INVESTIGATION AND DESIGN ANALYSIS OF ZAMRA RIVER DIVERSION AND SHILANAT CASCADE MICRO EARTH DAMS (SOUTH TIGRAY)

Abstract

Tigray region is improving its food production by undertaking a region-wide small dams construction program, which is intended for this purpose. As well, diversion weirs are being executed in large scale. Because of a lack of River flow data and design manuals, significant portion of the River diversion works and micro earth dams are not functioning to their designed capacity and surprisingly some of the River works have been poorly located. The specific location of study area is found in Alaje and Hintalo-Wejerat Woreda extended from Adigura to Hiwane town, which is bounded by latitude 12° 58'N and 13° 04'N and longitudes 39° 27'E and 39° 34'E. The main objective of this study is thus to investigate the current status and design analysis particularly for Zamra River • diversion and Shilanat cascade earth dam system. Accordingly, to evaluate the current situation of the project thorough field investigation was i(:onducted and necessary primary and secondary data were • collected for further analysis of this paper. As the size of the watershed is the most important factor in the determination of I design discharge; of the diversion structure, catchment delineation with . AVSWAT2000 model was carried out and hence, the design discharge (114.m 3 /sec) was determined using SCS technique. According to the work plan designed in the proposal, hydraulic, hydrologic, geologic and morphologic characteristics of Zamra diversion structure were adequately investigated and evaluated. Dam constructions in the region were intensively undertaken for the last ten years; yet most of them are not performing for their intended design efficiency. Of these Shilanat cascade dam is the one that has big critical problems and performing under low efficiency. Hence, to identify the problem behind, its hydraulic, structural, hydrological, environmental related to reservoir sedimentation and social conditions were intensively carried out. In the investigation and evaluation process, significant problems were identified and finally based on these problems possible remedial measures were recommended. 1