Assessing the performance of an irrigation scheme in Okyereko, Ghana

Abstract

Assessing the performance of an irrigation scheme is an important management function which will indicate the state of the scheme and suggest possible remedial measures to improve the effectiveness of the scheme. This study was conducted to assess the technical and agricultural performances of the Okyereko irrigation scheme in the Central Region of Ghana. Secondary data were collected from the scheme with respect to rainfall, yield for the period of 2011 to 2015 seasons whilst field measurements were carried out to determine the water supply and demand. This study assessed three technical performance indicators and two agricultural performance indicators during the 2014/2015 season. The V-notch and the rectangular weir were used to measure the water delivery and the Manning formula was used to calculate the flow-rates in canals. Water requirements were estimated using the modified Penman method. The results from this study indicated an overall scheme conveyance efficiency of 78.2%, a maximum dependability of irrigation intervals between water applications of 2 and a scheme relative irrigation supply of 1.38. The agricultural performance indicators, output per unit irrigation supply and water productivity per unit crop evapotranspiration (ET), were found to be 0.90 and 20.53 kgm-3, respectively for rice. This study recommends that farmers should be actively involved in all performance assessments and scheme organizations in order to improve the performance since the farmers are major stakeholders of irrigation schemes and are responsible for operation and maintenance after the introduction of Participatory Irrigation Management.