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5.4.3 Recent State-of-the Art GIS–Integrated Watershed
Modeling Systems
Recently, efforts have been made to bring several models under the
same framework using GIS interfaces that pre- and postprocess data
for several models through the use of a single graphical user interface
(GUI). Examples of such attempts are the USEPA Better Assessment
Science Integrating Point and Nonpoint Sources (BASINS) (USEPA,
2008) modeling system, WMS, developed by Brigham Young Univer-
sity (Environmental Modeling Systems, Inc. 2007), and AGWA, devel-
oped by the USDA Agricultural Research Services (ARS) Southwest
Watershed Research Center in cooperation with the USEPA Office of
Research and Development.

BASINS
According to the USEPA, “BASINS is a multipurpose environmental
analysis system for use by regional, state, and local agencies in per-
forming watershed- and water-quality–based studies” (USEPA 2008).
The system was designed to address three objectives:
1. To facilitate examination of environmental information,
2. To support analysis of environmental systems, and
3. To provide a framework for examining management
alternatives.
The primary goal of the BASINS system was to support develop-
ment of TMDLs required by Section 303(d) of the CWA. Because
traditional approaches to watershed-based assessments involve
many separate steps for data preparation, developing maps and
tables, and applying and interpreting models, and result in a lack of
integration, coordination, and time-intensive execution, BASINS
was designed to bring key data and analytical components “under
one roof” (USEPA 2008).
BASINS bring together a suite of interrelated components for per-
forming various aspects of environmental analysis (Fig. 5.2). Compo-
nents include (1) nationally derived databases with Data Extraction
tools and Project Builders, (2) assessment tools (TARGET, ASSESS,
and Data Mining) that address large- and small-scale characterization
needs, (3) utilities to facilitate organizing and evaluating data, (4) tools
for Watershed Delineation, (5) utilities for classifying DEMs, land use,
soils, and water quality observations, (6) Watershed Characterization
Reports that facilitate compilation and output of information on
selected watersheds, (7) an in-stream water quality model (QUAL2E),
(8) two watershed loading and transport models (HSPF and SWAT),
and (9) PLOAD, a simplified GIS-based model that estimates NPS
loads of pollution on an annual average basis.