Note: This page is no longer being maintained and is kept for archival purposes only.
For current information see our main page.
GWI Kurtz-Fernhout Software
Developers of custom software and educational simulations.
Home ... News ... Products ... Download ... Order ... Support ... Consulting ... Company
Garden with Insight
Product area
Help System
Quick start

Garden with Insight v1.0 Help: Phosphorus - Soluble P Loss in Surface Runoff

The EPIC approach is based on the concept of partitioning phosphorus into the solution and sediment phases as described by Leonard and Wauchope (Knisel, 1980). Because P is mostly associated with the sediment phase, the soluble P runoff equation can be expressed in the simple form [Equation 204] where YSP is the soluble P in kg/ha lost in runoff volume Q in mm, C(LP) is the concentration of AP in soil layer l in g/t, and k(d) is the P concentration of the sediment divided by that of water in m3/t. The value of k(d) used in EPIC is 175.

Equation 204

YSP = 0.01 * C(LP) * Q / k(d)
the equation used for runoff and percolation of P is very diffferent
in the code. This equation computes not kg/ha of P leached, but the
concentration of soluble p in the leached water. The equation is
meanPConcDuringWaterFlow_gPm3 = AP * min(0.75, Q / SW) / Q where
Q is runoff + percolation for the first layer, or percolation for others
This is then multiplied by runoff or percolation to get kg/ha.
YSP = SolublePLostInRunoffForLayer_kgPha
C(LP) = labilePConcForLayer_gPt
Q = runoffVolume_mm
k(d) = kPhosInSedimentOverWater_m3Pt = 175.0

Home ... News ... Products ... Download ... Order ... Support ... Consulting ... Company
Updated: May 4, 1998. Questions/comments on site to
Copyright © 1998 Paul D. Fernhout & Cynthia F. Kurtz.