Estimation of the impact of irrigation water abstraction on the Utengule swamp

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
University of Dar es Salaam
This study was carried out aiming at estimating the irrigation water requirement in the upstream catchments of the Utengule swamp in an attempt to analyze the contribution of the irrigation practice in reducing the total inflow in to the Mtera reservoir. The Utengule swamp is located up stream of the Mtera reservoir, which is the main source of power supply for Tanzania. To effect this, sixty-two small holders and large-scale irrigation schemes were identified. Irrigation water requirement for the identified schemes was estimated using the FAO computer programme, CROPWAT, assuming the crop growing in the whole irrigation field is rice. Eleven gauged river systems supplying water for the irrigation schemes were identified. The total inflow to the Utengule swamp was then estimated by correcting the gauged flow for irrigation water abstractions. Comparison was carried out between the amount of total inflow to the swamp with and without irrigation. The comparison indicated that the irrigation water abstracted was insignificant contributing to the reduction of the total inflow to the swamp. Even though, it was insignificant when compared with the total inflow, the monthly distribution of irrigation water abstraction showed considerable influence in the months November and December. The frequency of failure of each gauged river system to meet the corresponding estimated irrigation water demand was also analyzed and it was found that 80 % of the rivers failed to meet the requirement in the months November and December. Two out of 10 rivers do not fail in the whole of the irrigation season and only one river failed for all of the irrigation season. Finally the total inflow to the swamp and the outflow from the swamp, controlled at the gauging station 1 ka27, were also compared and it was found that only 114th of the total inflow was coming out as an outflow. The major reason for this small outflow was the considerable water lost from the swamp area by evaporation. The assumptions made and lack of sufficient data in the study could have made the results biased. So some of the possible solutions are included in the recommendation part of this study report.
Available in print form, EAF collection, Dr. Wilbert Chagula Library, class mark THS EAF TC 809.T34.B6 (1999 )
Irrigation, Utengule swamp, Runoff
Bogale, M.A ( 1999 ) Estimation of the impact of irrigation water abstraction on the Utengule swamp ,Masters dissertation, University of Dar es Salaam, Dar es Salaam.