Frank Braunschweig

Modelling the influence of nutrient loads on Portuguese estuaries

The effects of implementing Directive 91/271/EEC of 21 May 1991 (Waste Water Treatment Plan Directive) and Directive 91/676/EEC of 12 December (Nitrates Directive) are analysed in 7 Portuguese estuaries (Minho, Lima, Douro, Mondego, Tagus, Sado and Guadiana) and two coastal lagoons (Ria de Aveiro and Ria Formosa), with a modelling approach. MOHID Water Modelling System was used to perform simulations with three nitrogen load scenarios for each system: a reference scenario, a 50% nitrate removal by agriculture scenario and another with a 100% nutrients removal by waste water treatment plants (WWTP). It is shown that the interaction between hydrodynamic and ecological processes is an important feature to study trophic problems in estuaries. Ecological processes such as primary production only occur inside the system if the residence time of water is high enough to enable organismal activity and if the adequate conditions are found (e.g. light, nutrients, temperature). From the model results it is possible to conclude: (i) in systems with short residence time a reduction in nutrient load will only produce a decrease in nutrient transit and will not affect the system’s global ecological status (e.g. Douro Estuary); (ii) in systems with long residence time the effects will range from significant, when primary production is mostly limited by nutrients (e.g. Ria de Aveiro), to non-significant, when primary production in the system is light-limited (e.g. Tagus Estuary).

An advanced modelling tool for simulating complex river systems

The present paper describes MOHID River Network (MRN), a 1D hydrodynamic model for river networks as part of MOHID Water Modelling System, which is a modular system for the simulation of water bodies (hydrodynamics and water constituents). MRN is capable of simulating water quality in the aquatic and benthic phase and its development was especially focused on the reproduction of processes occurring in temporary river networks (flush events, pools formation, and transmission losses). Further, unlike many other models, it allows the quantification of settled materials at the channel bed also over periods when the river falls dry. These features are very important to secure mass conservation in highly varying flows of temporary rivers. The water quality models existing in MOHID are base on well-known ecological models, such as WASP and ERSEM, the latter allowing explicit parameterization of C, N, P, Si, and O cycles. MRN can be coupled to the basin model, MOHID Land, with computes runoff and porous media transport, allowing for the dynamic exchange of water and materials between the river and surroundings, or it can be used as a standalone model, receiving discharges at any specified nodes (ASCII files of time series with arbitrary time step). These features account for spatial gradients in precipitation which can be significant in Mediterranean-like basins. An interface has been already developed for SWAT basin model.

MOHID 2000 - A coastal integrated object oriented model

Mathematical modeling, although a recent science, can be considered old when the time scale used to measure its age is the information technology evolution. FORTRAN 77 has been the most popular programming language among hydrodynamic modelers over the last two decades. This language was adequate to the (low) complexity of the models, limited by the exiting computers. The fast increase of the computing capacity allowed the development of more complex and multidisciplinary models. The necessity of new programming techniques became clear. It was started the era of the Object Oriented programming. Object Oriented programming isolates different parts of the code and allows communication among them using simple and robust interfaces. MOHID 2000 is an integrated modeling tool programmed in FORTRAN 95, using an Object Oriented strategy. It is the evolution of a set of models originally programmed in FORTRAN 77. Taking advantage of the new language possibilities, with a single code it is possible to perform different simulations (1D, 2D or 3D) and use a variety of vertical discretizations. This technique has also turned easy to integrate hydrodynamic, water quality, sediment transport and pollutants dispersion simulations using eulerian or lagrangian formulations. Having in mind the development of a tool accessible to the final user, the modeler must think about on the algorithms and code, but also on pre and post processing of the model data. MOHID 2000 input data files can be constructed by a graphical user interface. Output files use the standard HDF format making results exploring simple and allows the use of different graphic packages.

The object-oriented design of the integrated water modelling system MOHID

With increasing computer power, the modelling tools for water resources, nowadays, not only integrate physical-based transport models with biogeochemical process models, but also couple surface water body models, groundwater models and hydrographic basin models. This paper describes how the MOHID Water Modelling System achieves the mentioned integration using object-oriented programming in FORTRAN 95. After a short historical overview of MOHIDs evolution, this paper focuses on the object-oriented design of the water modelling system MOHID and the way how object-oriented features are implemented in FORTRAN 95. Attention is also given to the way how the numerical software code interacts with the graphical user interface. It follows an exemplification of how the object-oriented design is useful for implementing complex system for two cases: the operational model of the Tagus Estuary and the coupling of the Trancao Basin model to the Tagus Estuary model.

AUTOMATED SYSTEM FOR NEAR-REAL TIME PREDICTION OF OIL SPILLS FROM EU SATELLITE-BASED DETECTION SERVICE

ABSTRACT 2017-244: The state-of-the-art in both operational oceanography, remote sensing, and computational capacity, enables now the possibility of developing near-real time, holistic automated se...

Dynamic Risk Assessment of Shoreline Contamination from Ships: Integrating an Oil Spill Model

Latest scientific and technological developments on coastal monitoring and operational oceanography have provided the opportunity of building complex and integrative decision support systems for co...