A feature of the kinetics used is that carbon (and the denitrified nitrogen) is lost rather quickly in the aquifer travel path, after which carbon limitation stops denitrification altogether. Time-of-travel loss calculations for percent of nonpond load that originated within the area of < 2 yr aquifer residence time are 64% when carbon is not limiting, but only 49% when carbon limitation is included, not greatly different from the constant-loss method. The time-of-travel loss method calculates loss rates based on aquifer travel times and denitrification reaction kinetics, evaluated separately for carbon-unlimited and carbon-limited cases. The constant-loss method, which assumes that all similar land uses have the same per unit area loading rate to surface water regardless of location within the watershed, predicts that 42% of the nonpond watershed nitrogen load originated within the zero to 2 yr time-of-travel zone, which is 40% of the contributing area. For the nitrogen load not intercepted by ponds, we compare two steady-state methods of analyzing nitrogen loss in the aquifer, one using a constant-loss factor and the other time-dependent loss rates. Approximately 10% of the total nitrogen load to the embayment is intercepted by fresh water ponds and delivered to the coast by connecting streams. This tecnologic development can be very useful in the management of information associated with numerical models.Įffects of aquifer travel time on nitrogen reaction and loading to Popponesset Bay, a eutrophic coastal embayment on western Cape Cod, Massachusetts, are evaluated through hydrologic analysis of flow and transport. The advantages of this module is that it will be open source, in order to make the flow model it will no longer be necessary to make format conversions required by both software, therefore making the modeling processes more efficient. The module we seek to create intends to integrate MODFLOW with GRASS GIS through a graphic interface, which will allow data stored in GRASS to be input parameters for the flow models used by MODFLOW. MODFLOW is written in FORTRAN and is freely accessible. Additionally we used the open source software MODFLOW, which solves the groundwater flow equations using a finite difference method, which makes use of a mesh (grid). This project seeks to develop an open source software that makes use of two tools that are available on the web, first the open source software Geographic Resources Analysis Support System (GRASS) GIS, that by means of Geographical Information Systems (GIS) is able to create, manipulate and display maps of georeferenced data, with the advantage that the data is in square gridded plane or space. Generally, systems that describe groundwater flow, do not allow analitical solution, so the methods used to solve these equations are of numeric nature, so it is necessary to use computational tools. To understand the behavior of a groundwater flow system it is necessary to know the equations that describe it, as well as the variables needed to solve it. 2 Description of Sample Problem Used in Examples. 2 Creating Geographic Information System Output Using Modtools.
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