Engineering Methods

This section describes engineering object methods that involve more than one object. The methods for each object are also described in Simulation Objects.

Spatial, Temporal, and Incremental Flow Disaggregation

New methods were added to the reservoirs, Control Point, and Computational Subbasins to allow the user to disaggregate flows spatially, temporally, and incrementally as follows.

Spatial disaggregation methods

Two approaches were added to allow flows to be spatially disaggregated throughout a subbasin. The WAM Precipitation Curve Number method uses the Water Availability Model (WAM) method to disaggregate known flows spatially throughout a computational subbasin. It uses the NRCS curve number, mean precipitation, and drainage area along with the known flow at a “gage” control point to calculate the unknown local inflows (Distributed Flow) at all other control points in the subbasin. For more information see WAM Precipitation Curve Number in Objects and Methods. The Drainage Area method disaggregates known flows spatially throughout a computational subbasin based on drainage area. For more information see Drainage Area in Objects and Methods.

Specified Factors temporal disaggregation method

The Specified Factors temporal disaggregation method takes the Distributed Flow (typically a monthly value in a daily timestep model--though this is user configurable) and temporally disaggregates it to be the same timestep size as the run control. The method multiplies the Distributed Flow by a Temporal Disaggregation Factor to obtain the Temporally Disaggregated Flow. For more information see Specified Factors in Objects and Methods.

Calculate Incremental Local Inflows category

In certain basins, local inflow data is input into the model as cumulative values, that is, the local inflows for a given control point or reservoir includes all of the upstream local inflows including water entering upstream objects. Because RiverWare must have distributed data, methods were added to compute incremental local inflows from cumulative local inflow data. Computation of incremental local inflows has two variations to it: with and without forecasting. In the simple case, forecasting is not necessary and the incremental local inflows can be calculated at the beginning of run for all timesteps in that run. In the more complex case, cumulative inflows are forecasted throughout the forecast period, then the forecasted incremental flows are calculated. This forecasting occurs at the beginning of each timestep. To facilitate these two variations, categories and methods were added to the Computational Subbasin, Control Points, Reservoirs, and Confluences.

Users will first need to set up one computational subbasin for each group of control points and reservoirs that contain cumulative local inflow data. The computational subbasin(s) must include all control points and reservoirs containing the cumulative local inflow data as well as all the intervening reaches and confluences. Each control point and reach should only be included in one computational subbasin.

For each computational subbasin, select a method from the Compute Incremental Local Inflows category. This enables the Reservoir Boundary for Incrementals category. If cumulative local inflow data is only cumulative until a reservoir is reached, select the Stop at Reservoirs method. Otherwise, select the Continue Through Reservoirs method if cumulative data continues through reservoirs, or Ignore Reservoirs if there is no cumulative data on reservoirs.

For each control point and reservoir in the computational subbasin several new methods must be selected. In RiverWare, local inflows are called “Local Inflows” on Control Points and “Hydrologic Inflows” on Reservoirs. In this discussion, we will use the terminology Local Inflows exclusively; please substitute Hydrologic Inflows anywhere a reservoir is referenced. First, Select either the Input Local Inflows or Forecast Local Inflows from the Local Inflow Calculation category. Next, select a method from the Calculate Incremental Local Inflows on Subbasin category. Depending on the Local Inflow Calculation, you can either select to calculate incrementals for the Full Run or calculate incrementals and forecast throughout the Forecast Period. For more information, see Incremental Local Inflows in Objects and Methods.

Revised: 08/02/2021