Vernal Pool Mitigation

 

Monitoring Program

 

 

Leo Anguiano

Geography 26 - Data Acquisition

Spring 2000

American River College

 

 

 

ABSTRACT

The primary focus of this paper is on the delineation of natural occurring vernal pools and the collection of attributes.  The property located in Sacramento is the area of study.  ArcView shapefiles were created from GPS points collected by a Trimble Unit and post-processed for differential correction.  The attributes collected so far have been inputted in ArcView tables for analysis comparison against newly constructed vernal pools.

 

 

 

INTRODUCTION

Vernal pools are unique wetlands that fill with rain water during winter and dry out by summer.  These pools vary in size from small depressions in the earth to large ponds.  A single pool can be home to hundreds of native plants and animals, many of which are found only in vernal pools.  Because they are home to endangered species, including several species of fairy shrimp and other invertebrates, pools are protected by law.  When pools are destroyed by development, they must be mitigated for.  Mitigation involves the process of monitoring existing and newly developed vernal pools through the collection of certain data elements for comparison / analysis.  The primary objective of the Company’s monitoring program is to determine the relative success of mitigation efforts as compared to established success criteria.  Monitoring is also designed to provide sufficient data to identify and evaluate the cause of problems in attaining success should they occur, and assist in devising appropriate corrective measures.

 

 

BACKGROUND

In October 1996, the Company implemented a vernal pool mitigation project as compensation for vernal pool losses associated with sand and gravel mining.  The mitigation was developed to satisfy requirements associated with the U.S. Fish and Wildlife Services’ (USFWS) approval to mine aggregate.

 

Part of this mitigation project was the construction and monitoring of 15 acres of vernal pools.  The gathering of monitoring information related to these pools began in 1997 by  Company personnel.

 

In order to properly monitor the newly constructed pools, an 80-acre parcel of land containing 10 acres of seasonal wetlands and natural vernal pools was set aside by the Company as a preservation area for the study and monitoring of these pools.   Information is also being gathered and collected from these natural vernal pools to compare against the constructed vernal pools.  The success criteria are such that the created pools must meet similar physical, hydrology, edaphic, and floristic/biological conditions as the natural pools.

 

An important aspect of the monitoring program is the development of a GIS database to properly analyze the information from both groups of vernal pools.  Delineation of the vernal pools is a part of this database that needs to be completed to properly analyze this information from a spatial perspective.

 

 

 

OBJECTIVE

This report will focus on the collection of attributes (photos and hydrology) and the delineation of ten randomly selected natural vernal pools and property boundary in the 80-acre parcel of land.  It is hoped that this information will allow the Company  to better monitor newly constructed vernal pools as part of their mitigation and monitoring agreements.

 

 

 

METHODS

 

 

Delineation

The 10 vernal pools (randomly selected by the Company personnel) were marked with a water measuring pipe at the deepest point of the pool.  These water pipes were used to differentiate the selected pools from other pools in the area.  The property boundary is surrounded by a cattle fence.  Delineation was conducted by the use of a Trimble GPS Unit capable of post-processing for differential correction.  The Datum used for creation of the files was NAD 27, California Zone 2.

 

The perimeter of the fence was used as a boundary.  A rover file was used to collect points as the boundary was slowly paced.  Points were being collected every 2 seconds or so.

 

The perimeters of the vernal pools were similarly paced, making sure that a rover file was used for each of the selected vernal pools for the collection of points.  The beginning and ending of the pools were marked with a flag for minimum overlapping.

 

After all the selected vernal pools were delineated, as well as some irrigated wetlands, post-processing was done through the Pathfinder Office Software.  Base files for differential correction were downloaded from http://www.fs.fed.us/database/gps/wsftp/ftpinfo.htm internet site.  The files were then exported as shapefiles for ArcView usage. 

 

Photos

Photographs were taken from permanent photo stations to document seasonal changes and vegetation development of both the constructed and natural pools.  Representative photos of existing plant species will continue to be taken during the peak flowering period.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hydrology Monitoring

Pool hydrology was measured by water depth and percent inundation.  Water levels in each of the pools was measured weekly from November through April.  Permanent gauges were placed in each pool at about its deepest point.  Two, three, or four gauges were placed in some of the larger pools with more than one low point.

 

The total area inundated in each pools was given a ranking based upon its percentage of inundation.  The following ranking system was used:

 

 

 

 

 

Vegetation Monitoring

Botanical surveys will be conducted in April.  Floristic data will include a list of the species present, plant cover estimates, and species composition.

 

 

 

RESULTS

Eight visits were made to the site between February and April, 2000.  Hydrology and photo images were gathered by Company employees visiting the site for monitoring purposes.  The creation of the shapefiles was done through ArcView.

 

Delineation

The image to the right indicates the vernal pools that will be used for comparison purposes against newly created ones.

 

Most of the vernal pools were under a tenth of an acre, averaging around 1000 square feet.  The largest of these (X10) was just over 3 acres large with several small islands.

 

There were several irrigated wetlands in the 80 acre parcel.  At some points, these irrigated wetlands actually joined some of the vernal pools as inlets/outlets, making the job of delineating these areas difficult.

 

 

 

 

 

The image to the left is a map of newly constructed pools the Company has mitigated for.  The vernal pools are colored in dark blue.  These will be compared to the sample pools for water depths, percent of inundation, vegetative cover, and  vegetative composition.

 

 

 

 

 

 

 

Hydrology

Water depth was monitored weekly from January to April.  Maximum depths were reached in mid-February due to low rain levels in December.  By the end of April almost all the pools were dry except for the largest, X10.

 

 

 

 

 

 

 

 

 

 

 

These water depth measurements will be compared to those of constructed pools.  The standard to be used is as follows:

 

Constructed pools will pond water to a depth and duration within the range of the control pools.

 

The range is defined as within 10 percent of range of the sampled pools.

 

 

 

Vernal Pool Inundation Table

 

Vernal Pools	Rank
	Jan-2000	Feb-2000	Mar-2000	Apr-2000
X1	1	2	3	2
X2	1	2	3	1
X3	0	1	2	2
X4	0	1	1	0
X5	1	1	2	0
X6	1	2	3	0
X7	0	1	3	0
X8	1	2	3	0
X9	0	1	3	0
X10	1	2	3	1
Rank	3 – Pool > 80% inundated 2 – Pool 50% to 80% inundated 1 – Pool < 50% inundated 0 – Pool not inundated

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Inundation levels will be used to analyze the natural pool’s water evaporation / drainage to those of the newly constructed pools.  By evaluating the color of the pool in the theme, one can evaluate which pools hold more water and at what time of the season they begin to dry up.

 

 

 

 

 

CONCLUSION

First year’s monitoring results will be evaluated after all information is collected.  Some of the analysis that is hoped to be gained from this are:

 

The indication that mitigated pools are establishing a native vernal pool flora and hydrology within target levels. Vegetative cover can be expected to reach an equilibrium level at some point while species richness will reach a peak and then begin to decline as the multitude of early success ional species give way to the more dominant species typical of the area.

 

Erosion indication through water overflow and sediment deposits.

 

 

 

REFERENCES

 

Company.  August 31, 1995.  Compensation Vernal Pool Monitoring Requirements.

 

Company Employees. April 2000.  Personal Communications.

 

Dept of Fish and Game, Wetlands Inventory and Conservation http://maphost.dfg.ca.gov/wetlands/vp_prog_rept/vpprogfin3.698.htm

 

USDA Forest Service, Global Positioning System Page.  http://www.fs.fed.us/database/gps/