Assessment of the Performance of Gezira Irrigation Scheme, Sudan

Abstract

The objective of this study was to assess the performance of the Gezira Irrigation Scheme, Sudan. To assess the performance, water supply indicators (Overall consumed ratio, relative water supply, relative irrigation supply, water delivery capacity and water delivery performance); cropping intensity; land productivity indicators; output indicators (Output per cropped area, output per command area and output per unit irrigation supply) and economical indicators (water productivity, relative water cost and benefit cost ratio) have been used. For this purpose, relevant secondary hydrological data, land and crops data and information for the period from 1970/71 to 2008/09 were collected from Ministry of Irrigation and Water Resources and Sudan Gezira Board. Ten-day average meteorological data for the period 1971-2000 and the average monthly meteorological data for period 1989-2008 for Wad Medani station were collected from Ministry of Science and Technology-Meteorological Authority. CROPWAT 8.0 software was used for estimation of crop water requirement and irrigation water requirement and the performance indicates methods were employed to determine the selected indicators. The water supply indicators such as seasonal overall consumed ratio during the seasons 1989/90-2008/09 ranged from 0.3 to 0.8, seasonal relative water supply values during the seasons 1970/71-2008/09 ranged from 1.1 to 2.7 and seasonal relative irrigation supply during the seasons 1970/71-2008/09 ranged from 0.8 to 2.0. These results indicate that the water supply vary from adequate to excessive compare to estimated demand. The water deliver capacity during seasons 1970/71-2008/09 values varied between 0.7 and 2.4 and the seasonal water delivery performance during seasons 1999/2000-2008/09 ranged from 0.71 to 0.91showing that the water is not a constraint in the scheme level but issues of effective management. The cropping intensity during season 1970/71-2008/09 ranged from 35% to 86%. The main crops grown by the scheme are sorghum, wheat, groundnutland productivity obtained from farmer's fields is due to many factors such us delay of sowing date and lack of fund for operation and maintenance and excess water supply. During the season 1995/96-2003/04, the output per cropped area of cotton ranged from 205.5 US$ per hectare to 700.618 US$ per hectare, wheat between 31.776 US$ per hectare to 625.251 US$ per hectare, groundnuts between 11.13 US$ per hectare and 145.25 US$ per hectare and sorghum between 21.85 US$ per hectare and 493.82 US$ per hectare. The output per command area ranged from per 51.3 US$ per hectare to 285.9 US$ per hectare and the output per unit irrigation supply ranged 7.7 US$/1000 m3 to 37.9 US$/1000 m3• The water productivity for sorghum ranged between 0.1 to 0.35 kg/m3, wheat ranged between 0.06 to 0.29 kg/m3, groundnuts ranged from 0.06 to 0.34 kg/m3 and cotton ranged between 0.07 to 0.17 kg/m3. The water productivity was low compared to international standard which is ranged between 0.20 to 2.5 kg/m3• The low level of water productivity was due to lack of proper water management and hence excessive water losses and low inputs. The economical indicators used were Relative water cost (RWC) and Benefit cost ratio (B/C). During the seasons 1991/92-2006/07 the RWC value varied from 0.03 to 0.07. The upper limit indicates uneconomical production. The benefit-cost ratio during the seasons 1970/71-2008/09 ranged between 0.01 and 2.0. The Gezira Scheme was moved towards the lower side of the range indicate no improvement in the economical production due to low profitability. Improving the performance of the scheme can be attained through proper planning of agricultural seasons by adoption of scientific methods for estimation of crop water requirement such as F AO methodology, insure adequacy of water supply, operation water service, increase soil fertility by proper application of fertilizers for cotton and wheat and growing of a legume crop, establish sustainable finance policy for water pricing and introduce a performance assessment program for monitoring the operation services.