Page 200 - Biosystems Engineering

178 Cha pte r F i v e

surfaces and in streams and well-mixed impoundments. It is incorpo-
rated into the Better Assessment Science Integrating Point and Non-
point Sources (BASINS) and Watershed Modeling System (WMS)
modeling systems (described later) and is extensively used for TMDL
studies. The model contains hundreds of process algorithms devel-
oped from theory, laboratory experiments, and empirical relations
from instrumented watersheds. There are three basic modules: Pervi-
ous Land Segment Module (PERLND), a watershed loading model
for pervious surfaces; Impervious Land Segment Module (IMPLND),
a watershed loading model for impervious surfaces; and, the Reach/
Reservoir Routing Module (RCHRES), a one-dimensional receiving
water model for simulating in-stream transport and transformation
processes. HSPF is based on the Stanford Watershed Model, Agricul-
tural Runoff Management (ARM), and Non-Point Source (NPS) models.
HSPF uses simple storage-based equations for flow routing. Flows in
streams are one dimensional. HSPF is one of the few comprehensive
models of watershed hydrology and water quality that allows for
integrated simulation of land and soil contaminant runoff processes
with in-stream hydraulic and sediment–chemical interactions. HSPF
uses continuous rainfall and other meteorologic input parameters to
compute streamflow hydrographs and pollutographs. HSPF simu-
lates interception, soil moisture, surface runoff, interflow, baseflow,
snowpack depth and water content, snowmelt, ET, groundwater
recharge, dissolved oxygen, biochemical oxygen demand, tempera-
ture, pesticides, conservatives, fecal coliforms, sediment detachment
and transport, sediment routing by particle size, channel routing, res-
ervoir routing, constituent routing, pH, ammonia, nitrite-nitrate,
organic N, orthophosphate, organic P, phytoplankton, and zooplank-
ton. HSPF can simulate one or many pervious or impervious unit
areas discharging to one or many river reaches or reservoirs. Frequency-
duration analysis can be done for any time series. Time steps from
1 minute to 1 day, divided equally within 1 day can be used. Time period
of simulation can be from few minutes to hundreds of years. HSPF is
generally used to assess the effects of land-use change, reservoir
operations, point or NPS treatment alternatives, flow diversions, etc.
A number of programs are available for pre- and postprocessing of
data for statistical and graphical analysis of data saved to the Water-
shed Data Management (WDM) file. The most famous application of
the HSPF model is the Chesapeake Bay Project.
KINEROS-2
KINEROS-2, an improved version of KINEROS (Woolhiser et al. 1990)
model, is an event-based model because it lacks a true soil moisture
redistribution formulation for long rainfall interval. Also, it does not
consider ET losses. The model is primarily useful for predicting sur-
face runoff and erosion for a rainfall event over small agricultural and
urban watersheds. Smith et al. (1995) suggest using a watershed size