**CALIFORNIA RANGELAND**

[]{.mark}

This scenario has been parameterized to represent pesticide application
on non-irrigated rangeland in Central California. The area of interest
(AOI) is primarily Alameda, Contra Costa, Solano, Sonoma, and Santa
Clara Counties. The AOI was selected based on the large extent of
rangeland and high degree of pesticide usage (Figure 1). Based on 2005
California pesticide use reporting (CalPIP, 2006), approximately 40% of
total product pounds applied to rangelands were applied in the AOI.
These counties also accounted for approximately 43% of the total
combined acres treated for all pesticides reported.

![](media/image1.png){width="3.513888888888889in"
height="2.5125in"}Rangeland in California is extensive; approximately
one-third (7.2 million acres) of all privately held lands in California
are grazed by livestock (Richards and George, 1996). Rangelands can be
grouped into three broad categories: dry annual grasslands, annual
grassland/hardwood range, and coastal prairies (Bartalome, 2002). Annual
grasslands are dominated by annual grasses and receive less than 12
inches of rainfall per year. Annual grassland/hardwood ranges consist of
annual understory grasses, with variable oak and shrub canopy receiving
12-40 inches annual rainfall. Coastal prairies have perennial grasses
with variable overstory and variable rainfall. Many of the rangelands
present today were cleared in the 1950's to 1970's to reduce competition
between hardwood species, such as oaks, and understory forage grasses.
Since the 1980's the benefits of tree canopy to provide wildlife habitat
has been realized and conservation/regeneration of oak hardwood
rangelands has been promoted in rangeland management (IHRMP, 2005).
Rangeland in Central California is generally not irrigated (M. Doran,
personal communication). However, pastureland in some areas is
irrigated. Irrigated pasture is an important source of forage for beef
cattle, sheep, horses and dairies. Herbaceous vegetation is generally
dominated by cool season grasses (ryegrass, orchard grass, tall fescue)
and cool season legumes (ladino clover, strawberry clover, trefoil).
Cool season irrigated pasture are most productive in the spring and
early summer. Hot weather dampens production as the summer progresses
(George et al., 1992). This scenario is not intended to represent
irrigated pastureland and application of this scenario to represent
irrigated pasture should be evaluated on a case by case basis. In
addition, although some range lands contain a significant amount of tree
cover, this scenario was parameterized to represent open rangeland in
order to model a more conservative field.

Because rangelands occur throughout the state of California (Figure 1),
there are over 250 soils listed as supporting irrigated and/or
non-irrigated pasture (used here as a surrogate for rangeland production
in order to identify representative soils). Soil selection was targeted
at the AOI, where the highest pesticide usage has been reported (CalPIP,
2006). Within the AOI, there are approximately 42 soils listed as
supporting irrigated and/or non-irrigated pasture (used as a surrogate
described above) (Table 5). Among these, Gaviota is the most common
*pastureland* soil; however it was not recommended as a representative
*rangeland* soil by an extension agent in the area of interest. Rather,
the agent suggested that Los Osos is a more representative soil of
rangelands. Los Osos is the second most common pasture supporting soil
in the AOI, is a hydrologic group C soil, and is among the steepest and
most erodible soils identified. Within the AOI, the Los Osos series is
located in Alameda, Contra Costa, Eastern Santa Clara, and Sonoma
Counties. The Los Osos series has a k factor ranging from 0.28 to 0.49
for pastureland supporting soils. Within the Los Osos Series, the Los
Osos and Milshom complex has the highest erodibility potential (k factor
= 0.49) but not the steepest slope on rangelands (USDA 2005). Because
rangelands are found on slopes as steep as 75%, the Los Osos Silty Clay
Loam 45-75 percent slopes, was selected on the basis that it is a more
conservative soil due to its steep slope. For pesticides that are more
influenced by sediment transport, the Los Osos and Millshom soils may be
a more conservative selection

Los Osos is a Hydrologic Group C soil. Group C soils represent roughly
41% of pasture supporting soils in the AOI (Table 5). The Los Osos
series consists of moderately deep, well drained soils that formed in
material weathered from sandstone and shale. Los Osos soils are on
uplands and have slopes of 5 to 75 percent (USDA, 2001). The soils are
well drained with very high runoff and slow permeability (USDA, 2001).
They are used mostly for range; limited areas are cropped to grain and
Sudan grass pasture. Vegetation is mostly annual grasses and forbs with
some perennial grasses, coastal sagebrush, and live oak. Los Osos soils
have an A horizon from 0 to 14 inches (0-36 cm) deep, a B horizon from
14 to 32 inches (36-81 cm) deep, and a C horizon from 32 to 49 inches
(81-124 cm) deep. Horizon B however is described as "very hard" with
very few roots and pores, therefore drainage is limited (USDA, 2001).
Los Osos Silty Clay Loam 45-75 percent slopes was used to parameterize
this scenario (USDA 2006).

The AOI lies between the meteorological stations of Sacramento and San
Francisco. The Sacramento weather station (W23232) was selected for this
scenario because it is roughly within 50 to 100 miles of the counties in
the AOI. The station receives approximately 18 inches of rainfall
annually. Approximately 60% of the rainfall occurs from January to March
(NOAA, 2006).

[Number range CHAPTER]{.mark}

+-----------------+----------+-----------------------------------------+
| **Table 1. PRZM |          |                                         |
| 3.12 Climate    |          |                                         |
| and Time        |          |                                         |
| Parameters for  |          |                                         |
| Central Coastal |          |                                         |
| California -    |          |                                         |
| Rangeland.**    |          |                                         |
+-----------------+----------+-----------------------------------------+
| **Parameter**   | *        | **Source/Comments**                     |
|                 | *Value** |                                         |
+-----------------+----------+-----------------------------------------+
| Starting Date   | Jan. 1,  | Meteorological File from Sacramento, CA |
|                 | 1961     | (W23232)                                |
+-----------------+----------+-----------------------------------------+
| Ending Date     | Dec. 31, | Meteorological File from Sacramento, CA |
|                 | 1990     | (W23232)                                |
+-----------------+----------+-----------------------------------------+
| Pan Evaporation | 0.75     | PRZM Manual Figure 5.1 (EPA 1998).      |
| Factor (PFAC)   |          | Value represents midpoint of range for  |
|                 |          | central/coastal California.             |
+-----------------+----------+-----------------------------------------+
| Snowmelt Factor | 0.0      | PRZM Manual, Table 5.1 (EPA 1998). San  |
| (SFAC)          |          | Francisco does not receive snowfall.    |
+-----------------+----------+-----------------------------------------+
| Minimum Depth   | 17.5     | Mid point of range (15-20), PRZM        |
| of              |          | Manual, Figure 5.2 (EPA 1998).          |
|                 |          |                                         |
| Evaporation     |          |                                         |
| (ANETD)         |          |                                         |
+-----------------+----------+-----------------------------------------+

[]{.mark}

  ----------------- ----------- ------------------------------------------
  **Table 2. PRZM               
  3.12 Erosion and              
  Landscape                     
  Parameters for                
  Central Coastal               
  California -                  
  Rangeland.**                  

  **Parameter**     **Value**   **Source/Comments**

  Method to         4 (MUSS)    Default value.
  Calculate Erosion             
  (ERFLAG)                      

  USLE K Factor     0.32 tons   NRCS Soil Data Mart Database, Alameda
  (USLEK)           EI^-1^\*    County, for Los Osos silty clay loam,
                                45-75% slopes.
                                (<http://soildatamart.nrcs.usda.gov/>).

  USLE LS Factor    25.6        Calculated according to Haan and Barfield
  (USLELS)                      (1978) equation: LS =
                                ((λ/72.6)^m^)((430x^2^ + 30x +
                                0.43)/6.613), where λ = slope length, x =
                                SLP/100 and m = constant. In this case, λ
                                = 400 m (default value) and m = 0.5 (EPA
                                2004).

  USLE P Factor     1           M. Doran, Livestock and Resources Advisor,
  (USLEP)                       UCCE. Rangelands are not tilled. No
                                practice factor, no contour plowing is
                                expected (EPA 2004).

  Field Area        172 ha      Area of Shipman Reservoir watershed (EPA,
  (AFIELD)                      1999)

  NRCS Hyetograph   2           PRZM Manual, Figure 5.12 (EPA, 1998).
  (IREG)                        

  Slope (SLP)       37.5 %      M. Doran, Livestock and Resources Advisor,
                                UCCE. Rangelands slopes in the AOI range
                                up to 75%

  Hydraulic Length  600 m       Shipman Reservoir (PRZM Guidance, EPA,
  (HL)                          2004)

  Irrigation Flag   0           Rangelands in the AOI are not generally
  (IRFLAG)                      irrigated (M. Doran, Livestock and
                                Resources Advisor, UCCE.)

  \* EI = 100                   
  ft-tons \* in/                
  acre\*hr                      
  ----------------- ----------- ------------------------------------------

[]{.mark}

[]{.mark}

[]{.mark}

+-----------------+----------+-----------------------------------------+
| **Table 3. PRZM |          |                                         |
| 3.12 Crop       |          |                                         |
| Parameters for  |          |                                         |
| California --   |          |                                         |
| r               |          |                                         |
| angeland/hay.** |          |                                         |
+-----------------+----------+-----------------------------------------+
| **Parameter**   | *        | **Source/Comments**                     |
|                 | *Value** |                                         |
+-----------------+----------+-----------------------------------------+
| Initial Crop    | 1        | Default value                           |
| (INICRP)        |          |                                         |
+-----------------+----------+-----------------------------------------+
| Initial Surface | 3        | 3 = Residue. Bartalome, 2002.           |
| Condition       |          | Recommends 100 to 1800 pounds residual  |
|                 |          | dry matter per acre, depending on slope |
| (ISCOND)        |          | and woody canopy cover.                 |
+-----------------+----------+-----------------------------------------+
| Number of       | 1        | Set to number of crops in simulation.   |
| Different Crops |          | Default value.                          |
| (NDC)           |          |                                         |
+-----------------+----------+-----------------------------------------+
| Number of       | 30       | Set to weather data in meteorological   |
| Cropping        |          | file Sacramento, CA (W23232)            |
| Periods (NCPDS) |          |                                         |
+-----------------+----------+-----------------------------------------+
| Maximum         | 0.2      | At their maximum growth, grasses may    |
| rainfall        |          | intercept as much as 20% of gross       |
| interception    |          | precipitation during individual storms  |
| storage of crop |          | (Dunne and Leopold, 1978).              |
| (CINTCP)        |          |                                         |
+-----------------+----------+-----------------------------------------+
| Maximum Active  | 30 cm    | M. Doran, Livestock and Resources       |
| Root Depth      |          | Advisor, UCCE.                          |
| (AMXDR)         |          |                                         |
|                 |          | Herbaceous rangeland grasses root as    |
|                 |          | deep as 30cm.                           |
+-----------------+----------+-----------------------------------------+
| Maximum Canopy  | 90%      | M. Doran, Livestock and Resources       |
| Coverage        |          | Advisor, UCCE.                          |
| (COVMAX)        |          |                                         |
|                 |          | Canopy cover for rangelands may reach   |
|                 |          | 90% at vegetation maturity.             |
+-----------------+----------+-----------------------------------------+
| Soil Surface    | 3        | 3 = Residue. Bartalome, 2002.           |
| Condition After |          | Recommends 100 to 1800 pounds residual  |
| Harvest (ICNAH) |          | dry matter per acre, depending on slope |
|                 |          | and woody canopy cover.                 |
+-----------------+----------+-----------------------------------------+
| Date of Crop    | 01/11/60 | M. Doran, Livestock and Resources       |
| Emergence       |          | Advisor, UCCE.                          |
|                 |          |                                         |
| (EMD, EMM,      |          | Plants emerge during November, reach    |
| IYREM)          |          | peak maturity in April. Grazing (i.e.,  |
|                 |          | harvest) occurs from December to May.   |
|                 |          | Emergence set to previous year to       |
|                 |          | ensure mature vegetation during first   |
|                 |          | year of simulation.                     |
+-----------------+----------+-----------------------------------------+
| Date of Crop    | 01/04/61 |                                         |
| Maturity        |          |                                         |
|                 |          |                                         |
| (MAD, MAM,      |          |                                         |
| IYRMAT)         |          |                                         |
+-----------------+----------+-----------------------------------------+
| Date of Crop    | 01/05/61 |                                         |
| Harvest         |          |                                         |
|                 |          |                                         |
| (HAD, HAM,      |          |                                         |
| IYRHAR)         |          |                                         |
+-----------------+----------+-----------------------------------------+
| Maximum Dry     | 0.0      | Not used in scenario.                   |
| Weight (WFMAX)  |          |                                         |
+-----------------+----------+-----------------------------------------+
| Maximum Canopy  | 91       | M. Doran, Livestock and Resources       |
| Height (HTMAX)  |          | Advisor, UCCE.                          |
|                 |          |                                         |
|                 |          | Rangeland grasses grow as tall as 36    |
|                 |          | inches (91 cm). This is true of         |
|                 |          | rangeland and not of irrigated pasture. |
+-----------------+----------+-----------------------------------------+
| SCS Curve       | 87, 86,  | Gleams Manual Table H-4, pasture/range, |
| Number (CN)     | 87       | non-CNT, hydrologic group C, poor       |
|                 |          | condition (USDA, 2000). No fallow       |
|                 |          | condition. Fallow set to residue value. |
+-----------------+----------+-----------------------------------------+
| Manning\'s N    | 0.110    | Sacramento Pasture, cool season         |
| Value (MNGN)    |          | (C21PCPCN). This file incorporates no   |
|                 |          | tillage and has a cover code (2)        |
|                 |          | representing first year grass, pasture  |
|                 |          | or hay crops.                           |
+-----------------+----------+-----------------------------------------+
| USLE C Factor   | 0.001    | Sacramento Pasture, cool season         |
| (USLEC)         |          | (C21PCPCN). This file incorporates no   |
|                 |          | tillage and has a cover code (2)        |
|                 |          | representing first year grass, pasture  |
|                 |          | or hay crops.                           |
+-----------------+----------+-----------------------------------------+

[]{.mark}

+---------+-------------------+---------------------------------------+
| **Table |                   |                                       |
| 4. PRZM |                   |                                       |
| 3.12    |                   |                                       |
| Los     |                   |                                       |
| Osos    |                   |                                       |
| Silty   |                   |                                       |
| Clay    |                   |                                       |
| Loam,   |                   |                                       |
| 45-75%  |                   |                                       |
| Slopes  |                   |                                       |
| Soil    |                   |                                       |
| Par     |                   |                                       |
| ameters |                   |                                       |
| for     |                   |                                       |
| Calif   |                   |                                       |
| ornia - |                   |                                       |
| range   |                   |                                       |
| land.** |                   |                                       |
+---------+-------------------+---------------------------------------+
| **Para  | **Value**         | **Source/Comments**                   |
| meter** |                   |                                       |
+---------+-------------------+---------------------------------------+
| Total   | 76 cm             | NRCS Soil Data Mart Database, Los     |
| Soil    |                   | Osos Silty Clay Loam, 45-75% Slopes.  |
| Depth   |                   | (<                                    |
| (CORED) |                   | http://soildatamart.nrcs.usda.gov/>). |
|         |                   |                                       |
|         |                   | According to extension agent (Morgan  |
|         |                   | Doran), Los Osos is a representative  |
|         |                   | soil type.                            |
|         |                   |                                       |
|         |                   | The fourth horizon was eliminated     |
|         |                   | because bedrock generally occurs at   |
|         |                   | depths from 18 to 48 inches (USDA,    |
|         |                   | 2006.                                 |
|         |                   |                                       |
|         |                   | Number range CHAPTERPRZM Scenario     |
|         |                   | Guidance (2004).                      |
|         |                   |                                       |
|         |                   | Adjusted using the relationship % OC  |
|         |                   | = % Organic Matter/1.724 (Doucette    |
|         |                   | 2000).                                |
+---------+-------------------+---------------------------------------+
| Number  | 4                 |                                       |
| of      |                   |                                       |
| H       |                   |                                       |
| orizons |                   |                                       |
| (       |                   |                                       |
| NHORIZ) |                   |                                       |
+---------+-------------------+---------------------------------------+
| Horizon | 10 cm (HORIZN =1) |                                       |
| Th      |                   |                                       |
| ickness | 10 cm (HORIZN =2) |                                       |
| (THKNS) |                   |                                       |
|         | 56 cm (HORIZN =3) |                                       |
+---------+-------------------+---------------------------------------+
| Bulk    | 1.25 g/cm3        |                                       |
| Density | (HORIZN =1)       |                                       |
| (BD)    |                   |                                       |
|         | 1.25 g/cm3        |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 1.25 g/cm3        |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Initial | 0.308 cm3/cm3     |                                       |
| Water   | (HORIZN =1)       |                                       |
| Content |                   |                                       |
| (THETO) | 0.308 cm3/cm3     |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.332 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Comp    | 0.1 cm (HORIZN    |                                       |
| artment | =1)               |                                       |
| Th      |                   |                                       |
| ickness | 5 cm (HORIZN =2)  |                                       |
| (DPN)   |                   |                                       |
|         | 4 cm (HORIZN =3)  |                                       |
+---------+-------------------+---------------------------------------+
| Field   | 0.308 cm3/cm3     |                                       |
| C       | (HORIZN =1)       |                                       |
| apacity |                   |                                       |
| (THEFC) | 0.308 cm3/cm3     |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.332 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Wilting | 0.173 cm3/cm3     |                                       |
| Point   | (HORIZN =1)       |                                       |
| (THEWP) |                   |                                       |
|         | 0.173 cm3/cm3     |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.215 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Organic | 1.16 % (HORIZN    |                                       |
| Carbon  | =1)               |                                       |
| Content |                   |                                       |
| (OC)    | 1.16 % (HORIZN    |                                       |
|         | =2)               |                                       |
|         |                   |                                       |
|         | 0.44 % (HORIZN    |                                       |
|         | =3)               |                                       |
+---------+-------------------+---------------------------------------+

[]{.mark}

[]{.mark}

  --------------------------------------------------------------------------- ------------ -------- -------------- ----------------- ---------- --------- ---------- ----------- ----------- --------- --------------- -------- --------------
  **Table 5. Pasture Bearing Soils of Alameda, Contra Costa, Solano, Sonoma,                                                                                                                                                    
  and Santa Clara Counties (California) Ranked by Area.**                                                                                                                                                                       

  **Soil**                                                                    **Total      **%      **Drainage**   **Erodibility**   **Slopes   **pH**    **OM (%)** **% Sand**  **% Silt**  **%       **Pasture                
                                                                              Acreage**    Area**                                    (%)**                                                   Clay**    (AUM)\***                

                                                                                                                                                                                                       **Irrigated**            **Non-Irr.**

  [GAVIOTA](http://ortho.ftw.nrcs.usda.gov/osd/dat/G/GAVIOTA.html)            106,351.00   17.38%   B/D            0.17-0.37         5-75       6.3-6.7   0.75       44.8-66.8   19.2-41.2   14        \-              0.75-1   

  [LOS OSOS](http://ortho.ftw.nrcs.usda.gov/osd/dat/L/LOS_OSOS.html)          104,241.00   17.04%   C              0.28-0.49         30-75      5.8-6.5   2-3        20-35.4     33.6-52     23.5-31   \-              0.75-1   

  [ALTAMONT](http://ortho.ftw.nrcs.usda.gov/osd/dat/A/ALTAMONT.html)          75,868.00    12.40%   D              0.2-0.24          3-75       7.2-7.5   1.5-2      22.1-23.3   27.9-29.2   47.5-50   12-18           1        

  [VALLECITOS](http://ortho.ftw.nrcs.usda.gov/osd/dat/V/VALLECITOS.html)      73,984.00    12.09%   D/C            0.28-0.37         15-50      6.3-6.5   1.5        41.6        37.4        21        \-              0.75     

  [LOS GATOS](http://ortho.ftw.nrcs.usda.gov/osd/dat/L/LOS_GATOS.html)        47,606.00    7.78%    C              0.24-0.37         30-75      6.1-6.7   2.5        39.8        37.7        22.5      \-              0.75-1   

  [MILLSHOLM](http://ortho.ftw.nrcs.usda.gov/osd/dat/M/MILLSHOLM.html)        31,223.00    5.10%    D              0.32-0.55         8-50       5.8-6.5   1.75-2     24.5-39.2   37.3-52     23.5      \-              1        

  [SAN YSIDRO](http://ortho.ftw.nrcs.usda.gov/osd/dat/S/SAN_YSIDRO.html)      22,229.00    3.63%    D              0.37-0.43         0-5        5.8-6.1   0.75       42.1-65.1   18.9-37.9   16-20     15              \-       

  [PESCADERO](http://ortho.ftw.nrcs.usda.gov/osd/dat/P/PESCADERO.html)        13,918.00    2.27%    D              0.2-0.28          0-2        5.6-7.3   2.5        28.1-35.4   29.4-33.6   31-42.5   \-              1.5      

  [WRIGHT](http://ortho.ftw.nrcs.usda.gov/osd/dat/W/WRIGHT.html)              13,615.00    2.23%    C              0.37              0-9        5.8       2.5        43          39.5        17.5      \-              12       

  [OMNI](http://ortho.ftw.nrcs.usda.gov/osd/dat/O/OMNI.html)                  11,468.00    1.87%    D              0.24-0.28         0-2        7.5-8.8   2.5-3.5    5.3-34.2    31.7-49.8   33.5-50   10              1.5      

  [SOLANO](http://ortho.ftw.nrcs.usda.gov/osd/dat/S/SOLANO.html)              10,589.00    1.73%    C              0.37              0-2        5.3-5.8   0.25-1.5   44.3-65.4   19.6-40.7   15        12              \-       

  [ARBUCKLE](http://ortho.ftw.nrcs.usda.gov/osd/dat/A/ARBUCKLE.html)          8,937.00     1.46%    B              0.32-0.37         0-30       6.1-6.7   0.75       43-65.9     19.1-38.5   15-18.5   12              \-       

  [COTATI](http://ortho.ftw.nrcs.usda.gov/osd/dat/C/COTATI.html)              8,612.00     1.41%    D              0.32              2-9        5.3       0.75       68.8        16.2        15        \-              12       

  [POSITAS](http://ortho.ftw.nrcs.usda.gov/osd/dat/P/POSITAS.html)            8,179.00     1.34%    D              0.37              20-40      5.8       1.35       42.1        37.9        20        \-              0.5      

  [CORNING](http://ortho.ftw.nrcs.usda.gov/osd/dat/C/CORNING.html)            7,375.00     1.21%    D              0.37              2-15       5.6       0.75       43          39.5        17.5      12              \-       

  [RED HILL](http://ortho.ftw.nrcs.usda.gov/osd/dat/R/RED_HILL.html)          7,091.00     1.16%    B              0.28              2-75       6.1       2          33.3-35.4   31.7-33.6   31-35     \-              1.5      

  [CONEJO](http://ortho.ftw.nrcs.usda.gov/osd/dat/C/CONEJO.html)              6,290.00     1.03%    C              0.2-0.24          0-5        6.7-7     2.5        35.4-39.2   33.6-37.3   23.5-31   12              \-       

  [SEBASTOPOL](http://ortho.ftw.nrcs.usda.gov/osd/dat/S/SEBASTOPOL.html)      5,921.00     0.97%    B              0.24              2-30       5         2          65.9        19.1        15        \-              12       

  [PARRISH](http://ortho.ftw.nrcs.usda.gov/osd/dat/P/PARRISH.html)            5,222.00     0.85%    C              0.24-0.32         30-50      5.8-6.1   2-3.5      35.4-39.2   33.6-37.3   23.5-31   \-              1        

  [BAYWOOD](http://ortho.ftw.nrcs.usda.gov/osd/dat/B/BAYWOOD.html)            4,840.00     0.79%    A              0.15-0.17         2-30       6.1-6.2   2.5        80.5-81.1   16.4-17     2.5       10-14           2        

  [ALO](http://ortho.ftw.nrcs.usda.gov/osd/dat/A/ALO.html)                    4,720.00     0.77%    D              0.2               30-75      6.7       2          23.3        29.2        47.5      \-              1        

  [DIABLO](http://ortho.ftw.nrcs.usda.gov/osd/dat/D/DIABLO.html)              4,631.00     0.76%    D              0.2               30-60      7-7.9     1.25-1.5   23.3-26.1   28.9-29.2   45-47.5   \-              0.75     

  [MARCUSE](http://ortho.ftw.nrcs.usda.gov/osd/dat/M/MARCUSE.html)            4,559.00     0.75%    D              0.2               0-2        8.5       0.75       22.1        27.9        50        12              \-       

  [MARVIN](http://ortho.ftw.nrcs.usda.gov/osd/dat/M/MARVIN.html)              3,115.00     0.51%    C              0.55              0-2        7.2       1.5        26.3        52.7        21        18              3        

  [LOS ROBLES](http://ortho.ftw.nrcs.usda.gov/osd/dat/L/LOS_ROBLES.html)      2,940.00     0.48%    B              0.37              0-5        7         2          35.4        33.6        31        16              \-       

  [MANZANITA](http://ortho.ftw.nrcs.usda.gov/osd/dat/M/MANZANITA.html)        2,473.00     0.40%    B              0.37              0-9        5.8       0.75       26.3        52.7        21        11              \-       

  [BOOMER](http://ortho.ftw.nrcs.usda.gov/osd/dat/B/BOOMER.html)              2,037.00     0.33%    B              0.37              2-30       6.1-6.3   2          39.8        37.7        22.5      12-14           \-       

  [ALVISO](http://ortho.ftw.nrcs.usda.gov/osd/dat/A/ALVISO.html)              1,857.00     0.30%    D              0.37              0-2        7.5       0.75       16.9        48.1        35        8               1        

  [SOBRANTE](http://ortho.ftw.nrcs.usda.gov/osd/dat/S/SOBRANTE.html)          1,779.00     0.29%    C/B            0.37-0.49         5-30       6.1-6.3   2          43          39.5        17.5      12              \-       

  [SHEDD](http://ortho.ftw.nrcs.usda.gov/osd/dat/S/SHEDD.html)                1,766.00     0.29%    C              0.43              30-45      8.2       1.5        9.1         64.9        26        \-              1        

  [VALDEZ](http://ortho.ftw.nrcs.usda.gov/osd/dat/V/VALDEZ.html)              1,587.00     0.26%    D              0.37              0-2        7.9       1.25       6.7         62.3        31        \-              1        

  [COLE](http://ortho.ftw.nrcs.usda.gov/osd/dat/C/COLE.html)                  1,466.00     0.24%    C              0.32-0.37         0-5        6.7       2.5        22.4-35.4   33.6-55.1   22.5-31   10              \-       

  [EGBERT](http://ortho.ftw.nrcs.usda.gov/osd/dat/E/EGBERT.html)              1,360.00     0.22%    D              0.24              0-2        6.5       12.5       33.3        31.7        35        12              \-       

  [DIBBLE](http://ortho.ftw.nrcs.usda.gov/osd/dat/D/DIBBLE.html)              1,090.00     0.18%    C              0.37              2-9        6.1       0.75       39.2        37.3        23.5      17              \-       

  [MILLSHOLM                                                                  766.00       0.13%    C              0.32              9-30       6.7       1.25       44.8        41.2        14        \-              1        
  VARIANT](http://ortho.ftw.nrcs.usda.gov/osd/dat/M/MILLSHOLM_VARIANT.html)                                                                                                                                                     

  [LOBITOS](http://ortho.ftw.nrcs.usda.gov/osd/dat/L/LOBITOS.html)            761.00       0.12%    C              0.28              9-45       5.3       2          41.6        37.4        21        \-              0.75     

  [AZULE](http://ortho.ftw.nrcs.usda.gov/osd/dat/A/AZULE.html)                546.00       0.09%    C              0.28              30-50      6.3-6.5   1.5        35.4        33.6        31        \-              1        

  [SAN ANDREAS](http://ortho.ftw.nrcs.usda.gov/osd/dat/S/SAN_ANDREAS.html)    441.00       0.07%    C              0.15              15-30      5.8       2.5        66.9        20.1        13        20              \-       

  [CLIMARA](http://ortho.ftw.nrcs.usda.gov/osd/dat/C/CLIMARA.html)            370.00       0.06%    D              0.2               30-50      7.5       1.5        22.1        27.9        50        \-              1        

  [BIGRIVER](http://ortho.ftw.nrcs.usda.gov/osd/dat/B/BIGRIVER.html)          29.00        0.00%    B              0.2               0-5        6.1       2          83.5        9           7.5       15              8        

  [REIFF](http://ortho.ftw.nrcs.usda.gov/osd/dat/R/REIFF.html)                2.00         0.00%    B              0.37              0-2        7         1.5        40          47          13        12              \-       

  [COOMBS](http://ortho.ftw.nrcs.usda.gov/osd/dat/C/COOMBS.html)              1.00         0.00%    B              0.37              2-5        5.6       0.75       39.2        37.3        23.5      13              \-       

  \*AUM = Animal Units Per Month. AUM equals the amount of forage necessary                                                                                                                                                     
  to feed one cow and her calf for one month                                                                                                                                                                                    
  --------------------------------------------------------------------------- ------------ -------- -------------- ----------------- ---------- --------- ---------- ----------- ----------- --------- --------------- -------- --------------

[]{.mark}

[]{.mark}

[]{.mark}

[]{.mark}

[]{.mark}

[]{.mark}

![](media/image2.png){width="5.997916666666667in"
height="4.645833333333333in"}

**Figure 1. California Hardwood and Herbaceous Areas in the AOI and 2005
Pesticide Usage (Pounds of Chemical Applied) by County.**

***Sensitive Parameter Uncertainties***

[]{.mark}

[Metfile]{.underline}

The San Francisco weather station (W23234) was selected for this
scenario because it is within roughly 50 to 100 miles of the counties in
the AOI. There are is some uncertainty with the meteorology in that
rangelands occur at a wide range of elevations through the state. Based
on the Official Soil Series Description for Los Osos soils (used for
this scenario), the soils are found at elevations of 100 to 3,500 feet
and mean annual precipitation is 14 to 40 inches (USDA, 2001). In
contrast, the majority of the California stations containing data for
PRZM at elevations below 100 meters and observe less than 25 inches of
rainfall per year. The PRZM metstation with the highest elevation in
California is in Eureka located in the Northwestern corner of the state
where little range land exists and pesticide are not frequently applied
(Figure 1). Based on this information, San Francisco is the most
conservative and representative station available.

[]{.mark}

[Crop Parameters]{.underline}

As discussed above, rangeland vegetation is a heterogeneous mixture of
trees and grasses. For the purposes of modeling, it was necessary to
select crop specific parameters (Table 3) that are representative of
rangeland plants. In order to model areas that would be more likely to
be subject to pesticide applications and susceptible to runoff, grassy
areas were selected for the conceptual model of this scenario, rather
than tree areas. This decision was necessary for the selection of
several sensitive parameters, including CN, USLEC and Manning's *n*
values.

[]{.mark}

[USLE LS Factor]{.underline}

The scenario USLELS value was calculated with the Haan and Barfield
equation (1978) using a 75% slope and an assumed 400-foot slope length,
as per PRZM scenario development guidance (EPA, 2001). LS values for
slopes longer than 300 feet or steeper than 18% are extrapolations
beyond the research data range, however, which increases uncertainty in
them. A 75% slope combined with a 400-foot slope length is so far past
the research data range that the uncertainty in the calculated value is
very great.

[]{.mark}

**Contacts**

Mr. Morgan Doran

Livestock & Natural Resources Advisor

University of California Cooperative Extension

Napa, Solano, Yolo and Sacramento Counties

501 Texas Street  

Fairfield, CA 94533

Phone: 707.784.1326

Fax: 707.429.5532

<mpdoran@ucdavis.edu>

[]{.mark}

**References**

[]{.mark}

Bartolome J.W., W.E. Frost, N.K. McDougald and J.M. Connor. 2002.
California Guidelines for Residual Dry Matter (RDM) Management on
Coastal and Foothill Annual Rangelands. Rangeland Monitoring Series,
University of California Ag and Nat Res Pub 8092. Oakland, CA. 8 p.
Available online:
[http://californiarangeland.ucdavis.edu/Publications%20pdf/8092.pdf](http://californiarangeland.ucdavis.edu/Publications pdf/8092.pdf)

CalPIP. 2006. 2005 Pesticide Usage Reporting. California Pesticide
Information Portal, CA Department of Pesticide Regulation. Accessed
December 4, 2006. Online at:
<http://calpip.cdpr.ca.gov/cfdocs/calpip/prod/main.cfm>

Dunne, T., and L. Leopold. 1978. Water in Environmental Planning. W.H.
Freeman an Company, New York. 818 pp.

Number range CHAPTEREPA. 1998. Carsel, R.F., J.C. Imhoff, P.R. Hummel,
J.M. Cheplick, and A.S. Donigian, Jr. PRZM-3, A Model for Predicting
Pesticide and Nitrogen Fate in the Crop Root and Unsaturated Soil Zones:
Users Manual for Release 3.0. National Exposure Research Laboratory,
Office of Research and Development, U.S. Environmental Protection
Agency, Athens, GA.

Number range CHAPTEREPA. 2004. Pesticide Root Zone Model (PRZM) Field
and Orchard Crop Scenarios: Guidance for Selecting Field Crop and
Orchard Scenario Input Parameters. November 15, 2001; Revisions July
2004.

George, M.R., Sands, P.B., Wilson, C.B., Ingram, R., and J.M. Connor.
1992. Irrigated warm- and cool-season grasses compared in Northern
California pastures. Cal. Agr. July-August:21-25. Available online:
[http://californiarangeland.ucdavis.edu/Publications
pdf/irrigwarmcoolgrasscompare.pdf](http://californiarangeland.ucdavis.edu/Publications pdf/irrigwarmcoolgrasscompare.pdf)

Haan, C.T. and B.J. Barfield. 1978. *Hydrology and Sedimentology of
Surface Mined Lands.* Office of Continuing Education and Extension,
College of Engineering, University of Kentucky, Lexington, Kentucky
40506. 286 p.

IHRMP. 2005. 2005 Annual Report of the Integrated Hardwood Range
Management Program. University of California, Division of Agriculture
and Natural Resources. Available online:
<http://nature.berkeley.edu/forestry/pdfs/ihrmpannualpress.pdf>

Richards, R.T. and M.R. George. 1996. Evaluating Changes in Ranch
Management Practices through Extension Education. J. Range Manage.
49:76-80.

NOAA. 2006. Climate Normals at Major Weather Observing Stations in all
50 States, Puerto Rico, and Pacific Islands. National Oceanic and
Atmospheric Administration (NOAA), Environmental Satellite, Data, and
Information Service. Online at:
[http://www1.ncdc.noaa.gov/pub/data/ccd-data](http://www1.ncdc.noaa.gov/pub/data/ccd-data/).

USDA. 2000. Knisel, W.G., and Davis, F.M., 2000, GLEAMS: Groundwater
Loading Effects of Agricultural Management Systems, Version 3.0:
Agricultural Research Service, U.S. Department of Agriculture,
Publication No. SEWRL-WGK/FMD-050199, 191 p.

Number range CHAPTERUSDA. 2001. Official Series Description LOS OSOS
Series. Information from the website:
[http://ortho.ftw.nrcs.usda.gov/osd/dat/L/LOS
OSOS.htm](http://ortho.ftw.nrcs.usda.gov/osd/dat/L/LOS OSOS.htm).

USDA. 2006. Soil Survey Areas of Alameda, Contra Costa, Solano, Sonoma,
and Santa Clara Counties, California. U.S. Department of Agriculture,
Natural Resources Conservation Service (NRCS), Soil Data Mart. March 1,
2006. Online at:
[http://soildatamart.nrcs.usda.gov](http://soildatamart.nrcs.usda.gov/).