| Water as natural resource in conditions adapted for the terrestrial ecosystems and the human activities is more and more scarce, which is origin of increasing tensions between the different social groups. The present-day capability of the human to modify the hydrologic cycle significantly adds to this scarcity, as much of quantitative form as of qualitative form, reason why the natural resource can be seen decreased, once again, of important form by the human activities.;Water quality in the superficial and groundwater bodies, depends on the natural characteristics of the river basin and human affections that take place in the same one, and it is a determinant aspect of the health of the aquatic ecosystems and the human activities that can be developed in a territory.;At the moment, a crucial step to be able to determine the situation of water bodies and its foreseeable future evolution consists of suitably knowing the hydrologic cycle in its terrestrial stage and as it affect human activities to it. Because the degradation of the quality of water generates negative external effects in the environment and finally, in all the human activities that they can have a very high impact, the European society, conscious of this situation, establishes by means of the Directive 60/2000/CE Frame of Waters (WFD) (EC, 2000) the development of a analysis process and performances to improve the state of all the European water bodies in 2015. One of the steps of this process is the "Analysis of Pressures and Impacts", in which one tries to identify the pressures that exercise the human activities and at the same time to relate them to the impacts that take place in the water bodies, so that the necessary measures can be established that greater effectiveness must to reduce the impacts of the human activities.;In this doctoral thesis it has developed a module or tool for the mathematical modeling of the hydrologic cycle and the quality of water to large basins, dedicating especial attention to the underground component and relations river-aquifer. The object of this module consist of being able to do simulation models that allow to know water flows, with their chemical characteristics, that take place in a hydrographic river basin. The module PATRICAL allows to construct spacely distributed models of the hydrologic cycle, getting the water flows that are produced in the different points from the river basin and piezometric levels in the aquifers, in addition includes the simulation of the nitrate contents and of the electrical conductivity of water in the soil, in means non saturated, in the aquifers and in surface waters bodies.;Besides, in this doctoral thesis has been defined a methodology of gradual application for the accomplishment pressures and impacts analysis established in the WFD, in order to simulation models that they are constructed with this tool they allow to make the most complex phase of pressures and impacts analysis, and also it will be able with them to quantify the effect of the measures that are defined in the future.;The practical utility of the tool and developed methodology is demonstrated with the application that have been made, the construction of a simulation model of a large basin, the Jucar River District of over 42,000 km 2, obtaining water flows that are produced in the same one and concentration values of nitrate and electrical conductivity in the superficial and underground water bodies. These results allow to identify the agents that cause chemical conditions modifications in the different points from the river basin, and in addition to know the historical evolution and the tendency towards the future. |
