Real-time IGW-NET Help
Server Lake Options
This interface is used to choose which size (order) lakes to import from the MAGNET Data Center, and to assign attributes to the imported features. Lakes are imported as head-dependent flux features.
Lake Orders
Lake orders are used to classify streams by size, ranging from "small" to "very large". Check the box next to each order to import it using this tool. When modeling at large scales (e.g., an entire watershed or basin), the impacts of "small", "middle", and "large" lakes is typically small, so the default setting in IGW-NET is to only import "very large" lakes.
The "Great Lakes" option is for important one or more of the North American Great Lakes. The "River Polygon" option can be used to import river/streams as polygons (zones) - a very useful feature at small scales (e.g., local or site-scale).
Size Category Based Attributes
This is the first (default) option for assigning attributes to the imported lakes. The lookup table allows for assigning the following properties based on the size (total area) or percentage (relative-area) of the imported feature:
• Leakance - leakage rate per unit area per unit head difference across the sediment, or the ratio: (riverbed sediment conductivity / riverbed sediment thickness) [units of L/T, e.g., m/day].
• Two-way One-way - option to define the lakes as a i) one-way head-dependent boundary condition (aquifer loss as surface seepage only); or ii) two-way flux boundary condition (water or enters or leaves the aquifer depending on the head gradient.
• Depth - average lake depth [units of L, e.g., m].
• Lake Name - the conceptual feature name assigned to all lakes of the order. The flux into and out of the model is grouped according to these different orders when displaying water-balance information.
The 'Percentile' option is available so the user may divide the lake polygons on the basis of relative-area. For relative size, 10% represents the polygons whose area exceeds 10% or less of all of the lake polygons in the model (these are the smallest polygons). Conversely, 100% represents the polygons with the largest area.
Constant Attributes
You can assign the same attributes to all lakes orders by choosing the radio button next to 'Constant'. Be default, all orders are given a leakance of 5 1/d, but you can use the provided text field to update this. You can also define a bottom elevation calculated as the lake stage minus some value (default: 3.3m) by checking the box next to 'Bottom=Stage-'.
Other assumptions are made when using this option. For example, the rivers are assumes to be a two-way head-depedent boundary condition, a depth and width is assumed, and the Order / Alias Name is assumed to be Stream.
TopE as Stage/Drain Bottom
By default, the lakes stages are extracted from the Top Elevation (TopE) data, or the Digital Elevation Model (DEM) (hence, the checked box next to 'TopE as Stage/Drain Bottom). This is also the case when modeling the streams/rivers as a one-way drain (surface seep).
To assign different stage values, consider drawing a lake feature, or using the 'Zone from a shapefile' tool (Conceptual Model Tools > Zones > Zones from a Shapfile).