Some aspects of the design and operation of water management systems

Abstract

This study deals with the design of water management systems. Attention is focused on that phase in the design process in which variants are developed and evaluated with emphasis on the evaluation. The proposed evaluation procedure combines an economic evaluation with an evaluation of the hydraulic qualities- The economic evaluation implicates the determination of the internal rate of return but reduces to the determination of the net present value of the cost if no agricultural production level can be defined- The evaluation of the hydraulic qualities involves the steady and non-steady design criteria for various land uses or for various return periods. The evaluation is presented in a balance sheet where the economic evaluation can be balanced against the degree to which the design fulfils the design criteria. This enables the designer to develop various variants while evaluating. An example of the application of the procedure is given- In search of a method to determine a nominal agricultural production level which is related to the water management scenario, a model was developed where all aspects related to crop yield were included on the condition that nutrient supply is optimal. All aspects include workability, crop development, harvest conditions etc. This model makes it possible to quantify the effect of different water management scenarios on crop yield. Two examples are presented where the model is applied