RIVER BASIN SEQUENTIAL WATER USE AND SALINITY EFFECTS ON CROP YIELD ECONOMICS.

摘要

The increasing use of water for irrigation, industry and municipal water supplies has led to an increasing need for careful planning for the usable water resources. Skilled planning and careful management are essential to achieve the level of efficiency in water use desired. Efficient use of water in a dynamic system such as a river basin, implies that the physical and economic systems be described with sufficient accuracy to quantitatively predict the system-wide effects of depletions and/or additions resulting from water use anywhere in the system.; An economic simulation model is combined with an existing hydrologic and salinity model (BSAMS) in order to predict management effects of sequential water use in a River Basin. The hydrologic, salinity and economic systems are closely interrelated in any water resource project. Comprehensive planning is difficult if the three systems are analyzed independently; hence, it is advantageous to incorporate all three systems into a single working model, now called the Sequential Use Model. This model uses functions which relate seasonal crop evapotranspiration and soil solution salt concentration to yields. In essence, the output from the hydrologic (seasonal evapotranspiration) and salinity (soil solution salt concentration) models become inputs into the economic model, which predicts the net return to the given hydrologic and salinity conditions.; The sequential use model is applied to an actual hydrologic unit, the Hadejia River Basin in Nigeria to demonstrate its applicability to management and planning problems. The model provides a means of determining the relative efficiency of water use with respect to production or net returns for several management alternatives. The marginal values of water can be evaluated for all alternative uses or cropping schemes and the most profitable can then be selected.