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Introduction
The NGMS is a scenario analysis tool to assess and visualize the impacts of abstractions on the groundwater resources and the surface water flows.
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Based on the scenario definition, the NGMS executes a sequence of data processing steps to preprocess the input to the groundwater model, to run the model and to postprocess the data. The output can be presented in time series graphs, accretion profiles or spatial plots. The system automatically computes differences for comparison of two scenarios (i.e the difference between two default scenarios, or the difference between a modified scenario and its default equivalent).
Since NGMS has been implemented using DelftFEWS-software, it relies upon some of the underlying FEWS-concepts. The conceptual merge of the NGMS outline with FEWS is discussed in a seperate page. A step-by-step configuration guide has been developed to assist the uploading of nwe models on the system.
Scenario types
Within her working and legislative procedures, the Environment Agency distinguishes a few types of scenarios. These types are also used within NGMS. The so-called 'default' scenarios are the scenarios/model runs that are pre-defined and approved by the Environment Agency. The so-called 'modified scenarios' are the what-ifs where input has been manuipulated via the NGMS.
Default scenarios
- Calibrated Historic - refref(Historic)
This default scenario/run refers to the pre-defined model run which has been calibrated for a historic period, using historic abstractions data.
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For each of the abovementioned scenarios, the following data processing steps are typically conducted:
- (adapt input files)
- run Modflow
- import Modflow results
- derived tributary inflows
- interpolate regular grids to points, sparse grids and longitudinal profiles
- compare runs
NGMS-FEWS terminology
whatif-scenario
Within the NGMS-software, a scenario or what-if scenario basically refers to the specification of the adjustment (if any) of the model data.
Runs
Within NGMS, a run (alias task run or forecast) refers to the output of a workflow (i.e. set of data processing activities), given a specific initial state (starting condition) and a scenario (to modify the input if needed).
Workflows
A workflow is the set of activities related to the pre-processing, running and post-processing of a model.
Within NGMS, various workflows are distinguished as not all runs require that all activities are executed.
E.g. a default run, such as the Calibrated Historic, or Naturalized run, just involves the execution of Modflow, with a set of input files, and the associated post-processing.
However, to run a modified scenario, some additional pre-processing activities are needed - to modify the Modflow input files - before the Modflow executable can be started.
The combination of data processing steps associated to a run, i.e. preprocessing, model execution, and postprocessing, is called a workflow. A run is identified by its workflow as well its scenario
Within the NGMS the following workflows are identified:
- _import
- _default_scenarios
- _ref(Naturalized)
- _ref(Historic)
- _ref(RecentActual)
- _ref(FullyLicenced)
Data processing steps
The typical composition of a workflow is:
- run Modflow
- derived tributary inflows
- interpolate regular grids to points, sparse grids and longitudinal profiles
- compare runs