ABSTRACT

Drainage-boards and polder districts in the Netherlands try to fulfil the agricultural demands with respect to water management by manipulating water levels in open water conduits. To get a more scientific basis for optimal manipulation, a case study has been carried out. In the framework of this study a model has been developed to simulate different alternatives of manipulating surface water levels. In this way the hydrological effects of maintaining high surface water levels during summer and of water supply for subsurface irrigation are obtained. By converting the hydrological effects in additional crop production, benefits and costs, the internal rate of return of projects for water conservation and water supply are calculated.