Hydrology of Small Scale Irrigation Project

  Ebissa G. K

Despite the huge potential of the area, existing traditional farming practice is not in harmony with the needs and requirements of developing a productive and sustainable agriculture in Ethiopia. The food security situation has continued to deteriorate because of various factors including shortage of rain fall, high population growth, deforestation, soil degradation, pest out break and other related factors are threatening food security situation of the area. Although the initiation of farmer’s traditional spate irrigation practice is appreciated, it is not in a position to provide sustainable supply source and effective utilization of water. Therefore, the development of Gondoro SSIP diversion irrigation is expected to contribute towards alleviating these problems thereby increasing food supply and income source to the community and also at local and regional levels This work on Gondoro small scale irrigation project consists of genuine work on the design of hydrology for the irrigation scheme for 80 hectares of land, which will be effectual through diversion of Gondoro River. This study includes back ground information and hydrologic design of the project within brief introduction. Hydrologic design is important for safety, economy and proper functioning of hydraulic structures. The proposed of hydrologic design is to estimate maximum, average or minimum flood which the structure is expected to handle. This estimate has to be made quite accurately in order that the project can function properly. Hydrological analysis has been conducted based on 23 years maximum daily rainfall data. The frequency analysis has been carried out by different statistical distributions methods. The most commonly distributions used to fit extreme rainfall events are: 2 parameter log normal, 3 parameter log normal, Pearson type III, log Pearson type III and Gumbel’s extreme value type I. All the candidate distributions has been tested by three different types of goodness of fit tests that give almost identical statically correlation coefficients. However, the standard Chi-squared errors and Kolmogorov Smirnov errors are significantly lower for the general extreme value distribution. Hence, this distribution has been selected as the best fit for this study. There is no gauging station on the Gondoro River or nearby river of similar catchment characteristics. Thus, it is preferred to base the flood analysis on rainfall data, which are better both in quantity and quality of data. The Gondoro river base flow was measured by using the floating method since the flow is very small to utilize other methods. In general, three types of estimating flood magnitudes (namely: the rational method, SCS method and gauged data method) can be applied for ungauged catchments. Since, the catchment area of Gondoro diversion scheme is 10.5km2, the SCS method is preferred. The SCS hydrograph method is selected for the analysis of the rainfall runoff hydrograph and computation of the design flood. The design discharge for the diversion weir corresponding to a return period of 50 years comes out as 33.5m3/s.

Keywords- Hydrology, Gondoro SSIP, Frequency analysis, SCS Method, Design Discharge

Unique Identification Number - IJEDR1702194
Page Number(s) - 1176-1198
Pubished in - Volume 5 | Issue 2 | May 2017
DOI (Digital Object Identifier) -   
Publisher - IJEDR (ISSN - 2321-9939)

  Ebissa G. K,   "Hydrology of Small Scale Irrigation Project", International Journal of Engineering Development and Research (IJEDR), ISSN:2321-9939, Volume.5, Issue 2, pp.1176-1198, May 2017, Available at :http://www.ijedr.org/papers/IJEDR1702194.pdf