Watershed attributes that are considered to describe nutrient input conditions are included as source variables in the regression equation; the nutrient-source variables to be tested in the SPARROW model for the SAGT area include atmospheric deposition, fertilizer application to farmland, manure from livestock production, permitted wastewater discharge, and land cover. Watershed attributes that are considered to affect rates of nutrient transport from land to water are included in the regression equation as land-to-water transport variables; the nutrient-transport variables to be tested in the SAGT SPARROW model include characteristics of soil, landform, and climate. Channel attributes considered as nutrient transport variables in the SAGT SPARROW model include reach time of travel and reservoir hydraulic loading. Datasets with estimates of each of these attributes for each individual reach or catchment in the reach-catchment network are presented in this report.
The dataset "mrb2_erf1" represents the stream network that was used to define the stream network within the SAGT SPARROW model area. The dataset Enhanced River Reach File 2.0 (erf1_2) was used as the source of the network, and was refined by splitting reaches where additional water quality stations were located for use in the SAGT SPARROW model.
The "mrb2_erf1" dataset is the foundation for the SPARROW model. It defines the flow pathways and the network for estimating loads and transport within the study area.
The ERF1_2 reach set was further enhanced for the SAGT nutrient SPARROW model by inserting 433 segment boundaries, which was accomplished by splitting 433 reaches into two segments each. The locations of the added boundaries, and thus of the added model computation nodes, correspond with the locations of sites where mean annual nutrient load could be estimated from monitoring data. Methods similar to those used by Brakebill and others (2001) for the Chesapeake Bay SPARROW model were used to create the additional reach segments: (1) load estimation sites were identified on the ERF1_2 stream network; (2) for sites located in the middle of a stream reach, the reach was split at that location; and (3) a unique node and reach was added to the upstream portion of the split reach. The segments added to the ERF1_2 through this procedure were assigned values between 65,747 and 66,462 for the unique reach identifier (the attribute "wshed").
The item WSHED was added as the unique identifier for reaches. If they
were split, the new value started at 65040 So all new arcs should be between 65040 and
80000.
STAID was used to tag the upstream section of an arc with the Station id
of the point coverage.
A frequency is run to check this. Other checks are done in
the z:\gis\elevations\100mgrid\run_agree.aml when catchments are created.
calc lrchtot = .00003797 * length / meanv /* converts TOT to days
additem STAID to the NAT - needed for SPARROW model
Arc Attribute Table, MRB2_ERF1.AAT:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
1 FNODE# 4 5 B -
5 TNODE# 4 5 B -
9 LPOLY# 4 5 B -
13 RPOLY# 4 5 B -
17 LENGTH 8 18 F 5
25 MRB2_ERF1# 4 5 B -
29 MRB2_ERF1-ID 4 5 B -
33 HUC 8 8 C -
41 SEG 3 3 I -
44 LEV 2 2 I -
46 PNAME 30 30 C -
76 OWNAME 30 30 C -
106 STAID 15 15 C -
121 FRAC 4 12 F 5
125 STRAHLER 4 5 B -
129 STATE1 2 2 I -
135 DEMIAREA 4 9 F 2
139 WSHED 4 5 B -
143 MRB_ID 6 6 I -
** REDEFINED ITEMS **
33 RR 11 11 C -
33 HUC2 2 2 I -
33 HUC4 4 4 I -
33 HUC6 6 6 I -
106 SITEID 8 8 C -
Item Name Description
FNODE# Internal number of the from node.
TNODE# Internal number of the to node.
LPOLY# Internal number of the left polygon, always zero.
RPOLY# Internal number of the right polygon, always zero.
LENGTH Reach length in meters.
HUC 8-digit Hydrologic cataloging unit of the reach.
SEG The 3-digit segment number.
LEV The stream level used for hierarchical relationships,
defined in RF1.
PNAME Name of the reach defined in RF1.
OWNAME Open-water name defined in RF1.
STAID USGS station identification number where water-quality
data was collected, assigned to the split reach.
FRAC Fractional diversion of load for reaches that share
to-nodes.
STRAHLER Strahler stream order of the reach.
STATE1 State FIPS (Federal Information Processing Standard)
code 1.
DEMIAREA Incremental drainage area for a given reach, in square
kilometers. This value is used in the SPARROW model.
May not be equal to the SQKM field because the
DEMIAREA may be manually adjusted to reflect know
drainage area values that do not match the calculated
values from the GIS analysis.
WSHED Unique identifier for each reach used in the
SPARROW model
MRB_ID Unique identifier for each reach used in the National
SPARROW model - reaches that were edited to split and
add stations have been differentiated by multiplied
the WSHED id by 10.
RR "River Reach" identifier. Key to RF1.
HUC2 2-digit Hydrologic region of the reach.
HUC4 4-digit Hydrologic subregion of the reach.
HUC6 6-digit Hydrologic accounting unit of the reach.
SITEID 8-character sampling site identification number (see
STAID).
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Generated by mp version 2.8.12 on Mon Aug 10 11:08:55 2009