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, to assign attributes to the imported features, and to control the display settings (lake order color and polyline thickness). Lakes are imported as head-dependent flux features.

Data Source

There are two processed datasetes available for lake import:
1) USA NHDplus - National Hydrography Dataset Plus High Resolution for the United States (including Hawaii, Peurto Rico, and portions of Alaska). Invalid lake polygon geometries have been fixed in the processed dataset. Link to USGS site.
2) Global Hydroshed - HydroLAKES shoreline polygons of all global (US and elsewhere) lakes with a surface area of at least 10 ha. HydroLAKES has been developed using a suite of auxiliary data sources of lake polygons and gridded lake surface areas. Again, invalid stream geometries have been fixed in the processed dataset. Link to HydroSHEDS site.

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).

Drawing Options (Conceptual vs. Server-based)

Users can control the line color and and line thickness (pixel size) of any of the lake orders imported into the model.

Note that the number of lakes being imported into the model impacts how they are displayed. If the number of lakes is less than the threshold (currently 8,000 ), the lakes are treated as 'conceptual zone features' and are automatically shown in the display, using the current set of drawing options (color, line thickness), when the user adds the conceptual image (CnptImage) overlay:
Other Tools > Utilities > Overlay CnptImage > Overlay

If the user updates the color and/or thickness of one or more orders when lakes are treated as conceptual zone features, the model must be re-run before the updated settings are available in the display.

If the number of stream segments is greater than the threshold, then they are treated as 'server lakes' and will only be shown in the disply then the user selects the suboptions from the CnptImage menu:
Other Tools > Utilities > Overlay CnptImage > check 'Server Lakes' box

If the user updates the color and/or thickness of one or more orders when streams are treated as server lakes, the model does not have to be re-run before the updated settings are available in the display; simply make the changes in this interface, and then uncheck and check the 'Server Lakes' option in the Overlay CnptImage menu.

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).