jueves, 31 de mayo de 2012
Time, space, water in soils and geomatics
The understanding of the interconnections among land use-land cover and water storage in soils it is of paramount importance due to hydrologic implications to different levels. Natural Water production either as underground water storage or direct overland flow is concerned with management and risk, particularly in regions with extreme climatic conditions as the Mediterranean. Also, the impact of land use-cover changes on the water regime is also seen as one of the major actors related to environmental and climatic changes.
The problem has, at least, a four dimension perspective: the vertical combination of factors, at short time the temporal (historical) evolution of the human activities expressed as the uses that cover the land, and finally the two dimensions of the water cycle components distributed on the territory. Thus, whatever approach dealing with the study of distributed impacts of changes in land cover on the water regime of soils needs to develop a modeling approach that will have to combine information from different sources and nature, with a minimum set of climatic, land cover (vegetation) and edaphic data.
Also, despite of level of sophistication applied to the model that is developed the programming has sort out the temporal dimension that can give some light in the evolution of the soil covers and its possible impacts on soils hydrology. The time line is also related to the use of climatic data (normally a representative time series of rainfall and temperature values) and some land cover scenarios that can expand from decades two centuries.
Many spatial software of general use (any recognize GIS) can be programmed to perform a spatial and temporal analysis of such characteristics. It is almost compulsory to develop a programming strategy to guaranty results in an efficient manner and to allow the recursive use of the model as many times as it is needed.
One such example is the methodology developed to in a work that study impact of land cover changes on the water content of soils during the last half of the 20th century in Eastern Spain, a region that has experience a dramatic change in socio-economic activities since 1950. Results show the general decrease of water storage capacity of soils due to agricultural intensification and, most important, soil imperviousness by artificial covers extension (what is known as anthropogenic soil sealing). Also, the work (actually a PhD thesis that can be downloaded from the University of Valencia digital repository at: http://tdx.cat/bitstream/handle/10803/9947/pascual.pdf?sequence=1) provides with all the batch routines developed with IDRISI GIS that made possible to run the model efficiently.