LORP Area Filter Applied:
- Northernmost 2025 point latitude: 36.9747 °N
- Filtered dataset now contains 1647 observations
Perennial Pepperweed Mapping
Noxious Weeds Monitoring 2025-2026 LORP Workplan
Summary
This data report covers the monitoring of Lepidium latifolium (perennial pepperweed) in the Lower Owens River Project (LORP) area from 2018 to 2025. The data is sourced from the ArcGIS Online Noxious Weeds 2025 feature service and provides updated spatial occurrence as of 2025.
“Perennial pepperweed (Lepidium latifolium), an introduced plant from southeastern Europe and Asia, is invasive throughout the western United States. It can establish in a wide range of environments and is a common problem in flood plains, irrigation structures, pastures, wetlands, riparian areas, roadsides, and residential site. Recent surveys identify perennial pepperweed as a weed problem in nearly all of California, and both the California Department of Food and Agriculture (CDFA) and California Invasive Plant Council (Cal-IPC) list it as a noxious weed of great ecological concern.” - UC IPM
California Invasive Plant Council (Cal-IPC) Rating: High
High – These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically.
California Department of Food and Agriculture (CDFA) Rating: -*
* – included in the CCR Section 4500 list of California State Noxious Weeds.
Data Overview
The dataset includes 1647 total observations across 8 years, with peak survey activity in 2025 (426 records).
Key Findings Summary
- Total Observations: 1647 records across all years (2018-2025)
- Peak Survey Year: 2025 with 426 observations
- Recent Activity: 852 observations in 2022-2025
- Historical Baseline: 795 observations in 2018-2021
- Data Coverage: 100% of records have complete date information (using observation date with creation date fallback)
Interactive Map Comparison
The following interactive map shows pepperweed populations across all years (2018-2025). Use the layer controls in the top-right corner to toggle between different years. The map includes all 1647 documented observations, with feature creation dates used when observation dates are unavailable.
Data Downloads
Complete dataset with all 1647 pepperweed observations
Study Area Boundaries
- North: 36.9747°N
- South: 36.5478°N
- East: -117.981°W
- West: -118.2343°W
- Center: 36.7612°N, -118.1077°W
Re-reading with feature count reset from 1 to 0
2025 Distribution - plants per site estimated from field observations
The following histogram shows the distribution of abundance values for all pepperweed point locations documented in 2025:
### 2025 Site Distribution
- **Total Sites**: 426
- **Small Sites (≤ 100 plants)**: 325 sites ( 76.3 %)
- **Large Sites (> 100 plants)**: 99 sites ( 23.2 %)
### Detailed Abundance Distribution
- **1 plants**: 57 sites
- **2 plants**: 135 sites
- **4 plants**: 133 sites
- **5 plants**: 99 sites
### Abundance Range
- **Minimum**: 5 plants
- **Maximum**: 200 plants
The interactive map above provides the primary visualization of pepperweed distribution patterns.
Recent Sites
Data Quality and Limitations
Data Sources
Primary Source: ArcGIS Online Noxious Weeds 2025 Feature Service
Last Updated: August 11, 2025
Coordinate System: WGS84 (EPSG:4326)
Limitations
- Data represents documented observations only
- Population estimates may vary based on survey timing and conditions
- Some areas may be under-sampled due to access constraints
- Abundance categories are based on field estimates
River Reach Analysis
Number of river reaches loaded: 6
Reach names: LORP Reach 1 LORP Reach 2 LORP Reach 3 LORP Reach 4 LORP Reach 5 LORP Reach 6
Sites before filtering: 1647
Sites after spatial join: 1647
Sites with reach assignments: 1647
### LORP Reach Distribution Summary
**Total Reaches Analyzed**: 6
**Years Covered**: 2018 - 2025
**Reaches with Data**: 6
### Reach Activity Summary
- ** LORP Reach 2 **: 999 sites
- ** LORP Reach 3 **: 423 sites
- ** LORP Reach 1 **: 163 sites
- ** LORP Reach 4 **: 47 sites
- ** LORP Reach 5 **: 12 sites
- ** LORP Reach 6 **: 3 sites
Occupancy Analysis
### Overall Occupancy Analysis
**Resolution**: 1/10 mile segments (600 total segments across 60 miles)
#### Overall Occupancy by Year
Table: Number of 1/10 mile segments occupied by pepperweed
| Year | Segments Occupied | Total Segments | Occupancy % |
|:----:|:-----------------:|:--------------:|:-----------:|
| 2018 | 15 | 600 | 2.5 |
| 2019 | 74 | 600 | 12.3 |
| 2020 | 86 | 600 | 14.3 |
| 2021 | 21 | 600 | 3.5 |
| 2022 | 37 | 600 | 6.2 |
| 2023 | 1 | 600 | 0.2 |
| 2024 | 87 | 600 | 14.5 |
| 2025 | 145 | 600 | 24.2 |
#### Reach-Specific Occupancy
Table: Percentage of each reach occupied by pepperweed (by year)
|LORP Reach | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|:------------|:----:|:----:|:----:|:----:|:----:|:----:|:----:|:----:|
|LORP Reach 1 | 23.7 | 52.6 | 39.5 | 2.6 | NA | NA | 10.5 | 55.3 |
|LORP Reach 2 | 3.1 | 17.6 | 23.9 | 5.0 | 15.7 | NA | 21.4 | 40.3 |
|LORP Reach 3 | 0.7 | 17.6 | 20.3 | 5.4 | 7.4 | 0.7 | 29.1 | 31.8 |
|LORP Reach 4 | NA | NA | 8.3 | 11.1 | 2.8 | NA | 19.4 | 11.1 |
|LORP Reach 5 | NA | NA | NA | NA | NA | NA | 2.9 | 17.6 |
|LORP Reach 6 | NA | NA | NA | NA | NA | NA | NA | 8.1 |
### Occupancy Summary Statistics
**Average Annual Occupancy**: 9.7 %
**Highest Occupancy Year**: 2025 ( 24.2 %)
**Lowest Occupancy Year**: 2023 ( 0.2 %)
**Most Occupied Reach**: LORP Reach 1 ( 30.7 % average)
**Least Occupied Reach**: LORP Reach 6 ( 8.1 % average)
River Mile Analysis
### Reach Boundaries (Northern Boundaries)
**Table showing minimum river mile for each reach (northern boundary):**
Table: Northern boundaries (minimum river miles) for each LORP reach
|LORP Reach | Min River Mile | Max River Mile | Reach Number | Label Position |
|:------------|:--------------:|:--------------:|:------------:|:--------------:|
|LORP Reach 1 | 0.1 | 3.9 | 1 | 0.1 |
|LORP Reach 2 | 3.7 | 19.6 | 2 | 3.7 |
|LORP Reach 3 | 19.7 | 34.5 | 3 | 19.7 |
|LORP Reach 4 | 34.5 | 38.1 | 4 | 34.5 |
|LORP Reach 5 | 39.0 | 42.4 | 5 | 39.0 |
|LORP Reach 6 | 49.7 | 53.4 | 6 | 49.7 |
**Using actual reach boundaries from data:**
# A tibble: 6 × 5
Name Min_RiverMile Max_RiverMile Reach_Num Label_Position
<chr> <dbl> <dbl> <int> <dbl>
1 LORP Reach 1 0.1 3.9 1 0.1
2 LORP Reach 2 3.7 19.6 2 3.7
3 LORP Reach 3 19.7 34.5 3 19.7
4 LORP Reach 4 34.5 38.1 4 34.5
5 LORP Reach 5 39 42.4 5 39
6 LORP Reach 6 49.7 53.4 6 49.7
### Reach Labels and River Miles
**Table showing reach labels and their river mile positions:**
Table: Reach labels and their river mile positions
|Reach Label | River Mile |
|:------------|:----------:|
|LORP Reach 1 | 0.1 |
|LORP Reach 2 | 3.7 |
|LORP Reach 3 | 19.7 |
|LORP Reach 4 | 34.5 |
|LORP Reach 5 | 39.0 |
|LORP Reach 6 | 49.7 |
### Reach Minimum River Miles
**Table showing minimum river mile for each reach:**
Table: Minimum river mile for each reach
|Reach | Min River Mile |
|:------------|:--------------:|
|LORP Reach 1 | 0.1 |
|LORP Reach 2 | 3.7 |
|LORP Reach 3 | 19.7 |
|LORP Reach 4 | 34.5 |
|LORP Reach 5 | 39.0 |
|LORP Reach 6 | 49.7 |
### Manual Reach Boundaries for Plot
Name Closest_Bin
1 Reach 1 0
2 Reach 2 4
3 Reach 3 20
4 Reach 4 35
5 Reach 5 39
6 Reach 6 50
### River Mile Distribution Summary
**Total River Miles Analyzed**: 61
**Years Covered**: 2018 - 2025
**River Mile Range**: 0 - 60
### Top 10 Most Active River Miles
- **River Mile 10 **: 269 sites
- **River Mile 4 **: 196 sites
- **River Mile 7 **: 157 sites
- **River Mile 5 **: 99 sites
- **River Mile 6 **: 94 sites
- **River Mile 28 **: 83 sites
- **River Mile 3 **: 77 sites
- **River Mile 30 **: 64 sites
- **River Mile 34 **: 59 sites
- **River Mile 29 **: 51 sites
Field Documentation
Field Documentation Images
Pepperweed observations with field photos:
Feature ID: 1369 | Date: 2025-04-02 | Abundance: 200 plants
Feature ID: 1370 | Date: 2025-04-02 | Abundance: 200 plants
Feature ID: 1371 | Date: 2025-05-14 | Abundance: 200 plants
Notes: Dense vegetative cluster around low ditch
Feature ID: 1398 | Date: 2025-07-30 | Abundance: 200 plants
Notes: Among the tule next to the water, north of the willow
Feature ID: 1401 | Date: 2025-07-30 | Abundance: 200 plants
Notes: Among tule next to water, south of willow
Feature ID: 1465 | Date: 2025-07-30 | Abundance: 200 plants
Notes: W BAHY + SCAC
Feature ID: 1467 | Date: 2025-07-30 | Abundance: 200 plants
Notes: 10-15m south of rivers edge
Feature ID: 1473 | Date: 2025-07-30 | Abundance: 200 plants
Notes: 8-10m from waters edge; 12-15m long stretch of LELA bordering large TARA
Feature ID: 1475 | Date: 2025-07-30 | Abundance: 200 plants
Notes: 20m long stretch 2-5m from river, dense
Feature ID: 1482 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1485 | Date: 2025-07-31 | Abundance: 200 plants
Notes: W/ ASFA
Feature ID: 1490 | Date: 2025-07-31 | Abundance: 200 plants
Notes: W/ dead BAHY
Feature ID: 1495 | Date: 2025-07-31 | Abundance: 200 plants
Notes: W) ASFA ELTR TYPHA
Feature ID: 1501 | Date: 2025-07-31 | Abundance: 200 plants
Notes: W/ ASFA
Feature ID: 1506 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1507 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1508 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1510 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1515 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1516 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1527 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1529 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1535 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1538 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1545 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1547 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1563 | Date: 2025-07-31 | Abundance: 200 plants
Feature ID: 1583 | Date: 2025-08-04 | Abundance: 200 plants
Notes: Along bank, flowering
Feature ID: 1598 | Date: 2025-08-04 | Abundance: 200 plants
Notes: Several large patches around this point
Feature ID: 1650 | Date: 2025-08-04 | Abundance: 200 plants
Feature ID: 1367 | Date: 2025-04-01 | Abundance: 100 plants
Field documentation images provide visual confirmation of pepperweed sites and help verify site characteristics.
Conclusion
The 2018-2025 data reveals expanding pepperweed distribution within the LORP area. The interactive mapping tool provides land managers with a visualization tool for identifying and prioritizing treatment areas over time.
This report will be updated as new data are added to the live feature service. The data source is available at: ArcGIS REST Service
Data Disclaimer
The data presented in this report are collected for monitoring and management purposes by the Inyo County Water Department. While every effort is made to ensure accuracy, field conditions, survey timing, and observer experience may affect data quality. Users should verify critical information independently before making management decisions.
Inyo County Water Department
© 2025 Inyo County, California. All rights reserved.
This analysis is automatically updated when new data is added to the ArcGIS feature service.
Citation
@report{untitled,
author = {},
publisher = {Inyo County Water Department},
title = {Perennial {Pepperweed} {Mapping}},
date = {},
url = {https://github.com/inyo-gov/noxious-weeds},
langid = {en}
}