Determining wastewater contributions and the spatial distribution of these flows throughout the network model is a key element of sewer collection system modeling. Models are loaded with existing and future flows (existing and future developments), depending on the type of analysis to be performed. All collection features, sewer trunks and available storage within the system are supporting elements that provide flow routing of these system loads. The variation of load during the course of a day must also be accounted for during a kinematic or dynamic wave analysis.

Temporal characteristics, typically represented by their respective diurnal variations (hydrographs), are also required. Generally, the sewer loading factors are first estimated for all loading categories. The temporal effects of sewage flows are then adjusted based on individual sewer production categories. A spatial intersection is then performed to geographically allocate these generated flows to the appropriate sewer manholes, thereby defining system loading. A load factor calculator is then used to modify load factors to match a known treatment plant inflow, thus completing the allocation process. H₂OMAP SWMM DWF Allocator was developed to assist stormwater and wastewater engineers to greatly improve, simplify and fully automate the process of generating and allocating sanitary loadings for existing system conditions and for various planning horizons.

H₂OMAP SWMM DWF Allocator

An indispensable master planning tool, H₂OMAP SWMM DWF Allocator gives you seven highly advanced and efficient geospatial methods for processing geometric polygons to accurately compute and load network models based on load type, location, and variation:

• Geocoded meter billing data (meter consumption database)
  
• Polygon Intersection - spatial intersection of multiple polygon layers
  
• Polygon Extraction - spatial summation of load category area polygon
  
• Closest (Nearest) Junction Method
  
• Closest (Nearest) Conduit Method
  
• Meter - Junction Allocation
  
• Meter - Conduit Allocation

The first method makes use of GIS layers to automatically geocode sewer loadings. The wastewater load at each junction is determined by identifying and summing all the flow data within its associated sanitary service area polygon. In the second method, sewer loadings are automatically calculated based upon a direct spatial intersection between wastewater load categorization polygons (e.g., land use and population polygons) and the sanitary service area polygons (also know as sewersheds or service basins). In the third method, junction loadings are generated by summing the individually assigned load category polygons. Both fourth and fifth methods work in conjunction with geocoded billing/meter data. The fourth method locates the junction closest to each billing meter by using efficient search algorithms and then allocates manhole loadings.

In the fifth method, search algorithms are used to locate the closest sewer conduit to each geocoded meter location. Loads are then assigned to the nearest manhole on either side of the conduit or divided based on a distance-weighted approach.

The meter-junction and the meter-conduit allocation methods allow the user the freedom to graphically determine which meters are tributary to which junctions and conduits in the sewer collection system.

Within a true GIS environment, H₂OMAP SWMM DWF Allocator also allows you to create, edit, manipulate, and manage all your GIS polygons and their associated data with incredible ease and astounding speed. These comprehensive capabilities will let you effectively utilize your engineering knowledge and experience and leverage your existing GIS data investments to strategically define/forecast your combined or sanitary sewer network flows for various planning horizons in your master planning effort.

Automated Service Area/Boundary Polygons

A complete GIS application software, H₂OMAP SWMM DWF Allocator also allows you to automatically create, edit, manipulate, move, and manage all your GIS polygons and their associated data with incredible ease and speed. A very powerful and efficient Thiessen polygon generation capability is provided that lets you automatically create a distinct service area polygon (contributing area) for any or all manholes. Thiessen polygons provide a means to divide an area into polygons by creating regions that bisect known points. These polygons typically signify the bounded region closest to each of the manholes.

Considerable flexibility (four useful and practical methods) is also provided for defining the boundary of the Thiessen polygons to ensure accurate representation of the sewer loads generated throughout the collection system.

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Application Dependent - H₂OMAP SWMM Suite.