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Sediment and water management are key issues in irrigation schemes that suffer from accumulation of sediment along canals. This accumulation creates problems with adequate water supply and may lead to water shortage. The aim of this study was to analyse improvement options for operation and maintenance in order to achieve better sediment and water management in irrigation canals. A model has been developed to simulate cohesive sediment transport in irrigation canals. The model is a useful tool to predict cohesive sediment deposition under different operation and maintenance scenarios. It has been calibrated and validated by using field data of the Gezira Scheme in Sudan and has been applied for different options of operation. The best operation scenario was found when the scheme was operated based on the crop water requirement during the period of high sediment concentration. When the inflow was reduced by 51% during this period in 2011, the reduction in deposition was 48%. Such types of adaptation will significantly reduce deposition and improve sediment and water management in irrigation canals. Copyright © 2016 John Wiley & Sons, Ltd.

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This scientific article aims to summarize the most important measurements of the quality of water for use in irrigation of various crops. The goal is to help professionals and researchers in the soil, water and environment field in the selection of appropriate alternatives to face potential problems that may occur because the use of low quality water in irrigation, which may adversely affect the characteristics of the soil and thus reduce productivity and quality of crops cultivated .The most important measurements, which are summarized in this article includes measurements of salinity risk, measurements the risks of both of soil sodicity and alkalinity ,soil permeability for water quality and the specific hazards of some toxic ions. Water class for Salinity Irrigation Water Salinity Remarks Class Description EC,(dS m-1) TDS,(ppm) C1 Low Salinity < 0.25 < 200 Used for irrigation for most crops on most soils. Some leaching required under normal irrigation practices, but excess irrigation is required in extremely low permeability soil. C2 Medium Salinity 0.25-0.75 200-500 Can be used if a moderate amount of leaching occurs. Plants with moderate salt tolerance can be grown in most instances without special practices for salinity control. C3 High Salinity 0.75-2.25 500-1500 Can't be used on soil with restricted drainage. Even with adequate drainage, special management for salinity control may be required and plants with good salt tolerance should be selected. C4 Very high Salinity > 2.25 > 1500 Not suitable for irrigation under ordinary conditions but may be used occasionally under very special circumstances .The soils must be permeable , drainage must be adequate , irrigation water must be applied in excess to provide considerable leaching , and very salt-tolerant crops should be selected. Table 2. Potential of irrigation problems based on salinity values Degree of problem Units Potential of Irrigation Problem Severe Slight to Moderate None > 3.0 0.7-3.0 < 0.7 dS/m ECw > 2000 450-2000 < 450 mg/l TDS Salt Index Researches indicated that the safety limits permitted (accepted safe limit) to salinity in irrigation water is 600 mg kg-1. When water containing salts in the range of 600 to 1200 mg.kg-1 , it is necessary to appreciated saltiness guide (Salt Index). Also, this assessment is used to predict the risk of sodic. It is defined with the relationship between mono-valent sodium ions (Total Na +) and divalent calcium ions in CaCO 3 (Total Ca 2+), which found in irrigation and the estimated, as ppm i.e., mg. l-1 and can be calculated by using the following formula for Singh (2005) : Salt index = [(Total Na +-24.5)-(total Ca 2+ in CaCO 3)] x 4.85 Water quality for irrigation according to the obtained value could be evaluated as: •Negative value, mean good water quality for use in irrigation.