Gezira Scheme (GS) is the largest irrigation scheme in Sudan covering an area of about 2.2 million feddan (0.9 Million ha). The scheme has huge irrigation and drainage networks. Due to different reasons, many of the drains run all throughout the year. Villagers and farmers are often use such an excess water (return flow) for tradition farming
and other domestic uses. The water coming from the drain is expected to carry some chemical residuals (pesticides, herbicides and fertilizers) which deteriorates the water quality and hence endangers drinking uses and lead to health hazards.
This study aims to monitor the spread and evaluate the hazard of the chemical residuals resulting from agricultural practices in GS along Wad Matar drain, as one of the largest collective drains in the scheme.
The drain starting from K99 (Al Basatna Irrigation Section) and ending at AlMaseed with a total length of about 154 km and around 30 villages are scattered along the drain.
Eleven locations, distributed along the drain, were selected as monitoring stations. Samples are taken on a monthly bases covering the summer season of the year 2016 (July – October). The monitored chemical parameters are; Electrical conductivity (EC), Total Dissolved Solids (TDS), Turbidity, pH, Total Hardness (TH), Alkalinity, Salinity, Nitrate, Phosphate, Chloride, Copper, Iron, Ammonia, Ammonium and Sulphate.
The sample analysis was carried out at the soil mechanics and water quality laboratory of the Hydraulics Research Center. The analysis reveals that, for most of the monitor stations, the levels of dispersed Sulphate, Nitrate, Hardness, Ammonia and Salinity are within the WHO standard range, whereas PH, TDS, Turbidity, Alkalinity, Copper, Ammonium, Iron, Chloride and Phosphate are beyond the WHO ranges. This indicates that there is a noticeable hazard in the use of agricultural drainage water, particularly in the Gezira scheme, and especially for domestic use.