Areal Nonpoint Source Watershed Environment Response Simulation

ANSWERS is a distributed parameter, event-oriented, non-point source pollution planning model developed to evaluate the effects of BMPs on surface runoff and sediment loss from agricultural watersheds. QUESTIONS is an affiliated model that provides an option to integrate ANSWERS with GIS.

Virginia Tech
Model Information
For more information about this model, go to
Spatial Resolution
The watershed is subdivided into uniform grid cells. Each cell is assumed to have uniform properties and land use metrics. Typically a cell is 0.4-1 hectares in area.
Temporal Resolution
The time step is 30 seconds for storm simulations and daily otherwise.
Output includes time series predictions of runoff and nutrient loads for the simulated weather events.
Intended User
Model Type
Inclusion of Climate Change
Climate conditions are not explicitly incorporated. Manipulation of weather data inputs would be the best way, but this is difficult if using QUESTIONS.
Geographic Region
Data Requirements
some data sets built in
Source Code Availability
open source
Computational Burden
Scenario Modeling
batch mode likely
Coding Language
FORTRAN, GUI, visual basic
Operating System
not applicable
Mathematical Approach
deterministic, simulation, situational
Maintenance Plan
not supported
Date of Last Known Update
User Manual
Documentation link not available