No abstract

The principal aim of this research is to solve problems of water-budget estimation in particularly indeterminate conditions, of the kind that are frequently encountered in the field, in which absence or insufficiency of hydrographic instrumentation prevents the adequate evaluation of runoff.To do this we have developed techniques that are based on the method of Kennessey (1930), in which the runoff coefficient of a watershed in estimated using three physiographic variables (slope angle, permeability, and vegetation cover) and a parameter that defines the climatic conditions of the local area. Our comparison of the Kennessey method with instrumental records from a wide variety of instrumented drainage basins in central Italy shows that the method provides reliable estimates of runoff. Our analysis also indicates the best criteria for its application, as shown by the examples and results presented in this article.This research enables us to present a new application of the method, namely the runoff coefficient map, which, in addition to its specific usefulness for the evaluation of runoff, has three advantages. First, it supplies a more realistic vision of the local distribution of runoff/rainfall ratios; second, it allows one to overcome the spatial constraints imposed by the narrow frame of reference represented by the watershed; and third, it makes an important contribution to the solution of other hydrogeological problems, such as the evaluation of the amount of water required for adequate recharge of the intake areas of deep aquifers or the maintenance of geothermal processes.Hence we propose this mapping technique as a valuable practical aid to regional hydrogeologic planning.The calculation of water-budgets usually precedes any form of applied hydrogeological study, as it enables the researcher to obtain a good estimate of the water resources of a particular area. The spatial frame of reference that is normally used in such analyses is the drainage basin, but it is always necessary to ascertain whether the surface water catchment coincides with the underlying groundwater basin if reliable estimates are to be obtained.The various parameters of the water-budget are usually determined from data recorded by suitably located instruments, and, in particular, runoff is calculated by integrating the discharges measured at the basin outflow point. However, even in well-instrumented regions, the density of measuring stations is often very limited, especially that of water-level recorders, which makes it extremely difficult to assess the water resources of an individual catchment accurately and still more difficult to appraise the contribution derived from portions of it, especially regarding the estimation of surface runoff.To overcome these difficulties, various more or less empirical indirect methods have been proposed to calculate the values of runoff. However, such methods have so far yielded only modest results, above all owing to the difficulties of singling out and evaluating, quantitatively and in their just p...

Hydrogeological research is in progress, utilizing GIS methods, with the principal aim of modelling the Olocenic alluvial aquifer of the River Cornia coastal plain (southern Tuscany, Italy), which has been exploited for drinking water, irrigation, and industrial uses. A consequence of exploitation has been the appearance of wide seawater intrusion. The alluvial aquifer has recently been subjected to new well fields for the supply of drinking water, with an increase of total average discharge of about 4!10 6 m 3 /year. This paper presents results obtained from updating and integrating basic knowledge and structuring the database. The hydrogeological study allowed the recognition of the extension of areas that are characterized by a hydraulic head under the sea level, the progressive salinization of the aquifer, and the increase of water deficit in the aquifer which is produced by a progressive extraction of water superior to the natural recharge. In addition, benefits and disadvantages resulting from the location of new well fields in a hydrogeologically favourable zone, and the boundary conditions for much of the area studied have been defined. The GIS was used as support for making and updating the tabular and spatial database with the aim of integrating the local and regional hydrogeological knowledge. This study will permit the realization of a numerical simulation of the groundwater flow of the aquifer aimed at correcting the management of water resources, by means of the GIS-modelling integration.

Dopo una breve introduzione sulle origini del termalismo e delle risorse\ud geotermiche nella Toscana Meridionale, si analizzano alcune situazioni idrogeologiche nelle quali è evidente il rapporto tra acqua termale e non e depositi di travertini in Provincia di Siena.\ud (1) Acquifero carbonatico di Pian del Casone (Colle di Val d’Elsa). E’ questo un esempio di acquifero contenuto in depositi carbonatici originati da acque fredde. Si riportano i risultati di ricerche sull’acquifero ospitato nei depositi pliocenici e pleistocenici delle zona di Colle di Val d’Elsa, dove emerge anche la sorgente termale “Caldane di S. Marziale”. Vi si analizzano\ud i rapporti idrodinamici e idrochimici esistenti tra il reticolo idrografico, rappresentato dal F. Elsa e dai suoi affluenti, e le locali acque sotterranee superficiali e profonde.\ud (2) Acquifero e termalismo a Rapolano Terme. Trattasi di un acquifero\ud ospitato all’interno di depositi di travertino; si illustrano i risultati di una ricerca finalizzata all’individuazione ed allo sfruttamento non elettrico\ud dell’acqua a media e bassa temperatura nella parte centro-settentrionale della Provincia di Siena. In essa sono stati analizzati i problemi relativi ai rapporti fra le acque termali di origine profonda e quelle di una falda freatica presente nei travertini affioranti nell’area di Rapolano Terme

The management of water resources, especially drinking water, is no longer the responsibility of single municipal councils or groups of councils because European Union, national and regional legislation created and appointed authorities and bodies for this purpose. Faced with a strategic problem such as the management of water resources, local government in Tuscany has the task of defining planning strategies in line with Regional law no. 65/2014. This study is part of research aimed at defining water management at province level in the framework of regional planning. The study area includes the whole Province of Siena, where we evaluated surface- and ground- water resources, during preparation of the land management plan (territorial coordination plan) of the province, with special attention to aquifers that the Regional government considers significant (Relevant Groundwater Bodies and therefore strategic for the Province. We compared the groundwater resources with the overall demand for water in the Province in order to assess the sustainability of activities determining that demand; we also evaluated the danger level and risk of contamination, defining the corresponding vulnerabilities for the whole Province. The vulnerabilities were matched with a series of rules aimed at regulating land use so as to minimise the risk of polluting groundwater.