Land use changes are altering the hydrologic system and have potentially large impacts on water resources. In recent years, water scarcity and irrational utilization have become the pivotal threats for sustainable development of catchments. The aim of optimal water resources management is to reallocate the limited water resources rationally among different water use sectors. This has to be based on fair, effective and sustainable principles through measures such as restraining water demand reasonably, increasing water supply effectively, and protecting the ecological environment positively. Land use and land cover are considered in a historical as well as current perspective to determine the types of activities that have occurred in the watershed and their potential as sources of pollution. It is important to consider the natural and cultural resources of the watershed as well as the human activities. The knowledge of the determining factors dynamics of water resources is made through the interdisciplinary approach in small basins or at plot scale. The data acquisition through experimental field or remote sensing allows a better understanding of the genetic mechanisms. A good knowledge of the impact of land use and land cover on water resources can be made based on the assessment of extended data series. The most known and used techniques for assessing the impact of land use are hydrological models.