After a general introduction and descriptions of how irrigation water is carried to the fields, we review problems with the management of Nile water for irrigation in the Gezira Scheme, Central Sudan. Subsequently the methodologies used in an on-farm experiment are described. From the results of a questionnaire, the farmers' present irrigation practices are discussed. Field data show that unattended, day and night, continuous flow irrigation of sorghum (dura) and groundnuts uses more water, and particularly so in drier years, than attended daytime watering (and night-time storage). This is mainly due to greater evaporation from water standing on the surface, because percolation is negligible. In this case study, in the order of 20-40% of used water was wasted on-farm. It is deduced that farmers evolved their present practice of watering groundnuts and sorghum out of the sheer necessity of engaging sharecroppers who themselves have to leave irrigation unattended because of their own need for additional off-farm income. Finally, some conclusions and recommendations are derived for a dialogue between authorities and tenants on more efficient water use. The new situation of tenants as “cost-sharing partners” could lead to better watering practices if they would pay for the water they use by volume and if the authorities would carry out maintenance to the full satisfaction of the tenants.

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Flooding in Bangladesh has considerable economic and sociological impacts. For this reason a map showing consistent and easily accessible flood level information would benefit the development of flood management programs which involve flood warning, flood zoning, flood proofing, and flood protection. Flood levels in Bangladesh are affected by many factors, which give rise to considerable joint probability problems when estimating extreme events. An approach which overcomes these difficulties is to generate contours of flood levels for particular exceedance probabilities using the time series of historical annual maximum water level data. This has been performed across Bangladesh and has resulted in the preparation of a flood level probability map.
Water level data have been analyzed from 266 stations, and a total of 131 out of the 266 stations examined were found to be stationary and independent. The average length of the data samples was 29 years. Stations that had less than 15 years of data were not included in the analysis.
Six different probability distributions were fitted against the annual maximum water level data at selected stations for comparison purposes. The results indicated that the Generalized Extreme Value distribution was the best among the six distributions. As a result the Generalized Extreme Value distribution has been adopted to develop the flood level probability map. At most of the gauging sites the Generalized Extreme Value distribution indicated the presence of an upper bound in the extreme flood levels.

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The Takaoka groundwater basin of Tosa city, Kochi Prefecture, Japan, is threatened by overdraft. An optimization model is presented for optimal operation of the Takaoka groundwater system during critical periods (dry periods). Using the available data and a previously developed finite-element simulation model, a linear programming (LP) model was formulated. Based on the modeling results, optimal pumping schedules and groundwater contour maps resulting from the optimal pumpage are presented for two prospective operating scenarios, A and B. Optimal pumping schedules differed significantly under the two scenarios, and groundwater levels improved appreciably under Scenario A. The results of Scenario B indicated that in the absence of any remedial measures in the Takaoka basin, the dry period pumpage at the existing wells should not exceed the suggested optimal pumpage. On the whole, in order to ensure long-term and sustainable utilization of the Takaoka groundwater resource, the most attractive operation policy seems to be one in which the excess groundwater pumped from most productive wells is transported to meet local water demands in the less productive areas of the basin.

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Recently, the impact of agriculture on the environment has been extensively discussed. For paddy farming, the conservation of irrigation water quality is one of the prerequisite conditions. Paddy fields themselves have a responsibility not to pollute public water bodies. In this study, the water quality environment in the Muda area of Malaysia was analyzed in comparison with a Japanese paddy field area through data collection and supplementary field survey. The results of water quality monitoring and studies conducted so far tell that the water quality environment in the Muda area does not have significant problems for irrigation purpose. The present paddy farming system including water management is basically contributing to water quality conservation. But some efforts to search for sustainable paddy farming are still desirable. Good management of paddy fields is essential for not only food production but also conservation of water quality and ecosystem.

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