water in the
watershed were conducted after sensitivity of hydrologic parameters had been identified using
SWAT-CUP model tool. The hydrological simulation performance evaluation using SWAT-CUP
were achieved with the objective function of calibration (R2=0.76 and NS =0.61) and Validation
(R2=0.69 and NS =0.74). This model evaluation was performed at monthly levels.
The Food and Agricultural Organization's guidelines for land evaluation were used to classify
irrigation suitability factors such as DEM, slope, soil characteristics like type, texture, depth,
drainage, land use/cover and proximity to water source and road. The land was then classified
into four suitability classes: highly suitable (S1), moderately suitable (S2), marginally suitable
(S3), and not suitable (N), which were determined by individually weighting the suitability factors
and finally weighted overlaid. Irrigation water requirement of five commonly grown major crops
(Tomato, potato, Cabbage, maize, sorghum) were computed from climate, crop and soil data
inputs using Crop Water Requirement (CropWat8.0) software. By weighing analysis of all
parameters 99.3 % of the study area was found in a range highly suitable to that of marginally
suitable whereas about 0.7 % was restricted for irrigation developments. The estimated total
annual available surface runoff water is 111.56Mm3/yr can irrigate 20,931ha,26163.2ha,29652ha
by surface, sprinkler, drip irrigation method respectively. Therefore, the findings of this study are
crucial to planners, decision-makers, community, and NGOs in order to develop the land and
water resource for irrigated agriculture that would enhance crop production and ensure food
security.
