**Barton Springs rangeland/pastureland**

This scenario has been parameterized to represent pesticide application
on pastures, grassland, and rangeland in the Barton Springs Segment
(BSS) of the Edwards Aquifer. Vegetation is generally dominated by
grasses, forbs and shrubs. In North America, rangelands include the
grasslands of the Great Plains including Midwestern United States to
Manitoba, Saskatchewan, and Alberta in Canada. Other types of rangelands
include US wetlands, Texas and Florida savannas, western US shrublands,
Alaskan and Canadian tundra, Mexican deserts, and alpine meadows in
mountain ranges throughout the North American continent (SRM 2004).

In the BSS, rangeland vegetation is a heterogeneous mixture of trees and
grasses. Common tree species include: ash juniper (a nuisance species),
oaks, hackberry and elms. Grass species including little blue stem, side
oats gramma, indian grass, switch grass, king ranch bluestem
(introduced) and kline grass (introduced) are typical. These areas are
composed of approximately 60-65% trees and 30-35% grasses (Perez 2006).
Although these landcovers contain a significant amount of tree cover,
this "crop" was modeled as a field crop rather than an orchard in order
to model a more conservative field.

Soils were selected based on their extent within the natural herbaceous
land cover in BSS and the potential to yield high-end runoff and
erosion. Based on a geospatial analysis of soils (USDA 2006) and land
use data (USGS 2003) for natural herbaceous areas as well as
conversations with local soil experts, Brackett soils were chosen to
represent rangeland/pastureland areas in the BSS (Table 5). Brackett
soils are found in both the contributing and recharge zones of the
Edwards Aquifer and are the most common soil on which rangeland is
located (USDA 2006; USGS 2003). Location of the Brackett soils was also
cross-checked with aerial photography to ensure that the soil chosen
coincided with natural herbaceous areas where pesticides may be applied.
According to a local extension agent (Cris Perez), rangelands reside on
a variety of soils; however Brackett is a common soil type of rangelands
in the BSS.

The Brackett series was selected for this scenario because it is both
highly representative of rangeland/pastureland areas in the BSS and
because it represents the 90^th^ percentile of vulnerability, drainage,
erodibility, and slope. The Brackett series is a Hydrologic Group C soil
which account for 23% of all soils in rangeland areas (Table 5).
Hydrologic Group C soils account for approximately 49% of natural
herbaceous soils in drainage. These soils are loamy, carbonatic,
thermic, shallow Typic Haplustepts which consist of very shallow to
shallow soils over bedrock. These well drained and moderately permeable
soils formed in residuum over chalky limestone bedrock (USDA 2001).
Brackett soils have a USLE K factor of 0.37 which includes the 90^th^
percentile of these soils in erodibility (Table 5). Slopes range from 1
to 60 percent (Soil Survey Staff, 2006); however the most typical range
for the Brackett series in rangeland areas is 1-8 percent (USDA 2006;
USGS 2003). Soil parameters for the "Brackett-Rock outcrop-Comfort
complex, 1 to 8 percent slopes" were selected from Soil Data Mart to
parameterize this scenario since this soil type is the most extensive
soil co-occuring with rangeland/pastureland within the Brackett series
(USDA 2006; USGS 2003). Data from Hays County were selected since the
majority of this landcover is located in this county.

The meteorological station selected for this scenario is located in
Austin, Texas. This station is the closest available weather station
that includes data required for PRZM.

Number range CHAPTER

+-----------------+----------+-----------------------------------------+
| **Table 1. PRZM |          |                                         |
| 3.12 Climate    |          |                                         |
| and Time        |          |                                         |
| Parameters for  |          |                                         |
| Barton Springs, |          |                                         |
| TX.**           |          |                                         |
+-----------------+----------+-----------------------------------------+
| **Parameter**   | *        | **Source/Comments**                     |
|                 | *Value** |                                         |
+-----------------+----------+-----------------------------------------+
| Starting Date   | Jan. 1,  | Meteorological File from Austin, TX     |
|                 | 1961     | (W13958)                                |
+-----------------+----------+-----------------------------------------+
| Ending Date     | Dec. 31, | Meteorological File from Austin, TX     |
|                 | 1990     | (W13958)                                |
+-----------------+----------+-----------------------------------------+
| Pan Evaporation | 0.69     | PRZM Manual Figure 5.1 (EPA 1998).      |
| Factor (PFAC)   |          |                                         |
+-----------------+----------+-----------------------------------------+
| Snowmelt Factor | 0.36     | PRZM Manual, Table 5.1 (EPA 1998).      |
| (SFAC)          |          |                                         |
+-----------------+----------+-----------------------------------------+
| Minimum Depth   | 25       | Mid point of range (20-30), PRZM        |
| of              |          | Manual, Figure 5.2 (EPA 1998).          |
|                 |          |                                         |
| Evaporation     |          |                                         |
| (ANETD)         |          |                                         |
+-----------------+----------+-----------------------------------------+

+-----------------+----------+-----------------------------------------+
| **Table 2. PRZM |          |                                         |
| 3.12 Erosion    |          |                                         |
| and Landscape   |          |                                         |
| Parameters for  |          |                                         |
| Barton          |          |                                         |
| Springs -       |          |                                         |
| rangeland       |          |                                         |
| /pastureland.** |          |                                         |
+-----------------+----------+-----------------------------------------+
| **Parameter**   | *        | **Source/Comments**                     |
|                 | *Value** |                                         |
+-----------------+----------+-----------------------------------------+
| Method to       | 4 (MUSS) | Default value.                          |
| Calculate       |          |                                         |
| Erosion         |          |                                         |
| (ERFLAG)        |          |                                         |
+-----------------+----------+-----------------------------------------+
| USLE K Factor   | 0.37     | NRCS Soil Data Mart Database, Hays      |
| (USLEK)         | tons     | County, for Brackett-Rock               |
|                 | EI^-1^\* | outcrop-Comfort complex, 1 to 8 percent |
|                 |          | slopes.                                 |
|                 |          | (<http://soildatamart.nrcs.usda.gov/>). |
+-----------------+----------+-----------------------------------------+
| USLE LS Factor  | 0.69     | Calculated according to Haan and        |
| (USLELS)        |          | Barfield (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 = |
|                 |          | 0.4 (EPA 2004).                         |
+-----------------+----------+-----------------------------------------+
| USLE P Factor   | 1        | No contour plowing is expected (EPA     |
| (USLEP)         |          | 2004).                                  |
+-----------------+----------+-----------------------------------------+
| Field Area      | 10 ha    | Default drainage area for standard      |
| (AFIELD)        |          | ecological pond (EPA, 2004).            |
+-----------------+----------+-----------------------------------------+
| NRCS Hyetograph | 4        | PRZM Manual, Figure 5.12 (EPA, 1998).   |
| (IREG)          |          |                                         |
+-----------------+----------+-----------------------------------------+
| Slope (SLP)     | 4 %      | Brackett-Rock Outcrop-Comfort Complex   |
|                 |          | Soil Slope range 1-8% (USDA 2006).      |
|                 |          | Midpoint of slope range (EPA, 2004)     |
+-----------------+----------+-----------------------------------------+
| Hydraulic       | 356 m    | Default value for standard ecological   |
| Length (HL)     |          | pond (EPA, 2004)                        |
+-----------------+----------+-----------------------------------------+
| Irrigation Flag | 0        | Cris Perez, NRCS - District             |
| (IRFLAG)        |          | Conservationist                         |
|                 |          |                                         |
|                 |          | Date: 3-16-06, Phone: 512-392-4050 x3   |
+-----------------+----------+-----------------------------------------+
| \* EI = 100     |          |                                         |
| ft-tons \* in/  |          |                                         |
| acre\*hr        |          |                                         |
+-----------------+----------+-----------------------------------------+

+-----------------+----------+-----------------------------------------+
| **Table 3. PRZM |          |                                         |
| 3.12 Crop       |          |                                         |
| Parameters for  |          |                                         |
| Barton          |          |                                         |
| Springs -       |          |                                         |
| rangeland       |          |                                         |
| /pastureland.** |          |                                         |
+-----------------+----------+-----------------------------------------+
| **Parameter**   | *        | **Source/Comments**                     |
|                 | *Value** |                                         |
+-----------------+----------+-----------------------------------------+
| Initial Crop    | 1        | Default value                           |
| (INICRP)        |          |                                         |
+-----------------+----------+-----------------------------------------+
| Initial Surface | 3        | Cris Perez, NRCS - District             |
| Condition       |          | Conservationist                         |
|                 |          |                                         |
| (ISCOND)        |          | Date: 3-16-06, Phone: 512-392-4050 x3   |
+-----------------+----------+-----------------------------------------+
| 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: Austin, TX (W13958).              |
| 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  | 43 cm    | Cris Perez, NRCS - District             |
| Root Depth      |          | Conservationist; Date: 3-16-06, Phone:  |
| (AMXDR)         |          | 512-392-4050 x3                         |
|                 |          |                                         |
|                 |          | Root depth depends upon the soil depth. |
|                 |          | In creek beds, grass roots will grow    |
|                 |          | 3-4'. On rolling hills, they will grow  |
|                 |          | 6-8". Therefore, this value set to      |
|                 |          | CORED.                                  |
+-----------------+----------+-----------------------------------------+
| Maximum Canopy  | 97%      | Cris Perez, NRCS - District             |
| Coverage        |          | Conservationist                         |
| (COVMAX)        |          |                                         |
|                 |          | Date: 3-16-06, Phone: 512-392-4050 x3   |
+-----------------+----------+-----------------------------------------+
| Soil Surface    | 3        | Cris Perez, NRCS - District             |
| Condition After |          | Conservationist                         |
| Harvest (ICNAH) |          |                                         |
|                 |          | Date: 3-16-06, Phone: 512-392-4050 x3   |
+-----------------+----------+-----------------------------------------+
| Date of Crop    | 01/03/61 | Cris Perez, NRCS - District             |
| Emergence       |          | Conservationist                         |
|                 |          |                                         |
| (EMD, EMM,      |          | Date: 3-16-06, Phone: 512-392-4050 x3   |
| IYREM)          |          |                                         |
|                 |          | Plants emerge from late February-March. |
|                 |          | They mature mid June. They go dormant   |
|                 |          | after the first frost, which occurs in  |
|                 |          | November.                               |
+-----------------+----------+-----------------------------------------+
| Date of Crop    | 15/06/61 |                                         |
| Maturity        |          |                                         |
|                 |          |                                         |
| (MAD, MAM,      |          |                                         |
| IYRMAT)         |          |                                         |
+-----------------+----------+-----------------------------------------+
| Date of Crop    | 15/11/61 |                                         |
| Harvest         |          |                                         |
|                 |          |                                         |
| (HAD, HAM,      |          |                                         |
| IYRHAR)         |          |                                         |
+-----------------+----------+-----------------------------------------+
| Maximum Dry     | 0.0      | Not used in scenario.                   |
| Weight (WFMAX)  |          |                                         |
+-----------------+----------+-----------------------------------------+
| Maximum Canopy  | 122      | Little bluestem (2-4\') is a typical    |
| Height (HTMAX)  |          | range plant for this soil (USDA 2006)   |
|                 |          | in this region (Cris Perez, NRCS).      |
|                 |          | Height data from                        |
|                 |          | [[http://texnat.tamu.edu/cmplants       |
|                 |          | /B-182/main.htm]{.underline}](http://te |
|                 |          | xnat.tamu.edu/cmplants/B-182/main.htm). |
+-----------------+----------+-----------------------------------------+
| SCS Curve       | 87, 83,  | Gleams Manual Table H-4, pasture/range, |
| Number (CN)     | 86       | non-CNT, hydrologic group C, poor       |
|                 |          | condition (USDA, 2000)                  |
+-----------------+----------+-----------------------------------------+
| Manning\'s N    | 0.110    | San Antonio Pasture, warm season        |
| Value (MNGN)    |          | (I93PWPWN). This file incorporates no   |
|                 |          | tillage and has a cover code (2)        |
|                 |          | representing first year grass, pasture  |
|                 |          | or hay crops.                           |
+-----------------+----------+-----------------------------------------+
| USLE C Factor   | 0.004    | San Antonio Pasture, warm season        |
| (USLEC)         |          | (I93PWPWN).                             |
+-----------------+----------+-----------------------------------------+

+---------+-------------------+---------------------------------------+
| **Table |                   |                                       |
| 4. PRZM |                   |                                       |
| 3.12    |                   |                                       |
| Bracke  |                   |                                       |
| tt-Rock |                   |                                       |
| O       |                   |                                       |
| utcrop- |                   |                                       |
| Comfort |                   |                                       |
| Complex |                   |                                       |
| Soil    |                   |                                       |
| Par     |                   |                                       |
| ameters |                   |                                       |
| for     |                   |                                       |
| Barton  |                   |                                       |
| Sp      |                   |                                       |
| rings - |                   |                                       |
| ran     |                   |                                       |
| geland/ |                   |                                       |
| pasture |                   |                                       |
| land.** |                   |                                       |
+---------+-------------------+---------------------------------------+
| **Para  | **Value**         | **Source/Comments**                   |
| meter** |                   |                                       |
+---------+-------------------+---------------------------------------+
| Total   | 43 cm             | NRCS Soil Data Mart Database, Hays    |
| Soil    |                   | County, for Brackett-Rock             |
| Depth   |                   | outcrop-Comfort complex, 1 to 8       |
| (CORED) |                   | percent slopes.                       |
|         |                   | (<                                    |
|         |                   | http://soildatamart.nrcs.usda.gov/>). |
|         |                   |                                       |
|         |                   | According to an extension agent (Cris |
|         |                   | Perez), rangelands reside on a        |
|         |                   | variety of soils. Brackett is a       |
|         |                   | common soil type of rangelands in     |
|         |                   | this area.                            |
|         |                   |                                       |
|         |                   | Additional data were listed for a     |
|         |                   | 4^th^ HORIZN. However, these were not |
|         |                   | included in this soil profile since   |
|         |                   | the 4^th^ HORIZN is composed of       |
|         |                   | bedrock.                              |
|         |                   |                                       |
|         |                   | Number range CHAPTERPRZM Scenario     |
|         |                   | Guidance (2004).                      |
|         |                   |                                       |
|         |                   | Adjusted using the relationship % OC  |
|         |                   | = % Organic Matter/1.724 (Doucette    |
|         |                   | 2000).                                |
+---------+-------------------+---------------------------------------+
| Number  | 3                 |                                       |
| of      |                   |                                       |
| H       |                   |                                       |
| orizons |                   |                                       |
| (       |                   |                                       |
| NHORIZ) |                   |                                       |
+---------+-------------------+---------------------------------------+
| Horizon | 10 cm (HORIZN =1) |                                       |
| Th      |                   |                                       |
| ickness | 5 cm (HORIZN =2)  |                                       |
| (THKNS) |                   |                                       |
|         | 28 cm (HORIZN =3) |                                       |
+---------+-------------------+---------------------------------------+
| Bulk    | 1.4 g/cm3 (HORIZN |                                       |
| Density | =1)               |                                       |
| (BD)    |                   |                                       |
|         | 1.4 g/cm3 (HORIZN |                                       |
|         | =2)               |                                       |
|         |                   |                                       |
|         | 1.4 g/cm3 (HORIZN |                                       |
|         | =3)               |                                       |
+---------+-------------------+---------------------------------------+
| Initial | 0.28 cm3/cm3      |                                       |
| Water   | (HORIZN =1)       |                                       |
| Content |                   |                                       |
| (THETO) | 0.28 cm3/cm3      |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.251 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Comp    | 0.1 cm (HORIZN    |                                       |
| artment | =1)               |                                       |
| Th      |                   |                                       |
| ickness | 5 cm (HORIZN =2)  |                                       |
| (DPN)   |                   |                                       |
|         | 4 cm (HORIZN =3)  |                                       |
+---------+-------------------+---------------------------------------+
| Field   | 0.28 cm3/cm3      |                                       |
| C       | (HORIZN =1)       |                                       |
| apacity |                   |                                       |
| (THEFC) | 0.28 cm3/cm3      |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.251 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Wilting | 0.164 cm3/cm3     |                                       |
| Point   | (HORIZN =1)       |                                       |
| (THEWP) |                   |                                       |
|         | 0.164 cm3/cm3     |                                       |
|         | (HORIZN =2)       |                                       |
|         |                   |                                       |
|         | 0.142 cm3/cm3     |                                       |
|         | (HORIZN =3)       |                                       |
+---------+-------------------+---------------------------------------+
| Organic | 1.16 % (HORIZN    |                                       |
| Carbon  | =1)               |                                       |
| Content |                   |                                       |
| (OC)    | 1.16 % (HORIZN    |                                       |
|         | =2)               |                                       |
|         |                   |                                       |
|         | 0.73 % (HORIZN    |                                       |
|         | =3)               |                                       |
+---------+-------------------+---------------------------------------+

  ------------ ----------- -------- ------------ -------- --------- -------- ------- -------- -------- --------
  **Table 5.                                                                                           
  Soils                                                                                                
  co-located                                                                                           
  with natural                                                                                         
  herbaceous                                                                                           
  areas of the                                                                                         
  Barton                                                                                               
  Spring                                                                                               
  Segment                                                                                              
  based on                                                                                             
  USDA 2006                                                                                            
  soils data                                                                                           
  and USGS                                                                                             
  2003 land                                                                                            
  use data.                                                                                            
  Bold font                                                                                            
  indicates a                                                                                          
  benchmark                                                                                            
  soil.**                                                                                              

  **Soil**     **Total     **%      **Drainage   **KF**   **Slope   **pH**   **OM    **Sand   **Silt   **Clay
               Acreage**   Area**   Class**               (%)**              (%)**   (%)**    (%)**    (%)**

  Brackett     8,540       22.8%    C            0.37     1 - 12    8        2       34       38       28

  Rumple       5,941       15.8%    C            0.32     1 - 8     7        2       34       37       30

  Doss         4,001       10.7%    D            0.32     1 - 5     8        2       7        49       44

  Real         2,518       6.7%     D            0.28     1 - 8     8        6       36       34       31

  Comfort      1,654       4.4%     D            0.32     1 - 8     8        6       28       29       43

  Volente      1,625       4.3%     C            0.32     1 - 8     8        3       7        54       39

  Bolar        1,591       4.2%     C            0.32     1 - 3     8        2       34       37       30

  Sunev        1,413       3.8%     B            0.32     0 - 1     8        2       18       52       30

  Krum         1,404       3.7%     D            0.32     0 - 1     8        2       26       29       45

  Purves       961         2.6%     D            0.32     1 - 5     8        3       23       29       48

  Denton       907         2.4%     D            0.32     1 - 3     8        3       6        48       46

  Austin       867         2.3%     C            0.32     1 - 3     8        3       7        48       45

  Tarpley      768         2.0%     D            0.32     1 - 3     7        3       30       30       40

  Lewisville   753         2.0%     B            0.32     0 - 1     8        2       8        51       41

  Tarrant      596         1.6%     D            0.32     5 - 18    8        5       22       28       50

  Speck        569         1.5%     D            0.32     1 - 3     7        2       34       37       30

  Crawford     485         1.3%     D            0.32     0 - 1     7        2       22       28       50

  Houston      406         1.1%     D            0.32     0 - 1     8        3       17       28       55
  Black                                                                                                

  Anhalt       353         0.9%     D            0.32     1 - 3     7        3       26       29       45

  Gruene       341         0.9%     D            0.28     1 - 5     8        2       28       29       43

  Heiden       295         0.8%     D            0.32     1 - 3     8        3       22       28       50

  Castephen    207         0.6%     C            0.32     3 - 5     8        2       34       32       34

  Alluvial     196         0.5%     A            0.15     0 - 1     8        1       90       0        5
  land                                                                                                 

  San Saba     187         0.5%     D            0.32     1 - 2     8        3       18       29       53

  Branyon      160         0.4%     D            0.32     0 - 1     8        3       22       28       50

  Seawillow    141         0.4%     B            0.32     1 - 3     8        1       35       34       31

  Tinn         99          0.3%     D            0.32     0 - 1     8        3       22       28       50

  Medlin       96          0.3%     D            0.32     1 - 8     8        2       22       28       50

  Oakalla      88          0.2%     B            0.32     0 - 1     8        4       18       48       34

  Boerne       73          0.2%     B            0.28     1 - 3     8        1       65       20       16

  Orif         61          0.2%     A            0.28     0 - 1     8        2       82       9        9

  Eckrant      57          0.2%     D            0.32     8 - 40    8        7       22       28       50

  Urban land   50          0.1%     D            0.00     0 - 6     0        0       0        0        0

  Altoga       46          0.1%     C            0.32     1 - 3     8        1       7        48       45

  Patrick      45          0.1%     B            0.32     2 - 5     8        2       28       29       43

  Eddy         15          0.0%     C            0.32     1 - 3     8        1       38       36       26

  Hardeman     2           0.0%     B            0.24     3 - 12    8        1       66       20       14

  Travis       1           0.0%     C            0.24     1 - 8     7        1       66       19       15

  Ferris       0           0.0%     D            0.32     8 - 20    8        1       18       29       53

  Gaddy        0           0.0%     A            0.17     0 - 1     8        0       84       7        10
  ------------ ----------- -------- ------------ -------- --------- -------- ------- -------- -------- --------

***Sensitive Parameter Uncertainties***

[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.

For USLEC and Manning's N values, the file for San Antonio Pasture, warm
season (I93PWPWN) was selected. This file incorporates no tillage (NT)
and has a cover code representing first year grass, pasture or hay crops
(2). This file was selected because it models a tillage system and crop
that seem appropriate for a rangeland or pastureland. A RUSLE data file
also exists for San Antonio range (I93RARAN) but incorporates a cover
code (6) which represents no cover (0-7% residue cover on soil surface
during critical period) and is commonly used with conventionally tilled
crops. This cover code did not seem appropriate to model a pastureland
which would have residue during the critical period. Therefore, the file
for range was not selected.

**References**

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.

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.

Perez, C. 2006. NRCS - District Conservationist. Personal conversations.
March 17 & 20, 2006.

Soil Survey Staff, Natural Resources Conservation Service, United States
Department of Agriculture. 2006. Official Soil Series Descriptions
\[Online WWW\]. Available URL:
\"http://soils.usda.gov/technical/classification/osd/index.html\"
\[Accessed 6 March 2006\].

SRM. 2004. Society for Range Management. "What are rangelands?"
<http://rangelandswest.org/whatarerangelands.html>. Last Revised: 23
March 2004. Accessed 14 March 2006.

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. Brackett
Series. Information from the website:
<http://ortho.ftw.nrcs.usda.gov/osd/dat/B/BRACKETT.html>.

USDA. 2006. Soil Survey Areas of Hays Counties, Texas. 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/).

USGS, National Mapping Division, Rocky Mountain Mapping Center. 2003.
Edwards Aquifer Land Use / Land Cover. Denver, Colorado.